Chilling and flight ability and mating competitiveness of sterile males of the Mediterranean fruit fly

The Sterile Insect Technique (SIT) is widely used to suppress or eradicate infestations of the Mediterranean fruit fly, Ceratitis capitata (Wied.). In large-scale programs, sterile males are chilled (4 degrees C) to allow their transfer and storage in the aircraft used for the releases. Sterile males may remain chilled for as long as 3h prior to release. Here, we describe the results of experiments that assessed the effect of chilling on flight ability and mating competitiveness of sterile male Mediterranean fruit flies held under conditions of low (plastic buckets) or high (emergence tower trays) density. Males from both densities were subject to 0 (no chill), 1, or 3h of chilling at 3days of age. Chill treatment had no effect on flight ability for males held at low density. However, for males held at high density, chilling for 1 or 3h significantly reduced flight ability below that observed for the no chill treatment. Consistent with the flight data, chill treatment had no effect on the mating success of males held at low density. However, among males held at high density, 3h of chilling significantly reduced mating success below levels observed for unchilled males or males chilled for 1h only in trials conducted 1day after the cold treatment. An auxiliary experiment revealed that this reduction in mating performance was temporary: in mating trials conducted 3days after 3h of chilling, sterile males derived from tower trays had similar mating success as unchilled males. Implications of these findings for Mediterranean fruit fly SIT are discussed.