Harm and control of onion thrips

I. Distribution and harm

Onion thrips, also known as tobacco thrips and cotton thrips, belong to Thysanoptera and thrips. It mainly harms onions, onions, garlic, leeks, melons, eggplant, cabbage and potatoes.

Both adults and nymphs suck plant tips and heart leaf sap with piercing mouthparts. The injured onions form many fine and long gray spots, the leaf tips are withered and yellow, and the leaves are twisted and withered in severe cases.

Second, morphological characteristics

Adults. The body length is 1 to 1.3 mm, light yellow to dark brown, etc. The wings are thin and transparent and there are many slender hairs on the periphery.

Eggs. It is 0.2 mm long, kidney-shaped and gradually oval.

Nymph. It is similar to an adult, with a body length of 0.3 mm to 0.6 mm. The body length of the 4th instar nymph (pseudo pupa) is 1.2 to 1.6 mm. The antennae are tilted to the back of the head and chest.

III. Living habits

It is widely distributed in China, with 6-10 generations a year in the north, mainly overwintering with adults and nymphs in the unharvested leaf sheaths of onions, onions and garlic, and a few as pseudo-pupae in remnant plants, weeds and soil. Annual damage can occur in South China. The adult nymphs began to do harm in the next spring. The adults are lively, good at flying and can spread by the wind, but they are afraid of light. They often feed on the leaves in the back or veins and axils of the leaves during the day, and feed on the leaves in the morning, evening, cloudy days and night, and enter the peak period of harm from May to June. Eggs are scattered in stem and leaf tissues and can engage in parthenogenesis. Males only appear in autumn. Females pierce the oviposition tube into onion tissue to lay eggs, and small protuberances can be seen on the leaf surface in the later stage of egg development. Newly hatched nymphs have the habit of social damage, and then disperse when they are a little older. The 1st instar and 2nd instar is the harmful period, the 2nd instar is buried in the later stage and passes through the 3th and 4th instar stage, and finally Eclosion into an adult. The insect likes warm and dry environmental conditions and harms vegetables such as greenhouse cucumbers in winter and early spring in the north.

IV. Prevention and control methods

1. Agricultural prevention and control. Clean the countryside in early spring and destroy withered branches, leaves and weeds in order to reduce the source of overwintering insects. Proper weeding and irrigation can reduce or reduce the harm.

two。 Chemical control. The favorable opportunity of damage caused by 1-year-old and 2-year-old nymphs should be seized for pesticide control. You can choose 1000 times each of 40% dimethoate EC, 50% dichlorvos EC, 50% Batan soluble powder, 40% diazinon EC, 50% malathion EC 1000 × 2000 times, or 10% cypermethrin EC 1500 × 3000 times, or 3% malathion powder and 2% dimethoate powder mixed with 1 ∶ 1, 1.5 × 2 kg per 667m2, sprayed when the dew is not dry in the morning. Although the above agents are of high efficiency and low toxicity. However, it still needs to be discontinued 7-10 days before harvest. In addition, tobacco lime water spray (1 ∶ 0.5 ∶ 50) also had better control effect.