Cardamom is popular worldwide. However, insect pests reduce its productivity. Chemicals used against the pest leave toxic residue in the harvest. Traces of pesticides in produce affect acceptance in the international market. Moreover, long term use of pesticides leads to pests developing resistance. So researchers look for safer pesticides with newer modes of action.
Diafenthiuron, which inhibits mitochondrial action, has been explored for pest management. But can diafenthiuron control cardamom pests effectively? Does it leave residue in harvested crops?
Stanley Johnson and his team from the Tamil Nadu Agricultural University, Coimbatore conducted field trials in cardamom plantations. They sprayed diafenthiuron thrice in the plantations at the recommended dose and at double the dose. The plants were sprayed again after an interval of 21 days.
The team collected cardamom from the plants before spraying and 7, 14 and 21 days after application. The results are encouraging. There was minimum damage to the capsules at double the recommended dose. The recommended dose was as good at pest control as standard pesticides. Neither leaves nor the plant as a whole showed any damage or injury after treatment even at double the recommended dose. Diafenthiuron thus effectively manages both the usual pests in cardamom – thrips and fruit/shoot borer.
Diafenthiuron is less toxic to bees but has high specific activity against both the insect pests of cardamom. “Most pesticides used against cardamom pests are highly toxic to honey bees. Since honey bees play a vital role in pollinating cardamom, we have to be careful about what we use,” says Stanley.
The team estimated the amount of diafenthiuron residue in the cardamom capsules using high performance liquid chromatography. There was no diafenthiuron residue in fresh or cured cardamom capsules. “Our research shows that the residues disappear within ten days”, says Stanley.
India earned nearly four and a half billion rupees from the export of 5,500 tonnes in 2015-2016. But in the recent past, there have been cases of exports being returned due to the presence of pesticides in cardamom. A pesticide that does not outlive its usefulness will come in handy at such times.
Int. J. Pest Manag., 65: 97-104 (2019);
Mabel Merlen Jacob
St. Mary’s College, Thrissur