The leaf eating black headed caterpillar, Opisina arenosella is a serious pest of coconut palm causing significant yield loss in all the coconut growing tracts of India. It infests coconut of all age groups and is a prolific feeder of coconut leaves. On the adult palms, the infestation starts on the outer whorls of leaves and due to the feeding damage the photosynthetic efficiency especially of the lower fronds will be impaired and in severe cases, whole plantation presents a burnt up appearance due to the drying of leaves. In case of severe out breaks the attacked leaves droop, bunches buckle and the immature nuts are shed heavily, in extreme cases feeding by the caterpillar on the green nut surface is also observed.
Severe incidence of O. arenosella in coastal Andhra Pradesh during 2015-16
In 2015-16 (October to May), a high infestation of black headed caterpillar was observed in all the coastal districts of A.P and incidence ranging from 42.8 to was 62.9 per cent was recorded. An outbreak of black headed caterpillar was recorded in Allavaram mandal (approximate acreage affected is 675 ha) and a medium intensity damage was observed in other coconut growing mandals viz., Katrenikona, Razole, Uppalaguptam mandals (approximate acreage affected is 300 ha) in Konaseema region of East Godavari district of Andhra Pradesh.
The larval parasitoids of black headed caterpillar viz.,Bracon hebetor and Goniozus nephantidis are found effective in managing the insect pest. In order to contain the outbreak from spreading to neighboring coconut growing mandals and to reduce the pest population in affected villages, Horticultural Research Station under the AICRP on Palms, Ambajipeta working under Dr YSR Horticultural University; Department of Horticulture, Government of Andhra Pradesh and M/s Noveeal Coconut producer company together planned to manage the outbreak with the financial assistance of Coconut Development Board, Kochi under community based plant protection activities LODP scheme. From October 2015 to April 2016 about 37,88,650 numbers of these parasitoids were produced in bio-control lab. at HRS., Ambajipeta for distribution and release in pest affected gardens in the affected mandals.
Usually the parasitoids G. nephantidis are to be released at the rate of 10 parasitoid/palm and B. hebetor at the rate of 20 parasitoid /palm in at least ten per cent of the infested palms in each village at fortnightly intervals in case of low (few damaged leaflets here and there) to medium (2–3 damaged fronds with clear drying) intensity damage. But as there is high intensity (all the lower whorls of leaves or entire crown damaged) inundative release of parasitoids was taken up. With the assistance of department of Horticulture and coconut producer societies formed under the Noveeal Coconut producer company the farmers were sensitized on pest identification, nature of damage and management of black headed caterpillar through bio-control and parasitoid release through field visits, village meetings, group discussions and press coverage. Regular field visits to pest affected villages and dissemination of information on larval stage based parasitoid release created awareness in the farmers community on effective monitoring and scheduling of parasitoid release in the affected gardens. A total of 8-12 release of parasitoids were made in each affected villages.
Parasitoid establishment and pest regulation
The parasitoid recovery studies were also undertaken randomly in the pest affected areas (10% sample palms) to ascertain the establishment and build up of these natural enemies in the pest affected gardens. Data on parasitoid establishment after third and six months of bio agents release revealed that the natural enemies established well in the affected gardens and bio-agents effectively paralysed O. arenosella caterpillars. The pest population showed a sharp decline after the parasitoid release. The larval population of O. arenosella in the affected gardens decreased by 34.1 to 75.9 per cent after three months and up to 59.6 to 100.0 per cent after six months of release of parasitoids and no leaf damage and pest population was recorded in the newly emerged leaves. The pupal population of the pest has also decreased by to 33.3 to 94.5 per cent and up to 92.8 to 100.0 after six months.
Eco-friendly and monetary benefit
The impact of biological control was clearly evident in the pest affected villages after six months. The inundative release of bio-control agents successfully regulated the larval stage of pest and the population dwindled and came down substantially in all the black headed caterpillar affected gardens. The self perpetuating parasitoids prevented the spread of the out break to other mandals and the joint efforts of the government organisations weaned and prevented the farmers from resorting top the use of hazardous insecticides monocrotophos and dichlorovas in the coconut ecosystem. The cost involved in bio-control was Rs 20.06 lakhs and the assumed cost of chemical intervention if resorted is Rs 63.18 lakhs (for 975 ha area). There was a saving of Rs 43.12 lakhs with compounded benefit of undisturbed natural ecosystem with self regulating biological control in operation. In the days where hazardous pesticides usage is becoming a matter of concern, this success of biological control as a alternate system, gives impetus to sustainable agriculture.
(Source: ICAR-AICRP on Palms, ICAR-CPCRI, Kasaragod)