Epsilon Open Archive

Abstract

The Guatemalan potato moth, Tecia (Scrobipalpopsis) solanivora, is a serious potato pest in Central America and adjacent South American countries. Recently, it has been introduced to the Canary Islands, Spain. Insecticide treatments are not sufficiently effective against eggs and larvae of Guatemalan potato moth, which are protected from sprays in soil crevices and in galleries inside potato tubers, respectively. Deregulation of insecticides and restrictions in the use of the few available insecticides, parallel to a public demand for reduction of pesticide use in potato production, have increased the interest in biological control techniques. Behaviour-modifying chemicals, including sex pheromones, which target the adult life stage, are a particularly promising alternative to insecticides for control of Guatemalan potato moth. The aim of this study was to study T. solanivora sex pheromone and to investigate the feasibility of pheromone-mediated mating disruption as environmentally safe control technique. Chemical analysis of female pheromone gland extracts confirmed two previously identified compounds (E)-3-dodecenyl acetate (E3-12Ac) and (Z)-3-dodecenyl acetate (Z3-12Ac), plus an additional, saturated compound, dodecyl acetate (12Ac). These three compounds elicited significant male antennal responses by GC-EAD. Field trapping studies showed that a 100:1:20-blend of these compounds formulated at 1000 μg on rubber septa, captured more males than the main compound alone. This trap lure can accordingly be used in field traps for detection and population monitoring. During two years, potato fields were treated with a 100:56:100-blend of the three pheromone compounds formulated in polyethylene tube dispensers. Male attraction to E3-12Ac and Z3-12Ac is optimal at a 100:1 blend ratio, and only few males were attracted to traps baited with a 100:50-blend. Mating disruption pheromone dispensers, containing these two compounds in a 100:56 ratio, did not attract males in the wind tunnel or in the field. The application rate of the 100:56:100-blend of the three pheromone compounds was 28 g/ha in the first, and 86 g/ha in the second year. In both years, T. solanivora male attraction to synthetic pheromone traps were almost completely suppressed, indicating that sexual communication was disrupted. During the second year, additional tests confirmed that the pheromone treatment prevented mate-finding and mating. Attraction to traps baited with live calling females was reduced by 89% in the pheromone treatment, during two months. In addition, matings in small field cages were significantly reduced. Visual observations showed that few males were observed in the pheromone-treated, as compared to the control field. At harvest, potato infestation was significantly lower in the treated field, as compared to control. Future studies will aim at the optimization of dispenser formulation, and area-wide implementation of the mating disruption technique for control of Guatemalan potato moth.