Entomopathogenic nematodes for control of diapausing codling moth (Lepidoptera: Tortricidae) in fruit bins.

Fruit bins infested with diapausing larvae of codling moth larvae, Cydia pomonella (L.), are a source of reinfestation of orchards and may jeopardize the success of mating disruption programs and other control strategies. Bins are not routinely treated for control of overwintering codling moth before placing them in orchards. Entomopathogenic nematodes provide a noninsecticidal alternative to methyl bromide that could be applied at the time bins are submerged in dump tanks at the packing house for flotation of fruit. Diapausing codling moth larvae in miniature fruit bins were highly susceptible to infective juveniles of Steinernema carpocapsae (Weiser). Immersion of bins in suspensions of S. carpocapsae ranging from 5 to 100 infective juveniles per milliliter of water resulted in 68-100% mortality. Immersion times of 1 or 5 min in suspensions with 5 infective juveniles of S. carpocapsae per milliliter of water, with and without Tween 80 (0.01%), yielded essentially the same mortality of codling moth larvae. Highest mortalities in codling moth larvae (88%) after treatment of bins in suspensions of 5 infective juveniles of S. carpocapsae per milliliter of water were observed after incubation for 24 h at 25 degrees C and 70% RH. Lowest mortalities (37%) were observed after incubation at 15 degrees C and 35% RH. Comparative tests conducted with Heterorhabditis marelatus Liu & Berry, Steinernema kraussei (Steiner), and S. carpocapsae with 5 infective juveniles per milliliter of water resulted in 21.7, 53.9, and 68.7% mortality, respectively. The use of miniature fruit bins as described in this article provides an effective means of assessing nematode efficacy without the cumbersome size of commercial bins.