Thrips belong to the order Thysanoptera. They are small in size but very harmful. They hide during the day and come out at night. Their rasping mouthparts harm plants, causing nutrient loss in plants and destroying their commercial value. They also spread viruses and harm plant health. They have caused great economic losses to growers.
In recent years, there are few single agents that can completely solve the damage of thrips. Generally, two or more types of agents are used to form a combination plan, or more efficient tank-mixed adjuvants are used to control thrips to reduce the economic losses caused by thrips.
Today, I will introduce some effective means and methods for controlling thrips.
Life habits of thrips
Thrips like warm and dry weather. The suitable temperature is 23℃-28℃ and the suitable air humidity is 40%-70%. They cannot survive in excessive humidity. When the humidity reaches 100% and the temperature reaches 31℃, all nymphs die. In the rainy season, if there is continuous rain and heavy rain, water will accumulate in the axils of onions, which can cause the death of nymphs. After heavy rain or watering, the soil becomes compacted, making it impossible for nymphs to enter the soil to pupate and pupae to hatch into adults.
Damage caused by thrips
Thrips suck the juice of young and tender tissues (twigs, leaves, flowers, fruits, etc.) of plants as adults and nymphs. The damaged young leaves and tender shoots become hard, curled and withered, the plant grows slowly, and the internodes shorten; young and tender fruits (such as eggplant, cucumber, watermelon, etc.) will harden after being damaged, and in severe cases, the fruits will fall, seriously affecting the yield and quality.
After the young leaves are damaged, the leaves become thinner, gray-white or gray-brown stripes appear on both sides of the midrib of the leaves, the epidermis is gray-brown, deformed, curled, and the growth potential is weak, which is easily confused with the damage caused by the side polyphagous tarsoneme.
After the young fruit is damaged, the epidermal oil cells rupture, gradually lose water and shrink, and the scars expand as the fruit expands, showing different shapes of corky silver-white or gray-white scars. However, a small number of them also occur in the waist and other parts of the fruit. This type of "scar fruit" can be roughly divided into three categories: one is a ring-shaped scar about 0.5cm away from the fruit pedicle, with a width of 2-3mm; the second is one or more irregular linear or tree-shaped scars about 1mm wide on the fruit surface; the third is one or more irregular circular scars the size of a button on the fruit surface or navel. Circular scars are often accompanied by tree-shaped scars. The scars are silvery white in the young fruit stage and feel rough when touched by hand; they are dark red or dark red on mature fruits, smooth and shiny.
Prevention and control methods
Agricultural prevention and control: remove weeds and dead branches and leaves in the field in early spring, burn or bury them in a centralized manner, and eliminate overwintering adults and nymphs. Strengthen fertilizer and water management to promote plant growth and reduce damage.
Physical prevention and control: Take advantage of the habit of thrips to tend to blue, set up blue sticky boards in the field to lure and kill adults, and the height of the sticky boards should be the same as that of the crops.
Chemical prevention and control: Conventional agents such as imidacloprid and acetamiprid are routinely used, and the prevention effect gradually decreases.
At present, the following control methods are being promoted internationally:
Thrips and planthoppers in rice seedling stage: Thiamethoxam varieties are recommended, 30% Thiamethoxam suspension seed dressing agent, 70% imidacloprid wettable seed dressing agent.
Vegetables: Solanaceae, melons, and beans use 25% Thiamethoxam water dispersible granules 3,000-5,000 times root irrigation to reduce the release of viral diseases and reduce the damage of underground pests.
Fruit trees: For crops such as mangoes that are severely damaged by thrips, 25% Thiamethoxam spray can be used, but the dosage should be increased, such as 800 times spray, and high-content avermectin benzoate and bifenthrin can be mixed.
Tobacco: Imidacloprid and clothianidin can be used for root irrigation before transplanting or root spraying during planting; 25% imidacloprid 1,000 times, 25% Thiamethoxam 3,000-5,000 times.
Highly resistant thrips, such as thrips on beans, eggplants, peppers and other crops in Guangxi and Shouguang, are of various types and extremely resistant. Conventional ingredients such as thiamethoxam and imidacloprid are difficult to prevent and control. Alux + cypermethrin + tolfenpyrad, a compound product, has a better control effect.
Prevention and control precautions
According to the characteristics of thrips hiding during the day and coming out at night, it is recommended to use the medicine in the afternoon.
Thrips are highly concealed, and the pesticide needs to be systemic or add silicone adjuvants, and try to choose a pesticide with a long lasting effect.
If conditions permit, it is recommended to combine root irrigation and foliar spraying.
Take precautions in advance, don't wait until it is flooded before using the medicine. When planting vegetables during high temperatures, if there is no mulch, it is best to spray the middle and lower parts of the plants and the ground at the same time, because these places are the habitats of thrips nymphs.
