Beauveria Endophytes Can Curb Grasshopper Pests

By Andrew Porterfield

Grasshopper species, including Dichroplus maculipennis, are common insect pests. They have been known to cause widespread damage to crops such as corn, soybeans, and wheat, by devouring the leaves and stems of targeted plants.

The only means of controlling D. maculipennis so far is with chemical pesticides, which can have environmental consequences. Researchers have therefore been looking for other, biological solutions to reduce the impacts of grasshoppers.

In Argentina, where several outbreaks of D. maculipennis wreaked losses on ranches and farms between 2008 and 2011, a research team led by Sebastian Pelizza of CEPAVE (Central de Estudios Parasitologicos y de Vectores, or Center for Parasitological and Vector Studies, part of the National University of La Plate), looked at the possibility of using the soil fungus Beauveria bassiana to combat D. maculipennis swarms and outbreaks. His study was published on line in April in the open-access Journal of Insect Science.

B. bassiana is an endophyte: It takes up residence in a host plant and thrives without harming the plant. It also is known to be parasitic to insects. It’s often used for biological control of insect pests of agricultural plants, but Pelizza’s study is the first to look at B. bassiana‘s ability to resist D. maculipennis in corn. D. maculipennis is one of 18 species of grasshopper pests found in Argentina but is considered one of the most significant pests, especially in the grassland Pampas region of the country. The region is an important agricultural center for the country, and much of the native grasslands has been converted to grow soybean, corn, sunflower, and wheat. Corn is a major crop for Argentina—about 36 metric tons a year was produced in 2015, and that amount is increasing, thanks to a number of regulatory changes including removal of a corn export tax.

Pelizza’s team inoculated 300 corn plants with B. bassiana fungal strains to test grasshopper consumption of corn plants, 350 corn plants to test grasshopper reproductive ability, and 50 plants to test whether grasshoppers preferred corn with the fungal endophyte. An equal number of control plants did not have the B. bassiana inoculate.

The results showed significant impact of B. bassiana on grasshoppers. Daily consumption of control corn (without the inoculate) was twice that of corn plants with B. bassiana. Grasshopper fecundity was also impacted: females laid only 17.7 eggs during a 15-day feeding period while feeding on inoculated plants, compared to females that laid 27.2 eggs during the same time while eating control plants. Fewer embryonated eggs were seen in females feeding on inoculated plants, too. Finally, many more grasshoppers preferred to feed on control (untreated) plants (more than 300 mg of plant), compared to just 25 mg of treated plants.

The mechanism by which B. bassiana thwarts consumption and preferences of D. maculipennis is not known. The researchers noted also that about 70 percent of dead grasshoppers developed growth of B. bassiana on their bodies. This could mean that the fungus was in the bodies of these insects while they were alive and was affecting reproductive activity and possibly feeding behavior. Further studies are necessary to study this possible mechanism, as well as whether B. bassiana endophytes could produce substances toxic to humans.

“The effects of B. bassiana on consumption, fecundity, and food preferences of D. maculipennis have never been studied when used as an endophyte microorganism in corn,” Pelizza and his colleagues write. “This appears to be an interesting tool that could be considered to control this species of grasshopper pest.”

Andrew Porterfield is a writer, editor, and communications consultant for academic institutions, companies, and nonprofits in the life sciences. He writes frequently about agriculture issues for the Genetic Literacy Project. He is based in Camarillo, California. Follow him on Twitter at @AMPorterfield or visit his Facebook page.