Pecan Nut Casebearer Season Fast Approaching

As we transition into May, it’s time to start thinking about Pecan Nut Casebearer. 

 

The pecan nut casebearer (PNC), Acrobasis nuxvorella Neunzig, is one of the most devastating nut-feeding insects that occur in both Native and Improved pecans and is found throughout pecan growing regions. In Oklahoma, adult casebearer moths generally deposit eggs mid-May or early June, depending on the location in the state. Eggs are deposited on the tips of nuts shortly after tree pollination. After hatching, the larvae burrow into nuts. Each larva may damage an entire cluster. The primary means of controlling this insect is the use of a well-timed application of insecticide based on infestation levels from each individual orchard.

 

Description: Adult casebearer moths (Fig. 1) are gray to dark gray, have a dark ridge of scales on the forewings, and are about 1/3 inch in length. In Oklahoma, the pecan nut casebearer completes two to three generations per year. This pest overwinters in the tree. Larvae develop into pupae, and ultimately moths emerge after pollination. Female casebearer moths begin laying eggs on pecan nuts (Fig. 2), resulting in first-generation larvae that feed on pecan nuts and generally cause the most damage. (Fig. 3-4).

 

 

Second-generation PNC begin appearing ≈ 45 days after first generation, feeding primarily on pecan shucks. Unless populations are extremely high, little damage is created from second or third generation larvae. 

 

Scouting: Scouting for PNC should begin one to two weeks before potential nut entry by larvae. A cluster is infested if eggs are found, or evidence of larval entry is observed. Examine 10 nut clusters per tree across several trees. If 2 or more clusters are infested before 310 clusters have been examined, an insecticide application should be made as soon as possible. If less than two clusters are found infested, sampling should be repeated in two to three days.

 

Pheromone-baited traps for PNC are available. The pheromone (sex attractant) mimics the chemical emitted by female casebearer moths and attracts males to a sticky trap. Trap captures can be used to detect the arrival of PNC into an area and provide a signal of when the first significant nut entry by larvae may occur (Fig. 5-6).

 

 

In general, 2-3 pheromone traps are sufficient in determining emergence patterns of PNC moths in a particular orchard. Consider additional traps where orchard conditions vary, such as bottomland versus upland areas. (Get traps out as early as possible after May 1, especially in southern areas of the state, to identify the first flight). 

 

Based on university research, we suggest that scouting begin 7-10 days after the capture of the first PNC moth(s) (Biofix). This allows plenty of time to anticipate the first significant nut entry, which should occur 12 to 16 days after initial moth capture.

 

Scout regularly. A heavy moth flight may not necessarily translate into a successful and/or heavy oviposition (egg-laying) cycle. In Oklahoma, during the period that mating and subsequent oviposition occurs, moths are exposed to many environmental influences that can affect survival and successful propagation.

 

Insecticide applications should be properly timed to achieve the best control. Whenever possible, biological insecticides or insect growth regulators (IGR), MoA group 18, should be used for controlling PNC instead of synthetic pyrethroids, carbamates, or organophosphates. The latter materials, while effective, can result in reduction of parasite and predator populations, which help control primary pests. 

 

More information on the pecan nut casebearer and it’s control can be found at EPP-7189, The Pecan Nut Casebearer and CR-6209, Commercial Pecan Insect and Disease Control