Pecan Nut Casebearer
In Texas, adult casebearer moths deposit eggs during mid to late April or early May. 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. Scouting for PNC and using pheromone traps to generate a PNC Forecast are the best methods to determine when to scout the orchard and determine, if needed, the best timing of an insecticide treatment to control PNC.
Most pecan growers in the county and the county agent’s office run Pecan Nut Casebearer (PNC) traps to aid in determining the best time to scout for PNC eggs and the best time to begin spraying for PNC. This has been a nutty year for weather, it seems like January was warmer than April. The cool nights have most likely affected trap catch consistency, here are results for two orchards. There was several days difference in trap dates from the two locations, but it does give us some potential days to start scouting.
Using this forecast for orchard #1, it is predicted that 25 to 50% of all the PNC eggs expected in this orchard would be present May 11-14, for orchard #2, it is May 16-19. The period of 25-50% oviposition is the optimum time to first scout the orchard to determine if sufficient PNC eggs are present to justify an insecticide application.
Too few eggs are likely to be present prior to this time to make a treatment decision. The first nut entry by PNC larvae usually occurs near 90% oviposition (May 21 for orchard 1, May 25 for orchard 2 in this case). Thus, scouting for eggs at 25-50% oviposition provides time (6-8 days) to apply an insecticide, if necessary, to kill hatching larvae before they tunnel into pecan nutlets. If few eggs are present on the dates of 25-50% oviposition (orchard #1-May 11-14, orchard #2-May 16-19), the orchard should be scouted again 2-3 days later to determine if the egg infestation has increased to a treatment threshold. If not, egg infestation levels should again be determined by a third inspection 2-3 days later (at 90% oviposition) to determine if an insecticide treatment is needed.
This is a lot of explanation to let you know due to the difference in catch dates for these two orchards you would want to emphasis your scouting efforts between May 11 and May 22.
To scout for eggs, examine 10 nut clusters per tree. If 2 or more nut clusters are infested before 310 clusters have been examined, then infestations will be large enough to destroy 5 percent or more of your crop. If less than two nut clusters are found infested, sampling should be repeated in two to three days. Nut clusters with eggs should be tagged with a ribbon or tape and checked daily to determine egg maturity. Insecticides should be applied within one to two days after the eggs hatch.