Field studies with the synthetic sex pheromone and inhibitor of the red bollworm Diparopsis castanea Hmps. (Lepidoptera, Noctuidae) in Malawi

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Abstract
The synthetic sex pheromone of Diparopsis castanea Hmps., dicastalure, is a 4:1 synergistic combination of 93% trans:7% cis-9,11-dodecadien-1-yl acetate (IV) and the unattractive compound 11-dodecen-1-yl acetate (IIB). Both cis and trans-9-dodecen-1-yl acetate (IIA), the latter occurring in the female pheromone gland, are potent inhibitors of male attraction, as little as 10–4 mg IIA significantly reducing the attractiveness of virgin females in pheromone traps for more than one month in the field. Inhibition is typically close range, although higher concentrations are inhibitory when placed at up to 1 m from the female. IV and IIB also reduce male catch in female-baited traps, but dicastalure does not. Recently mated females, confined with virgins, reduce male catch, thereby indicating release of an unknown inhibitor. When formulated in a suitable extender, such as corn-oil, dicastalure may be released from sealed polyethylene vials or from cellulose acetate cigarette filters, and inclusion of the antioxidant 2:6-di-tort-butyl-p-cresol (BHT) prolongs the attractiveness of 1 mg dicastalure formulations beyond 25–30 days. Release from polyethylene is more efficient than from either polypropylene or cellulose and moth catch over a five-week period is linearly related to the logarithm of pheromone concentration. Significant communication disruption, as measured by reduced trap catches of male Diparopsis, occurred when female-baited traps in 100 m2 cotton plots were surrounded by point sources of either dicastalure (synthetic females) or the inhibitory IIA acetate (anti-females). Since dicastalure is occasionally less attractive than virgin females, efforts are being made to improve pheromone slow release formulations.