New Delhi, March 19: Tiny wasps from Israel have helped protect India’s eucalyptus plantations from another exotic insect that scientists believe entered India about six years ago, attacking the trees used in the construction, fibre, medicinal, and paper industries.

Scientists from the National Bureau of Agriculturally Important Insects (NBAII), Bangalore, who procured the wasps from collaborating entomologists in Israel have deployed them for biological control of the gall pest of eucalyptus in eight states across India.

The wasp, named Quadrastichus mendeli, is a natural predator of another wasp called Leptocybe invasa, a eucalyptus-ravaging gall pest that surfaced in India in Tamil Nadu’s Villipuram district in 2002 and had spread across several states by 2007.

“The pest lays eggs on very young eucalyptus plants and creates hard blister-like lumps, causing stunting of plants,” said Arakalagud Shylesha, a senior entomologist at the NBAII. “This has become a widespread problem by 2007,” Shylesha told The Telegraph.

The NBAII contacted Israeli scientists who had a few years ago identified Quadrastichus mendeli as a possible biological control agent for eucalyptus pests. The Bangalore institute procured about 500 wasps and conducted a series of experiments in isolation to study how the exotic insect would behave in India. The import itself required a formal approval from India's plant quarantine department that tracks the flow of exotic species into India.

“We had to be sure that this exotic wasp does not pose any threat whatsoever to other insects or plants in India,” Shylesha said. “We first studied how the wasps would interact with honey bees and other insects and plants found here.”

The scientists then multiplied the wasps, infected pest-ravaged eucalyptus trees with the wasps, and distributed them for release in affected plantations, expecting the wasps to emerge and move into other eucalyptus trees. The first mass release was achieved in early-2010, he said.

“We’ve seen a significant drop in pest infestation over the past two years,” Shylesha said. The gall infestation levels had touched 60 per cent of trees in some plantations by 2007, but have now reduced to 10 per cent, he said.

Shylesha has described the use of Quadrastichus mendeli against gall in eucalyptus in a paper accepted for publication in the Journal of Biological Control. The NBAII scientists distributed the wasps to industry organisations and forest agencies for multiplication and distribution to farmers.