Damage symptoms
Thrips cause damage to plants by piercing the cells of the surface tissues and sucking out their contents, causing the surrounding tissue to die. The resulting silver-grey patches on leaves and the black dots of their excreta indicate their presence in the crop. The vigour of the plant is reduced by loss of chlorophyll. When infestations become serious the leaves themselves can shrivel.
Onion thrips (Thrips tabaci) is found mostly along the main leaf veins, with most damage evident where these veins join. Fruit damage, for instance in cucumber, only occurs if the crop is heavily infested. In some countries, the onion thrips (Thrips tabaci) has been identified as an important vector of tomato spotted wilt virus.
