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diff --git a/old/65808-0.txt b/old/65808-0.txt deleted file mode 100644 index 3f29e88..0000000 --- a/old/65808-0.txt +++ /dev/null @@ -1,1854 +0,0 @@ -The Project Gutenberg eBook of Pecan Diseases and Pests and Their Control, -by David W. Rosburg - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: Pecan Diseases and Pests and Their Control - -Author: David W. Rosburg - D. R. King - -Release Date: July 9, 2021 [eBook #65808] - -Language: English - -Character set encoding: UTF-8 - -Produced by: Stephen Hutcheson and the Online Distributed Proofreading - Team at https://www.pgdp.net - -*** START OF THE PROJECT GUTENBERG EBOOK PECAN DISEASES AND PESTS AND THEIR -CONTROL *** - - - - - MP-313 - NOVEMBER 1958 - - - - - PECAN DISEASES AND INSECTS - AND THEIR CONTROL - - - TEXAS AGRICULTURAL EXPERIMENT STATION ... - TEXAS AGRICULTURAL EXTENSION SERVICE - College Station, Texas - - - - - Key to Pecan Diseases - - - DISEASES OF THE LEAVES - Olive spots on underside page 5 Scab - Downy, buff, or greenish-yellow lesions page 7 Downy Spot - Small, reddish-brown to gray spots on page 6 Brown Leaf Spot - underside - Dark brown to black lesions on veins page 6 Vein Spot - and stems - Tiny white tufts of fungal growth on page 9 Articularia Leaf Mold - underside - Small olive green velvety spots. By page 7 Leaf Blotch - midsummer, black pimple-like dots - appear in the spots - Leaflets yellowish, mottled, narrowed page 8 Rosette - and crinkled with reddish-brown spots, - may be perforated - Broomy type of twig growth, bunching of page 8 Bunch Disease - leaves - DISEASES OF THE NUTS - Small black sunken or raised spots page 5 Scab - which may fuse to cover entire surface - of shuck - Pink spore masses on shuck surface page 9 Pink Mold - DISEASES OF THE ROOTS - Galls of various sizes on larger roots page 7 Crown Gall - Splitting and deterioration of bark of page 10 Cotton Root Rot - infected roots, strands of buff-colored - fungal growth may be present - NONPARASITIC PLANTS ON THE LIMBS AND BARK - Whitish-gray mosslike masses on the bark page 9 Lichens - Accumulations of grayish strands page 9 Spanish Moss, Ball Moss - hanging from limbs and twigs or - ball-like growth on limbs and branches - - - - - Key to Pecan Insects - - - INSECTS ATTACKING THE NUTS - Olive-green caterpillars up to ½ inch page 10 Pecan Nut Casebearer - long feeding in the nuts, or later in - the season, in the shucks - White caterpillars up to ⅜ inch long page 11 Hickory Shuckworm - tunneling in the shucks - White legless grubs feeding in the nuts page 12 Pecan Weevil - in late summer - Green or brown bugs sucking the sap page 12 Stink Bugs and Plant - from the nuts Bugs - INSECTS ATTACKING THE FOLIAGE - Soft-bodied yellow insects producing page 13 Aphids - honeydew or small black insects causing - yellow blotches on the foliage - Tiny green arthropods in webs near the page 13 Mites - midrib, leaves appear scorched - Caterpillars feeding in gray cases page 14 Pecan Leaf Casebearer - about ½ inch long in the spring; small - winding blotches produced in the leaves - in the summer - Olive-green caterpillars tunneling in page 10 Pecan Nut Casebearer - the shoots in the early spring - Tiny caterpillars in light brown page 15 Pecan Cigar Casebearer - cigar-shaped cases about ¼ inch long - Galls on the leaves, twigs and nuts page 14 Pecan Phylloxera - Leaves eaten in the early spring by a page 14 Sawfly - light green caterpillar which leaves - the midribs and veins intact - Beetles feeding on the foliage at night page 15 May Beetles - Caterpillars in large white webs page 15 Fall Webworm - encasing entire branches - Caterpillars with long soft hairs page 16 Walnut Caterpillar - feeding in colonies on the foliage - without producing webs - Dark gray, active caterpillars up to 3 page 16 Pecan Catocala - inches long feeding on the foliage in - early spring - Masses of frothy white foam enclosing page 16 Pecan Spittlebug - tiny, light green insects in the spring - Tiny greenish caterpillars feeding in page 16 Pecan Bud Moth - the terminals and axils of the buds on - young pecan trees - INSECTS ATTACKING THE LIMBS, TRUNK AND TWIGS - Beetle girdling twigs and limbs in late page 17 Pecan Twig Girdler - summer and fall - Holes about ⅛ inch in diameter in dying page 17 Red-shouldered - limbs Shot-hole Borer - White borers with an enlargement behind page 17 Flatheaded Borers - the head tunneling underneath the bark - of trunk and limbs - Limbs encrusted with scales, which page 18 Obscure Scale - closely resemble the color of the bark - - - - - CONTENTS - - - Key to Pecan Diseases 2 - Key to Pecan Insects 2 - Spray Schedule for the Control of Pecan Diseases and Insects 4 - Introduction 5 - Pecan Diseases and Their Control 5 - Scab 5 - Brown Leaf Spot 6 - Vein Spot 6 - Leaf Blotch 7 - Crown Gall 7 - Downy Spot 7 - Bunch Disease 8 - Rosette 8 - Lichens 9 - Articularia Leaf Mold 9 - Pink Mold 9 - Spanish and Ball Moss 9 - Cotton Root Rot 10 - Pecan Insects and Their Control 10 - Pecan Nut Casebearer 10 - Hickory Shuckworm 11 - Pecan Weevil 12 - Stink and Plant Bugs 12 - Aphids 13 - Mites 13 - Pecan Leaf Casebearer 14 - Pecan Phylloxera 14 - Sawflies 14 - May Beetles 15 - Pecan Cigar Casebearer 15 - Fall Webworm 15 - Walnut Caterpillar 16 - Pecan Catocala 16 - Pecan Spittlebug 16 - Pecan Bud Moth 16 - Twig Girdler 17 - Red-shouldered Shot-hole Borer 17 - Flatheaded Borers 17 - Obscure Scale 18 - Application of Fungicides and Insecticides 18 - Spray Equipment 18 - Literature Cited 19 - - - - - SPRAY SCHEDULE FOR THE CONTROL OF PECAN DISEASES AND INSECTS - - - Name of spray and Insect or Spray materials, Remarks - time of application disease to be per 100 gallon - controlled - - Prepollination Scab, downy Zineb,[A] 2 pounds If phylloxera is a - spray, when first spot, vein spot problem, see page - leaves are 14. - one-third grown - First cover spray, Scab, downy Zineb, 2 pounds - when tips of small spot, vein - nuts have turned spot, leaf - brown and nut blotch, brown - casebearer eggs are leaf spot - observed - Pecan nut 3 pounds 50 percent - casebearer, wettable DDT, or 1 - pecan leaf pound 25 percent - casebearer wettable parathion, - or 1 pint nicotine - sulfate plus 2 - quarts summer oil, - or 5 pounds 40 - percent wettable - toxaphene, or 3 - pounds 25 percent - wettable malathion - Rosette Zinc sulfate, 2 If rosette is a - pounds problem, include - zinc sulfate in - spray. - Second cover spray, Scab, downy Zineb, 2 pounds - 3 to 4 weeks after spot, vein Zinc sulfate, 2 - first cover spray spot, leaf pounds - blotch, brown - leaf spot - Rosette - Third cover spray, Scab, brown Zineb, 2 pounds If aphid or mite - 3 to 4 weeks after leaf spot, infestations are - second cover spray liver spot, severe, use - aphids, mites insecticides - recommended on page - 13. - Walnut If walnut - caterpillar, caterpillars or - fall webworm fall webworms are a - problem, use - insecticides - recommended on - pages 15 and 16. - Rosette Zinc sulfate, 2 - pounds - Fourth cover spray Pecan weevil 6 pounds 50 percent For control of - wettable DDT weevils, apply - spray when as many - as three weevils - can be jarred from - a tree. If scab is - present add 2 - pounds zineb to DDT - spray. - -[A]Zineb. Zinc ethylene bis dithiocarbamate. Manufactured by Rohm & Haas - Co., trade name Dithane Z-78: E. I. DuPont Co., trade name Parzate. - - - - - Pecan Diseases and Insects and Their Control - - - David W. Rosberg and D. R. King - - Respectively, associate professor, Department of Plant Physiology and - Pathology, and associate professor, Department of Entomology. - -The pecan tree must be protected from attack by the many destructive -diseases and insects that affect it to produce a bountiful nut crop. - -The diseases that affect the pecan, especially those caused by fungi, -are rapidly spread throughout the trees in an orchard in the early -spring. During this season of frequent rains, the spores of the disease -fungi germinate and invade the young tender tissues of the shoots, -leaves and nuts. Under conditions of prolonged damp weather, when the -humidity remains high, the disease organisms reproduce at a rapid rate -and cause severe shedding of leaves and nuts. - -Pecans are attacked by more than 20 species of insects that cause damage -to leaves, nuts, twigs, buds, branches and even the bark. The -development of commercial pecan acreages has provided ideal conditions -for the increase in severity of both disease and insect damage because -of the abundant food supply in a concentrated planting of pecans. In its -natural habitat the pecan is less subject to the devastations of -diseases and insects. - -The many destructive insects and diseases must be controlled for -successful pecan production. The pecan grower must also understand the -nature and habits of the various disease and insect pests that threaten -his crop and use certain cultural practices which help to reduce damage -from diseases and insects. - - - - - _Pecan Diseases and Their Control_ - - -The diseases which affect the pecan are of four different types: namely -fungus, bacterial, virus and physiological. The fungus diseases, the -most numerous and widespread, are caused by small microscopic molds. -Approximately 12 different fungus organisms cause harmful diseases of -the pecan. - -The bacterial disease organisms, unlike the disease producing fungi, are -single celled and can be seen only under a microscope. Bacterial -diseases are fewer and of less economic importance than fungus diseases. - -Virus diseases are caused by extremely small agents which can be seen -only under special ultra-microscopes such as the electron microscope. -Plant viruses are protein substances, but their exact nature is unknown. - -Physiological disorders (sometimes called physiological diseases) are -caused by a variety of environmental conditions. A physiological -disorder in a pecan tree may result from infertile soil, excessive -moisture, or the absence or degree of available nutritional mineral -elements to the growing tree. These various environmental factors have -special adverse effects, manifested by specific symptoms caused by -insufficient levels of a given nutritional mineral element or elements, -which are easily corrected by supplying the tree the necessary mineral -elements either through soil application or foliage sprays. - - -SCAB - -Pecan scab, caused by the fungus _Cladosporium effusum_ (Wint.) Demaree, -is the most destructive disease of pecans in Texas. The fungus invades -the young rapidly growing shoots and leaves and later the developing -nuts. Severely infected nuts on highly scab-susceptible varieties fall -or fail to develop, resulting in a total nut crop loss. Early season -defoliation often occurs in seasons of frequent rains and high humidity -which facilitate the rapid development and spread of the scab fungus. - -The scab fungus overwinters in infected shoots and in old shucks and -leaves in the trees. In the spring when temperature and moisture -conditions become favorable, the fungus begins to grow in the shoot -lesions, old leaves and shucks, and within a few days produces great -numbers of spores. These spores are spread by wind and rain to newly -developed leaves where they germinate and invade the tender tissues, -initiating primary infection. The fungus produces a great abundance of -spores on the surface of these primary infection sites and spreads -throughout the tree and infects young shoots, leaves and nuts. - -On the leaves, primary infection lesions occur on the lower leaf -surfaces and are characteristically olive brown, somewhat elongated in -shape and vary in size from a barely discernible dot to lesions -one-fourth inch or more in diameter. Frequently, adjacent lesions -coalesce, forming large very dark lesions. Primary scab lesions commonly -occur on or along the leaflet veins but often may be found between the -veins on the underleaf surface. On the nuts, scab lesions appear as -small black dots, which are elevated or sunken in older infections. -Adjacent lesions on the nuts may coalesce forming large sunken black -lesions, Figure 1. When infection is severe, the entire nut surface is -black in appearance, development is arrested and the nuts drop -prematurely. - - [Illustration: Figure 1. Scab lesions on leaves and nuts of Delmas - variety. Note concave lesions and overall scabby appearance of - severely infected nuts.] - - [Illustration: Figure 1. Infected nuts.] - -Pecan varieties vary in their susceptibility to scab disease. Among the -highly susceptible varieties are: Burkett, Delmas, Schley, Moore, -Halbert and most western varieties. Moneymaker, Success and Curtis are -moderately resistant. Mahan, Stuart and Desirable varieties are highly -resistant to the scab fungus. However, this character of resistance -varies, depending on the area of the state, local environmental -conditions and the particular strain of the scab fungus present. - -Scab disease development is favored by rainy periods and cloudy days -when the humidity remains high and leaf surfaces are wet. Under these -conditions, spores of the fungus in contact with the wet leaf surface of -a pecan leaflet or nut germinate rapidly, invade the tender tissues and -initiate infection within 6 hours. Lesions resulting from these -infection sites, become visible to the naked eye within 7 to 14 days, -depending on environmental conditions. A period of warm dry weather -after infection occurs may retard lesion development. - -_Control._—The control of pecan scab disease depends primarily on the -protection of tender leaf, nut and shoot surfaces with proper -application of an effective fungicide. A protective film of fungicide -chemical prevents scab fungus infections by killing the spores -immediately after their germination, thereby preventing invasion of -susceptible tissues. Unfortunately, once the fungus has invaded the -tissues it becomes protected from chemical attack and produces spores in -great abundance. Therefore, thorough coverage of leaf, nut and shoot -surfaces with a fungicide chemical must be maintained to prevent -secondary infections, ([6], [10], [11]). - -Sanitation measures, such as removal of old attached shucks and leaf -stems in trees and plowing or disk harrowing under fallen leaves and -shucks help reduce primary infections. See spray schedule, page 4, for -scab disease control. - - -BROWN LEAF SPOT - -The brown leaf spot disease fungus _Cercospora fusca_ (Heald and Walf) -Rand affects only mature leaves and usually does not appear until the -latter part of May or mid-June. Primary lesions develop on the lower -leaf surfaces as small dots, which gradually enlarge and become reddish -brown with a grayish cast. The shape of the lesions may be circular or -irregular, especially where two or more lesions develop adjacent to one -another, Figure 2. In seasons favorable for brown leaf spot development -pecan trees may be completely defoliated within 3 to 4 months if the -disease is not controlled. Most pecan varieties which are maintained in -a vigorous state of growth are resistant to brown spot disease. - -_Control._—See spray schedule, page 4. - - -VEIN SPOT - -Vein spot disease is caused by the fungus _Gnomonia nerviseda_. The -symptoms of the disease are similar to the leaf lesion symptoms of scab -disease, but vein spot disease, unlike scab disease, affects only the -leaves. Lesions of vein spot disease develop on the veins or stems of -leaflets and leaves, are usually less than one-fourth inch in diameter -and are characteristically dark brown to black. Leaflets and leaf stems -which are severely affected drop, resulting in premature defoliation. - -The fungus lives in fallen leaves over the winter. The following spring -when temperature and moisture conditions are favorable, spores formed in -special structures called perithecia are forcibly discharged into the -air and carried by wind currents to the newly formed spring foliage, -initiating primary infections. - -_Control._—See spray schedule, page 4. - - -LEAF BLOTCH - -Leaf blotch disease is caused by the fungus _Mycosphaerella dendroides_ -(Cke.) Demaree and Cole. The disease occurs mainly in trees of poor -vigor, which may be due to neglect, infertile soil, rosette or -overcrowding. Nursery trees are particularly susceptible to the disease. - -The fungus overwinters in fallen leaves. In the early spring, large -numbers of spores produced in the old leaves on the ground are carried -by wind currents to the young leaves in the tree, where they germinate -and rapidly invade the tender leaf tissue. - -The disease symptoms first appear on the undersurface of mature leaves -in early summer, as small olive-green velvety spots. By midsummer black -pimplelike dots become especially noticeable in the leaf spots after the -surface spore masses have been removed by wind and rain, giving the -diseased areas of the leaves a black, shiny appearance. When the disease -is severe, infected leaflets are killed, which causes defoliation of the -trees in late summer or early fall and results in reduced tree vigor and -increased susceptibility to disease and insect attack. - -_Control._—Leaf blotch disease can be controlled effectively in the -early spring by disking under old fallen leaves that harbor the fungus -pathogen. - -In areas where a spray program for the control of scab disease is -carried out, leaf blotch usually is not a damaging disease. In -localities where leaf blotch disease occurs in the absence of other -pecan diseases, two applications of fungicide will control the disease -effectively. The first spray should be applied after pollination when -the tips of the nutlets have turned brown and the second spray -application should be made 3 to 4 weeks later. See spray schedule, page -4. - - -CROWN GALL - -Crown gall disease, caused by the bacterium _Agrobacterium tumefaciens_ -(E. F. and Town.) Conn., often is damaging to pecan trees. Nursery trees -as well as trees in bearing pecan orchards are susceptible to the -disease. - - [Illustration: Figure 2. Brown leaf spot diseased pecan leaflet - showing typical symptoms. Lesions are circular to irregular in - shape.] - -The development of galls is confined primarily to larger roots near the -base of the tree trunk, although small roots may become infected and -galls develop on them. The smaller galls are under the soil surface and -cannot be detected unless the soil is carefully removed from around the -roots, Figure 3. Large galls, often 10 to 18 inches in diameter, develop -on larger roots and may protrude well above the surface of the soil. - - [Illustration: Figure 3. Crown gall disease symptoms on young - infected pecan tree.] - -Galls on nursery trees develop at or below the soil surface on the -taproot and larger secondary roots. - -_Control._—All infected nursery trees should be dug and immediately -burned. Crown gall-diseased orchard trees sometimes can be saved by -digging the soil from around large roots and removing the exposed galls. -Where galls were removed, the damaged root surfaces should be painted -with a creosote-coal tar mixture (one part creosote to three parts coal -tar) to prevent spread of the disease[9]. Cultivation of the soil around -the trunk base of infected trees should be avoided to prevent root -wounds and spreading of the crown gall pathogen. - - -DOWNY SPOT - -Downy spot disease, caused by the fungus _Mycosphaerella caryigena_ -(Ell. and Ev.) Damaree and Cole, attacks all pecan varieties. Only -leaves are susceptible to the disease. Primary infection of new leaves -in the spring occurs from spores produced in specialized fruiting bodies -in old overwintered leaves. The downy spots appear usually during the -summer months on the lower surfaces of leaflets. The downy character of -the lesions is due to the production by the fungus of thousands of -minute spores on the surface of each spot. The spores are spread by wind -and rain to adjacent leaves and to neighboring trees. After spore -dissemination is complete, the lesions visible from both leaf surfaces -are one-eighth to one-fourth inch in diameter and greenish yellow. Later -in the season the lesions turn brown due to the death of the leaf cells -in the diseased area. - -Moneymaker and Stuart varieties are most susceptible to downy spot -disease although all pecan varieties are moderately to slightly -susceptible. - -_Control._—Disk under old fallen leaves in the early spring before the -leafbuds begin to swell. This practice covers the leaves with soil and -prevents the discharge of spores into the air, thereby controlling -primary infection of new leaves. In seasons when heavy rains make early -spring disking impossible, downy spot disease can be controlled by -spraying the trees as indicated in the spray schedule on page 4. - - -BUNCH DISEASE - -Although the cause of bunch disease is not known, evidence indicates it -is an infectious disease, which suggests that the causal agent may be a -virus. - -Trees affected with bunch disease show the bunching symptom, which is -due to excessive growth of slender succulent twigs from lateral buds -that normally remain dormant. In moderately affected trees one or -several branches will show the “bunch” growth symptom. Bunching in -severely affected trees may involve all main branches which produce -thick masses of sucker-like growth and few, if any, nuts. - -Observations indicate that the Stuart variety is the most resistant to -bunch disease. - - [Illustration: Figure 4. Rosette die-back symptoms of pecan tree - showing severe zinc deficiency.] - -_Control._—There is no known effective control for bunch disease. Early -detection of the first symptom of bunch and pruning out of the affected -branch may prevent spread of the disease throughout the tree. When the -tree is severely affected, and limbs are involved, the tree should be -destroyed to protect nearby healthy trees from infection. - -For propagation purposes, all bud or scion wood should be taken only -from bunch disease-free trees. - - -ROSETTE - -Rosette is a nutritional deficiency disease caused by certain soil -conditions which make zinc unavailable to the pecan tree. All pecan -trees require zinc for growth. - -Trees showing the first symptom of zinc deficiency have yellowed tops. -The individual leaflets when examined are yellowish and mottled. The -next season the foliage may be yellowish and the leaflets narrowed and -crinkled. More severely affected trees produce foliage which is a -yellowish to reddish-brown overall color, and the leaflets are very -narrow with reddish-brown spots and may be perforated. Shoots are much -shortened and the leaves are produced in compact bunches of dense -foliage. - -Trees affected by rosette for several seasons have many dead shoots and -small branches from the dying-back of each season’s growth, Figure 4. -Such trees are greatly stunted, of poor vigor and produce few, if any, -nuts. - -_Control._—Rosette is controlled readily by applying zinc sulfate to the -tree either as a foliage spray or in the dry form as a soil application. -Where a disease and insect spray control program is being carried out, -zinc sulfate may be added to the spray mixture. - -Foliage spray. Two pounds zinc sulfate (36 percent) per 100 gallons of -water. - -First application: after pollination when tips of nutlets turn brown. - -Second application: 3 to 4 weeks later. - -Third application: 3 to 4 weeks later. - -Soil application. Application of zinc sulfate to the soil, particularly -in a large orchard is a more expensive operation, but it provides longer -protection against rosette. - -In highly alkaline soils, or soils that readily fix zinc and make it -unavailable to the tree, foliage spray applications of zinc sulfate are -more economical because of the excessive rates required to supply -available zinc through the soil. - -Rate of application of zinc sulfate: Mildly rosetted trees—apply 5 -pounds zinc sulfate (36 percent) annually for 2 to 3 years. Severely -rosetted trees—apply 5 to 10 pounds zinc sulfate (36 percent) annually -until rosette symptoms disappear. - -Time and method of application: Apply zinc sulfate to the soil around -trees in late February or early March. Broadcast zinc sulfate under the -tree from the trunk to several feet beyond the limb canopy. Disking, -harrowing, or any operation that mixes the zinc sulfate with the soil, -is desirable to prevent washing away and surface soil fixing of zinc. - - -LICHENS - -Lichens commonly are found growing on the branches and trunks of pecan -trees, especially in humid areas and river bottom orchards having poor -air drainage. - -Lichens are nonparasitic to the pecan tree, but merely attach themselves -to the bark surfaces. Lichens grow equally well on rocks, fence posts, -bricks and other objects. There are several types of lichens that occur -on pecan trees, none of which are damaging except perhaps in appearance -to the trees in cases of extremely heavy infestations, Figure 5. - - [Illustration: Figure 5. Lichens commonly found on the bark of pecan - trees. Left, a fan-shaped type. Right, an erect-branched type.] - -_Control._—The occurrence of lichens in trees regularly sprayed with -copper-containing fungicides is rare. - - -ARTICULARIA LEAF MOLD - -Articularia leaf mold caused by the fungus _Articularia quercina_ (PK) -Hoehn is a disease of minor occurrence and importance. The disease -occurs most commonly following rainy periods and in areas of high -relative humidity in the leaves of trees of poor vigor. - -The fungus produces on the lower surfaces of the leaves a conspicuous -growth of white tufts which contain masses of spores, Figure 6. - - [Illustration: Figure 6. Articularia leaf mold fungus, showing white - tufts on lower leaf surfaces of pecan leaflets.] - -_Control._—Articularia leaf mold does not occur in trees or in orchards -which have been sprayed for disease control. - -A single application of fungicide such as zineb at 2 pounds per 100 -gallons of water when the disease is first detected is usually -sufficient to control Articularia leaf mold disease. - - -PINK MOLD - -Pink mold, _Cephalothecium roseum_ Corda, usually occurs on nuts -infected with the scab fungus. The pink mold fungus apparently enters -the nuts through scab lesions on the shucks and continues to produce -masses of pink spores on shuck surfaces until late fall. The fungus -sometimes invades the kernel of thin-shelled pecan varieties causing -“pink rot” which is characterized by an oily appearance of the nut shell -and a rancid odor. - -_Control._—Pink mold rarely occurs on the shucks of nuts in the absence -of scab disease. In areas where scab disease control is regularly -practiced pink mold is not a problem. - - -SPANISH AND BALL MOSS - -Spanish moss, _Tillandsia usneoides_, and Ball moss, _Tillandsia -recurvata_ L., are not parasitic to the pecan tree and are similar to -lichens in that they both derive their food from the air, rain or -atmospheric moisture. - -Neglected orchards in areas of high humidity or poor air drainage are -most troubled with Spanish moss and Ball moss. When large and excessive -growths of Spanish moss develop in pecan trees, the shading effect to -the leaves is detrimental to tree vigor, bearing and growth, Figure 7. - -_Control._—The Spanish moss plant like the pecan tree requires sunlight -for vigorous growth. A pecan tree kept in a vigorous state of growth -produces dense foliage that effectively shades accumulations of Spanish -moss and retards its growth. - -Spanish moss is not a problem in pecan trees in orchards which are -sprayed with fungicide for disease control. Both Spanish moss and Ball -moss can be controlled by spraying pecan trees with 6 pounds of lead -arsenate per 100 gallons of water[3]. Do not allow livestock to graze in -orchards sprayed with lead arsenate. - - -COTTON ROOT ROT - -Cotton root rot disease is caused by the fungus _Phymatotrichum -omnivorum_ (Shear) Dvgg., a soil-inhabiting pathogen that attacks a wide -range of host plants including the pecan. - -The roots of the pecan tree are invaded during the summer when growth of -the fungus in the soil is most active. The infected roots are killed, -disrupting the transportation of water to the leaves, Figure 8. Trees -diseased by cotton root rot produce yellow foliage, and shedding of -leaflets occurs during dry periods. Diseased trees usually die 1 to 3 -years after becoming infected. - - [Illustration: Figure 7. Spanish moss accumulation in pecan trees - reduces vigor from excessive shading.] - - [Illustration: Figure 8. Cotton root infected with cotton root rot - fungus. Note the splitting and general deterioration of the root.] - -_Control._—An effective control for cotton root rot disease has not been -developed. - -New orchards should not be planted in soil having a history of cotton -root rot disease. - - - - - _Pecan Insects and Their Control_ - - -PECAN NUT CASEBEARER - -The pecan nut casebearer, _Acrobasis caryae_ Grote, is the major pest of -pecans in Texas. Early in the spring, the overwintered generation feeds -first in the buds and then in the developing shoots, causing them to -wilt and die. Succeeding generations feed on the nuts during the late -spring and summer, Figure 9. Severe infestations may destroy the entire -crop of pecans. - -The adult is a light gray moth which is about one third inch in length. -The wings are gray, and the forewings have a ridge of dark scales across -them about one-third the distance from the base. The moths fly at night -and spend the day in concealment. - -The young larvae are white to pink, but later become olive gray to green -and attain a length of about one-half inch. - -This insect passes the winter as a partially grown larva in a tiny -silken cocoon called a hibernaculum, which is usually attached to a bud, -Figure 10. In the spring, the larvae feed for a short time on the buds, -after which they tunnel in the developing shoots until they reach -maturity, Figure 11. Pupation usually occurs in these burrows, and the -moths emerge in late April and May. - -Two or 3 days after the adults emerge, they deposit eggs on the tips of -the nuts, Figure 12. Each female may deposit from 50 to 150 eggs. The -eggs, which are just visible to the naked eye, are greenish white when -they are deposited but assume a reddish appearance a few days later. The -first-generation larvae hatch from the eggs in 4 or 5 days and migrate -to the buds below the nuts to feed. After a day or two, they enter the -nuts, usually at the base, and feed in them, each larva frequently -destroying an entire cluster. Bits of frass and webbing may be observed -projecting from the injured nuts. Upon reaching maturity, the larvae -pupate in the nuts and emerge as adults in June and early July. - - [Illustration: Figure 9. Injury to nuts caused by first generation - larvae of the pecan nut casebearer.] - -The adults deposit eggs in grooves on the tips or bases of the nuts. -Second-generation larvae which hatch from these eggs also feed in the -nuts. Less injury is produced by this generation because the nuts are -larger and each larva requires only one or two nuts to complete its -development. Pupation takes place in the hollowed out nuts, Figure 13, -and the moths emerge from late July to early September. - -A third generation usually follows, but the shells of the nuts have -become hard, and only a few of them are penetrated by the larvae. -Instead, they feed in the shucks. A number of third-generation larvae -construct hibernacula, while the remainder pupate and appear as adults, -emerging from late August to October. These adults deposit eggs, which -hatch into fourth-generation larvae. If nuts are available, their shucks -constitute the principal food of the larvae of this generation. In the -absence of nuts, the larvae feed on buds and leaf stems. Overwintering -hibernacula are constructed by the partially grown larvae by the middle -of November[2]. - -_Control._—The necessity for control of this pest may be determined by -examination of the trees when the shoots appear in the spring. If a -number of them are wilted, the following control measures probably will -be required. - -A spray application should be made when eggs of the first generation -appear on the tips of the young nuts in late April or May. The period of -egg deposition usually coincides with the completion of pollination, at -which time the tips of the nuts turn brown. Satisfactory control may be -obtained by using any of several insecticides. See spray schedule, page -4. - -Ordinarily, only one application of spray is required to control the nut -casebearer. However, if trees surrounding the treated area are not -sprayed, moths may enter the sprayed area and a serious infestation of -second-generation larvae may develop. Under these circumstances, a -second spray may be required in June or early July when -second-generation eggs are deposited[6], [11]. - - -HICKORY SHUCKWORM - -The hickory shuckworm, _Laspeyresia caryana_ (Fitch), frequently causes -severe injury to pecans. In the late summer and fall the shucks are -tunneled out. As a result, the nuts are slower to mature and the kernels -do not develop properly. The shucks stick to the nuts and fail to open, -thus increasing the difficulty of harvest. - -The adult shuckworm is a dark, grayish-black moth with a wing span of a -little over one-half inch. The larva is white with a light brown head. -It attains a length of three-eighths inch at maturity. - -The winter is passed by the larvae in fallen pecan or hickory shucks. -They pupate in late winter and emerge as adults during the spring. The -adults deposit eggs principally on hickory trees on the leaves and young -nuts, and the larvae feed in developing nuts in early summer. - -Succeeding generations develop in pecan shucks. Before pupating, the -larvae cut a hole to the outside, and then spin a cocoon. When the moth -emerges, the empty pupal skin is left projecting from the hole and can -be seen afterward on the shuck. As many as five generations may be -completed each year before the last generation larvae go into -hibernation. - -_Control._—No economical chemical control for the shuckworm has been -developed. Cultural measures will aid in reducing populations. Plowing -during July and August to turn under the infested shucks is relatively -effective. The larvae are unable to mature in the decaying shucks, and -the adults cannot emerge from the soil. Care should be taken to -completely cover the fallen shucks, but the depth of plowing should be -regulated or damage to the roots will result. - - [Illustration: Figure 10. Location of overwintering cocoons, or - hibernacula, of the pecan nut casebearer.] - - -PECAN WEEVIL - -The pecan weevil, _Curculio caryae_ (Horn), is a late-season pest of -pecans in Texas. In years when severe infestations occur, this insect -may destroy a large portion of the pecan crop. The kernels are eaten out -by the larvae. - -The adult is a brownish weevil which is about three-eighths inch long. -The female has a snout which is as long as the body; the male’s is -somewhat shorter. - -The weevil appears in late August and early September. After the nut -kernels have hardened, the female chews a hole in the shell and deposits -her eggs in little pockets in the nuts. Creamy white grubs hatch from -the eggs and feed inside the nuts during the fall, attaining a length of -about three-fifths inch. When they reach maturity, the grubs chew a hole -about one-eighth inch in diameter in the shell, emerge from the nut and -drop to the ground in late fall and early winter. They burrow in the -soil to a depth of 4 to 12 inches and construct a cell. Some individuals -remain in the larval stage until the following fall when pupation -occurs. Other larvae do not transform to pupae until the succeeding -year. The adults appear during the summer, following pupation. The -entire life cycle requires from 2 to 3 years, most of this time being -spent in the soil. - - [Illustration: Figure 11. Overwintered larva of the pecan nut - casebearer and characteristic injury to the developing shoots.] - -_Control._—Frequently, certain trees in the orchard are more heavily -infested than others, since the adults usually do not go far from the -tree upon which they developed. The time at which insecticide -applications should be made to control this insect can be determined by -jarring the trees. Begin checking the first week in August. A large -sheet should be placed under a tree and the limbs jarred with a padded -pole. The weevils drop to the ground and remain motionless for a short -period, at which time they may be counted. When three or more weevils -are jarred from each tree, an application of spray containing 6 pounds -of 50 percent DDT wettable powder per 100 gallons of water should be -made[8]. - - [Illustration: Figure 12. Eggs of the first generation pecan nut - casebearer deposited on the tips of the young nuts.] - - -STINK AND PLANT BUGS - -The adults of several species of stink bugs and plant bugs suck the sap -from young pecan nuts causing an injury known as black pit, in which the -interior of the nuts turns black. The injured nuts fall from the trees -before the shells harden. - -Feeding by the insects after shell hardening, Figure 14, produces brown -or black spots on the kernels. Areas affected taste bitter, but the -remainder of the kernel is unaffected. - -Stink bugs are familiar to everyone. Plant bugs resemble them and are -usually shades of brown, smaller and narrower in body outline. - -Plant bugs and stink bugs overwinter in the adult stage in debris on the -ground. In the spring, the adults are attracted to growing vegetation -such as cover crops or weeds, where they deposit their eggs. The -immature bugs develop on low-growing vegetation. When they reach -maturity, their wings are fully developed and they fly to pecan trees. A -few eggs may be deposited on pecan trees, but the young bugs apparently -are unable to develop on them. Only the adults are present in sufficient -number to inflict economic injury. There may be as many as four -generations each year. - -_Control._—Although certain insecticides will control these pests, the -number and frequency of spray applications necessary for control would -not be economical. - -Care should be taken to keep weeds down in the orchard during the -growing season. Winter cover crops should be plowed down early in the -spring so they will not be attractive to the adults coming out of -hibernation. If this operation is delayed, the bugs will leave the cover -crop when it is removed and migrate to the trees in large numbers. - - -APHIDS - -These soft-bodied insects appear during the summer and fall. They suck -the sap from the leaves, causing them to turn yellow or brown and fall -to the ground. Heavy infestations may cause defoliation in the late -summer reducing the nut crop in the current and succeeding year. - -The black pecan aphid, _Melanocallis caryaefoliae_ (Davis), is about -one-sixteenth inch long when full grown, robust and greenish black. Its -back is decorated with tubercles. - -Bright yellow blotches up to one-fourth inch in diameter appear around -the punctures produced by the feeding of this insect. - -The yellow aphids, _Monellia_ spp., which attack pecans inflict injury -similar to that caused by the black pecan aphid. However, the large -yellow blotches on the leaves do not result from their feeding. A sticky -substance called “honeydew” is secreted by these insects creating an -ideal medium for sooty mold fungus to develop[5]. - -Both black and yellow aphids overwinter in the egg stage in crevices in -the bark. In the spring the eggs hatch, and the aphids begin feeding on -the leaves. Many generations are completed each year. Only females, -which may be wingless or winged, are produced during the growing season. -The winged individuals fly to different parts of the tree or to other -trees. In the fall, males and females appear and eggs are deposited -under the bark. - - [Illustration: Figure 13. Pupa of the second generation of the pecan - nut casebearer in a hollowed out nut.] - -Usually, these insects are not present in sufficient numbers to cause -serious injury until mid or late summer. Infestations earlier in the -season rarely assume damaging proportions. As is the case with mites, -aphid populations may increase, following the application of certain -insecticides applied for the control of the pecan nut casebearer or -following treatment with bordeaux mixture for pecan scab disease -control. - - [Illustration: Figure 14. Southern green stink bug on developing - nuts.] - -_Control._—When damaging infestations appear, the trees should be -sprayed with either 1 pound of 12 percent gamma BHC wettable powder; or -1 pint of 40 percent nicotine sulfate plus 3 pounds of soap; or 1 pound -of 25 percent parathion wettable powder[9]. - - -MITES - -These tiny pests attack the leaves usually on the underside causing -irregular brown areas to appear. Trees which are heavily infested appear -scorched and may lose their leaves in late summer or fall. - -Mites usually are light green and are just large enough to be seen -without the aid of a hand lens. They are wingless and feed principally -on the underside of the leaves along the midrib. Colonies of them -produce webs in which molted skins and eggs may be found. The life cycle -of mites is very short and several generations occur each year. Large -populations may develop during the late summer and fall. - -The use of certain insecticides for the control of the pecan nut -casebearer or bordeaux mixture for scab control frequently contributes -to increases in mite populations later in the season. - -_Control._—Mites may be controlled in three ways when damaging -infestations develop. An application of 2 pounds of wettable sulfur per -100 gallons of water may be made; 6 pounds of wettable sulfur per 100 -gallons of water may be added to the spray applied for the control of -the nut casebearer; and repeated applications of zineb included in a -regular spray schedule for pecan scab control will effectively control -mites. However, a single application of zineb is not effective[7]. - - -PECAN LEAF CASEBEARER - -On occasion, this insect, _Acrobasis juglandis_ (LeB.), develops to -damaging numbers and causes economic injury. Early in the spring the -larva feeds on unfolding leaves and buds. It may prevent leaf -development for weeks, resulting in a greatly decreased yield of nuts. - -The adult is a dark gray moth marked with brown. Its forewings, which -have a spread of about two-thirds inch, are gray with black blotches. -There is a reddish mark near the base of the forewings. - -The immature larva is brown, but changes to dark green as it develops to -a length of one-half inch. It has a shiny, brownish black head and is -enclosed in a gray case which completely covers the body and is borne in -a position nearly perpendicular to the leaf on which the larva is -feeding. - -The pecan leaf casebearer overwinters as an immature larva in a -hibernaculum around a bud. It emerges in late March or early April as -the buds open. The larvae mature in April, May and June and transform -into pupae within their gray cases, Figure 15. The moths are present -from May until early August. Eggs are deposited during this period on -the underside of the leaves. The larvae which hatch from these eggs -develop slowly, and do not attain a length of more than one-sixteenth -inch during that season. They construct little winding cases in which -they live. Their feeding produces irregular blotches on the leaf -surface, Figure 16. Before the leaves drop in the fall, the larvae -migrate to the buds, and construct their overwintering hibernacula. Only -one generation is completed each year. - -_Control._—Control of this insect is accomplished by spraying for the -pecan nut casebearer. See spray schedule, page 4. The insecticides -recommended for nut casebearer control also reduce infestations of the -leaf casebearer. - - [Illustration: Figure 15. Overwintered larvae of pecan leaf - casebearer in their cases.] - - [Illustration: Figure 16. Summer injury to the leaves by the pecan - leaf casebearer.] - - -PECAN PHYLLOXERA - -The pecan phylloxera, _Phylloxera devastatris_ Perg., and the pecan leaf -phylloxera, _P. notabilis_ Perg., produce galls on the new growth of -pecans. Leaves, twigs and nuts may be affected. - -The galls are conspicuous swellings, Figure 17, which attain a size of -from one-tenth to 1 inch in diameter. They are caused by a soft-bodied -insect which is closely related to aphids. - -The winter is passed in the egg stage in crevices in the bark. In the -spring, the egg hatches and the tiny nymph feeds on the tender, young -growth, apparently secreting a substance which stimulates the plant -tissues to develop into galls. - -After the nymph reaches maturity, a number of eggs are deposited inside -the gall. The young nymphs of the succeeding generation develop within -the gall, which splits open in 1 to 3 weeks, liberating them. Several -generations follow during the summer and fall, as long as there is fresh -young growth on the tree. From 4 to 5 weeks are required for each -generation[4]. - -_Control._—The dormant oil spray recommended for obscure scale control -will prevent the development of phylloxera. If dormant oil is not -applied, use 2 pints of nicotine sulfate plus 6 pounds of soap; 3 pounds -of 25 percent malathion wettable powder; or two and a half pounds of 10 -percent gamma isomer BHC wettable powder per 100 gallons of water when -the leaves are one-third grown. - - -SAWFLIES - -Sawfly larvae, _Periclista_ sp. and others, feed on the foliage of -pecans during April and early May. The larvae, which are light green, -chew holes in the leaves. Usually the midrib and veins are left intact, -giving the leaflets a lacy appearance, Figure 18. - -The adults closely resemble wasps, except that they are not -“wasp-waisted.” - - [Illustration: Fig. 17. Developing galls of the pecan phylloxera. - Note the open gall on the lower leaf.] - -_Control._—The larvae may be controlled with an application of 2 pounds -of 50 percent DDT wettable powder or 1 pound of 25 percent parathion -wettable powder per 100 gallons of water. - - [Illustration: Figure 18. Sawfly injury to pecan foliage.] - - -MAY BEETLES - -Many species of May beetles may damage pecans early in the spring. The -beetles appear only at night and spend the day concealed beneath the -surface of the soil. They feed on the young leaves and prevent the -foliage from developing. - -Beetles of the most common species are one-half to three-fourths inch -long and shiny dark brown. They are attracted to lights and are observed -commonly on porches or screen doors at night. The larvae are the -grubworms, or white grubs, which feed in the soil on the roots of many -plants. - -The female beetle deposits eggs in the soil, where the larva develops. -Most species require two summers for the larva to mature. Pupation is -accomplished in a cell which is constructed in the ground in the fall of -the second year. The beetles emerge the following spring. Both larvae -and adults may be found in the soil during the winter. - -_Control._—May beetles are usually a problem in orchards which are not -cultivated because the larvae feed on the roots of the sod cover. -Cultivation of the orchard periodically will reduce the food supply of -the grubs, and smaller infestations of adults will appear the following -year. Where cultivation is not feasible, sprays will control the adults. -Apply 2 pounds of 50 percent DDT wettable powder; 4 pounds of lead -arsenate; or 1 pound of 25 percent parathion wettable powder per 100 -gallons of water when damage by this insect is severe[9]. - - -PECAN CIGAR CASEBEARER - -The pecan cigar casebearer, _Coleophora caryaefoliella_ (Clem), may be -damaging in some years. The larva feeds on the leaves, producing tiny -holes. It constructs a light brown, cigar-shaped case about one-fourth -inch in length which encases it throughout development. - -_Control._—The spray applied for control of the nut casebearer will -usually prevent significant injury by the cigar casebearer. See spray -schedule, page 4. - - -FALL WEBWORM - -The webs produced by the fall webworm, _Hyphantria cunea_ (Drury), are -familiar to everyone. Leaves are eaten by the larvae which live in -loosely woven, dirty white webs, Figure 19. - -The adult is a white moth which may have black or brown spots on the -forewing. Its wings have a span of about 1 inch. - -The larvae are pale yellow spotted with black. They attain a length of 1 -inch when full grown and are covered with long black and white hairs. - -The insect overwinters as a pupa in lightly woven cocoons in debris on -the soil or under the bark. In the spring the adults emerge and lay -masses of greenish white eggs on the leaves. The caterpillars which -hatch from the eggs feed on the leaves in colonies under webs which they -construct. After feeding for a month to 6 weeks, the larvae crawl down -the tree and pupate in loose cocoons in debris, under bark, or in loose -soil. Adults appear during the summer and deposit eggs for the second -generation. The larvae of this generation feed extensively until fall, -crawl down the tree and pupate for the winter. - -_Control._—Light infestations on a few trees can be eliminated by -pruning out the affected branches and burning them. If this method of -control is not practicable, the trees should be sprayed with 2 pounds of -50 percent DDT wettable powder; 1 pound of 25 percent parathion wettable -powder; or 3 pounds of lead arsenate per 100 gallons of water[9]. - - [Illustration: Figure 19. Web of the fall webworm on a pecan limb.] - - -WALNUT CATERPILLAR - -During the spring and summer, the walnut caterpillars, _Datana -integerrima_ G. & R. and others, may strip the leaves from branches or -entire small trees. The adult is a moth with a wingspan of 1½ to 2 -inches. The forewings are light brown with darker wavy lines. The -hindwings are lighter in color without lines. - -The immature larva is reddish brown with narrow yellowish lines that -extend the length of the body. The full-grown larva is almost black with -two grayish lines on the back and two on the sides. Many long, soft gray -hairs are distributed over the body. - -This insect overwinters in the pupal stage in the soil. The adult -emerges in the spring and deposits eggs in masses on the underside of -the leaves, Figure 20. The larvae feed in colonies on the leaves for -about 3 weeks. At periodic intervals, the groups of larvae move to the -trunk to molt and, after shedding their skins, they return to the leaves -to feed until the next molt. They do not encase themselves in webs. -There are two generations each year, the first appearing in late spring -and early summer, the second in later summer and fall. Larvae of the -second generation complete development and crawl down to pupate in the -soil. - -_Control._—When these insects become abundant enough to defoliate -portions of the tree, they may be controlled by applying a spray -containing 2 pounds of 50 percent DDT wettable powder; 3 pounds of lead -arsenate; or 1 pound of 25 percent parathion wettable powder per 100 -gallons of water. - - [Illustration: Figure 20. Walnut caterpillar adults and egg mass on - a pecan leaflet.] - - -PECAN CATOCALA - -Several species of catocalas, Figure 21, among them _Catocala maestosa_ -Hlst., may strip the leaves of pecans in the spring leaving only the -midribs. The caterpillars are very dark gray and attain a length of -about 3 inches when full grown. They are very active when disturbed and -move with a looping motion. Both the caterpillars and the moths are well -camouflaged. When they rest on the trees during the day, their color so -harmonizes with the color of the bark that they are frequently -indistinguishable. - -_Control._—One application of 2 pounds of 50 percent DDT wettable powder -per 100 gallons of water controls this pest. Although the majority of -catocala larvae reach maturity before the time to spray for the nut -casebearer, a number of them will be killed when the recommended spray -is applied for the latter insect. - - -PECAN SPITTLEBUG - -In the spring and early summer a number of buds and small nuts may be -covered with foamy white masses. Inside these masses are several small -insects called spittlebugs, _Clastoptera obtusa_ (Say). The white froth -is produced probably to maintain an artificial high humidity, which is -required for development. The adults resemble leafhoppers and fly -actively during the summer. - -This insect has not been known to cause any significant injury on pecans -in Texas. - - -PECAN BUD MOTH - -The pecan bud moth, _Gretchena bolliana_ (Sling.), damages nursery stock -and freshly top-worked pecans. The greenish larvae feed in the axils of -the newly set buds and in the terminals of young trees, causing -extensive branching. There are several generations each year. - - [Illustration: Figure 21. Moth of the pecan catocala.] - -_Control._—This insect may be controlled by applying a spray containing -2 pounds of 50 percent DDT wettable powder per 100 gallons of water. - - -TWIG GIRDLER - -The adult twig girdler, _Oncideres cingulata_ (Say) (_O. texana_ of some -authors), girdles twigs and branches, weakening them so that they fall -off or die on the tree, Figure 22. This insect is active during the late -summer and early fall. Many twigs may be found on the ground under a -severely infested tree. Secondary branching may occur and the number of -bearing twigs is reduced. - -The twig borer is a grayish brown beetle one-half to five-eighths inch -in length with a broad gray band over the middle of the wing covers. Its -head is reddish brown and bears a pair of long antennae, which extend -beyond the abdomen on the male. - -The larva is a white legless grub about three-fourths inch long when it -reaches maturity. - -This insect overwinters as a partially grown larva in a twig on the tree -or ground. It develops rapidly in the spring feeding in the twig. -Following pupation, the adult emerges in late August or early September. -The female systematically girdles twigs and deposits eggs in the severed -portion since the larva is unable to develop in healthy sapwood. The -eggs hatch in a few weeks into larvae which remain small until the -following spring when they complete development, pupate and emerge as -adults in the late summer and fall. There is one generation annually, -although some individuals require 2 years to mature[1]. - -_Control._—Infestations may be reduced by removing girdled branches from -the trees and the ground and burning them. - -Chemical control is also effective. The trees should be sprayed with 4 -pounds of 50 percent DDT wettable powder per 100 gallons of water when -the first injured branches are observed in late August or early -September. Two or three applications at 2-week intervals may be required -for most effective control[9]. - - -RED-SHOULDERED SHOT-HOLE BORER - -The red-shouldered shot-hole borer, _Xylobiops basilare_ (Say), and -other shot-hole borers also injure trees in a devitalized condition. The -larvae feed in wood, pupate and emerge as adults through round holes -about one-eighth inch in diameter in the bark. Many of these holes may -be observed in close proximity to each other. - -_Control._—Since this insect feeds on dying or dead wood, prunings and -dead limbs should be removed from the orchard and burned. - -Adequate fertilizer and water will keep trees in a healthy condition and -prevent injury by this pest. - - -FLATHEADED BORERS - -The flatheaded apple tree borer, _Chrysobothris femorata_ (Oliv.), and -other species of flatheaded borers attack unhealthy or recently -transplanted pecan trees by burrowing in the bark and sapwood of the -large branches and trunk. Their presence is indicated by the appearance -of darkened, depressed areas in the bark from which traces of frass may -protrude. When these portions of the bark are removed, shallow winding -burrows packed with sawdust may be observed. The burrows usually are on -the sunny side of the trunk or branch, but may extend completely around -and penetrate the wood to a depth of 2 inches. Young trees may be -girdled by this insect. - -The adult beetle is about one-half inch long, broad and blunt at the -head end and tapering to a point posteriorly. Its wing covers, which -have a metallic sheen, are dark colored and corrugated. - -The larva, or borer, which is legless and yellowish white, attains a -length of 1¼ inches when full grown. Immediately behind the head is a -broad, flattened expanded area from which the insect takes its name. - -The winter is passed by larvae in varying stages of development within -the tree. In the spring, they change to pupae in their burrows, emerging -as adults during the spring and summer. The female beetles deposit their -eggs in cracks or bruises in the bark. The larvae which hatch from these -eggs feed during the remainder of the season and pass the winter. There -is only one generation each year. - - [Illustration: Figure 22. Adult twig girdler and characteristic - injury to twig.] - -_Control._—The beetles are attracted to trees or areas of trees in a -devitalized condition, induced by transplanting, drouth, sunscald, -bruises or poor growing conditions. The trees must be kept in a healthy, -vigorous condition by proper fertilization and watering. On young or -transplanted trees, wrapping the trunks in early spring before the -adults appear is the only effective control known for these insects. -Injury can be prevented by thoroughly wrapping the entire trunk from -ground level to the branches with heavy paper or other wrapping -material. The wrapping should be tied securely with twine and should be -maintained on the tree for 2 years. Regular observations should be made -to see that the twine does not girdle the tree. - -In older trees, the borers can be removed with a sharp knife. Care -should be taken to injure as little of the healthy wood as possible. If -the wound is extensive, it should be trimmed and then painted with a -commercial tree paint or with a mixture of one part creosote and three -parts coal tar. Dead and dying limbs and trees should be removed from -the orchard each year and burned before the following spring. If they -are not burned, the borers in them may mature and re-infest surrounding -trees. Commercial tree borer preparations are of little value in -controlling this insect. - - -OBSCURE SCALE - -The obscure scale, _Chrysomphalus obscurus_ (Comst.), is a pest of -considerable importance, particularly in the more arid portions of the -State. The tiny insect under its scale covering sucks the sap from the -limbs and branches, causing them to lose their leaves and die back from -the tips. The tree is so devitalized by the feeding of this insect that -it is made vulnerable to attack by wood borers. - -The scale covering over a full-grown female is about one-eighth inch -long and is usually dark gray, and closely resembles the bark of the -tree. Infested limbs appear to have had wood ashes sprinkled over them, -Figure 23. Numerous pits appear in the bark where the insects feed, -producing a roughened appearance. - - [Illustration: Figure 23. Severe infestation of obscure scale on a - pecan twig.] - -The winter is passed by the female scales under their coverings on the -bark. Eggs laid in the spring hatch into tiny, salmon-colored crawlers -which move about for a short time, then settle down and insert their -beaks. While they are feeding, a scale covering develops which is made -up of secreted wax and cast skins. - -The females never move again from the spot they have selected, but the -adult males develop wings and emerge from their scale coverings to mate -with the females. Only one generation is produced each year. - -_Control._—When damaging populations develop, a spray application of 3½ -gallons of 97 percent miscible dormant oil per 100 gallons of water -during the dormant season will keep this pest under control. - - - - - _Application of Fungicides and Insecticides_ - - -When possible, fungicides for disease control and insecticides for -insect control should be combined in the spray tank and applied to the -trees in one operation. The spray materials should be applied evenly and -thoroughly to all the leaf and nut surfaces to provide a chemical -barrier to disease organisms and insects. Do not neglect the tops of the -trees. Diseases and insects can harbor and multiply in all unsprayed -areas of the tree. - -Thorough coverage with spray materials is essential for effective -control. As a guideline, apply approximately 1 gallon of spray mixture -for each foot of tree height. Apply 20 gallons to a 20-foot tree and 40 -gallons to a 40-foot tree, etc. - - - - - _Spray Equipment_ - - -Various types of spray machines for application of fungicides and -insecticides to pecan trees are available. The spray machines employ -either a high pressure hydraulic pump, high pressure centrifugal pump or -low pressure high air velocity systems. All the machines are portable -and are equipped with a gasoline engine or operate from a truck or -tractor power takeoff shaft. - -For pecan spraying, a tank having a minimum capacity of 300 gallons is -desirable. The pump should deliver 20 to 30 gallons per minute and -maintain a pressure of 400 to 600 pounds per square inch while -operating. A spray gun which is adjustable to produce a mist spray for -spraying small trees or the lower canopy of large trees and a narrow -stream that will reach the tops of tall trees is essential. - -For safety and durability high pressure rubber hose having an inside -diameter of three-fourths inch should be used with all high pressure -spray machines. - - - - - _Literature Cited_ - - -[1]Bilsing, S. W., 1916; Life history of the pecan twig girdler. Journal - Econ. Ent. 9:110-115. - -[2]Bilsing, S. W., 1927; Studies on the biology of the pecan nut - casebearer. Texas Agricultural Experiment Station Bulletin 347, 71 - pp. - -[3]Bilsing, S. W., 1941; An economical method of removing Spanish moss - (_Tillandsia usenoides_) and Ball moss (_Tillandsia recurvata_) from - trees. Texas Agricultural Experiment Station Progress Report 747. - -[4]Dobbins, Traber Norman, 1932; The biology of the pecan phylloxera. - Master’s Degree Thesis, Texas A. and M. College. - -[5]Dorman, Harvey S., 1934; The life history of the yellow pecan aphid - _Monellia nigropunctata_ Granovsky. Master’s Degree Thesis. Texas A. - and M. College. - -[6]King, D. R. and David W. Rosberg, 1955; Experiments for the control - of pecan insects and diseases, 1954. Texas Agricultural Experiment - Station Progress Report 1786. - -[7]King, D. R. and David W. Rosberg, 1956; Control of _Tetranychus - hicoriae_ McG. on pecans. Journal Econ. Ent. 49 (3):404-5. - -[8]Nickels, C. B., 1952; Control of the pecan weevil in Texas. Journal - Econ. Ent. 45 (6): 1099-1100. - -[9]Osburn, M. R., A. M. Phillips, William C. Pierce, and John R. Cole, - 1954; Insects and diseases of the pecan and their control. USDA - Farmers Bulletin 1829, 56 pp. - -[10]Rosberg, David W., 1950; Control of pecan diseases in 1950. Texas - Agricultural Experiment Station Progress Report 1330. - -[11]Rosberg, David W. and D. R. King, 1954; Pecan disease and insect - control experiments in Texas, 1953. Texas Agricultural Experiment - Station Progress Report 1671. - - - - - _Your County_ EXTENSION AGENTS - - - [Illustration: Extension agents] - -can furnish you the latest information on farming, ranching and -homemaking. They represent both The Texas A. & M. College System and the -United States Department of Agriculture in your county. - -Most county extension agents have their offices in the county courthouse -or agriculture building. They welcome your visits, calls or letters for -assistance. - -This publication is one of many prepared by the Texas Agricultural -Extension Service to present up-to-date, authoritative information, -based on results of research. Extension publications are available from -your local agents or from the Agricultural Information Office, College -Station, Texas. - - -Cooperative Extension Work in Agriculture and Home Economics. The Texas -A. & M. College System and United States Department of Agriculture -cooperating. Distributed in furtherance of the Acts of Congress of May -8, 1914, as amended, and June 30, 1914. - -10M-3-59. Reprint. - - - - - Transcriber’s Notes - - -—Silently corrected a few typos. - -—Retained publication information from the printed edition: this eBook - is public-domain in the country of publication. - -—In the text versions only, text in italics is delimited by - _underscores_. - - - -*** END OF THE PROJECT GUTENBERG EBOOK PECAN DISEASES AND PESTS AND THEIR -CONTROL *** - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the -United States without permission and without paying copyright -royalties. 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