Effect of bait formulation and number of traps on detection of navel orangeworm (Lepidoptera: Pyralidae) oviposition using egg traps

Authors: HIGBEE, BRADLEY - Paramount Farming Company, Inc; Burks, Charles - Chuck

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2010
Publication Date: 2/25/2011
Citation: Higbee, B.S., Burks, C.S. 2011. Effect of bait formulation and number of traps on detection of navel orangeworm (Lepidoptera: Pyralidae) oviposition using egg traps. Journal of Economic Entomology. 104(1):211-219.

Interpretive Summary: Despite recent advances in pheromone chemistry, ovipositional traps in which eggs laid by female navel orangeworm are counted continue as the primary means for monitoring this primary pest and timing treatments in almonds and pistachios. In this study, we used field trapping experiments to examine the frequency distribution of eggs on traps at various parts of the field season, and the relative importance of the attractiveness of the bait and the number of traps examined. We found that preference for pistachio- over almond-based bait could be clearly distinguished when the number of eggs per trap was high. This was not, however, the case in the periods when treatment decisions need to be made, during which there are typically few eggs per trap. This is in part because of a highly skewed distribution of eggs on traps (i.e., many counts of 0 and a few high counts). This is the first study to document frequency distribution of navel orangeworm eggs on egg traps, and its findings will aid crop managers and pest control advisors to use egg traps more efficiently to guide pest management for navel orangeworm, which is the most important insect pest of the almond and pistachio industries, together worth ˜$2.5 billion annually (unprocessed).

Technical Abstract: Egg traps are the primary tool for monitoring egg deposition of the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), and for timing treatments for this pest in almonds and pistachios. We compared, in almond and pistachio orchards, the number of eggs per trap in traps baited with almond meal, pistachio meal, or the current standard commercial bait. When considering cumulative eggs captured over an extended period, traps baited with pistachio meal prepared from previous-crop nuts generally captured a similar number of eggs compared to the commercial bait, and more eggs than those baited with almond meal prepared from previous-crop nuts. However, differences in eggs per trap between bait formulations were not as evident when examining individual weeks, particularly in weeks with few eggs per trap, as is typical when treatment decisions are made. The variance in eggs per trap was generally greater than the mean and increased with the mean and, when mean eggs per trap was low, most traps did not have eggs. We discuss implications of these findings for the relative importance of bait type and trap numbers for monitoring, and for experiments comparing egg trap performance.