Efficacy of a postharvest spirotetramat spray against armoured scale insects on kiwifruit vines

Abstract

Spirotetramat (Movento®) is a phloem-and xylem-mobile insecticide developed and registered for use pre-flowering to control armoured scale insects on kiwifruit vines in New Zealand. In a field study in 2010-11, the effectiveness of a postharvest application was investigated. A single spray of spirotetramat plus adjuvant(s) reduced the percentage of scale-infested fruit from 49% on control vines to less than 7.5% on spirotetramat-sprayed vines 12 months later. No residues were detected in the fruit. Applying spirotetramat with a penetrating adjuvant (Engulf®) provided the best result, with only 1.5% of the fruit infested. Despite the high pest pressure, counts of scale insect crawlers on sticky bands remained very low for 18 months after treatment. Uptake of spirotetramat into the mature kiwifruit leaves occurred in less than 24 h and was not affected by leaf age. Translocation out of the leaf was slow and decreased with leaf age, indicating that a postharvest spray should not be applied to canopies exhibiting advanced senescence. These results show that a single postharvest application of spirotetramat plus adjuvant(s) can provide excellent season-long control of armoured scale insects on kiwifruit while minimizing the risk to crop pollinators and the potential for residues in fruit. © 2013 The Royal Society of New Zealand.