Scientists shine light on tobacco ‘night thief’

For decades, the tobacco cutworm, or the ‘night thief’ as it is known in Japan, had wreaked havoc on more than 100 crops, emerging as a major pest across Asia.

Now, a consortium of Indian-Chinese-Japanese scientists, has unravelled the mystery behind the pests’ destructive nature by using molecular biology techniques. They have sequenced its genome, peeped into its basic mechanism of action, and are confident to tame it.

The tobacco cutworm, or Spodoptera litura, causes heavy crop-yield loss, ranging between 10 to 30 per cent. It is widely found throughout tropical and sub-tropical areas of Asia, especially in India, China and Japan. The main crops that come under the pests’ attack include castor, cotton, groundnut, amaranthus, chillies, sunflower, pulses and cole-crops.

The pest multiplies rapidly in tropical conditions. It’s short life cycle and high rate of population increase and outbreak make it a lethal enemy for a wide range of crops.

It is nicknamed ‘night thief’ because it feeds during the night and disappears into the soil by day, according to Arun Kumar of Hyderabad-based Centre for DNA Fingerprinting and Diagnostics. To top it all, the pest has developed resistance to every class of pesticide used against it, including the biopesticide Bt, foxing scientists and farmers who are trying to fight it effectively.

Research project Nearly 40 Asian researchers, mostly drawn from the silkworm community, launched the Spodoptera litura genome project as an international collaboration, in cooperation with the Fall Army Worm International Public Consortium (FAW-IPC) about four years ago.

They were looking at comparing the genetic make-up, differences and similarities between silkworm and tobacco cutworm, which are from the same generic species.

According to Arun Kumar, Rajendra Chilukuri and Archana Tomar, scientists of CDFD, who are part of the project, the findings will lead to development of new pest management strategies to control major agricultural pests such as Spodoptera litura.

In the population genetics study they found that the tobacco cutworm expanded throughout South East Asia by migrating along the South India-South China-Japan axis.

It seems to have piggybacked on typhoons in Japan-China and monsoons in India to spread its reach.

En route it has adapted well to the changing ecological conditions with diverse host plants and insecticides, surviving and adapting with the help of its expanded detoxification systems. The pest has the extraordinary gift of identifying the toxin in a crop and quickly neutralising it. It repeats this in different plants.

“We have caught and understood this trait which was hitherto unknown,” Arun Kumar told Business Line.

The findings have been published in Open Access journal. The research work was supported by the grant of the One Thousand Foreign Experts Recruitment Program of the Chinese government.

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