Nov 3, 2016
Suicide hatch crop may be partial answer to eastern Idaho’s PCN dilemma

Can a weed play a role in efforts to help eastern Idaho potato growers rid fields of the pale cyst nematode (PCN) and restore quarantined acreage to potato production?

Idaho researchers Pamela J. S. Hutchinson and Louise-Marie Dandurand have been testing the efficacy of using litchi tomato (also known as sticky nightshade and fire and ice plant) as a non-host trap crop in helping eliminate PCN in some eastern Idaho fields.

PCN is an internationally recognized quarantine pest. For every 20 eggs per gram of soil there can be up to a 1 ton per acre yield loss. The cyst is actually the dead body of an adult female nematode and each cyst can contain several hundred eggs.

PCN eggs only hatch when an appropriate host, such as potatoes, produces an appropriate chemical hatching factor. Without a host present the cysts can remain dormant in the soil for up to 40 years.

According to the USDA’s Animal and Plant Health Inspection Service (APHIS) PCN has been found in the eastern Idaho counties of Bonneville and Bingham. APHIS currently has 9,853 regulated acres, of which 2,897 acres are identified as infested with PCN. Potatoes cannot be grown in PCN infested acres until the fields are cyst free.

Litchi tomato is a non-host trap crop that stimulates egg hatching without supporting nematode reproduction.

Dandurand, director of the University of Idaho’s PCN project in Moscow, has been testing litchi tomatoes’ efficacy as a PCN trap crop in five-gallon micro plots.

“What we’ve done is planted litchi tomato in infested soil with PCN,” Dandurand said. “Then after 12 weeks we take those cysts out. We count how many eggs are left and generally, with litchi tomato, we find 40 to 50 percent reduction in the number of eggs. But then when we take those cysts that have that remaining egg population and plant them with potato and then we take some cysts that have been exposed to just bare soil and plant those with potato to compare the reduction rate between the two, thenthan we find that the ability of the nematode to reproduce on potato after litchi tomato is greatly reduced.”

Dandurand said researchersthat they had seen an 87 percent reduction in the ability of PCN to multiply compared to being left in bare soil.

“We consider that an incredible reduction in the population of PCN after litchi tomato,” Dandurand said.
Dandurand said that in terms of eradicating PCN, there is no one silver bullet and that multiple strategies need to be considered.

Hutchinson, a potato cropping systems weed scientist at the University of Idaho’s Aberdeen Research and Extension Center, is overseeing larger test plots in Shelley that pertain to herbicide management of litchi tomato to contain the weed and prevent proliferation beyond the PCN regulated acres.

For the past two years, 2015 and 2016, Hutchinson has overseen large scale planting of up to 50 acres of litchi tomato in eastern Idaho.

“What happens is litchi tomato sends out a root exudate that stimulates pale cyst nematode eggs to hatch,” Hutchinson said in this video. “The nematodes come over to the litchi tomato roots and they cannot survive, grow and multiply in litchi tomato roots. They can in potato roots, however.”

Hutchinson has a dual role in the PCN research program.

“Growers need to control weeds such as hairy nightshade in the litchi tomato field because you won’t be reducing your viable cyst because it can live off the hairy nightshade,” Hutchinson said. “One of the things I’m working with, as a weed scientist, is how to have a herbicide that controls hairy nightshade, and other weeds, but is safe to the litchi tomato.

“The second part of it is we want to make sure that litchi tomato does not become a weed,” she said. “So we need to be able to control and kill litchi tomato at the end of the growing season and, if we do see some volunteer plants the next year in grain or whatever crop they’re rotating, to be able to kill it fairly easily in the rotation crop.”

Hutchinson and her crew closely monitor the litchi tomato plants and when the plants begin producing berries they apply a chemical vine kill used on potatoes to destroy the plants before they produce mature berries containing litchi tomato seeds.

“When ever you introduce a new species into an environment you want to make sure it doesn’t become a pest,” Hutchinson said. “So we want to make sure litchi tomato doesn’t become weedy.”

By Bill Schaefer

75 Applewood Dr. Ste. A
P.O. Box 128
Sparta, MI 49345


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