Field evaluation of a slow release pheromone formulation to control the American bollworm, Helicoverpa armigera (Lepidoptera : Noctuidae) in Pakistan

Trials to control the American bollworm, Helicoverpa armigera (Hubner) by t he technique of mating disruption were carried out in the Pakistan Province of Punjab during the 1996 cotton season. A slow release PVC resin formulat ion, Selibate(R) HA, containing a 97:3 mixture of the major (9Z-hexadecenal ) and minor (11Z-hexadecenal) components of the female sex pheromone of H. armigera was applied at a rate of 40 g active ingredient ha(-1) during Augu st 1996. The formulation was applied around the terminal portion of the cot ton plant by hand using local labour at a rate of c. 250 pieces per hectare . The efficacy of the formulation was compared to conventional insecticide regimes to control H. armigera on four farmer practice fields situated at l east 1 km to the north, south, east and west of the pheromone treated area. A high degree of trap catch shutdown (indicating mating suppression) was o bserved throughout the pheromone treated area during the whole of the seaso n compared to non-pheromone treated farmer practice fields. Night observati ons confirmed that mating disruption occurred in the pheromone treated area as a smaller percentage of mated females were collected from this area com pared to farmer practice fields. A majority of mated females collected from the pheromone treated area mated only once, whereas females in farmer prac tice fields had undergone multiple matings. A greater percentage of tethere d female H. armigera moths retrieved from farmer practice fields had succes sfully mated compared to tethered females retrieved from the pheromone trea ted area. Release rate data of H. armigera pheromone from the formulation s how that c. 70% was released during the two month trial period. However, th e highly dispersive pre-oviposition flight behaviour of females meant that the area treated was not sufficient to eliminate the problem of gravid fema les migrating in from surrounding areas, and ovipositing therein. The impli cations of using the technique of mating disruption to control large strong flying insects like H. armigera are discussed.