B-1238

TABLE OF CONTENTS

Pest Management Principles

Biological Control

Policy Statement for Making Pest Management Suggestions

Insecticide Application

Chemical Use Precautions

Pecan Pests

• Phylloxera
• Pecan Nut Casebearer
• Walnut Caterpillar
• Fall Webworm
• Yellow Aphids
• Hickory Shuckworm
• Spider Mites
• Black Pecan Aphid
• Stink Bugs and Leaffooted Bugs
• Pecan Weevil
• Red Imported Fire Ant

Additional Insecticide Products Registered For Use In Pecans

Seasonal Pest Profile and Development Stages of the Pecan

The pecan is an important horticultural crop in Texas. Improved varieties are grown on about 175,000 acres throughout most of the state. In addition, Texas has more than 700,000 acres of native pecans. Only about 10 percent of this acreage is managed other than being harvested. Many insects feed on the leaves, nuts, branches and buds of the pecan tree and can reduce the tree's productive potential. Some insects directly reduce production by feeding on the nuts. Other pests cause indirect damage as their feeding depletes the tree's reserves to such an extent that nut production is reduced the following year.

This guide discusses the management of insect and mite pests of commercial pecans. Extension publication L-1140, "Homeowner's Fruit and Nut Spray Schedule," describes the control of pests attacking pecans near homes and in other non-commercial plantings.

Pest Management Principles

For many years, insect damage to pecans was minimized by following an insecticide spray schedule based upon crop development. This approach was effective, relatively inexpensive, and fit well with a preventive fungicide spray program. However, the scheduled application of insecticides has had to be reevaluated because of the loss of effective insecticides due to high reregistration costs, the lack of new insecticides, poor insecticide control, secondary pest outbreaks and renewed concerns about the effects of insecticides on humans and the environment. The routine use of insecticides causes pests to become resistant, destroys natural enemies of pecan pests and adds to production costs.

The term "pest management" applies to a philosophy used in the design of pest control programs. Pest management uses the most compatible and ecologically sound combination of available pest suppression techniques that provide long-term production profits. These management techniques include: cultural control, such as destroying crop residues which serve as overwintering sites of some pests, and selection of varieties with pest resistance; and biological control, or the use of natural enemies Ln sup- press pest populations.

Insecticides are important in pecan pest management but they should be used wisely and only when needed to prevent economic loss. The decision to apply an insecticide should be based upon established treatment thresholds of insect density or damage as determined by frequent or- chard surveys or other monitoring techniques (traps). Insecticides should not be added to fungicide or zinc sprays unless it has been determined that an insect pest has or will exceed a treatment threshold. The insecticide and rate should be carefully selected according to effectiveness, hazard to the applicator and impact on beneficial insects.

Studies have shown that insecticide applications are sometimes followed by outbreaks of aphids, mites or leaf miners. This may result from the destruction of natural enemies that were holding these secondary pests in check. Insecticides also may have physiological effects on the tree or the pests which favor pest survival or increased reproduction.

Use of pyrethroid insecticides (Ammo®, Cymbush®, Asana® or Pydrin®) or carbaryl (Sevin®) has sometimes been followed by outbreaks of aphids or spider mites. If pyrethroid insecticides are used, they should be applied no more than once per season, either for pecan nut casebearer or hickory shuckworm control. Pyrethroids should not be used in orchards with a history of mite or aphid outbreaks following their use. The frequent use of carbaryl (Sevin®) may also cause increases in aphid and mite infestations.

Biological Control

Insect and mite populations are often held below damaging levels by adverse weather, inadequate food supply and natural enemies. It is important to recognize the impact of these natural control factors and, where possible, encourage their action.

Biological control is the use of living organisms (parasites, predators and diseases) to reduce pest numbers. Important natural enemies of pecan pests include lace- wings, spiders, lady beetles, assassin bugs, predatory mites and a great variety of tiny wasps which parasitize insect pests.

Biological control includes the conservation, augmentation and importation of natural enemies. Existing populations of natural enemies can be conserved in the orchard by minimizing insecticide applications and by using insecticides that are least toxic to the natural enemy. As an ex- ample, B. t. (Bacillus thuringiensis) formulations (Dipel®) are toxic only to certain moth caterpillars and not to insect predators or parasites. Ground covers such as legumes can provide food and shelter for natural enemies. Unsprayed, native pecans serve as reservoirs of natural enemies that can move into adjacent sprayed orchards.

Augmentation involves the purchase and release of natural enemies on a periodic basis. Research is underway to determine if such releases are effective and practical for control of pecan pests.

Natural enemies can also be imported from other countries, colonized and released. Once established, these natural enemies maintain themselves without further releases.

Policy Statement for Making Pest Management Suggestions

The information and suggestions included in this publication reflect the opinions of Extension entomologists based on field tests and use experience. Our management suggestions are a product of research and are believed to be reliable. However, it is impossible to eliminate all risk. Conditions or circumstances which are unforeseen or unexpected may result in less than satisfactory results even when these suggestions are used. The Texas Agricultural Extension Service will not assume responsibility for risks. Such risks shall be assumed by the user of this publication.

Suggested pesticides must be registered and labeled for use by the Environmental Protection Agency and the Texas Department of Agriculture. The status of pesticide label clearances is subject to change and may have changed since this publication was printed. County Extension agents and appropriate specialists are advised of changes as they occur.

The USER is always responsible for the effects of pesticide residues on his livestock and crops, as well as for problems that could arise from drift or movement of the pesticide from his property to that of others. Always read and follow carefully the instructions on the container label.

Insecticide Application

Thorough coverage of trees is essential for maximum pest control. Low-volume sprayers (mist blowers, air blast sprayers, speed sprayers, etc.) use forced air as the carrier to deliver a concentrated spray mix and require proportionately less water than high-volume hydraulic sprayers. Concentrated low-volume spraying saves water and time but not pesticides, since the same amount of pesticide is needed for each tree to obtain control. Carefully follow the sprayer manufacturer's directions for mixing spray materials and for calibration.

Chemical Use Precautions

Select suggested materials according to their effective- ness, degree of safety and cost. All suggested materials are poisonous, but proper handling reduces the hazards associated with their use. Comply with the manufacturer's label directions for handling all toxic chemicals.

Residues: The Environmental Protection Agency (EPA) has established pesticide residue tolerances on pecans. These regulations establish the amount of a specific chemical that can be present in or on pecans at harvest. Always consult the product label for specific restrictions, and be sure the pesticide used is registered for use on pecans and is used only in accordance with specific application instructions.

Caution: All pesticides are poisonous to something; some are poisonous to man, animals and nontarget crops, etc. They should be used with caution and stored out of reach of children, irresponsible persons, livestock and household pets. Properly dispose of leftover spray materials and containers.

Pesticide Drift: Avoid drift to adjoining land and take precautions against pond and stream contamination.

Symptoms of Poisoning: Some symptoms of pesticide poisoning are headaches, nausea, cramps, blurred vision, weakness, muscular twitching and diarrhea. If any of these symptoms occur during or following the handling of any pesticide, consult a physician immediately.

Pecan Pests

PHYLLOXERA

Damage: Phylloxera are tiny, soft-bodied insects closely related to aphids. These insects cause conspicuous swellings, called galls, to form on leaves, twigs and nuts. The two most important species attacking pecans are the pecan leaf phylloxen and the pecan phylloxera. The pecan leaf phylloxera forms galls on leaves only and extensive infestations may cause some defoliation. The pecan phylloxera is the most damaging species because it attacks the shoots and nuts. Extensive infestations of this species can destroy the nut crop and reduce the tree's vitality and subsequent production.

Biology: Phylloxera survive the winter as eggs in bark crevices. In spring, the tiny nymphs emerge during budbreak and feed on new growth. Nymphs secrete a substance while feeding that stimulates plant tissue to develop abnormally, creating galls. The young phylloxera are soon completely enclosed in the galls, which range in size from 1/10 inch to 1 inch in diameter. Phylloxera feed inside the gall and complete two generations. Galls then crack open and winged, adult phylloxera emerge to lay eggs.

In the case of the more destructive pecan phylloxera, no additional galls are formed. Females hide in protected places on the bark and die, with their eggs remaining inside the protective bodies of the mothers throughout the winter. Some adult females of the pecan leaf phylloxera which emerge from spring galls may also overwinter. However, other females lay eggs and the hatching nymphs form a second or third generation of galls during one season, if new growth is available.

Control: Native trees and improved varieties vary in their susceptibility to phylloxera. Phylloxera can not fly far and infestations move slowly from tree to tree. For these reasons, control is often achieved by treating only those trees with phylloxera galls. Survey the orchard in May and mark trees with galls for treatment the following spring.

Insecticides for phylloxera must be applied after egg hatch in the spring but before nymphs are protected inside galls. Treat after bud break when growth is 1 to 2 inches long. Phylloxera infestations also can be reduced with a dormant oil spray applied to tree trunks and limbs during the dormant season. Thorough coverage is essential to en- sure that eggs are killed.

PECAN NUT CASEBEARER

Damage: The pecan nut casebearer is the most damaging insect pest of Texas pecans. It is found in almost all the pecan growing areas of Texas and can cause serious crop loss every year if left uncontrolled. The casebearer larva or caterpillar feeds inside pecan nuts. First generation larvae feed inside small nutlets from April to June. This generation is most damaging as a single Larva often destroys all the nutlets in a cluster. Larvae of later generations require just one or two nuts to complete their feeding, as pecans are Larger at that time.

Biology: The adult casebearer is a gray moth about 1/3- inch long. A ridge of dark scales runs across the forewings. The moths are active only at night when they mate and lay eggs on pecan nuts. Most eggs will be found on the tips of the nutlets. Each female iays 50 to 150 eggs during her 5- to 8-day life. The eggs are greenish white to white, changing to pink or red prior to hatch.

Casebearer eggs hatch in 4 to 5 days and young larvae crawl to nearby buds below the nuts to begin feeding. The empty egg shell is white and remains on the nut. The tiny larvae feed for a day or two on a bud below the nut cluster and then enter the pecan nut, often tunneling in at the base. Silk and black frass (excrement) are often visible on the outsides of infested nuts. Larvae feed inside pecan nuts for 3 to 4 weeks, depending upon the temperature. Larvae are olive grey to jade green and reach a length of about 1/2 inch. Full-grown larvae pupate in the pecan nut and the adult moth emerges about 9 to 14 days later.

The pecan nut casebearer completes several generations each year. Adults of the overwintering generation emerge in April and May and lay eggs on pecan nutlets soon after pollination. First generation larvae mature to moths. which lay second generation eggs in grooves on the tips or bases of nuts, or on buds. Second generation larvae attack the nuts in mid-summer about 42 days after nut entry by first generation larvae. Third generation eggs are deposited on nuts from late July to early September. These larvae feed only in the shucks if the pecan shells have hardened to prevent penetration into the kernel. Many third and later generation larvae do not feed, but crawl to the base of a dormant bud and construct a tough, silken cocoon in which to spend the winter. In the spring, these immature larvae leave the cocoon, which is called a hibernaculum. They feed on buds and tunnel in developing shoots until they are full-grown. Larvae then pupate in shoot tunnels or in bark crevices. Casebearer moths soon emerge to lay first generation eggs on nutlets.

Control: Insecticide applications must be accurately timed to control newly hatched casebearer larvae before they enter the nuts. Once inside the nuts, larvae are protected from insecticides.

Nuts should be carefully examined for casebearer eggs in the spring to determine if treatment is necessary and to determine the correct timing of the insecticide application. Insecticides should be applied within 2 to 3 days after the first eggs hatch. At this time, the first larvae will begin entering the nuts. Infested clusters can be flagged to monitor egg hatch. By delaying the treatment until the first nut entry occurs, the residual activity of the insecticide is maximized. However, the time required to treat the orchard, and possible delays caused by weather, should be considered so that the insecticide can be applied before significant nut entry occurs.

Often a single, carefully timed insecticide application provides adequate control for first generation casebearers. A second insecticide application may be required if unhatched eggs are found 7 to 10 days after the first application.

Peak egg lay often occurs during a 2-week period in late April to early May in the southern and coastal areas, or late May and early June in north Texas. Spring temperatures influence casebearer development; cool, rainy weather can delay moth activity and egg laying. Thus, the period of egg laying can vary as much as 2 weeks from year to year depending upon spring weather.

Several methods have been used to determine when to look for first generation casebearer eggs. One of the most successful is the use of a computer model that predicts egg laying activity and nut entry based upon spring temperatures. These predictions are available for most pecan producing areas of the state and can be obtained at your county Extension office. The computer model should not substitute for field scouting for casebearer eggs. The date of first significant nut entry, as predicted by the computer model, is the optimum predicted spray date. Begin scouting for eggs at least a week before the predicted date, as local weather conditions near the spray date can influence egg laying.

Growers should inspect nuts to determine if casebearer infestations are large enough to justify treatment. A sampling plan has been developed to determine if infestations warrant an insecticide application. The plan is based upon the assumption that treatment is justified when infestations are large enough to destroy 5 percent or more of the nuts expected to be harvested. The sampling plans based upon research in Texas. is as follows:

1) Begin searching for eggs at least a week before the predicted date of first nut entry as described above. Tag egg infested clusters to monitor egg hatch.

2) Begin intensive sampling, as described in 3 below, when the first casebearer eggs hatch. This date is predicted by the casebearer computer model but should be confirmed by monitoring actual egg hatch in the orchard.

3) Examine ten nut clusters per tree. A cluster is considered infested if it has a casebearer egg or nut entry. Treat if two infested clusters are found before 310 clusters (31 trees) are examined. If fewer than two of 310 clusters are infested, stop sampling.

4) Sample again 3 to 5 days later or 1 to 2 days before the date of first significant nut entry as predicted by the computer model.

5) Treat if two infested clusters are found before 310 clusters are examined, as before. Otherwise, stop sampling after 310 clusters.

6) Sample a third time 2 days later. A third sample is especially important if cold, rainy nights have delayed egg-laying.

7) If three infested clusters are found before 310 clusters have been inspected on the third sample, then treatment should be considered.

8) Pecan nuts should also be examined for second generation casebearer eggs about 6 weeks after first generation eggs were found. Treatment should be considered if 2 percent of the pecans are infested with eggs.

WALNUT CATERPILLAR

Walnut caterpillars feed together in large numbers on pecan leaves, but do not construct silken webs like fall webworms. Larvae eat leaves, leaving only the mid-ribs and leaf stems, and large infestations can defoliate entire trees. This insect is found throughout Texas east of the Pecos River. Although economic infestations are uncommon, severe and widespread outbreaks of walnut caterpillar have occasionally occurred in Texas.

Biology: Walnut caterpillar moths emerge in the spring and deposit eggs in masses of 500 or more on the undersides of leaves. The egg masses are round, about the size of a half-dollar and are not covered with hairs or scales. Eggs hatch in about 10 days and larvae feed for about 25 days. Young larvae are reddish-brown with yellow lines running the length of the body. Full-grown larvae are about 2 inches long, black with grayish lines and are covered with long, soft, gray hairs. Larvae congregate in large masses on the trunk and scaffold branches to shed their skins before crawling back to complete their feeding on leaves. Most of the foliage is consumed by these final stage larvae and defoliation can occur very quickly. Mature larvae crawl to the soil to pupate. A generation is completed in about 6 to 8 weeks and there are two to three generations each year (see Extension publication L-1835, "The Walnut Caterpillar").

Control: Since the walnut caterpillar does not construct tents or webs, infestations often go unnoticed until leaf damage becomes obvious. Look for egg masses or leaf feeding to detect infestations early. Egg masses can be detected at night by shining a flashlight on the undersides of leaves and looking for white spots about the size of a half dollar. Caterpillars cause 80 percent of their damage during the last 3 to 4 days of feeding. Smaller larvae are easier to kill with insecticides than larger larvae, and control of this stage prevents serious damage. Insecticide treatment may be necessary if large infestations threaten to defoliate trees.

FALL WEBWORM

Biology: Mature larvae are about 1 inch long, pale yellow or green, and covered with tufts of long, white hairs. The adult is a white moth with dark spots on the wings. Female moths emerge in the spring and deposit eggs in masses of several hundred on the undersides of pecan and other tree leaves. The eggs are greenish-white and covered by grey hairs left by the female. There are two to four generations each year, depending upon locality in the state. The last or fall generation is usually the most damaging (see Extension publication L-1811 "Fall Webworms").

Control: Many insect parasites and predators feed on fall webworm larvae and reduce their numbers. Also, insecticides applied for other pecan pests help reduce webworm densities. If webs are common and the potential defoliation appears unacceptable, spot spraying of infested trees may be practical. The insecticide spray must penetrate the web to be effective

YELLOW APHIDS

Aphids are small, soft bodied insects that suck sap from pecan leaves. There are two species of "yellow aphids," the blackmargined aphid and the yellow pecan aphid. Both species are bright yellow and their injury, biology and control are similar.

Damage: Yellow aphids have piercing-sucking mouth- parts for removing water and plant nutrients from leaf veins. As they feed, aphids excrete large amounts of excess sugars. This sticky material, called honeydew, collects on leaves. Honeydew serves as a food source for sooty mold which can cover leaves during conditions of high humidity. The shading effect of sooty mold can reduce photosynthesis. Studies have also shown that aphid feeding can reduce leaf efficiency and large, late-summer infestations can defoliate trees. This leaf injury and loss can reduce cur- rent and subsequent yields and quality because of lower carbohydrate production.

Biology: Yellow aphid eggs survive the winter hidden in bark crevices on twigs and tree trunks. Immature aphids, called nymphs, hatch from the eggs in the spring and begin to feed on newly expanded leaves. Nymphs mature in about a week and give birth to live young. All individuals are females that reproduce without males during the spring and summer. In late September and October, males and females develop and females deposit overwintering eggs.

Aphids have a short life cycle and high reproductive capacity, so infestations can quickly increase during favorable conditions. Yellow aphid infestations often reach a peak by mid-summer and then suddenly decline after 2 to 3 weeks. Natural enemies, including lacewings, lady beetles, spiders and other insects, can suppress aphid infestations if they are present in sufficient numbers. Insecticides applied for aphids or other pests can sometimes destroy these natural enemies, allowing aphids to increase to even greater densities than before treatment.

Control: Frequently inspect leaves to monitor yellow aphid densities. Examine trees throughout the orchard to obtain a representative sample. Yellow aphids increase more rapidly on some varieties (e.g., Cheyenne) than on others. Treatment should be considered when yellow aphids average 25 or more per compound leaf. Scouting the orchard on a 4- to 5-day schedule will determine if yellow aphid numbers are increasing or decreasing and indicate the need for insecticide treatment. Do not base the need for treatment on the amount of honeydew alone, as infestations often decline rapidly ("crash") because of weather or physiological effects. Thorough spray coverage is important in controlling aphids.

Insecticides do not consistently provide adequate control of yellow aphids. Aphids may become tolerant to an insecticide used frequently in an orchard. An insecticide that is effective in one orchard may be ineffective in a nearby orchard. A number of studies have shown that in some cases the application of pyrethroid insecticides (Asana® Ammo®, Cymbush®) for casebearer or aphid control may be followed by large increases in yellow aphids.

Several soil applied systemic insecticides are registered for aphid control in pecans. These treatments are preventive and may be justified in areas where aphids annually exceed economically damaging levels. The use of these soil applied insecticides is discouraged in areas where ground water contamination could occur.

Hickory Shuckworm

Hickory shuckworm is an important, late-season pest of pecans throughout much of Texas.

Damage: Shuckworm larvae tunnel in the shuck, interrupting the flow of nutrients and water necessary for normal kernel development. Infested nuts are late in maturing, of poor quality and scarred. Damaged shucks stick to the nuts and fail to open, creating "sticktights" that reduce harvesting efficiency. Infestations occurring before shell hardening may cause nuts to fall.

Biology: The adult shuckworm is a dark brown to grayish-black moth about 3/8 inch long. Moths are active in the spring before pecan nuts are available. These moths deposit eggs on hickory nuts and on pecan buds. Larvae on pecan feed in phylloxera galls in the spring. Later in the season when pecan nuts are present, moths deposit their eggs singly on the nuts. The egg is attached to the shuck with a creamy white substance visible on the surface of the shuck. The egg hatches in a few days and the tiny larva burrows into the shuck to feed for about 15 to 20 days. Mature larvae are about 1/2 inch long, and cream colored with light brown heads. Pupation occurs in the shuck and the moth soon emerges. Several generations are completed each year. Shuckworms overwinter as full-grown larvae in old Pecan shucks on the tree or the orchard floor.

Control: Pecans are most susceptible to hickory shuckworm damage after the gel stage. If the orchard has a history of shuckworm damage, insecticide treatment should be made when pecans reach the half-shell hardening stage. A second application 10 to 14 days later may be needed. Removing and destroying old shucks and dropped nuts, in which shuckworms overwinter, can reduce shuckworm infestations.

Pheromone traps that attract and capture hickory shuckworm moths are available commercially. Guidelines for using trap catches to determine the need for treatment have not been validated in Texas.

SPIDER MITES

The pecan leaf scorch mite is the most important spider mite attacking pecans.

Damage: Large numbers of these tiny mites feed under thin, silken webs often found on the undersides of pecan leaves. Mites suck plant sap, causing irregular brown spots on infested leaves. Infestations often develop first along the leaf midrib. Damaged leaves appear russeted or scorched. Large infestations can result in leaf loss, especially if trees are under moisture stress

Biology: Scorch mites overwinter as adults in the rough bark of limbs. Adult females begin laying eggs in the spring. Mites can complete a generation in 5 to 15 days and are more numerous during hot, dry weather. Natural enemies of scorch mites, including predatory mite species, are important in controlling these pests.

Control: Scorch mites prefer the shady, interior portion of the tree and significant damage can occur before infestations are detected. Check water sprouts and shady, lower branches to detect early mite infestations. Mites may increase following the use of some insecticides (e.g., Sevin®) applied for hickory shuckworm, aphids or other pests. Monitor the orchard for mites when the weather is hat and dry and after insecticides are used. Spray when mites are present and damaging leaves. Mark infested trees or areas to determine if spot treatment is practical.

BLACK PECAN APHID

The black pecan aphid is much more destructive than the yellow aphid species. Three black pecan aphids per compound leaf can cause severe leaf damage and defoliation. Like the yellow aphids, the black pecan aphid feeds on the undersides of leaves and occurs throughout the pecan growing region of Texas.

Damage: While feeding, the black pecan aphid injects a toxin that causes the leaf tissue between major veins to turn bright yellow. These damaged areas, up to 1/4 inch across, turn brown and die. Infested leaves soon fall. Premature defoliation reduces nut fill and the following year's production.

Biology: The black pecan aphid is pear-shaped. Nymphs are dark olive-green while adults, which may be winged, are black. Like the yellow aphids, all summer forms are females that reproduce without mating. Male and female forms appear in the fall and females deposit eggs which overwinter on branches.

Densities often are very low until August or September, when infestations often increase rapidly.

Control: Monitor the orchard frequently for black pecan aphids and their characteristic leaf injury. Since these aphids feed singly and can be damaging in low numbers, examine leaves closely. Pecan varieties differ in their susceptibility to black pecan aphid injury. Consider the ex- tent of leaf damage and aphid numbers. In general, treat when black pecan aphids average more than three per com- pound leaf. In most cases, black pecan aphids are not as difficult to control with insecticides as are the yellow aphids. Natural enemies are important in maintaining low numbers of black pecan aphids.

STINK BUGS and LEAFFOOTED BUGS

Several species of stink bugs and leaf-footed bugs feed on pecan nuts. Infestations frequently develop on field crops or weeds and then move into pecans.

Damage: Stink bugs and leaf-footed bugs suck sap from developing nuts. Nuts injured before the shells harden fall from the tree. Feeding after shell hardening causes brown or black spots on the kernel. Affected areas taste bitter.

Biology: These bugs overwinter as adults beneath fallen leaves and in other sheltered places on the ground. Adults lay eggs on many crops and weeds, where populations in- crease during the summer. Fields of soybeans, other legumes and sorghum may be sources of adults that fly to pecans. Infestations are usually greatest from September through shuck split.

Control: Weed control in and near the orchard will help suppress stink bugs and lessen the possibility of their moving into pecans. Cypermethrin (Ammo®, Cymbush®), esfenvalerate (Asana®) or carbaryl (Sevin®) applied for other pests may also control stink bugs and leaffooted bugs.

PECAN WEEVIL

The pecan weevil is the most damaging late-season pest of pecans where it is found in Texas. Infestations are often localized and vary a great deal within orchards.

Damage: Adult weevils begin to emerge from the soil in August and feed on nuts in the water stage, causing them to drop. After the kernel has entered the dough stage, the nut is susceptible to egg laying and attack by pecan weevil larvae. Infested nuts remain on the tree while the developing larvae consume the kernel. Full-grown larvae chew a round hole through the shell and emerge from the nut in late fall or early winter.

Biology: The life cycle of the pecan weevil - egg, larva, pupa and adult - usually is completed in 2 years but can require 3. Adult weevils begin emerging from the soil in August; their numbers peak from late August through early September. Rainfall, soil moisture and soil type influence the ability of the weevils to emerge from the soil. Drought can delay adult emergence until rain or irrigation loosens the soil.

Adult weevils feed on nuts and live for several weeks. Once nuts reach the gel stage, they are suitable for egg laying. For this reason, early-maturing varieties are infested first. The female weevil drills a hole through the shell and deposits one or more eggs within the developing kernel. A single female lays eggs in about 30 nuts.

Larvae hatch from the eggs and feed for about 30 days inside the nut, destroying the kernel. Emergence of full-grown larvae from nuts begins in late September and continues as late as December. Larvae burrow 4 to 12 inches into the soil and construct a cell, where they remain for 8 to 10 months. Most of the larvae then pupate and transform to the adult stage within a few weeks. However, the adults remain in the underground cell for an additional (second) year before emerging from the soil the following summer. Those larvae (about 10 percent) that did not pupate after the first year remain as larvae for 2 years and then emerge from the soil as adults the third year.

Control: Foliar insecticides are currently the most effective treatment for pecan weevil. Once nuts reach the gel stage, insecticide should be applied if adult weevils are present. It may be necessary to continue spraying at 7- to 10-day intervals until shuck split, as long as monitoring shows weevils are emerging in significant numbers.

Certain trees have greater weevil infestations than others. These "scout" trees can be used to monitor the presence of adult weevils. Refer to Extension publication L-1808, "Sampling for Adult Pecan Weevils in Texas," available from your county Extension office. One monitoring method involves jarring limbs to knock adult weevils onto a sheet placed on the ground. Wire cone traps also can be placed beneath trees to capture adult weevils as they emerge from the soil. The number of captured weevils can be recorded periodically. Trap information can help you decide when and how long to continue insecticide sprays in relation to crop maturity. Information on the construction and operation of wire cone traps is available from your county Extension agent or Extension entomologist.

Pecan weevil infestations spread slowly unless aided by man. Infested nuts can be the source of a new infestation and should not be transported to uninfested orchards. Also, infested nuts should be destroyed after harvest.

Early harvest, before weevil grubs have exited from the nuts, also aids in control. Since grubs are physically removed from the orchard by early harvest, this practice can reduce weevil infestations if done each year.

RED IMPORTED FIRE ANTS

Fire ants can be a problem in pecan production when they interfere with operations such as grafting, mowing and harvesting; or, they may damage drip or sprinkler irrigation systems. Chlorpyrifos (Lorsban®) is registered for use in pecan orchards as an orchard floor spray for fire ants. Bendiocarb (Rotate® 2.5G) is registered for use only in nonbearing pecan orchards. The publication B-1536, "Fire Ants and Their Control," is available from your county Ex- tension agent. It describes management and control practices for fire ants.

Protecting Bees and Other Pollinators from Insecticides

Pollination is important in producing many seed crops which may be planted near pecan orchards. Bees may be killed if cover crops such as clovers, alfalfa or vetch are flowering in the orchard during insecticide application. The insecticide applicator and beekeeper should cooperate closely to minimize bee losses.

To prevent heavy losses of bees, don't spray or allow insecticide to drift directly on colonies. Bees cluster on the fronts of their hives on hot evenings. Pesticide drift or direct spray at this time generally results in high mortality.

Additional Insecticide Products Registered for Use in Pecans

(Note: The information below is presented only to complete the list of available products. Inclusion of these products does not constitute a recommendation for their use in Texas pecan production.)

aldicarb (Temik® l5G) - Special local need registration for Texas for control of aphids on producing and newly transplanted trees 1 to 5 years old. Do not allow live- stock to graze the treated area and do not harvest hay or forage from the treated area. See the label for additional restrictions.

disulfoton (Di-Syston® l5G) - Registered for control of aphids by commercial growers or professional applicators only. Do not harvest nuts within 80 days of treatment and do not graze grass under treated trees. See the label for additional restrictions.

parathion 8-E - Registered for the control of aphids, mites, pecan nut casebearer, fall webworms and twig girdlers. Do not apply after shuck split See label for additional restrictions.

Seasonal Pecan Pest Profile

The development of various pecan pests is usually closely related to the seasonal development of the pecan. A/though the severity of insect problems cannot be predicted on a seasonal basis, producers should frequently determine tree and nut development to aid them in predicting insect problems and planning control strategies. The seasonal pecan pest profile indicates the possible insect problems associated with various developmental stages of the pecan.

The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.

Educational programs conducted by the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, age or national origin.

Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, Texas Agricultural Extension Service, The Texas A&M University System.

3M --9-92, Reprint
HORT 5, ENT

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Last modified: April 11, 1997 by E. Cross