Placement of Pheromone Traps within the Vegetation Canopy to Enhance Capture of Male European Corn Borer (Lepidoptera: Pyralidae)

European corn borer, Ostrinia nubilalis (Hubner), pheromone traps are typically placed in the open or above vegetation to monitor adult presence and abundance in areas where moths are likely to aggregate. After noting in another study that more moths were captured in traps overgrown with vegetation than in traps above it, replicated field experiments were conducted at 2 locations in Delaware to determine if placement of traps within the vegetation was more effective than traps placed above the canopy. At Newark, 3.83 times more males were captured in traps baited with Z-pheromone lure when traps were placed just below the canopy top in mixed weedy vegetation compared with traps 3 m away with the pheromone source 50 cm above the plant canopy. At Laurel in a monoculture of developing wheat, 2.72 times more males were captured in traps baited with E pheromone lure which were placed below the top of the canopy versus traps above the canopy. Greater variation in male moth captures was associated with greater diversity of the weedy sample location relative to samples in wheat monoculture. Also, traps placed within vegetation resulted in less variation in mean moth captures versus traps placed above the canopy. This indicates that a better estimate of the population may be obtained by placing traps within vegetation. Results suggest that males are more likely to respond to calling females within the vegetation as opposed to above the canopy. Placement of pheromone traps with the pheromone source below the top of the canopy appears to be critical for maximizing their effective capture of European com borer male moths. We suggest that enhancement of pheromone lures within vegetation may be caused by water vapor and volatiles associated with plants.