Coconut is a major crop in Ramanathapuram district, Tamil Nadu. Except during the North East monsoon season the region has dry weather throughout the year.
This weather condition is very much favourable for black headed caterpillar attack on the trees. Severity of attack is evidenced during February-August.
The caterpillars feed on the chlorophyll content of the leaves from the lower surface. Infested leaflets turn greyish brown in colour and dry. Severe infestation presents a burnt up look for the tree. Pest intensity reduces during the onset of monsoon.
The female moth lays white coloured eggs on the lower surface of the leaves. Newly hatched larva is greenish brown in colour with brown stripes which and constructs galleries on the lower surface of the leaflets.
Grown up larva is light green having dark brown head. Pupa is dark brown in colour and adult is a greyish white small moth. The total life cycle is completed in about two months.
Remove and burn infested leaves during summer season. Release larval parasitoids under the trees periodically from January at fortnight’s interval (4-6 releases) to check the population of the pest.
In case of severe outbreaks first go for insecticide treatment to reduce the pest population up to 50 per cent and release parasitoids after three weeks. The parasitoids are available at Coconut Research Station, TNAU, Aliyar Nagar on demand basis.
Spray malathion 50 EC at 0.05 per cent or dichlorvos at 2 ml with 1 ml of sticking agent per litre of water on the undersurface of the leaves in case of severe infestation.
Root feeding with monocrotophos 36 WSC 10 ml diluted with 10 ml of water helps to minimise the infestation (harvest the nuts 45 days after root feeding). Make a slanting hole in the stem about 1.5 m above ground level and inject 10 ml of monocrotophos 36 WSC and plug the hole with clay mixed with copper oxychloride.
(Dr. J. Ramkumar, Assistant Professor (Agrl. Entomology) and Dr. R. Durai Singh, Programme Coordinator Krishi Vigyan Kendra, TNAU Ramanathapuram – 623 503
Source: The Hindu