UC Riverside

The navel orangeworm, Amyelois transitella Walker (Lepidoptera: Pyralidae), is the most significant insect pest of almonds, pistachios, and walnuts. Tolerance for A. transitella feeding damage is < 2% due to yield loss, increased processing costs, and its association with aflatoxins. To maintain this level of control, several integrated pest management (IPM) strategies are used. However, these strategies are not coordinated among growers or applied uniformly. Consequently, gaps remain in management that can be exploited by migrating A. transitella. These gaps can be better managed by understanding A. transitella’s dispersal ability and movement between orchards. The goals of this dissertation were to (i) examine A. transitella dispersal in the field, (ii) discover potential intrinsic biomarkers obtained from larval diet, and (iii) evaluate the influence of larval diet on flight capacity and nutritional profiles of adults.Mark-release-recapture methods evolved over four years in a series of studies. Trap comparison studies demonstrated that A. transitella was more effectively captured from a greater distance with pheromone lures rather than blacklights. Additionally, mass-reared A. transitella were recovered in fewer numbers than locally-reared moths. Several new methods to trace the movement of A. transitella through intrinsic biomarkers sequestered in the larval diet were compared. Non-polar compounds showed greater classification accuracy than polar metabolites and stable isotopes of amino acids, predicting the larval host of A. transitella in controlled settings. Accuracy with lipids declined when applied to field-collected insects of unknown origin. A carotenoid, lutein, was shown to be highly concentrated in both pistachio kernels and pistachio-reared A. transitella, showing promise for future targeted studies. Common larval diets showed diverse nutritional profiles. However, these differences were not as clear in adult A. transitella macronutrient composition and generally did not influence flight performance. Amyelois transitella’s ability to compensate for differences in diet quality to reduce negative impacts on flight capacity is not surprising for a polyphagous insect. This dissertation project highlighted the role of larval diet in dispersal and provided insight into the prospects and limitations of tracing moth movement at the landscape scale to improve IPM programs.