Coaxing Them Out of Their Cysts

U of I researchers find natural ways to hatch and kill the pale cyst nematode

There are few natural enemies that can drain Idaho’s economy like the pale cyst nematode (PCN). When these microscopic worms are found in a field, potato production must stop. Then a years-long process begins to treat and deregulate the field for potato production.

Worse, few options for treatment are available.

Enter Matt Morra and Louise-Marie Dandurand in the University of Idaho’s College of Agricultural and Life Sciences (CALS). They are collaborating on a project to find innovative and environmentally friendly ways of combatting this reviled potato pest.

Their promising weapons: mustard seeds and litchi tomatoes.

“Mustard seed meal extract has nematicidal properties, and it also contains a chemical compound that enhances egg hatching,” said Morra, a professor in the Department of Soil and Water Systems. Morra is an expert in environmental chemistry and was able to isolate and produce these beneficial compounds for potential commercial use.

Dandurand is a research associate professor, nematology expert and director of U of I’s Pale Cyst Nematode Project. She conducted trials to measure the effectiveness of Morra’s compounds.

“Eggs are the survival structure for PCN and are protected by a cyst, which is the wall of the dead female,” Dandurand said. “They can sit there protected for decades waiting for a hatch stimulus to come along. An opportune time to kill them is when they hatch.”

Testing the Results

In a U of I research greenhouse, Dandurand is now studying the effectiveness of Morra’s hatching compound when combined with a trap crop: the litchi tomato. The plant’s roots emit a natural substance that coaxes the pale cyst nematode to hatch. However, the roots do not allow the pest to reproduce.

Dandurand says that litchi tomato can be an important tool to stop PCN reproduction. The pest’s population can increase by up to 35 fold in a single season when present in fields where potatoes are grown. Introducing litchi tomato plants in those same fields can decrease PCN populations by 25 to 50 percent in a season.

When properly timed and combined with litchi tomato plantings, Dandurand says the hatching and nematicidal compounds can deliver an effective and environmentally friendly one-two punch to the pale cyst nematode.

“Eggs are the survival structure for PCN and are protected by a cyst, which is the wall of the dead female,” Dandurand said. “They can sit there protected for decades waiting for a hatch stimulus to come along. An opportune time to kill them is when they hatch.” – Louise-Marie Dandurand

“All this works in the lab. We can even achieve up to a 100 percent kill rate if we apply enough of the nematicidal compound,” Dandurand said.

Thanks to these promising trials in the lab and greenhouse, Dandurand and Morra are taking their research to the field, where they will study various combinations of timing and applications in outdoor test plots during the 2018 growing season. The Idaho State Department of Agriculture is reviewing an invasive species permit to allow for the litchi tomato field trials.

“It’s exciting to see these compounds going to larger scale trials,” Morra said. “Not long ago, these compounds were being distributed from a beaker. Soon they’ll be distributed from a tank.”

A Growing Need for Solutions

The pale cyst nematode was first found in the United States in 2006. Since then, Federal and State Departments of Agriculture have been working with the Idaho potato industry to quarantine and eradicate the PCN infestation and restore exports lost after the pest’s detection in other countries.

From 2007-2014, the primary tool for PCN eradication was methyl bromide, a soil fumigant. In 2015, the USDA’s Animal and Plant Health Inspection Service ceased methyl bromide fumigations in response to public concerns.

With few chemical fumigant alternatives remaining, new approaches are needed. Dandurand and Morra hope their combination of biopesticides and cultural practices using the litchi tomato will one day achieve wide adoption.

“Chemical options not only kill the pale cyst nematode; some can kill both beneficial and non-beneficial microbes,” Morra said. “Natural solutions tend to be safer and can be equally effective — while also helping potato growers satisfy the demand for organic foods.”

About the Pale Cyst Nematode Project

The University of Idaho Pale Cyst Nematode Project was started in 2011 to combat the threat of PCN. The program conducts research to support a major PCN quarantine and eradication effort led by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA-APHIS). The project supports these efforts in part by conducting viability bioassays of nematode cysts recovered from fumigated fields. Also through the program, scientists at the University of Idaho, Cornell, Connecticut Agricultural Experiment Station (CAES), Institut National de la Recherche Agronomique (INRA), Agriculture and Agri-Food Canada (AAFC), The James Hutton Institute (JHI), and USDA Agricultural Research Service are investigating novel alternative eradication strategies, including the use of trap crops and biopesticides, either individually or in combination. Through the Globodera Alliance (GLOBAL) Project research is also under way to develop potatoes with resistance to PCN. Research for the U of I Pale Cyst Nematode Project is financially supported by the Idaho Potato Commission, Northwest Potato Research Consortium, Idaho State Department of Agriculture, USDA-APHIS, USDA-ARS, and USDA-NIFA.

Specific federal grant-funded sources include:

• “Pyramiding biofumigants and trap crops for eradication of Globodera pallida,” was funded under USDA National Institute of Food and Agriculture (NIFA) grant No. 2017-51102-27271. The total amount of federal funds for the project is $499,998, which amounts to 100 percent of the total cost of the project.
• “Risk Assessment and Eradication of Globodera spp. in U.S, Production of Potato,” was funded under USDA National Institute of Food and Agriculture (NIFA) grant No. 2015-69004-23634. The total amount of federal funds for the project is $3,200,000, which amounts to 100 percent of the total cost of the project.
• “Farm Bill: PCN Eradication,” was funded under USDA Animal and Plant Health Inspection Service grant No. FAIN: AP17PPQFO000C375. The total amount of federal funds for the project is $441,000, which amounts to 100 percent of the total cost of the project.
• “Farm Bill: PCN Immunity,” was funded under USDA Animal and Plant Health Inspection Service grant No. FAIN: AP17PPQFO000C376. The total amount of federal funds for the project is $410,000, which amounts to 100 percent of the total cost of the project.

Article by Phillip Bogdan, Office of Research and Economic Development
Published in May 2018