DESCRIPTION OF THE PESTS
Blossom thrips adults are minute insects, about 0.03 inch long, with two pairs of wings. The flower thrips are widely distributed throughout the districts of Himachal Pradesh. Thrips are generally 1mm to 1.5mm long and pale yellow, black or brown in color. Thrips are small, slender insects, with four long, narrow wings fringed with hairs. . It feeds on a number of plant tissue and hence damages tree fruit. Mainly it damages the buds and flowers of the apple tree. Thrips also damages the surface of the fruit as it feeds on fruit and this feeding weakens flowers and fruit stems. Thrips species feed on a large variety of apple plants by puncturing them and sucking up the contents. It is very difficult to predict the damage as it does not occur every year. They also visits many other flowering plants as well as tree fruits, and if those plants are flowering at the same time the thrips population can be minimized and chance of damage can be reduced.
Generally thrips gets attracted to the flowers of apples as well as other crops and weeds. The main damage occurs by egg-laying which punctures the newly formed fruit before petal fall. The site where egg-laying is done generally results in russeting or a yellow patch known as PANSY SPOT. The green varieties golden delicious, granny smith shoes more damage from thrips. Pre-bloom feeding of thrips weakens the flowers resulting in poor fruit set. Too much presence of thrips in an orchard can reduce the fruit setting by 60%.
The eggs are cylindrical and dome shaped. These eggs are laid in the incision of the fruit, stem or leave made by the female. Only one egg is deposited in one incision. The egg deposited here is protected by the plant tissue.
The young thrips are white in color and are smaller than the adult. They starts feeding on the plants by sucking its contents. The first two instars are wingless and are called larvae.
The third instar, called the prepupa, is inactive, does not feed and has wing buds.
Thrips remains in this stage for almost 4-10 days and becomes adult. In this stage they are pale yellow in color and are slightly bigger than the larva stage.
Adults have a life span of about 10- 30 days. The whole generation of a thrips lives for about 40 days under ideal conditions for the pest. The adults are about 1mm long and two pairs of wings on either side. These wings are covered with hairs folded flat over the back. The two sexes looks similar but male is smaller and lighter in color.
They can be monitored by shaking the bud or the flower on a white piece of paper. Adults can be seen easily without magnification but larvae are difficult to see. Sample 6-8 clusters of flowers per tree and 4-6 trees in a orchard block. . Sample in the morning, preferably at the same time of day, as thrips densities can change dramatically throughout the day if the weather is warm and calm, which is when they tend to fly. if there are more than 1 to 2 adult females per cluster in apple, there is a risk of fruit damage due to egg laying. Feeding damage may occur at different densities.
Thrips predators are adults of (minute pirate bug), (Orius tristicolor) and larvae of green lace wigs. They attack thrips in the growing season of apple and reduces thrips populations. Another way is to keep the orchard ground clean and free from weeds, by doing so thrips can not make its food and can’t find its shelter and gets reduced at very considerable rate.
Thrips can be controlled chemically by applying THIACHLOPRID @ 200ML/ 200 LITRES OF WATER.
Apply 200gms of Thiamethoxam per 200 litres of water at pink-bud stage.
Apply 200m.l. of carbosulphan per 200 litres of water .