Insect identification > Thysanoptera > Onion thrips

Onion thrips

The onion thrips (Thrips tabaci Linde.). - This pest is present practically everywhere in Europe and the United States, having first been noticed here about 1872. The adult is about a twenty-fifth of an inch long, rather light yellow, but turning brown as it becomes older. It feeds on a great variety of plants but, being the species which is particularly injurious to growing onions, is generally known as the onion thrips.

The onion leaves are whitened by the removal of their juices, and soon begin to bend sharply downward, and later they may curl or twist and even die, an area much affected in a field being noticeably pale colored and the plants stunted, while the bulbs make little growth.

Winter in the North is spent as the adult in protected situations such as in dead grass close to the ground or in rubbish left on the field. In spring the young onion plants are attacked soon after they come up, first in the bud, later on the leaves, in which the eggs are laid.

The life cycle from egg to adult is influenced by the temperature, varying from a little less than 3 weeks to over a month, and in the most southerly states the generations overlap so that practically all stages may be found at the same time. Sometimes in the North this insect becomes a greenhouse pest on roses, carnations, cucumbers and tomatoes, though the greenhouse thrips (Heliothrips hoemorrhoidalis Bouche) is most often responsible for this injury.