NMSU Researchers Investigate Pecan/Hickory Parasite
Las Cruces – The hickory shuckworm, a pest found in pecan and hickory nuts, is appearing in parts of New Mexico for the first time since the 1990s. While shuckworms are easily managed, the New Mexico State University Cooperative Extension Service is trying to gauge exactly how far they may have spread. Anyone suspecting damage from the parasite anywhere in the state is asked to bring pecan husk samples to their local county Extension agent.
"We've experienced this pest before. It can be managed, both with conventional and organic procedures and products, as long as producers are aware they have it," said Carol Sutherland, NMSU's Extension entomologist and New Mexico's state entomologist. "For commercial growers, and especially backyard pecan growers, if they see damage not familiar to them, and especially if they're disappointed with their crop this year, please send a sample of mined husks or husks stuck to the nut to your county agent."
Hickory shuckworm larvae attack developing hickory and pecan nuts. This year they have been found in commercial pecans collected in October near Roswell and in backyard pecans collected in Carlsbad in late November. Shuckworms were previously confirmed from central and southeastern New Mexico in the early 1990s before disappearing for unknown reasons.
"The pecan harvest presents an excellent time to survey for these potentially significant pests, answer questions and possibly assist growers, large and small, as they plan their pecan management strategies in the future," Sutherland said.
Sutherland said these parasites can be easily overlooked. Symptoms include shucks adhering to nuts or failing to split and release nuts; shucks exhibiting one or more pinhole-sized exit holes; and shucks mined with small, winding trails - the largest slightly larger than a pencil lead in diameter. Some parts of the shuck also may be hollowed out. Small, white, multi-segmented caterpillars with light reddish-brown head capsules and three pairs of short thoracic legs may also be visible with magnification.
She said basic sanitation practices at harvest can significantly reduce local infestations the following spring. Commercial producers may till immature nuts, shucks or plant trash into a waste area on their premises, but tillage close to trees can significantly damage root systems. Backyard growers should gather and dispose of their fallen immature nuts and nut trash by deep burial or bagging this waste for the landfill.
Composting shuck and nut waste may not kill overwintering pupae if the pile is not correctly prepared and maintained. Since damage to this year's nut crop has already occurred, no insecticide treatments are needed now. Various insecticides already labeled and registered for pecans in New Mexico, and likely used for pecan nut casebearer, may be applicable to hickory shuckworm, both for commercial conventional and organic producers. Both conventional and organic producers should check the labels on pecan insecticides they may already use to determine if hickory shuckworms are listed.