The hot and humid weather in the northern region was instrumental in the huge build-up of whitefly that caused massive damage to the cotton crop in Punjab and Haryana, forcing both states to look for ways to contain it.
Use of "cocktail of insecticides" by some "ignorant" cotton growers, which led to killing of "friendly insects" to keep a check on whitefly, was another reason, experts said.
"It is hot and humid weather condition, which was the main reason for whitefly attack," said Hisar-based Haryana Agricultural University (HAU) vice-chancellor Krishan Singh Khokhar.
"Initially, June saw heavy rains which made climate humid. Hot and humid climate favours whitefly. July and August did not see well distributed rains, which also led to build-up of whitefly. This is the major factor," said HAU Director of Research, SS Siwach.
Farm scientists further pointed to farmers using a number of insecticides to contain the spread of whitefly that led to the flare-up of the problem. "Another factor is that worried farmers used cocktail of insecticides for spraying, which compounded the whitefly problem," said Siwach.
The heavy spray of insecticides on cotton, they added, also killed friendly insects which usually eat up nymphs of whitely. '
The attack of whitefly is considered as more damaging as the pest thrives on Bt cotton plants that contain more juice. "Leaves of Bt cotton have more juice and whitefly lives on by sucking juice. We have about 95 per cent area under Bt cotton which proved favourable for the pest to spread fast. You will not find heavy damage in desi cotton," said Khokhar.
Scientists have also warned against use of unrecommended insecticides. "Spurious pesticides are also one of the reasons behind the whitefly attack," said the HAU VC.
Notably, agro-chemical company Bayer CropScience has claimed that "lack of awareness" among cotton growers about life cycle of whitefly has contributed to the damage.
Meanwhile, whitefly has started spreading to other crops including sugarcane, guar and bajra though it is not alarming at the moment.
Of the total cotton area of 4.50 lakh hectares in Punjab, nearly 1.36 lakh hectares have come under the whitefly attack. In Haryana, out of 5.80 lakh hectares, about 3 lakh hectares of cotton area were affected by whitefly.
A 5-member committee of agriculture experts was constituted to find ways to control the impact of whitefly on cotton crop, which is expected to submit its report in one month.