IRRI: Insecticide abuse in rice production causes planthopper outbreaks

Date:12-23-2011


The International Rice Research Institute (IRRI) has called for a ban on certain insecticides in rice production as part of its new action plan to reduce planthopper damage to rice crops in Asia that costs millions of dollars.

At a conference, Threats of Insecticide Misuse in Rice Ecosystems – Exploring Options for Mitigation, held this month in Hanoi, Vietnam, IRRI brought together leaders in the rice industry to advance towards a “greener game plan” to manage brown planthoppers. Attendees included policymakers, agricultural scientists, researchers, extension workers, and industry leaders.

Planthoppers are pests that suck sap from rice plants, causing them to wilt and die. They also transmit three viral diseases that stunt rice plants and prevent grain formation. In large numbers, they cause significant damage.

"We need to seriously rethink our current pest management strategies so we don’t just cope with current outbreaks, but prevent and manage them effectively in the long run,” said Dr. Bas Bouman, head of the Crop and Environmental Sciences Division at IRRI and leader of the Global Rice Science Partnership (GRiSP) program on sustainable production systems.

According to Dr. K.L. Leong, an insect ecologist at IRRI, planthopper outbreaks occur when there is a breakdown in the ‘ecological resistance’ of a rice farm.

This refers to beneficial predators such as spiders and bugs that feed on planthoppers, keeping the planthopper populations below outbreak levels. When insecticides are misused or used indiscriminately, these predators are killed inadvertently, causing planthopper outbreaks.

In addition, growing three rice crops a year or using the same varieties over a large area and for a long period of time can lead to pest outbreaks due to the adaptation and buildup of pest populations.

The action plan recommends two major principles – enhancing biodiversity and regulating the marketing and use of insecticides, including the banning of certain outbreak-causing insecticides in rice.

With IRRI’s support, Thailand banned the use of two insecticides in rice that cause planthopper outbreaks – abamectin and cypermethrin – three months ago.

Also, in March this year, the Vietnamese province of An Giang started adopting ecological engineering practices such as growing flowers in nearby paddies to nurture planthopper predators.

"With the two leading rice-exporting countries, Thailand and Vietnam, showing such leadership in better pest management, we remain optimistic that, in the future, planthopper outbreaks will lessen in their frequency and severity,” Dr. Bouman concluded.