Effect of abundance of the navel orangeworm on sampling range and interference between pheromone traps

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

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2012
Publication Date: 1/23/2013
Citation: Burks, C.S., Higbee, B.S. 2013. Effect of abundance of the navel orangeworm on sampling range and interference between pheromone traps. Environmental Entomology. 42(1):143-149.

Interpretive Summary: The navel orangeworm in the principle insect pest of almonds and pistachios; these crops are both high-value and important exports. The area from which monitoring traps baited with sex pheromone attract males is important to their use in detection and monitoring this pest. Using a cross-shape array of pheromone traps in almonds and pistachios, at 400 m intervals, we found a greater inequality between the proportion of males in outer v. inner traps at low abundance, and trap dominance changed with respect to wind and row direction between low and medium abundance. These results show that the range and direction from which males are drawn to pheromone traps for navel orangeworm is density dependent and, at low densities, is greater than 400 m. These findings will aid interpretation of pheromone trap data and will aid the use of pheromone trapping data for the protection of tree nut crops from navel orangeworm.

Technical Abstract: The sampling range of pheromone traps for the navel orangeworm Amyelois transitella Walker (Lepidoptera:Pyralidae) and its association with abundance was investigated by examining mutual interference within cross-shaped arrays of nine wing traps baited with virgin females and placed at 400 m intervals in three 256 ha blocks of almonds and three of pistachios. The proportions of males captured in the different positions were compared to the mean males for all traps, used as an index for abundance. For means between 0 and 50 males per trap per week, the distribution was unequal between trap positions and the greatest proportion of males were captured in the northern-most trap (i.e., the within-row direction). Between 50 and 100 males per trap per week, most males were captured in the western-most traps and fewest in the center, and proportions were equal in other trap positions. Above 100 males per trap per week, the proportion of males captured was more nearly equal for all trap positions. These results demonstrate that the sampling range of pheromone traps for navel orangeworm is density dependent and, at low densities, is greater than 400 m. They also indicate that abundance affects the impact of direction (orientation) of trap interference. At low density, female-strength pheromone traps sample males from beyond the block in which they are placed for orchard blocks of <50 ha.