B. Quarantine new plants and treat before placing them among established plants. Thrips Thrips feed by rasping on the plant surface and drinking up the fluid. They can be found on the leaves, blossoms, buds and leaf sheaths of plants. Thrips leave tiny black drops of excrement in the feeding areas. Thrips also are vectors for certain plant diseases.
Thrips attack the foliage, buds and flowers of many vegetable, ornamental and flowering plants.
B. Use the botanical insecticides azadirachtin or pyrethrins. The latter three predators commonly are found in the garden during the summer and can be captured relatively easily and brought indoors for thrips control in small greenhouses and sun porches. B. Use a forceful spray of water to reduce numbers of thrips on sturdy plants. High humidity is detrimental to many thrips species. Periodically flood earthen greenhouse floors to drown pupating thrips.