Extension Agent: It's time to scout for pecan nut casebearer

By Peter J. McGuill
April 30, 2013 at midnight
Updated April 29, 2013 at 11:30 p.m.

One of the most important nut-infesting insect pests of pecan is the pecan nut casebearer.

It is found in all pecan-growing regions of Texas and in southeastern New Mexico. Casebearer larvae tunnel into nutlets shortly after pollination, often destroying all nutlets in a cluster.

The most effective and reliable control method is a well-timed insecticide applications made in spring to kill hatching larvae before they tunnel into the nutlets. However, insecticides should be applied only if infestations and nut load justify treatment.

The adult casebearer is a gray to almost black moth about one-third of an inch long. They have a ridge of dark scales followed by a band of lighter color runs across the forewings. Moths are active only at night when they mate and lay eggs on pecan nuts.

Their eggs are oval, flat and tiny - just large enough to be seen with the unaided eye. When first laid, eggs are greenish-white or white. Tiny red spots soon appear on the egg, giving it a pink color before it hatches.

First-generation casebearer eggs are typically deposited on pecan nutlets soon after pollination. Eggs hatch in four to five days. Young larvae crawl to nearby buds to begin feeding, leaving empty white egg shells on the nut.

The tiny larva feeds for a day or two on a secondary bud at the base of a compound leaf before it enters the pecan nut. Larvae generally tunnel in at the base of the nutlet. Silk and black frass (excrement) are often visible outside infested nuts.

First-generation larvae usually can cause the most economic loss. For this reason, control is directed primarily at this spring generation. Insecticide applications must be timed accurately to control newly hatched casebearer larvae before they enter the nuts. Once inside, larvae are protected from insecticide treatments.

In spring, examine nutlets carefully for casebearer eggs to determine whether egg infestations are high enough to justify treatment and when to apply insecticide. Often, most eggs are laid during a two-week period in late April to early May in Victoria County.

Weather affects when eggs are laid because spring temperatures determine how quickly the overwintering generation develops. Because of the cool spring that we have had this year, I would expect a later than normal egg lay. To anticipate when eggs will be laid, growers can trap moths using pheromone traps or determine daily heat units in the spring.

Begin scouting for eggs at least a week before this anticipated date, as area weather conditions near the spray date can influence egg laying. Scout the orchard for eggs and nut entry to determine if infestations justify treatment and to confirm the predicted spray date.

Be careful when applying insecticide sprays in backyard and urban areas because spray may drift onto nearby gardens, pets and living areas. In home landscapes, use only products containing spinosad, carbaryl, malathion or Bacillus thuringiensis and are labeled for pecans.

Before purchasing and applying any insecticide, always read the label to determine if the product is labeled for use on the target plant or site. Follow mixing instructions and safety precautions.

Bill Ree, Extension Agent- IPM, Texas A&M AgriLife Extension Service contributed to this article.

Brush control workshop

The Victoria Soil and Water Conservation District will have its 2013 Annual Brush Control Workshop on May 15 at the South Texas Electric Cooperative Park. The event will be held from 8 a.m.-4 p.m. and focus on brush management and electric fencing.

There is a registration fee of $30 for this event and, it is limited to the first 60 people that register. Six CEUs for TDA pesticide applicators will be offered. For more information or to register, call the Victoria SWCD/NRCS at 361-576-1129, Ext. 3.

Peter J. McGuill is the Victoria County extension agent - ag and natural resources. Contact him at 361-575-4581 or pjmcguill@ag.tamu.edu.



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