Hickory Shuckworm

[Originally posted on August 14, 2010]

The adult hickory shuckworm (Cydia caryana) is a small moth.  Before shell hardening, larvae tunnel into nuts, causing them to drop.  Entrance holes can often be detected by a white stain around the hole.  After pecan shells harden, larvae tunnel in the shucks and prevent kernels from developing properly.  Heavily infested nuts are likely to be poorly filled and mature later than pest-free nuts.  Injured portions of the shucks may stick to the nut shell interfering with processing and staining the shells.

Shuckworms overwinter as larvae in shucks on the ground or in trees.  Moths may begin to appear in mid-February but most moths may continue to appear well into summer.  Early in the spring, the shuckworm feeds primarily on native hickory and is often found in phylloxera galls on pecan trees.  Thus,  one of the most effective control strategies for hickory shuckworm is targeting of phylloxera galls in the spring.    Several generations of shuckworm occur each year.   Few pecan nuts become infested with shuckworms before June.  Pecans are most susceptible to damage from the shuckworm during the water through gel stages.

Until recently the standard tool for monitoring of shuckworm was a blacklight trap.  If using a blacklight trap, use at least two per orchard for sampling.  Operate traps at least three nights per week and check after each night’s operation, beginning in early June.  Apply shuckworm control when there is an increase in the number of shuckworm moths in blacklight catches for three consecutive trapping periods and when the number of captured moths reaches seven in any one blacklight trap;  or when four or more moths are caught in any blacklight trap for three trapping periods.  Pheromone traps are also available.  If pheromone traps are used, treat according to the guidelines provided for the traps.

If an orchard has a past history of high incidence of nut drop caused by hickory shuckworm prior to shell hardening , apply a shuckworm spray during June.  Monitor and continue sprays until pecans reach the half-shell hardening stage based on blacklight and or pheromone traps.

Taken from Bugwoodwiki