Onion fly trap catch as affected by release rates ofn-dipropyl disulfide from polyethylene enclosures

n-Dipropyl disulfide loadings of at least 1 μl and 10 μl in polyethylene enclosures were required to effect significant trap catches of onion fly,Hylemya antiqua (Meigen), females and males, respectively. Corresponding release rates for this threshold for trap catch were ca. 100 μg/hr. Catches increased with loadings up to 100 μl/capsule but then plateaued. As determined gravimetrically, the release rate from enclosures containing a reservoir of chemical remained constant under isothermal conditions but increased exponentially as a function of temperature.