Impact of climate change on navel orangeworm, Amyelois transitella (Walker) population dynamics in tree nut crops in California

The navel orangeworm, 
Amyelois transitella

(Walker)
,

is the most challenging pest of all three major tree nuts – almonds, walnuts, and pistachios, in California. The larval stage of navel orangeworm feeds on nutmeat and causes direct yield. Also, infested nuts become a favorite spot for the aflatoxin producing fungus to colonize, and that reduces the crop value due to the aflatoxin contamination. Temperature increase can directly affect the developmental rates, behavior, and overall population dynamics of this pest, and it is critically important to understand these dynamics with respect to climate change. The objective of this paper was to quantify changes in the timing and number of navel orangeworm generations in almonds, walnuts, and pistachios in the Central Valley of California using projections from ten general circulation models (GCMs) under two emission scenarios. The results suggest that navel orangeworm will complete its life cycle much faster under climate change. The results also suggest that under future climate change, navel orangeworm can complete one additional generation in a season, and that will likely pose significant risks to nut crop industries. This study will ultimately help to strategize and develop an effective integrated pest management (IPM) program to manage this pest.