Effectiveness of spinosad and mineral oil based commercial products on oviposition and egg hatching of grapholita funebrana treitschke

Laboratory trials were performed to evaluate the action of spinosad and mineral oil on eggs of Grapholita funebrana Treitschke, the key pest in plum orchards. Fruits of cultivars Angeleno, President and Stanley were used in the trials. The first set of tests was carried out by introducing two mated females of G. funebrana into a cage together with fruits of a single cultivar. The second set of trials tested the three cultivars simultaneously. In all trials, one third of the fruits of each cultivar was treated with mineral oil, another third with spinosad and the final third was left untreated. Treatments were carried out before introducing mated females into the cages. The number of fruits with eggs, the number of eggs laid on each fruit and the number of hatched eggs were recorded. The number of eggs per fruit recorded in all trials was the same, indicating that plum moth females, after choosing the fruits for oviposition on the basis of the cultivar or the applied product, tend to use all suitable fruits in the same way. Oviposition in terms of number of fruits was significantly lower in mineral oil and spinosad treatments in all trials, compared to the control. Differences between the two products were found in trials carried out with Angeleno alone and with the three cultivars together. The percentage of egg hatching on the fruits was always significantly lower with spinosad treatment compared to the mineral-oil treatment and the control. In the trials carried out using the three cultivars, the number of infested fruits was significantly higher for Angeleno and no differences in the hatching percentages were found among the cultivars. The ovicidal and antiovideponent activities of commercial products containing mineral oils or spinosad could represent an interesting tool to reduce G. funebrana damage, both in organic and conventional plum orchards.