Abstract: The European cherry fruit fly, Rhagoletis cerasi (L.) (Diptera: Tephritidae), is a
highly destructive pest. Methods to control it are limited and alternatives are needed.
Observations of cherry fruit flies suggest that females exert much effort to penetrate
cherries at color change stage (from green to yellow) for oviposition. Therefore, the
question arose as to whether a physical barrier on the fruit surface could reduce
oviposition. The effects of different commercial horticultural oil products on R. cerasi
oviposition were evaluated in a series of laboratory, semi-field and field experiments.
In the laboratory experiments, the rate of successful oviposition on fruits treated with
0.25% v/v of the rapeseed oil product Telmion was significantly reduced by 90% compared
to the untreated control. In semi-field experiments, deposits of 1% of rapeseed, mineral and
paraffinic oil significantly reduced oviposition for up to 3 days. Semi-field experiments
indicated that the oil products lose efficacy within 3 to 6 days after application due to
degradation. Although treatments with the rapeseed oil product Telmion reduced
infestation rates in an on-farm field experiment, the infested fruit clearly exceeded the level
of market tolerance of 2%. Further research is needed to assess whether combinations of oil
products, higher application rates and different formulations might improve field efficacy.