Size-Dependent Mating Success in Pink Bollworm moths: Insights into Mating Disruption Effects

Mating disruption is an environmentally friendly pest management technique that interferes with pheromone communication in moths, disrupting males’ ability to locate females, thereby reducing pest populations in agricultural systems. This study explores how mating disruption affects mating success and size distribution in the pink bollworm ( Pectinophora gossypiella ), a major cotton pest worldwide. The species pheromone normally consists of a 1:1 ratio of Z,Z- and Z, E-7,11-hexadecadienyl acetate isomers, although larger females emit a slightly higher proportion of the Z,Z isomer. The synthetic pheromone used for disruption matches the average blend ratio (1:1 ZZ:ZE), assumed to represent the most abundant medium-sized females. We hypothesized that in pheromone-saturated environments, males would face difficulties locating medium-sized females whose pheromone resembles the synthetic blend. Consequently, we predicted reduced mating success for medium-sized females, potentially shifting body size distributions in the population. To test this, we compared the mating success of large, medium, and small females from a laboratory “naïve” population, never exposed to synthetic pheromone, and from a field population exposed to pheromone for many generations, with and without synthetic pheromone. We also measured pupal weights to assess body size differences. Results showed that medium-sized females experienced significantly reduced mating success in the presence of synthetic pheromone. Additionally, moths from mating disruption–treated fields were, on average, larger than those from the lab. Because larger females are more fecund, laying substantially more eggs than medium- or small-sized females, their increased mating success could partially counteract the suppression effect of the mating disruption strategy.