Field evaluation of eight substrates for dispensing pheromone of the southwestern corn borer (Lepidoptera: Pyralidae)

Eight substrates (polyvial, two plastic laminates, two membrane systems, and three rubber septa) were evaluated for dispensing synthetic sex pheromone of the southwestern corn borer (SWCB), Diatraea grandiosella Dyar, in field studies during the spring and summer adult flights in Texas. Wire-cone traps baited with an orange plastic laminate substrate captured significantly more SWCB males during the 3-wk spring flight than did traps baited with a blue plastic laminate, rubber septa, or polyvial. All of the release substrates were as attractive as or more attractive than a freshly prepared substrate (changed weekly) after 2 wk of exposure. The third week of exposure, only the Trece red rubber septum (Trece, Salinas, Calif.) and polyvial were significantly less attractive than the freshly prepared septum. During the 3-wk summer evaluation, the membrane-type and plastic laminate substrates captured more SWCB than the other commercially prepared substrates. By the second week of exposure, the attractancy of the polyvial and Trece red rubber septum was significantly less than that of the freshly prepared septum. Pheromone recovery from substrate types ranged from 0 to 82.3% and 2.6 to 75.4% of the initial 1.5 mg concentration following the spring and summer flights. Ratios of the three pheromone components changed during pheromone release,but the changes did not impair attractancy. Attractancy of all substrates was significantly less than that of freshly prepared septa after 3 wk of exposure, indicating that all substrates should be replaced after 2 wk