Relationship of almond kernel damage occurrence to navel orangeworm (Lepidoptera: Pyralidae) success

ALaboratory and field studies are reported that assess navel orangeworm (Amyelois transitella (Walker)) development and damage on 11 almond varieties that represent both expected and outlying hull split and shell seal A. transitella damage. Twenty neonate larvae were introduced to almonds of three treatments for each variety: scratched (1 mm scratch through the pellicle), shelled (shell removed but pellicle intact), and unshelled (shell intact and exhibiting the tightest shell seal for the variety). Success was evaluated as moth emergence and degree-days (DD) to emergence. In 2010-2011 and 2011-2012, 10 replicate rows containing randomized strands of 20 unshelled, uninfested almonds from each variety were placed in the field for both the fall and spring A. transitella flight. The almonds were returned to the lab before the initiation of the second spring A. transitella flight and categorized by presumed cause of damage (bird damage, A. transitella damage, or both types of damage). Damage, variety, and their interaction significantly impacted A. transitella survival and DDs to emergence in male moths. Female moth DDs to emergence were significantly impacted by damage alone. Damage from birds and A. transitella damage were positively correlated, and A. transitella damage associated with bird damage was more common than A. transitella damage alone. Nonconspecific damage may have a significant impact on A. transitella populations in the field, and bird damage may have repercussions beyond its direct impact on marketable yield.