A Detailed Guide to the Harm Caused by Thrips on Orchids and Their Control Methods

In recent years, orchid growers often talk about this:Orchidsafter budding, the flower buds develop black spots, shrink, wither and drop off; when plain-colored orchids bloom, from a distance they look like variegated orchids, but up close there are brown spots at the base of the petals and the lip; when new leaves are half-grown, not far from the base there is a section about one cm long with rough-surfaced brownish-yellow rust spots, suspected to be "Ballas disease." In fact this is not a disease but an insect pest. The chief culprit is a thrips. The scientific name of thrips is Thrips tabaci, also known as onion thrips and cotton thrips. It has omnivorous feeding habits and a wide range of hosts, with more than 350 known host species. It mainly damages scallions, onions, garlic and plants of the Cucurbitaceae and Solanaceae families, and also damagesorchids, and in recent years quite severely. Thrips are very tiny insects, smaller than a small ant. The adult body length is 1.2-1.4 mm, and the body color ranges from pale yellow to dark brown. With six legs, one pair of antennae and two pairs of feathery wings, they are active and good at flying. When you press and pinch one with your fingers, it instantly vanishes without a trace. The adults and nymphs of thrips suck the sap of the host with their rasping-sucking mouthparts. They mostly gather in the heart leaves, tender buds and inside flower buds to cause damage. When damaging scallions, chives and garlic, they form many fine, dense, elongated grayish-white spots on the scallion tubes and chive and garlic sprouts. When damagingorchids, the above symptoms appear. After growing orchids for several years, when viewing the flowers for a while, the damage of thrips to the flowers often makes orchid growers losetheir confidence in growing orchids, which shows how severe the damage is. Thrips eggs are 0.2 mm long, and the nymphs have two instars. The first-instar nymph is 0.37 mm long, white and transparent. The second-instar nymph is 0.9 mm long, with a body color from pale yellow to orange-yellow. The prepupa resembles the second-instar nymph, has already grown wing buds and can move but does not feed, with a body length of 1.2-1.4 mm. The pupa has very large wing buds, with the antennae pressed against the back of the thorax. In the Jianghuai region, thrips produce 8-10 generations a year. Adults or nymphs overwinter in the leaf sheaths of scallions and garlic, or in the dead branches and fallen leaves of hosts, in peas, cabbage, grass clumps, orchid leaf axils and soil crevices. They begin activity in March each year, and cause the most severe damage after entering May, continuing until late autumn. Adults are afraid of light, mostly hiding during the day and active at night. They reproduce by parthenogenesis in summer, and only engage in sexual reproduction in autumn and winter. Each female lays more than 50 eggs at a time, with the highest reaching more than 180. Low temperature, high temperature and high humidity are all unfavorable to their growth. At 20°C-25°C, with relative humidity below 60 percent, dry climates cause the greatest damage. In addition, near villages and vegetable plots there are more sources of the pest, and the damage is more severe. Thrips are small and easily killed by chemicals. Insecticides such as dimethoate, dichlorvos, pyrethroids and organophosphorus compounds all have very good killing effects on thrips. Dual-purpose orchid disease and pest control agents also have a very good effect on killing thrips. However, thrips live inside flower buds and leaf axils, and these places are often blind spots for spraying, so attention should be paid to these blind spots when spraying. When choosing pesticides, it is best to choose those with systemic and fumigant action, for a better effect. As for spraying time, choose early March when thrips begin activity, the new shoot growth period from May to June, and the flower bud period, spraying twice each time with a one-week interval. When spraying in winter, also pay attention to soil crevices to kill overwintering thrips. When spraying acidic insecticides, acidic fungicides and foliar fertilizers such as monopotassium phosphate and urea can also be mixed in, so that pest killing, disease control and topdressing are carried out at the same time, achieving three results in one go. Address: Zhejiang Huangyan Ocean Aquatic Products Co., Ltd. Telephone: 0576-42772581 139576O9879 Wang Deren