A Detailed Guide to the Latest Control Methods for Onion Thrips

Onion thrips, also known as tobacco thrips and cotton thrips, mainly damages onions, chives, garlic, cucumbers and solanaceous vegetables in vegetable fields, and is mainly distributed in Northeast China, Beijing, Hebei, Zhejiang, Jiangsu, Guizhou, Guangdong, Guangxi, Hainan, Taiwan, China, Shaanxi, Ningxia, Xinjiang, Tibet, Inner Mongolia and other provinces and regions. Now let us take a look at how to control onion thrips!

Symptoms of Onion Thrips Damage

Onion thrips adults and nymphs damage the heart leaves, tender buds and young leaves of the above-mentioned hosts. Throughout the entire growing period of onions, insects of all stages are active and feeding, causing connected patches of silvery-white streaks to form on the leaf surface after the onions are damaged. In severe cases, the leaves become distorted, yellowed and withered. From a distance, an onion field looks like it is suffering from “drought”, seriously affecting the quality and yield of onions. In the north, people have the habit of eating onions raw. Because onion thrips damage has been severe in recent years, the leaves are covered with feeding marks and can no longer be eaten raw.

Occurrence Pattern of Onion Thrips

In North China, onion thrips produces 8 to 10 generations a year. It mainly overwinters as adults in the leaf sheaths of overwintering Welsh onions, onions and garlic, in soil crevices, or among dead leaves and weeds, and emerges from dormancy when onions and garlic turn green again. Adults are active and can spread with the wind. They fear strong light and mainly feed in the morning and evening, mostly feeding and causing damage on shaded sides and between leaf axils. They can reproduce by parthenogenesis, and eggs are laid singly in the tissues of host stems and leaves. Nymphs are not very active and mostly concentrate at the base of leaves to cause damage, dispersing to cause damage only when slightly older. After the 2nd-instar nymphs mature, they burrow into the soil, molt into the prepupal and pseudopupal stages, and finally emerge as adults. One generation of thrips takes 20 to 35 days, and this is extended when temperatures are low. The optimum conditions for its occurrence on onions are a temperature of 23 to 28°C and a relative humidity of 40 to 70%. High temperature and high humidity, and storms, inhibit its occurrence.

Control Measures for Onion Thrips

The main measure for controlling onion thrips is to clean up the field. In early spring, remove weeds and residual plant debris from onion and garlic fields and their surroundings, and burn them in a centralized manner to eliminate overwintering insect sources. At the same time, strengthen fertilizer and water management. Especially in dry weather, attention should be paid to watering to promote plant growth and destroy the ecological environment favorable for onion thrips occurrence.

Chemical Control of Onion Thrips

For chemical control of onion thrips, spray treatments such as 3% acetamiprid emulsifiable concentrate at 2000 times dilution, 10% imidacloprid wettable powder at 1500 times dilution, 4.5% beta-cypermethrin at 1000 times dilution, and 99% mineral oil at 150 times dilution can be used. Because onion leaves are relatively smooth, a leaf spreader or neutral laundry detergent can be added during spraying to increase adhesion and improve the spraying effect.