|Burks, Charles - Chuck|
Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2011
Publication Date: 4/13/2011
Citation: Burks, C.S., Brandl, D.G., Higbee, B.S. 2011. Effects of natural and artificial photoperiods and fluctuating temperature on age of first mating and mating frequency in the navel orangeworm, Amyelois transitella. Journal of Insect Science. 11(48):1-11.
Interpretive Summary: Mating disruption is being developed as a pest management tactic for the navel orangeworm, the principal insect pest of California’s almond crop. The current study provides necessary data for future experiments examining the impact of delayed mating under environmental conditions typical of those experienced by the first (spring) and second (early summer) navel orangeworm flights. Weak illumination at the end of the dark phase of a daily photoperiod increased mating frequency of 1-day old navel orangeworm moths from 50 to 90% under long days and constant warm conditions. In a laboratory environmental chamber programmed to simulate spring photoperiods and temperature fluctuations mating frequency was 5, 30 and 50%, respectively, for 1, 2, and 3-day old moths. Treatments with weak illumination had no effect on these mating frequencies, which were similar to data gathered in the field. We conclude that the first age examined in delayed mating experiments should be 1 day post-eclosion for flight 2 conditions, but 3 days post eclosion for flight 1 conditions. These data will be used as the basis for delayed mating experiments, which will help determine whether mating disruption treatment must be started in March for optimum efficacy, or if treatment started in May might be more cost-effective.
Technical Abstract: We examined the effect of weak illumination during part or all of scotophase on mating frequency of navel orangeworm, Amyelois transitella (Walker), in environmental chambers under long photoperiods and constant warm temperature (colony conditions) or shorter photoperiods and a cooler thermoperiod intended mimic spring conditions in our region. These data were compared to mating frequencies in sentinel females placed in the field during the first three weeks of May. Under colony conditions weak illumination in the final hour of scotophase resulted in ~90% mating on the first day after eclosion; significantly greater mating compared to complete darkness throughout the scotophase, weak illumination throughout scotophase, or weak illumination for both the first and last hour of scotophase. In an environmental chamber programmed to simulate spring conditions, little mating occurred on the first night after eclosion and three nights were required for >50% of females to mate. There was no difference in mating frequency with between moths exposed to complete darkness throughout scotophase and those provided with weak illumination in the last half hour of scotophase or throughout scotophase. This delay in age of first mating was consistent with field observations with sentinel females at May in our location. We conclude that, along with greater longevity and later oviposition, first mating occurs at a later age in spring conditions compared to summer conditions in this species. Planned studies of the effect of delayed mating in first and second flights will need to take these factors into account.