The effects of oil adjuvant on the degradation of spirotetramat and its metabolites in apple cultivation.

Spirotetramat is a frequently used insecticide in integrated pest management (IPM) strategies against rosy apple aphid (Dysaphis plantaginea) and woolly apple aphid (Eriosoma lanigerum) in apple cultivation. It is known that paraffin oil adjuvants increase the effect of spirotetramat against aphids. In contrast, there is a knowledge gap regarding the effects of co-applied paraffin (mineral or petroleum) oil on the degradation of spirotetramat and its metabolites (B-enol, B-keto, B-mono, and B-glu), which has not been previously investigated. Spirotetramat combined with formulated paraffin oil was tested against two aphid species and the residues of spirotetramat and its metabolites on leaves and apples were quantified using Liquid Chromatography coupled with tandem Mass Spectrometry (LC-MS/MS). The results showed that spirotetramat is highly effective against D. plantaginea, decreasing infestation by almost 100%. Furthermore, spirotetramat was shown to be effective against E. lanigerum, the reduction in infestation ranged between 67.9 and 97.7% during the last validation date. The addition of paraffin oil increased the effect of spirotetramat and affected its degradation, indicating that its efficacy could be connected to its metabolites. B-mono and B-glu were the most persistent metabolites in apple fruit overall when paraffin oil was applied.