The leaf webber, Diaphania pulverulentalis, is one of the serious pests which infests mulberry predominantly in winter season in many parts of southern states.
The female moth lays 150-200 eggs at the rate of 1 to 2 eggs per apical shoot of mulberry plant and they hatch into larvae after 4 days.
The larvae have 5 stages (instars) which last for 15 days and then pupate into the soil or in dry leaves. Pupal stage lasts for 9-10 days. The total lifecycle completes with in a month’s period.
The larvae defoliate on the apical shoot after webbing the tender leaves together and inhibit the growth of plants. Hence farmers face shortage of tender leaves to rear chawki (young age silkworms).
Collection and burning of dried leaves from the infested garden and deep ploughing followed by flood irrigation to expose the hidden pupae to their natural enemies like bird predators is the best method to reduce the emergence of moths. Setting light traps in the mulberry gardens attracts and kills the moths enmasse. The larvae can also be collected and destroyed mechanically by hand picking.
Release of the pupal parasitoid, Tetrastichus howardii at 20,000 numbers per acre and the larval parasitoid Bracon bravicornis at 200/acre 15 days after pruning , Trichogramma chilonis at 3 cc/ acre sprayed 10 days after pruning assures significant reduction in the incidence.
Spraying of dichlorovos at 1ml/litre of water (200–250 litres of solution/acre) two times at the interval of 10 days is recommended in case of severe infestation.
It is advisable to use the mulberry leaves for silkworm rearing 10-12 days after spray of the insecticide.
N. Sakthivel AND B. Mohan
Research Extension Center
Central Silk Board
Srivilliputtur, Tamil Nadu