PestmediumMay–Sep

Thrips (thunderflies)

Thysanoptera

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How to spot it

Thrips are tiny, elongated insects that become particularly active on warm, muggy days, which is why they are also called thunderflies. They suck on leaves, shoots and flowers and leave behind silvery shiny patches as well as fine black specks of excrement on the underside of the leaf. Flowers often become deformed and get unsightly feeding damage along the edges, and young shoots can look stunted in growth. If you look closely, or with a magnifying glass, you can make out the slender, yellowish to dark insects between the petals.

Prevention

Choose robust varieties suited to the site and make sure the plants stand airily, since crowding encourages an infestation. Regular, sufficient watering keeps the plants resilient, because weakened specimens are attacked first. You can pick off and remove infested flowers and leaves to keep the population in check. Beneficials such as predatory mites and lacewing larvae, as well as blue or yellow sticky traps, help you detect an infestation early and reduce it.