The quality of mulberry leaves fed plays a vital role in growth and development of silkworms and silk production. However, incidence of pests often affects the leaf quality and yield.
Sap suckers
Mulberry thrips, Pseudodendrothrips mori , a sap sucking tiny insect pest now poses a big challenge to sericulture causing severe damage in mulberry in all seasons especially in the tropical zones. Almost all popular varieties are found susceptible.
Mulberry thrip sucks the sap by piercing the ventral side of tender leaves with its mouth part that leads to a dappled appearance due to numerous blotches on its surface.
Heavy incidence of the pest causes abrupt decline in leaf moisture and nutrient content. The leaves become unfit to feed the silkworms. The estimated leaf loss due to the pest is about 30-40 per cent of the total yield produced.
Incidence of the pest affects the mulberry leaves used for feeding the silkworms. This has a direct link to poor growth of worms and susceptibility to diseases followed by heavy mortality. Live silkworms that escape mortality spin only flimsy cocoons with poor silk content which leads to economic loss to the farmers.
Chemical measures are often found partially effective as the thrips develop resistance to the insecticides. At the same time, application of long persisting chemicals is hazardous to the silkworms. However, spray of dimethoate at 2ml/lit found effective and leaves could be fed to the silkworms 20-25 days after spray.
Effective approach
Release of green lacewings, Chrysoperla at 1,000 numbers per acre, 10 days after spray is useful. Population of thrips is naturally reduced during monsoon. The pest is observed to flare up mainly during summer and monsoon failure. Spray of strong jet of water is an effective and eco-friendly approach to control the pest successfully.
(N.Sakthivel, Scientist, and R.Balakrishna, Scientist, Research Extension Center, Central Silk Board, Srivilliputtur – 626 125, Tamil Nadu &Regional Sericultural Research Station, Salem – 636 003, Tamil Nadu, email: sakthivelcsb@hotmail.com, Mobile:098427 61789)
