New approaches to aphid control in strawberries combining botanicals with natural enemies'

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Aphids continue to infest UK strawberries and cause extensive losses, by removing nutrients from plants, vectoring viruses as well as distorting and contaminating fruits and foliage with their excreted honeydew. While several species attack the crop, the potato aphid (Macrosiphum euphorbiae) has in recent years been the most problematic for growers, particularly in early spring. The insecticides that are approved for aphid control are either inconsistent in their efficacy or have a negative impact on the biologicals that are introduced to control aphids and other insect and mite pests. In addition, insecticide resistance has evolved in another important aphid pest of strawberries (cotton-melon aphid, Aphis gossypii), further reducing effective control options. These problems, combined with recent and likely future withdrawals of pesticides, make reliance on conventional insecticides unsustainable for future control of aphids.In this project, the student will test new plant-derived compounds with demonstrated insecticidal activity. These products (including two that showed very promising aphicidal activity in the AHDB MOPS project) have been selected for further in-depth investigation because they act via mechanisms that are unlikely to lead to resistance problems, and preliminary tests have indicated no residual toxicity to natural enemies. Following initial bioassays to compare the insecticidal activities of selected plant-derived compounds against potato and cotton-melon aphids, the student will explore their modes of action, and particularly behavioural effects on the insects. In addition to their direct effects on insects, these compounds also have potential as elicitors of plant natural defence processes, and the student will also investigate this possible mode of action. Their effects on the biology and behaviour of aphid natural enemies (particularly parasitoids) will also be explored.