Designed in the US for the removal of horse droppings from paddocks by suction, a tractor-mounted suction machine has been modified and is being used commercially by one UK grower to remove pests, particularly leaf hoppers from mint and thyme. HDC project FV 330 set out to examine the efficiency of the machine in removing pests and establish what, if any, reduction in pest damage followed use of the machine.
On flowering thyme, numbers of leaf hoppers in treated plots were 70 per cent lower than in untreated plots immediately after passage of the suction machine. Also non-target insects, both pests like aphids and beneficials like honeybees, were 75 per cent lower in treated thyme plots. Avoiding using the machine during flowering would have reduced the impact on bees. On mint, leaf hopper numbers were 66 per cent lower and non-target insects were 85 per cent lower in the treated plots. However, it was evident that there was a "flushing effect" as the tractor passed that redistributed pests into neighbouring areas before the suction inlets could remove them as the machine was rear-mounted.
Disappointingly, repeated use at weekly intervals of the machine on a mint crop did not reduce leaf hopper damage. This was most likely due to re-invasion of treated plots from neighbouring untreated areas but it was considered that the flushing effect also contributed. The results of the project suggest that it may be possible to increase the efficacy of the machine by simple modifications.
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