What damage does thrips pest infestation cause to Welsh onion? How to prevent and control it?

Thrips infestation can occur all year round, mainly occurring in open fields in the three seasons of spring, summer and autumn, and occurring more severely in greenhouses in winter. If Welsh onion is attacked by thrips infestation, the impact on the yield and quality of Welsh onion is very great. Let's learn about it together below What damage does thrips pest infestation cause to Welsh onion? How to prevent and control it?

I. What damage does thrips pest infestation cause to Welsh onion?

Welsh onion thrips, also known as tobacco thrips and cotton thrips, is relatively large in size, with a body length of about 1.2-1.4mm, and body color ranging from light yellow to dark brown. It has 8-10 generations per year, with overlapping generations. Welsh onion thrips has a wide host range, reaching more than 30 species. The main crops damaged include Welsh onion, onion, garlic and other Liliaceae vegetables, as well as Cucurbitaceae and Solanaceae vegetables and cotton, etc. Protected cultivation environmental conditions are favorable for the occurrence of thrips. Because of its fast reproduction speed, if not controlled in time, it will cause disastrous damage, seriously affecting plant growth and fruit quality.

The peak occurrence period of Welsh onion thrips pest infestation is in autumn or November-December when winter begins, and March-May is the second peak period. Female adults mainly reproduce by parthenogenesis, occasionally by sexual reproduction, and males are extremely difficult to see. Eggs are scattered in the mesophyll tissue, with each female laying 22-35 eggs. Female adults live 8-10 days. The egg stage in May-June is 6-7 days. Nymphs feed on the underside of leaves until the late instar stage, then stop feeding, fall into the surface soil and pupate.

Thrips likes warm, dry weather. Its suitable temperature is 23℃-28℃, and suitable air humidity is 40%-70%; it cannot survive when humidity is too high. When humidity reaches 100% and temperature reaches 31℃, all nymphs die. In the rainy season, if there is continuous cloudy and rainy weather, water accumulates between the leaf axils of Welsh onion, which can cause nymphs to die. After heavy rain or watering, the soil becomes compacted, so that nymphs cannot enter the soil to pupate and pupae cannot hatch into adults.

II. How to prevent and control Welsh onion thrips pest infestation?

1. Clean the field

In early spring, remove weeds and residual plant debris and fallen leaves in Welsh onion and garlic fields and around them, and burn them in a centralized manner to eliminate overwintering pest sources;

2. Strengthen fertilizer and water management

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 to the occurrence of Welsh onion thrips.

3. Chemical control

Spray imidacloprid, pymetrozine, nitenpyram, thiamethoxam, and dinotefuran in time. They can also control piercing-sucking pests such as mirids and leafhoppers; at the same time, they can be mixed with pyrethroids, emamectin benzoate, chlorfenapyr, etc. to also control leaf-feeding pests such as diamondback moth, beet armyworm, and cotton bollworm. Adding fungicides such as difenoconazole, phenamacril, tebuconazole, dimethomorph, and propamocarb can also control various diseases such as downy mildew, brown spot, and Phytophthora blight. When thrips damage is relatively severe, spinetoram can be used for control. Pay attention to rotating pesticides to reduce thrips resistance to the agents. However, because Welsh onion leaves are relatively smooth, a leaf spreader or neutral laundry detergent can be added during spraying to increase adhesion and improve spraying effectiveness. When occurrence is severe, spray continuously at intervals of 5 to 7 days. Control of pests that bore into Welsh onion leaves must be timely to avoid increasing the difficulty of control after boring.