The European corn borer, Ostrinia nubilalis, is a moth recognized as a significant agricultural pest, particularly damaging to maize, also known as corn. This insect, originally from Europe, was first reported in North America in 1917 and has since spread across much of the continent. The caterpillars of this moth cause considerable harm by tunneling into various parts of the corn plant, leading to reduced yields and weakened stalks that can break before harvest. Understanding the reproductive biology of these moths, especially the role of the female, is important for developing effective management strategies to mitigate their impact on crops.
Female Moth Pheromones
Female European corn borer moths produce chemical signals known as sex pheromones. These are primarily composed of (Z)-11-tetradecenyl acetate and (E)-11-tetradecenyl acetate. Their relative proportions define the Z and E strains. Z-strain females produce a blend of approximately 97% (Z)-11-tetradecenyl acetate and 3% (E)-11-tetradecenyl acetate.
E-strain females produce a nearly opposite blend: about 1% (Z)-11-tetradecenyl acetate and 99% (E)-11-tetradecenyl acetate. Pheromones are synthesized in specialized glands within the female moth’s abdomen. Enzymes called fatty acyl reductases regulate these specific ratios, creating the distinct Z:E ratios characteristic of each strain.
Attracting Mates
Female European corn borer pheromones primarily attract male moths for reproduction. Males detect these airborne chemical signals over considerable distances using specialized antennae, even at very low concentrations. This triggers a behavioral response, prompting males to fly upwind towards the pheromone source, following the scent trail.
Attraction is highly specific to the blend produced by their own strain’s females, ensuring reproductive isolation between Z and E strains. Pheromone release and male attraction are most active at dusk, aligning with the species’ mating behavior. Once males locate the female, mating occurs, leading to egg-laying and life cycle continuation.
Pest Management Strategies
The understanding of female European corn borer pheromones has led to successful agricultural pest management strategies. One primary application is monitoring, using pheromone traps to detect moths and assess population density. These traps contain synthetic lures that mimic female moth scent, attracting males.
Monitoring trap data helps farmers determine moth flight timing and peak egg-laying periods, allowing for more effective, precisely timed pesticide applications when necessary. This approach minimizes indiscriminate insecticide use. In regions where both Z and E strains coexist, separate traps are often used for accurate monitoring, placed at least 30 meters apart to prevent pheromone interference.
Another strategy is mating disruption, saturating the environment with synthetic pheromones. Releasing large amounts of female pheromone confuses male moths, preventing them from locating actual females for mating. This widespread dispersal creates false trails, preventing successful reproduction and reducing the pest population. Mating disruption is an environmentally friendly alternative to broad-spectrum insecticides, as it targets the pest without harming beneficial insects or impacting soil health.