1. and Pheromone Trap Data
Historical Analysis of Corn Earworm Populations in New Jersey Using Blacklight
and Pheromone Trap Data
Joseph Ingerson-Mahar and Kris Holmstrom, Rutgers Vegetable IPM Program
Objective 1 – To review 17 years of blacklight trap data collected by the Rutgers Vegetable IPM Program to ascertain if local corn earworm (Helicoverpa zea (Boddie) (CEW) populations are declining (Storer et al, 2001; Adamczyk and Hubbard, 2006). Nine sitess were selected in the northern, central, and southern region of the state with 3 sites per region (Fig. 1). The seasonal catches of CEW at these sites were averaged over the days of operation and plotted in a bar graph (Fig. 2). Figure 3 was produced by averaging the moths/day across all 9 locations and plotted by year.
Results. Figure 2 shows that high variability exists in the trap counts from year to year, as well as, between farms even when physically close. Overall, it appears that the annual population s are declining, especially in the past 6 years (Fig. 3).
Objective 2 – To compare trap counts between blacklight and pheromone CEW traps . Since 2008, 7 farms in southern New Jersey have employed Harstack (pheromone) traps additional to blacklight traps to provide information on distant CEW populations. Pheromone traps usually catch greater numbers of CEW moths than blacklights (Fig. 5). Despite their different methodology we should expect to see similar population trends.
Blacklight and pheromone trap counts from 5 farms were compared on (Fig. 4). Since the pheromone traps are deployed as sweet corn begins to silk, the same days were used to compare both trap types through the silking stage.
Results. Large numbers of CEW moths were occasionally trapped (Fig. 5) in contrast to the respective blacklight traps. Using linear correlation analysis (Campbell, et al, 1992) the blacklight/pheromone trap correlation at the 5 farms only agree for the Green Creek (P<0.05, r2=0.51) and Woodstown (P<0.05, r2=0.69) sites.  While the overall trend in both trap types for all sites was one of declining CEW catches, the lack of significant correlation between trap types at 3 of the 5 sites poses some difficulties when trying to develop insecticide spray schedules based on blacklight catch when only pheromone traps are available for use. 
What does this mean for our farmers? Despite declining populations CEW remains a primary pest and cannot be ignored. However, spray schedules may be extended so that the frequency of spraying may be reduced. Where farmers have both blacklight and pheromone traps we are recommending that they use the most conservative recommendation.
Figure 3 – averaged moth counts across all 9 blacklight trap locations
Figure 1 – map of blacklight locations
Figure 4 – map of 5 farms with blacklight and pheromone traps
Literature cited
Adamczyk, J.J. and Hubbard, D., Changes in populations of Heliothis virescens (F.)(Lepidoptera: Noctuidae) and Helicoverpa zea (Boddie) in the Mississippi Delta from 1986 to 2005 as indicated by adult male pheromone traps. J. Cotton Sci, 10:
Campbell, C. D., J. F. Walgenbach and G. G. Kennedy Comparison of Black Light and Pheromone Traps for Monitoring Helicoverpa zea (Boddie) in Tomato. J. of Agric.l Ent. 9 (1): 17-24
Storer, N. P., J. W. Van Duyn, and G. Kennedy Life history traits of Helicoverpa zea on non-Bt and Bt transgenic corn hybrids in Eastern North Carolina. J. of Econ. Ent. 94(5):