Behavioural responses of female Queensland fruit fly, Bactrocera tryoni, to mineral oil deposits

Behavioural responses of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), females to fruit dipped in water and fruit dipped in 0.5% (vol/vol) aqueous emulsions of a mineral oil were determined and analysed. The mineral oil was an nC20-22 distillation fraction of the base oil used to produce an nC23 horticultural mineral oil. Females caged with oil-treated fruit had significantly longer prelanding intervals than females caged with water-dipped fruit. The latter was attacked immediately or shortly after being caged with flies whereas some oil-dipped fruit was not attacked within 180 min. The percentage of landings that led to oviposition on water- and oil-treated fruit were 58 and 13%, respectively, and the percentages ovipositing after probing were 74 and 25%, respectively. Likewise, average times spent probing were 7 vs. 31 s whereas average times spent ovipositing were 321 vs. 223 s. Females spent less than half as much time on oil-treated fruit than on water-treated fruit. Transition probabilities of rejection, when applied to the behaviour sequence indicated that oil-treated fruits are about nine times less likely to be infested with B. tryoni.