Pecan Insect
Credits: Dr. Charles Rohla, Noble Research Institute; Becky Carroll, Oklahoma State University; Dr. Eric Stafne, Mississippi State University
| Name | Latin Name | Description | Life Cycle | Symptons | Edit |
|---|---|---|---|---|---|
| Phylloxera | Phylloxera notabilis, P. russelae, P. devastatrix | The adults and nymphs are tiny, soft-bodied, cream colored insects resembling aphids. They are rarely seen. | Phylloxera overwinter in the egg stage in protected places on branches. The young insects appear in spring about the time the buds unfold. The insect inserts its (beak) into new leaf or terminal growth and a gall forms that soon envelopes the insect. The insect matures within the gall and lays a large number of eggs. Young hatch from these eggs and develop into winged forms. Usually, in late May or early June the gall splits open and releases the insects. Infestations may start on one tree and spread out to others. There are several generations per year. | Galls appear on leaflets or growing terminals. Leaflets with 4 or more galls may drop. Severe infestations may produce partial defoliation of affected trees and may interfere with photosynthesis. Terminals infested by P. devastatrix have galls where the nut clusters would normally develop. This is the most damaging phylloxera. | |
| Pecan Nut Casebearer | Acrobasis nuxvorella | Adult casebearer moths are gray to dark gray, have a dark ridge of scales on the forewings, and are about 1/3 inch in length. Mating and egg deposition occurs during the night, and female casebearers can deposit 50 to 150 eggs during their five to eight day life span. Eggs are small and oval shaped. The first generation of eggs is laid singly at or near the calyx lobes of nuts after pollination. PNC eggs are white when first laid, and then change to red three to five days before hatching. When larvae hatch they are white to yellow in color and feed initially on buds. Full grown larvae are greenish-gray reach about 1/2 inch in length. | In Oklahoma, the pecan nut casebearer completes two to three generations per year. Overwintering larvae develop into moths that emerge from late May to early June. After tree pollination, female casebearer moths begin laying eggs on pecan nuts. These eggs result in first-generation larvae that feed on pecan nuts and generally cause the most damage. Second-generation PNC begin appearing in mid-July. Larvae feed primarily on pecan shucks. Little damage is created from second-generation larvae. Third-generation PNC hatch 30 to 40 days later and feed for a short time (if at all) on shucks. Each small larva forms a tightly woven, protective silken case near a bud or leaf scar for overwintering. These larvae emerge in the spring and feed by tunneling into shoots. Pupation of the overwintering generation occurs in these tunnels formed from feeding, and adults emerge the following spring to deposit the first generation of eggs on pecan nuts. Sex ratios of these moths vary over the season. The proportion of female moth numbers increases over the season. With increased numbers of female moths emerging, damage may increase. | As the larvae grow and move to developing nuts, the will bore into the base of one or more nuts. Black excrement (frass) and silk at the base of nuts indicates larval entry. They remain in the nut and feed for four to five weeks. Full-grown larvae will pupate inside the pecan and emerge 9 to 14 days later. | |
| Hickory Shuckworm | Clydia caryana | The adult hickory shuckworm is a small, grayish colored moth about 3/8 inch long with a wing span of approximately 1/2 inch. They often rest on nut clusters or foliage close to clusters. The immature larvae are small white caterpillars. Full grown larvae are approximately 1/2 inch long, with creamy to dirty-white bodies, reddish brown heads, and black spots over their abdomens. The pupae are found within the tunneled areas of the shuck, or protruding from small exit holes made by the larvae. They are golden brown to dark tan. Pupae are approximately 1/4 to 1/3 inch long. | Hickory shuckworm overwinters as mature larvae within the shucks on the ground or on the tree. Pupation occurs within the shuck, usually in late winter or early spring, with adult emergence beginning in late March or early April. Moths emerging in the spring, prior to nut formation, lay their eggs on pecan foliage, the galls of pecan phylloxera, and nuts of early developing hickories. Shuckworms hatching from eggs deposited on the foliage will generally die before completing their life cycle; however, those larvae developing within phylloxera galls or hickory nuts are able to complete their life cycle, thus maintaining the population until nut formation occurs. During the summer months, female shuckworms begin to deposit their eggs on the nuts. After nut formation occurs, shuckworm populations usually increase with each succeeding generation. The number of generations per year will vary from two to five depending on location. | The hickory shuckworm attacks from the time nuts are first formed until harvest. Prior to shell hardening, larval feeding within the nut causes premature nut drop. After shell hardening, larvae are confined to feeding within the shuck. Damage resulting from the shuck mining activities of the larvae include poor kernel development, shuck sticking, scarred and discolored shell, and delayed nut maturity. Except for premature nut drop, shuckworm damage usually goes unnoticed. | |
| Pecan Weevil | Curculio caryae | The pecan weevil exhibits four life stages: egg, larva, pupa and adult. When fully grown, pecan weevil grubs have a creamy white body that is about ¾ inch long with a reddish-brown head capsule. The pupal stage of the pecan weevil is a whitish, mummified-looking version of the adult. The adult pecan weevil is a light-brown to grayish snout beetle, measuring about ½ inch in body length. The snout of male pecan weevils is about half the length of the female’s, and curves primarily at the tip. Antennae of the male also appear to attach to the snout half the distance from the face. Female pecan weevils possess a longer snout, which curves gradually. Antennae of the female pecan weevil attach to the snout about 1/3 the distance from the face. | Pecan weevils usually lay eggs in pecan when the fruit is at dough stage. The eggs are generally deposited on the distal end of maturing pecan, where development of the seed embryo and cotyledon begin. Egg hatch occurs within 6 to 14 days after deposition. Pecan weevils exhibit four larval instars; however, while the first three average approximately 13 days each in duration, the final instar may feed for five to nine days, but will spend from one to two years in the soil, without feeding. Most larvae penetrate the soil to a depth of six to nine inches. Once they have reached their final resting depth, larvae will construct a hard, almost impenetrable earthen cell, where they will remain until they emerge. About 90 percent of the larvae that enter the soil the first year after feeding on pecans spend one year in the soil before pupating. The remaining 10 percent will not pupate until the following year. This makes the total time from first entering the soil as larvae to exiting as adults approximately two or three years. Two important events dictate the timing of pecan weevil emergence and damage on pecan including rainfall and nut maturity. In Oklahoma, peak emergence of weevils generally occurs from late August to mid-September; however, this timing can occur earlier or later depending on soil moisture. Typically, weevil emergence increases three to four days after a 1 to 2 inch rainfall. Soil moisture alone does not dictate weevil emergence. Another important cue is nut maturity. While the pecan weevil cannot sense nut maturity from beneath the soils surface, this timing has been fixed through years of selection. The average longevity of adult weevils is generally between 15 to 30 days. Generally, female pecan weevils live longer than males and those that emerge early in the season live longer than those that emerge later. | The female weevil chews a hole through the pecan shuck, withdraws her snout, turns around and probes through the hole with her ovipositor until she reaches the shell. The female weevil must grip tightly onto the shuck and rotate around the initial penetration site. This process creates tracking marks on the shuck. After feeding within a nut, larvae will chew exit holes about 1/8 of an inch in diameter in the shell, emerge from the nuts, and drop to the ground. After emergence from the soil, pecan weevils enter the tree by either crawling up the tree trunk or flying directly to the canopy or trunk. Pecan weevils cause different kinds of damage, depending on the stage of fruit development at the time of attack: Dropped and punctured nuts, larval feeding within partially matured nuts, and ovipositional damage. | |
| Aphids - Black Aphid | Black Aphid, Melanocallis caryaefoliae | Black pecan aphids are small, soft bodied insects with piercing sucking mouthparts. Black aphids are a "dull" black in color. Shiny, polished, black, parasitized yellow aphids are often confused with the black pecan aphid. | Black pecan aphids have similar life cycles. Black aphids overwinter as eggs. Wingless females hatch in March and migrate to the newly emerging pecan leaves. These females give birth to living young without mating. This first field progeny is also female and give birth to subsequent generations of aphids without mating. In early fall, winged females and males mate, and the females lay eggs that will overwinter. There are 20-30 generations of aphids per year. | Black pecan aphids can significantly reduce pecan yields. Aphids suck photosynthates from leaves, excrete "honeydew", and reduce the flow of nutrients to nuts. Black aphid damage is characterized by small, chlorotic areas on the leaflets. Heavy infestations cause rapid leaf drop. Black aphids can cause premature leaf drop, reduced nut quality, and subsequent yield reductions the following season. | |
| Webworms | Hyphantria cunea | The adults are moths with a wingspan of about 1 inch. They are white and often have black or brown spots on their forewings. Mature larvae are yellow, black-spotted, covered with white and black hairs and are about an inch in length. | The fall webworm overwinters as a pupa. Moths appear during April and May. The moths lay their eggs on the leaves in masses partly covered with white hairs. Larvae hatching from these eggs construct webs over the leaves and feed inside the webs. When mature, larvae crawl to the ground and spin hairy cocoons beneath loose debris near the surface of the soil. | The larvae feed in colonies and produce large, white webs on the tree branches in late summer and fall. They feed on both surfaces of the leaves and enlarge the web as they spread. | |
| Walnut Datana | Datana integerrima | Adults are moths with light-brown wings marked with dark-brown, wavy lines. The hind wings are lighter brown, without lines. Moths have a wingspan of about 1 1/2 to 2 inches. Immature larvae are reddish-brown, with narrow cream colored lines that extend the length of their body. Mature larvae are black, nearly 2 inches long, and thickly covered with long, white or grayish hairs. | The walnut datana overwinters as a pupa in the soil. Moths emerge in the spring and deposit white eggs in masses on the undersides of leaves. The resulting caterpillars move down to a large limb or to the trunk and form a compact mass. After shedding their skins, they migrate back toward the ends of branches and resume their feeding. Caterpillars molt several times during development. The first generation appears in June and July, and the second generation in late August and September. | Larvae feed in groups but do not form webs. They are capable of eating all the leaves on small trees or on individual limbs of large trees. | |
| Twig Girdler | Oncideres cingulata | Twig girdlers are grayish-brown beetles, 1/2 to 5/8 long, with reddish-brown heads bearing long antennae. Larvae are whitish, legless grubs that are found inside the twigs. | The insects overwinter as eggs or grubs inside severed limbs. The grubs grow slowly during the fall and winter months but in spring they grow rapidly. They normally complete their growth, pupate, and emerge as beetles during the latter part of August. The adults lay eggs in the tips of twig and then girdle the twigs. Twig girdlers generally complete their life cycle in one year. | The adult girdles the pecan twigs in late summer and fall. This girdling causes the injured branch to break off or hang loosely on the tree. | |
| Stink Bugs | Nezara viridula | The southern green stink bug adult is shield-shaped, light green, about 1/2 inch long and has an offensive odor. | The bugs overwinter as adults in leaf litter or other shelter near the orchard. In the spring, they lay eggs in clusters underneath leaves of weeds, cover crops or low growing plants. There may be as many as four generations per year. Pecans normally are attacked only by mature bugs which fly to the trees from other plants. | The southern green stink bug, leaffooted bug and similar bugs sometimes cause black pit and kernel spot of pecan nuts. Black pit is indicated by a darkening of the insides of the immature nuts which is followed by premature drop. Pecan weevils and shuckworms cause similar conditions. Kernel spot consists of brown spots from 1/16 to 3/16 inch in diameter that forms a pithy porous area. The injury cannot be detected until the nuts are shelled. Nuts will drop if bugs attack them before shell hardening; after shell hardening, spots will form on the kernels. The bugs can feed through hardened shells. The severity of black pit or kernel spot depends upon the abundance of plant bugs on the native plants and cover crops that are present. | |
| Mites | Spider mites are very small and often cannot be seen without magnification. The newly hatched mite has 6 legs but all other active stages have 8 legs. Several different species exist in Oklahoma. Several common species spin fine, irregular webs over the infested parts of plants but other species spin little or no webbing. | Some species overwinter as adults and others overwinter as eggs. They hatch or become active as the weather warms in the spring. Hot, dry weather is favorable for most spider mites and during the summer months they can complete a generation in 7 to 14 days. Mite infestations can increase rapidly and cause extensive damage to plants in a short time. Infestations usually decline as the weather becomes cooler and wetter in the fall. | Damage occurs when the mites suck plant juices with their small, needle-like mouthparts. Damage is indicated by yellowing and bronzing of leaves. Dense populations can cause significant damage. | ||
| Leafhopper | Adult grape leafhoppers are pale yellow, with red markings on the wings. They are about 1/8 of an inch in length and somewhat wedge-shaped. Immature forms are green or greenish-white and lack the markings and wings of the adult. | Leafhoppers overwinter as an adult in leaf litter or grasses. After feeding for about two weeks after emerging, the females begin laying eggs in leaf tissue. Eggs generally hatch in about 10 to 20 days depending on temperature. Nymphs reach maturity in 3 to 5 weeks, also depending on temperature. There are three generations per year in Oklahoma. | Feeding by this insect causes the leaves and fruit to appear stippled with very white spots. Eventually, these spots turn brown and may cause the leaves and fruit to shrivel. The leaves may become pale yellow in color and assume a very sickly appearance. Nymphs and flying adults may be noticeable on the undersides of leaves. | ||
| Twig Prunner | Elaphidionoides villosus | The adult beetle is about one-half of an inch long, slender, grayish-yellow, with long antennae. It has spines on the first few joints of the antennae. | During the spring, about the time of budding and new growth, adult beetles start to emerge. The adult female will chew a hole in the bark at a leaf axil near a twig tip and lay an egg. The larva bores into the twig and feeds on the wood as it tunnels toward the base of the twig. The larva will continue to feed for a time but will overwinter as a pupa in the fallen twig or branch. Twig pruners produce one generation a year. | When full-grown (late summer), the larva begins to make concentric cuts through the wood outward from the center and usually stops chewing at the thin bark layer. The larva moves back into the severed portion of the twig. Infested branches, which can range in diameter from 1/2 inch to 2 inches, usually break and fall to the ground. During the fall, small branches with smooth, concave cuts accumulate under infested trees. | |
| Leaf-footed bug | Leptoglossus phyllopus | The leaffooted bug adult is narrower than the stink bug, light to dark brown, and about 1/2 inch long. The leaffooted bug has a flattened leaf-like segment in the hind legs. | The bugs overwinter as adults in leaf litter or other shelter near the orchard. In the spring, they lay eggs in clusters underneath leaves of weeds, cover crops or low growing plants. There may be as many as four generations per year. Pecans normally are attacked only by mature bugs which fly to the trees from other plants. | Leaffooted bug and similar bugs sometimes cause black pit and kernel spot of pecan nuts. Black pit is indicated by a darkening of the insides of the immature nuts which is followed by premature drop. Pecan weevils and shuckworms cause similar conditions. Kernel spot consists of brown spots from 1/16 to 3/16 inch in diameter that forms a pithy porous area. The injury cannot be detected until the nuts are shelled. Nuts will drop if bugs attack them before shell hardening; after shell hardening, spots will form on the kernels. The bugs can feed through hardened shells. The severity of black pit or kernel spot depends upon the abundance of plant bugs on the native plants and cover crops that are present. | |
| Flatheaded Apple tree borer | Chrysobothris femorata | The adult is a broad, oval, flattened beetle about 1/4 to 1/2 inch in length. The beetle is metallic colored and marked with spots and irregular gray bands. The underside is a bronze color and the sides beneath the wings are a metallic greenish blue. The egg is pale yellow, flattened, disk-like, wrinkled, and about 1/16 inch in diameter. The larva is yellowish white, legless, and about 1 inch long when fully grown. The three thoracic segments are broadened and compressed, giving the larva the appearance of having a large flattened head. The larvae within their galleries nearly always assume the curved shaped of a horseshoe. The pupa is somewhat more yellow than the larva and resembles the adult in structure. | Adults appear from March to November, but they are most abundant during May and mid-August to mid-September. Beetles are active and take flight quickly when disturbed. On hot, clear days, they may be found on the sunny side of trunks and larger branches. The female spends much time running over the surface, probing the bark with her ovipositor for places to oviposit. Females mate and begin ovipositing in 4 to 8 days; they live about 1 month after emergence. Each female lays about 100 eggs, depositing them singly in cracks or crevices of the bark, under bark scales, and at bark injuries. Eggs hatch in 8 to 16 days. The newly hatched larva chews through the bark and feeds in the phloem and surface of the sapwood. As soon as the larva is fully developed, it tunnels from the cambium area radially into the sapwood where a pupal chamber is prepared by plugging the burrow tightly with frass; here, it overwinters as a larva. The larva pupates during the following spring or summer. The pupal stage lasts about 8 to 14 days. Adults emerge by cutting small oval emergence holes through the bark. Normally there is one generation per year. | Points of infestation can usually be detected by white, frothy sap oozing from cracks in the bark. The bark gradually assumes a darkened, wet or greasy appearance. Little or no frass is ejected except at cracks in the bark. Injured areas usually become depressions, and later the bark may split at the injured sites. Attacks occur most often on the sunny aspect of the tree. The burrows under that bark are broad and irregular and filled tightly with fine, sawdustlike frass. In young trees with thin bark, the tunnels are usually long and winding, sometimes encircling the tree. In older trees with thick bark, the burrows are confined to a circular area under the bark. Wounds may be enlarged year after year by succeeding generations. Attacks area often associated with injuries. Trunks may be attacked at any point above ground level; branches may also be attacked. | |
| Apple twig borer | Amphicerus bicaudatus | Adult is an elongate, cylindrical beetle, about 1/4 to 1/2 inch long and 1/16 to 1/8 inch wide. Color varies among beetles from reddish brown to almost black. Larva is white with brown head and mandibles, curved body, three pairs of thoracic legs, thoracic segments enlarged; mature larva about 1/2 mm long. | Adults overwinter in living twigs, emerge in early spring and deposit eggs from April to June in the bark of twigs and small branches. Young larvae burrow into the twig and tunnel along the stem. Larvae mature and pupate in fall and early winter. This twig borer has one generation per year. | The insect breeds in injured, diseased, dying, and recently dead trees. Twigs and branches of living hosts may wilt, droop, and die back. Examination of twigs reveals single round entrance holes 1/8 inch in diameter immediately above buds. A beetle may be found in the tunnel from late fall through winter and spring and sometimes until early summer. | |
| Thrips | The western flower thrips and the tobacco thrips are two very destructive species. Adult thrips are usually less than 1/16 inch in length. The adult western flower thrip is yellow or yellow-orange; the tobacco thrip adult tends to be dark brown to black in appearance. Adult thrips have two pair of fringed wings. Larvae are very small at about 1/100 inch in length. They are white or cream-colored during the first instar, turning more straw-colored during later stages. There is a pupal stage that occurs in the soil. | Thrips have a unique life cycle. The adult lays her eggs in plant tissue. The larvae hatch and enter two (maybe more) instars before entering the pre-pupal and pupal stage in the soil. The pupae emerge as winged adults and migrate back to the plants or out of the field. The entire cycle from egg to adult requires from 12 to 16 days. | Thrips cause noticeable damage to seedling stage plants. They rasp the leaves and terminal buds with their sharp mouthparts and feed on the escaping juices. Leaves may turn brown on the edges, develop a silvery color, and may become distorted and curl or cup upward. Early, moderate to severe thrips injury can delay maturity. They cause various types of mechanical injury to the fruiting structures. These include pits, buckskin, black specks, raised blisters and cat-facing. This is the more significant damage caused by thrips. | ||
| Hickory Shoot Curculio | Conotrachelus aratus | Adults are small, dark gray to reddish brown beetles about 3/16 inch long, with slightly curved snouts approximately one-third their body length. Larvae are small, legless, creamy-white grubs with brown heads. Larvae bore in the pith of new shoot growth on pecan and hickory. | Adults overwinter in ground trash or debris in and around pecan orchards. Adults normally emerge from overwintering during March and April, mate, and oviposit in tender new growth. Larvae hatch and tunnel in shoots and leaf stems for 2 to 4 weeks. Fully-grown grubs exit the shoots through irregular, round holes, drop to the ground and pupate in the soil. Typically, adults emerge from the soil in August and September, although there may be some adult emergence throughout the summer. These adults are thought to overwinter. There is normally only one generation per year. | Larvae tunnel in tender shoots and leaf stems, weakening the shoots and sometimes causing terminal breakage or die-back. If breakage or die-back is not evident, injury may be recognized as small, sunken, brackish, triangular spots where eggs were laid in new shoots, or as irregular holes in the shoots following larval emergence. Heavy infestations (50% or more of terminals) may occur. Infestations are frequently heaviest in young trees and other trees not under a good spray program in late summer and early fall the previous year. | |
| Sawflies | Periclista spp. | Adults are small, bee-like insects about 1/5 inch long. Larvae are leaf-green in color, about 1/10 inch long upon hatching and about 5/8 inch long when fully grown. The larvae have six to eight pairs of abdominal prolegs. | Adults emerge from the ground in April and deposit small pale-green eggs in the tissue of pecan leaflets. The eggs hatch and larvae feed on the undersides of leaves. Upon completing their development, larvae enter the soil 1 to 3 inches deep where they construct cocoons and overwinter. | Sawfly larvae generally feed on the underside of leaves and chew round holes in the leaflet. Feeding holes start small but increase in size as larvae develop. Damaged leaves often have a shot-like or lacy appearance. | |
| Spittlebug | Clastoptera schatina C. obtuse | Adults are small, about 1/8 inch long, brown, with a reddish tinge, and have darker brown areas on the middle of the forewings. The nymphs are small, about 1/16 inch long, creamy-white to green and wingless. | Spittlebugs overwinter in the egg stage in the bark on twigs of the previous season’s growth. Nymphs appear in spring soon after the nuts are set and may be seen throughout the summer. | Spittlebugs suck juices from buds, tender shoots, or nut clusters in spring and mid-summer. Heavy infestations rarely kill terminal shoots; however, damage may result in a smaller crop. Older nuts are reduced in quality. Infestations are characterized by the white, spit-like froth that covers the nymphs. | |
| Aphids - Black-Margined | Black-Margined Aphid, Monellia caryyella | Black-margined pecan aphids are small, soft bodied insects with piercing sucking mouthparts. Black-margined aphids are characteristically yellow in appearance. Tolerance to aphids, particularly the black aphid, varies among cultivars. | Black-margined pecan aphids overwinter as eggs. Wingless females hatch in March and migrate to the newly emerging pecan leaves. These females give birth to living young without mating. This first field progeny are all female and give birth to subsequent generations of aphids without mating. In early fall, winged females and males mate, and the females lay eggs that will overwinter. There are 20-30 generations of aphids per year. | Black-margined pecan aphids can significantly reduce pecan yields. Black-margined aphids suck photosynthates from leaves, excrete "honeydew", and reduce the flow of nutrients to nuts. Damaging infestations of aphids can cause whole leaves to turn yellow or chlorotic and possibly drop. Black aphid damage is characterized by small, chlorotic areas on the leaflets. Heavy infestations cause rapid leaf drop. Aphids can cause premature leaf drop, reduced nut quality, and subsequent yield reductions the following season. | |
| Aphids - Yellow Pecan Aphids | Yellow Pecan Aphid, Monelliopsis pecanis | Yellow pecan aphids are small, soft bodied insects with piercing sucking mouthparts. Yellow aphids are characteristically yellow in appearance. Black aphids are a "dull" black in color. Shiny, polished, black, parasitized yellow aphids are often confused with the black pecan aphid. | Yellow pecan aphids overwinter as eggs. Wingless females hatch in March and migrate to the newly emerging pecan leaves. These females give birth to living young without mating. This first field progeny are all female and give birth to subsequent generations of aphids without mating. In early fall, winged females and males mate, and the females lay eggs that will overwinter. There are 20-30 generations of aphids per year. | Yellow pecan aphids can significantly reduce pecan yields. Aphids suck photosynthates from leaves, excrete "honeydew", and reduce the flow of nutrients to nuts. Damaging infestations of yellow aphids can cause whole leaves to turn yellow and possibly drop. Heavy infestations cause rapid leaf drop. Aphids can cause premature leaf drop, reduced nut quality, and subsequent yield reductions the following season. | |
| Pecan Catocala | Catocala piatrix | The catocala caterpillar can grow to 3 inches long but it is often difficult to find because its grey mottled appearance is the perfect camouflage for hiding in the bark of pecan trees. Catocala is the largest caterpillar to commonly feed on the foliage of pecans and hickory. The caterpillar remains hidden and motionless during the day and feeds on pecan foliage after dark. The catocala is commonly known as an underwing moth. | Catocala emerge in late April to early May. Larvae feed on leaves to mid-June. | Catocala caterpillars chew large angular sections out of pecan leaflets giving the foliage a tattered appearance. The amount of foliage lost is generally minimal unless outbreaks occur in conjunction with other defoliators such as sawflies or unicorn caterpillars. Economic damage is rare in well managed orchards. One generations is seen per year with infestations which can be more damaging on young trees. |