How habitat structure affects predation of codling moth (Cydia pomonella)

The codling moth (Cydia Pomonella [L.]) is a severe pest of apples and pears worldwide. Fifth-instar codling moth larvae are vulnerable to natural enemies when they leave the tree canopy and seek a location to pupate or overwinter on the orchard floor. This poster presents research testing the hypothesis that codling moth fifth-instar larvae will experience increased mortality in the presence of natural enemies in low complexity orchard floors compared with high complexity orchard floors. To do this, habitat complexity in field cages was manipulated in two treatments by mowing the vegetation under the tree canopy and removing litter (low complexity) or leaving the vegetation undisturbed (high complexity). Natural enemy abundance in field cages was manipulated by adding a predatory insect species, adding an entomopathogenic nematode species, or leaving the enemy population unchanged (control). We found that the mortality of codling moth sentinel prey was affected significantly by natural enemy presence and orchard floor complexity. In general, codling moth mortality was higher in nematode treated cages than untreated cages. Also, nematode infection rates were higher compared with controls in low complexity cages, but not in high complexity cages. There was no effect of the addition of predatory insect species to field cages regardless of orchard floor complexity. However, at one field site codling moth mortality in high complexity control cages was greater than in low complexity controls due to the presence of a native insect predator. The implications of these results for orchard floor management in apple agroecosystems are discussed.