The species Thrips tabaci is commonly known as the Onion thrips. This pest is troublesome when infestation levels are high and can lead to significant damage to onions. Thrips can be also found in a wide variety of cultivated crops such as garlic, cabbage, celery, tomatoes, beans and cucumber, as well as weedy plants, thus emphasizing the importance of scouting and control.
The mature Onion Thrips are pale and yellow to dark brown. They can grow up to 2 mm in size with clear, hairy wings. The nymphs are similar in shape but smaller in size and pale yellow in color. Damage is caused by both nymphs and adults. Their feeding results in silvery white, mottled lesions on the leaves surface. When infestation is high, the entire plant can take on a white or straw like appearance. Thrips can also vector viruses and bacterial diseases,
To find thrips, leaves must be parted to expose the youngest emerging leaf in the centre of the plant, where thrips occur most often. Adult thrips may also be found on older leaves, particularly where leaves have folded over, providing a sheltered area. They are most likely found at field borders, near woods or in the vicinity of grain or field crops. Threshold guidelines are as follows: 3 thrips per leaf for cooking onions, and 1 thrip per leaf for Spanish onions and green bunching onions.