If you own a pecan tree one of the pests you’ll want to be on the lookout for is the pecan nut casebearer, which is among the most important economic pests of pecans.
The larvae of the casebearer bore into and gobble up developing nuts. When shrunken pecan nut clusters are spotted on the tree, it is probably due to first generation casebearers. Scouting for these pests should begin just a couple weeks from today.
The first generations of casebearers begin showing up in early spring, emerging as rather plain looking half inch long tan moths. The can be identified by a dark stripe on their wings just behind their heads. Overwintering larvae from third or fourth generations emerge out of their protective silk cover to feast on tender buds before nuts develop. They soon pupate into their adult moth form and mate, eventually laying as many as 150 eggs in a season.
Casebearer eggs are white, turning pink and occasionally red before they hatch. The first generation is the most damaging. Larvae will feed for about five weeks, then settle within a nut and pupate into an adult moth. A lone larva can quickly destroy an entire nut cluster. Second, third and fourth generations cause less damage. As these later generations surface, they are quickly filled up by feeding on larger nuts making them likely to move from there to other nuts. Hardened shells also provide more protection from damage during later generations.
Scouting makes use of traps baited with the scent (pheromones) of females. The traps fool male moths into landing on a tacky surface where they can be spotted. Once monitoring reveals that moths are being caught, you should begin inspecting the nut clusters for eggs. Inspection of nutlets should be done throughout May. If the tree is used for production rather shade, then insecticide sprays may be needed when more than ten percent of the cluster have eggs. If the tree is being grown for shade only then controls aren’t necessary. Casebearers don’t usually cause serious injury to pecan tree health. In fact, they may provide a benefit by reducing the amount of weight that limbs support.