Thrips

Thrips are small, <1/16 inch (15 mm) slender insects. Adults usually have wings with feathery hairs that enable them to fly. Many of the economically important species of thrips have piercing-sucking type mouth parts and are not capable of rasping plant tissue. In Hawaii, the melon thrips (Thrips palmi Karny) and the Western flower thrips (Frankliniella occidentalis) commonly infest cucumber plantings. Melon thrips tend to live and feed on the leaves. Leaf edges tend to curl downward after heavy thrip feeding. Serious damage often occurs during the early crop stages. Population pressures can be especially high during hot and dry conditions. Local research has shown that cucumber tolerates substantial foliar damage before economic damage occurs. Growers should protect their crops from damage levels (an average of more than 9 thrips per leaf from sampling 50 randomly chosen leaves in a small 0.5 Acre cucumber planting) early in the season when the highest quality fruit and most of the total yield is produced. The practice of weekly insecticide treatments to suppress melon thrips when populations are low to moderate is not warranted. Melon thrips are resistant to many organophosphate and pyrethroid insecticides. Consult with your Agricultural Extension Agent, Entomology Specialist, or agrichemical representative for information on current effective registered pesticides.

                              

   Unlike the melon thrips which prefer to feed on the leaves, the Western flower thrips tend to live and feed in cucumber flowers. The Western flower thrips can cause fruit scarring when they feed on immature fruit. Damage appears as silvery, web or streak like scarring which may be accompanied by fruit malformation. Laboratory analyses may be required to accurately identify the thrips species present in your field. Natural enemies of thrips include minute pirate bugs, spiders, and predaceous mites.