In a relief for cultivators troubled by mealy bug pests, a city university has done breakthrough research enabling mass breeding of a ‘predator’ butterfly to help destroy the plant sucking bugs that destroy economically important crops.
“Indian cultivators for years have been battling the threat by six species of mealy bugs, which reproduce rapidly and feed on crops like coffee, cocoa, grapes, fig guava, mango, sugarcane, mulberry, vegetable crops and several ornamental plants, causing huge crop loss,” Dr M.G. Venkatesha, Department of Zoology, Bangalore University, told PTI.
Mealy bugs attack flower and fruits of crops. A single mealy bug lays 500-100 eggs and has a 30 day life cycle. The menace is estimated to cause a loss of $750 million in US and several millions in India, he said.
Pesticides were not effective as their bodies have a kind of wax-coated finish which did not allow it to settle on them. The only method used so far to control mealybugs was deployment of biological control agents like predatory ladybird beetles and wasp parasites,which had to be imported.
However, under a UGC-sponsored research project, a major breakthrough was achieved by successfully breeding a predator butterfly found in India, under laboratory conditions, paving the way for mass breeding and deployment on mealy bug infested fields, he said.
The butterfly, also known as ape fly, as its pupa resembles a monkey’s face, has for years been found in India.
But efforts by many universities and horticultural universities in the last three decades to grow them under laboratory conditions for mass breeding had not yielded results.
“These butterflies do not mate in captivity, raising a huge challenge in terms of mass breeding them for use as biological control agents against mealy bugs”, he said.
However, a research scholar in the department has generated conducive conditions, making it possible to get the predator butterfly mate in captivity, a major breakthrough, he said.
Out of the total butterfly population, 99 per cent of larvae feed on plants and one per cent was carnivorous.
“The apefly or Spaligis epius is one such potential indigenous predator found in India. It measures less than an inch and is brown in colour with a 20 day life cycle. The caterpillar of this butterfly are carnivorous and can feed voraciously on mealy bugs in the field” said Dr Venkatesha.
A single caterpillar can feed on 2500 mealybug eggs and 200 adult mealybugs in its eight day cycle. “It can significantly bring down mealy bug population in a field”, he said.
Using the technique, this butterfly could be bred in a lab.
A pumpkin with mealy bugs could be bred for two to three months in a lab till it is completely covered with it. Following it, larvae of these butterflies could be cultivated on the pumpkin. A single pumpkin could harvest 60 larvae of the predator butterfly.
“The larvae along with mealy bugs can be taken off the pumpkin with a gentle brush onto a container and manually transferred to plants on the field. The larvae can survive with mealy bugs for two to three days during transportation”, he said. Once they are on the plants, they grow rapidly and destroy the mealy bugs.
The breakthrough offers huge hope for cultivators and also holds potential of exporting these larvae to countries facing the mealy bug menace, especially those which have hot and humid weather conditions.
The predatory butterfly is also found in Burma, Sri Lanka, Philippines Java, Bangladesh and Thailand. Using the technique developed by Bangalore University, these countries could also benefit from it. The results cannot be patented as it is a biological matter, he said. The technique right now might be suitable to tropical or sub tropical climates.
“It took two years to develop this mating and breeding technique and we plan to hold workshops to disseminate this information. Findings of the study have been published in a scientific journal, Springer Verlag”, he said.