Growing pest resistance to insecticide threatens agribusiness

Brazil urgently needs to implement an integrated pest management plan to prevent the problem from becoming uncontrolled, researchers say.

By Elton Alisson  |  Agência FAPESP – Increasing resistance to insecticides has hindered the control of agricultural pests in various parts of the world. One of the reasons for the increase is indiscriminate spraying of crops with these agrochemicals.

According to experts, Brazil is under severe threat from this problem, which may affect crop yields if it is not controlled. Scientists say an integrated pest management plan is urgently needed to prevent the growing resistance of agricultural pests from reaching a threshold above which they could become uncontrollable. The need for such a plan was highlighted by researchers who took part in the FAPESP-BBSRC Workshop on Antimicrobial Resistance (AMR) and Insect Pest Resistance in Agriculture, held on October 5-6 at FAPESP’s headquarters in São Paulo, Brazil. 

The event was organized by FAPESP in partnership with the Biotechnology & Biological Sciences Research Council (BBSRC), one of the United Kingdom’s seven research councils, which work together as Research Councils UK (RCUK). Its aims included discussion of advances in research to control antimicrobial resistance and pest resistance to insecticides in agriculture.

A new call for proposals was issued during the event by FAPESP in partnership with BBSRC to support research in these areas.

“The key factor in the evolution of a pest’s resistance to insecticide is selection pressure in the shape of continuous use of the same product without effective implementation of resistance-management strategies,” said Celso Omoto, a professor at the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP) in Brazil.

“As the proportion of insecticide-resistant individuals increases in the field and they in turn reproduce, they transmit the genes responsible for resistance to their offspring, and the insecticide gradually becomes unable to control the population of this pest,” Omoto told Agência FAPESP.

The problem is particularly severe in countries such as Brazil, with tropical agriculture, where corn, soybeans and cotton can be grown all year round. This intensifies the use of insecticides to combat crop pests, and their resistance increases much more rapidly.

“What’s needed is a strategy we call integrated pest management, or IPM,” Moto said. “ The ‘i’ stands for the integration of different control tactics, but in Brazil, people think it’s ‘i’ for insecticide, and out of inertia, they implement pest management using only insecticide.”

According to data from researchers in the area, in the last 12 years, the use of agrochemicals has increased 172% in Brazil, compared with 90% in the rest of the world.

The total spent on agrochemicals in Brazil was R$9.7 billion in 2012, for example. In 2014, it was R$12 billion, with insecticides accounting for R$4.6 billion.

According to Omoto, irrigated farming is one of the factors that have contributed to this growth in insecticide use, which is hindering the control of agricultural pests in Brazil. In recent years, government programs have increasingly offered incentives for the use of irrigation, which enables crops such as rice, corn and soybeans to be grown during the dry season and with high value added.

On the downside, the system gives rise to “green islands” – large areas in which crops and hence pests are concentrated, so that insecticide spraying of the areas concerned is far more frequent than under normal agricultural conditions.

“Selection pressure favoring individuals resistant to insecticide is very strong in these ‘green islands’. And these survivors of insecticide go on to colonize the first crop [of the next season], which is the most important for most farmers,” Omoto said.

GM varieties and other strategies

Rational use of genetically modified (GM) crop varieties engineered to express proteins with insecticidal activity obtained from the bacterium Bacillus thuringiensis (Bt) would reduce the application of insecticide and hence the resistance of pests to the product, Omoto argued. 

Less use of insecticide due to adoption of GM crops to control pests would ensure biological control by allowing these insects’ natural enemies to survive.

“Australia has implemented an IPM program that is a world-class example,” he said. “The program has led to a reduction in insecticide application and permitted the survival of agricultural pests’ natural enemies in croplands, thanks to rational use of Bt technology in cotton growing integrated with other pest management strategies. This can be done in Brazil as well, but only if the Bt technologies available are adequately implemented.”

Growing insect-resistant GM crops without taking other measures for integrated pest management such as the use of refuge areas in plantations heightens the risk of increased resistance because the GM plants concerned continuously express the Bt insecticidal protein, leading to strong selection pressure. 

“Non-Bt plants are grown in refuge areas to produce individuals susceptible to Bt technology,” Omoto said. “They’re crossed with insecticide-resistant individuals to break the resistance of pests to these insecticidal proteins.”

Other pest management strategies were discussed at the event, such as biological control by breeding pests’ natural enemies for release into plantations and by editing pest genomes. 

A group of scientists from Rothamsted Research in the UK have developed a research program called “Smart Crop Protection” to deliver improved detection, monitoring, prediction and control of insect pests, weeds and diseases in real time and to integrate genetic, chemical, ecological and agronomic approaches in “evolution-smart” pest management strategies.

“Some of the program’s principles are that current pesticide-dominated crop protection strategies aren’t sustainable and that next-generation crop protection strategies require new targets and novel interventions,” said Mike Birkett, a chemical ecologist at Rothamsted.