Exploring a Biological Control Method for Organic Rice in Southern Florida

May 8, 2023
University of Florida researchers sweep rice fields in the Everglades Agricultural Area for the rice stink bug. Photo credit: University of Florida Everglades Research and Education Center.

BELLE GLADE, Florida – For nearly a century, farmers in southern Florida have been using parasitic wasps, rather than pesticides, as the go-to pest management method in sugarcane. Now University of Florida researchers are hoping to perfect the use of biologicals in organic rice production.

In the Everglades Agricultural Area, confined around Lake Okeechobee, sugarcane is king; Florida produces more sugarcane than any other state. But when sugarcane harvest is done, many farmers switch to rice in the crop rotation.

“In this region of Florida, flooding plays a key role in soil sustainability and nutrient management. This is where rice is a great fit,” said Julien Beuzelin, an entomologist at the University of Florida Institute of Food and Agricultural Sciences Everglades Research and Education Center. “But, specifically in organic rice, there are more pests and more yield losses.”

Beuzelin and his colleagues received a $19,982 Southern Sustainable Agriculture Research and Education (SSARE) On-Farm Research Grant to study the efficacy of biological control on the rice stink bug in the hopes of emulating the successful pest management program in sugarcane to control the sugarcane borer using parasitoids.

“The sugarcane biological control program is self-sustaining, but we are not there yet with rice,” said Beuzelin. “We have good environmental conditions for parasitoids because of our warm winters, so using biological control in rice has potential. If successful, the solution for organic production can also be applied to conventional rice.”

rice stink bug eggs on a rice blade
University of Florida researchers check rice stink bug eggs harboring potential parasitoids. Rice stink bugs cause yield reductions by feeding on rice florets and sucking content from rice grain. Photo credit: University of Florida Everglades Research and Education Center.

Rice stink bug damage in Florida is caused by two main species, Oebalus pugnax and Oebalus insularis. Stink bugs cause yield reductions by feeding on rice florets and sucking content from rice grain. In addition, the damage invites pathogens, which result in discolored kernels and poor milling quality.

In the first year of the two-year project, Beuzelin, along with graduate student Carolina Tieppo Camarozano, surveyed both organic and conventional rice fields to determine rice stink bug egg parasitism and predation rates, and to identify parasitoids emerging from stink bug eggs and adults. Camarozano has experience in rearing and handling egg parasitoids.

“We wanted to see what we had in the field,” said Beuzelin. “These surveys will represent the first research step towards understanding the role of natural enemies and how they can be manipulated for rice stink bug management.”

Researchers conducted three surveys for both stink bug adults and eggs – sweeping 9 fields for each survey in both organic and conventional rice in July, August and September of 2022. In addition, they sampled each field by checking plants for eggs harboring potential parasitoids.

Another strategy the researchers evaluated was identifying parasitoids with sentinel eggs. These eggs were laid by adult stink bugs in the lab, then killed so no stink bugs emerged. The eggs were then clipped to rice plants to trap parasitoids.

Rice stink bug sentinel eggs clipped to rice blades.
Rice stink bug sentinel eggs clipped to rice blades to trap parasitoids. Photo credit: University of Florida Everglades Research and Education Center

Preliminary data verified that tachinid flies parasitize adult rice stink bugs, but parasitism was low. “That’s consistent with what was reported in other states, so that’s no surprise,” said Beuzelin. “What is exciting is that we found high parasitism in stink bug eggs by parasitic wasps (Telenomus sp.), anywhere from 60 to 70 percent.”

Beuzelin said that Telenomus sp. is a common parasitoid that is produced commercially as a biological control. “Releasing wasps to increase parasitism and decrease stink bugs might represent a viable area-wide management strategy,” he said. “The ultimate goal of the project is to protect conventional and organic rice yields in Florida while decreasing reliance on pyrethroid applications.” Researchers will repeat the study this year, doubling the sample size and improving the method of trapping parasitoids using sentinel eggs. Field experiments will be conducted during late summer 2023 to determine whether parasitoids released in field cages have the potential to control rice stink bugs under Florida conditions.

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Topics: Biological Control, Organic Agriculture, Pest Management, Rice
Related Locations: Florida, South