Pecan Nut Casebearer
In Texas, adult pecan nut casebearer (PNC) moths deposit eggs on the tips of the nutlets during mid to late April or early May. A single female PNC may lay from 5- to 150 eggs over the course of her lifetime. After hatching, the larvae burrows into nuts. Each larva may damage an entire cluster. If you have high numbers of PNC, then you might expect considerable loss of yield in your orchard. Low numbers and a big crop may not warrant a spraying as the PNC may actually help thin your heavy crop load. It is a management call, but you have no idea without good scouting data. 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 determine biofix and 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 run pecan nut casebearer (PNC) traps. The traps are checked daily until PNC moths are captured consistently for two consecutive days; the first date of consistent captures is what we refer to as the biofix date. This date helps us to know when to efficiently scout for PNC eggs.
The county agent’s office also ran traps this year. Like every year the weather has been all over the place this spring, warm early and then cool. The cool nights have most likely affected trap catch consistency. However, we did recently hit biofix on the traps we were running. Begin scouting your orchard for Pecan Nut Casebearer eggs on the dates when 25-50% of all eggs are expected to be present Using this forecast it is predicted that 25 to 50% of all the PNC eggs expected in this orchard would be present May 24-27. 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 (June 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.
To scout for PNC eggs, examine 10 nut clusters per tree. If two 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 present on the dates of 25-50% oviposition (May 24-27), the orchard should be scouted again 2-3 days later (at 75% oviposition) 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. 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.