Kansas State University and University of Queensland researchers join forces to combat insect pest

Anna Whitfield and Ralf Dietzgen

Researchers at Kansas State University and the University of Queensland in Australia have joined forces to attack and control a microscopic pest that can be devastating to the fruit, vegetable and flower industries.

Ralf Dietzgen, an associate professor in agriculture and food innovation at the University of Queensland, is spending three months at K-State as a Fulbright Senior Scholar in a quest to gather data and develop control measures for the small insect known as thrips.

Dietzgen is working directly with plant pathology professors Dorith Rotenberg and Anna Whitfield, who are co-directors of the Center of Excellence for Vector-Borne Plant Virus Disease Control.

Not known to grow larger than 3 millimeters, thrips are voracious eaters, using their asymmetrical mouths to puncture the surface of food crops, flowers and leaves and suck up their contents.

Of equal concern to researchers is that thrips are vectors, or carriers, of more than 20 viruses that cause plant disease, especially the tospoviruses, which also multiply in thrips. Given the right conditions, such as those found in greenhouses, thrips can reproduce exponentially and form large swarms that can transmit viruses to healthy plants.

“They’re very challenging to control, for several reasons,” Whitfield said. “For one, the insect is hard to kill. It is resistant to many insecticides. You can’t just spray crops and hope to control the spread of thrips and tospovirus.

“But secondly, the viruses that thrips can spread are very diverse and can change quickly. I call tospoviruses the influenza of the plant virus world. The predominant virus threat may change because they can switch genome segments and can develop resistance to control measures based on genetic changes. So the viruses have a lot of diversity themselves.”

Whitfield said Dietzgen’s lab in Australia is one of a few in the world that studies viruses that replicate in insects and plants.

“The thrips are a significant pest and have an impact on food security and then on top of that they transmit viruses which cause disease symptoms on the produce, like ring spots, which make them unmarketable,” Dietzgen said.

He noted that when thrips feed on flower buds, the developing fruits often become misshapen. “So you have peppers that are crooked and unmarketable,” Dietzgen said.

“We are studying thrips and the viruses they transmit at the molecular level with the goal of developing applied control strategies,” Whitfield said. “We think that better understanding the molecular mechanisms of the interaction is essential for developing sustainable control strategies for thrips and tospoviruses.”

Dietzgen recently saw first-hand the devastation that thrips-transmitted viruses can cause. One Queensland grower who provides fresh tomatoes for a large supermarket chain lost most of his crop one year due to a tospovirus transmitted by thrips. The lost crop was valued at more than $500,000.

“By the time the grower saw the disease effects, the thrips had moved on and the virus had been left behind,” Dietzgen said.

“The virus that Ralf is studying isn’t in the U.S. just yet, but thrips insects are able to move around easily so that they could appear hidden in a shipment of produce,” Whitfield said. “Any shipment of vegetables or plants that is traveling around the world could have similar pathogens and pests in it. As a control measure, we are trying to develop broad spectrum, durable resistance using different technologies.”

While Dietzgen’s stay at Kansas State University is relatively short, the researchers hope their new partnership will help lead to long-term solutions for agriculture.

“Both of our labs have generated large sets of genomic data that we’re starting to compare during my stay,” Dietzgen said. “By doing that, we hope to come up with potential targets for pest and disease control for longer term crop protection. We are asking, ‘What are the functions of these potential molecular targets and can we interfere with them?’”

Rotenberg and graduate student Derek Schneweis have compiled large sets of data outlining the messenger RNA molecules in thrips. Whitfield said their work may give new insight into how to control thrips in horticultural crops, as well as how to protect those crops from tospoviruses and other plant disease.

The prestigious U.S. Fulbright program is the largest educational scholarship of its kind, and was created after World War II by U.S. Sen. J. William Fulbright. It operates between the U.S. and 155 countries.

More than 20 Fulbright Scholarships are awarded each year to Australian students, postdoctoral researchers, academics and professionals to pursue studies or conduct research in the United States.

In 2014, Kansas State University became the first U.S. educational partner of the Australian-American Fulbright Commission. Each year since, the university has hosted Fulbright Scholars from Australia to study and collaborate with Kansas State University researchers.

Kansas State also helped form the Oz to Oz program to encourage exchanges with faculty at Australian universities, often as seminar speakers.