Influence of fig fruit ripeness on navel orangeworm egg deposition and larval development

Navel orangeworm, Amyelois transitella (Lepidoptera: Pyralidae) (NOW), is a significant pest of multiple tree crops in California, primarily almonds and pistachios but also walnuts and figs. Recently, NOW populations and infestation have been increasing in figs, likely due to the expansion of tree nut acreage in key fig production regions. Since most studies of this pest have focused on tree nuts, little is known about NOW activity in figs. Here, we conducted a study to evaluate NOW egg deposition and larval development on fig fruits at different stages of maturity in an experimental fig orchard (var. “Black Mission”) at the UC Kearney Agricultural Research and Extension Center (Parlier, CA). Figs in four different stages of development (new, intermediate, mature, and overripe) were caged and inoculated with mated adult NOW females. After five days, the cages were removed, and all NOW eggs were counted on the fruits, branches, and cage material. For the larval development experiment, individual fig fruits were isolated in cages and inoculated with NOW eggs, and after three weeks the number of larvae inside the fruit was assessed. Results indicate that both the proportion of NOW eggs laid on fig fruits, as well as larval survival, was highest on overripe and mature fruits, suggesting that immature fruits are not only less preferred, but also appear to be of lower host quality for NOW.