PECAN NUT CASEBEARER (PNCB): Acrobasis nuxvorella (Neunzig) Order - Lepidoptera: Family -Pyralidae

DISTRIBUTION: PNCB is found throughout pecan growing regions from Florida to southern New Mexico.

DESCRIPTION:Eggs (Fig 2) are small, oval (0.5-1 mm), and white to whitish-green, gradually changing to a pinkish color before hatching, and are found on the flower end of developing nuts. Larvae (Fig 3) have three pairs of thoracic legs and five pairs of prolegs and are intense purplish-brown with green undertones when mature, lighter when young. Mature larvae are 10-17 mm long. Pupae (Fig 4, pupae in nutlet) are yellow-brown and about 6-9 mm long. Adult PNCB moths (Fig 1) are 8-10 mm long and are uniformly gray to dark gray with little or no white or contrasting scaling on the upper side of the forewings. A dark band of scales runs across the base of each forewing.

HOSTS: Pecan.

DAMAGE: As overwintering larvae emerge, they feed on developing buds and then bore into young, tender shoots. First generation larvae feed on buds and newly set nuts. A single larva may destroy from one nut to all the nuts in a cluster; infested nuts are often held together with frass-covered silk. This is the most damaging generation. Later generation larvae feed on a single nut or, if the shell has hardened, at the shuck base, where it does little damage. Light infestations may result in desirable thinning; heavy infestations may ruin the nut crop.

INSPECTION TIPS: Pheromone traps are used to detect adults. Look for exit holes at the bases of shoot diebacks. PNCB eggs are found at the tip of the nutlet, either on the top or hidden just under tiny leaves. The empty eggshell remains on the nut. Also look for small larvae feeding on the buds just below the nut cluster. Once the larvae have begun to feed on a nutlet, silk and black frass often become visible on the outside (Figs 5 & 6 ). Open damaged nut clusters and inspect for larvae and pupae. Inspect for silk cocoons (hibernacula) at bud unions on bare root nursery stock.

LIFE CYCLE: PNCB completes two to four generations per year. Tiny larvae (2-3 mm) overwinter in silk cocoons (hibernacula) on the host twigs. Larvae exit their cocoons in spring and attack the nearest buds as soon as they start to swell. As host development continues, the larvae start feeding on elongating shoots. Some larvae pupate in the hollowed out shoots, others move to bark crevices on large limbs or the trunk for pupation. Adults coming from these pupae lay eggs on developing nuts, usually one per cluster. Larvae from this generation and subsequent generations feed exclusively on nuts and almost always pupate in the damaged nuts. As the weather cools in fall, small last generation larvae migrate from their feeding sites to their overwintering sites, where they form small silk cocoons

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