Interrelation of mating, flight, and fecundity in navel orangeworm (Lepidoptera: Pyralidae) females

Authors: ROVNYAK, ANGELA - Iowa State University; Burks, Charles - Chuck; GRASSMAN, AARON - Iowa State University; Sappington, Thomas

Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2017
Publication Date: 4/18/2018
Citation: Rovnyack,, A.M., Burks, C.S., Grassman, A.J., Sappington, T.W. 2018. Interrelation of mating, flight, and fecundity in navel orangeworm (Lepidoptera: Pyralidae) females. Entomologia Experimentalis et Applicata. 166(4):304-315. https://doi.org/10.1111/eea.12675.
DOI: https://doi.org/10.1111/eea.12675

Interpretive Summary: The navel orangeworm is a key pest in almond and pistachio, crops worth >$5 billion in pre-processed form. A substantial dispersal capacity has been documented for the navel orangeworm and is important to its pest potential, but interactions between flight and reproduction are not well understood. A flight mill experiment found that unmated females flew later in the night, and for shorter times and distances, compared to mated females. There was no evidence that moths that flew more laid fewer eggs. These data indicate that navel orangeworm females probably do not disperse far prior to first mating, and that subsequent flight does not greatly diminish the number of eggs laid. These data will help pest management research and extension personnel refine mating disruption and monitoring systems for control of this important pests.

Technical Abstract: The navel orangeworm Amyelois transitella (Walker) (Lepidoptera: Pyralidae) is an economically important pest of nut crops in California. Improved management will require better understanding of insect dispersal, particularly relative to when mating occurs. A previous study demonstrated a more robust laboratory flight capacity compared to other orchard moth pests, but it was unclear how mating affects dispersal, and how dispersal affects fecundity. In this study, 1 to 2 day old females were allowed to fly overnight on a flight mill either before or after mating, respectively, and were then allowed to oviposit. Data on fecundity were compared between treatments to minimally-handled or tethered-only control females. Females that mated before flight flew for significantly longer duration and distance than those flying prior to mating. However, timing of flight relative to mating did not affect fecundity, nor did any measure of flight performance. In another experiment, females were forced to fly for designated durations from 3 min to 2 h, and there was no effect on fecundity. Together, our data revealed no obvious trade-off between flight activity and reproductive output. The results suggest that most females mate and oviposit in or near their natal habitat, but that some may disperse potentially long distances to oviposit elsewhere. Distances measured on the flight mills (mean ~15 km for mated females) may overestimate net displacement in the field where flight tracks are often meandering. The findings are discussed in the context of refining tactics for management of navel orangeworm damage in tree nuts.