Agronomy Zebra Chip Update

Zebra Chip Update

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[deck]Researchers are working hard to improve management strategies for the spreading disease.[/deck]

North American researchers are working hard to improve management strategies for a disease that continues to spread.

Zebra chip disease has been a growing issue in the last decade as the potato psyllid continues to migrate further north in the United States. The vector of zebra chip disease is the potato psyllid, an insect that can transmit the disease—however, not all psyllids are carriers of the pathogen.

According to Donald Henne, professor at the Texas AgriLife Research Subtropical Pest Management Laboratory located in Weslaco, Texas, new research has proven that potato psyllids have made their way over the Canadian border this year. “Although a few potato psyllids have been collected from a commercial potato farm in the Carberry, Man., area, they are not carriers of the zebra chip pathogen, at least at this time,” explains Henne. “I did expect psyllids to show up in Manitoba this year, given the very mild winter and spring experienced further south. This allowed psyllid populations to increase and migrate north earlier than usual. As far as I know, this is the first collection of potato psyllids in Manitoba. However, it is not unprecedented to find them this far north. There are old records of potato psyllids from Alberta and Saskatchewan, as far north as Saskatoon.”

“I am not surprised that psyllids are making their way this far north,” says Eugenia Banks, potato specialist for the Ontario Ministry of Agriculture, Food and Rural Affairs. “A couple of years ago I asked an associate researcher if infected psyllids could reach Ontario. And the answer was yes, they might be carried by high winds from the United States and land on potato fields. It was just a matter of time.”

Zebra chip disease can reduce potato yields and quality, which can become economically burdensome to growers. Afflicted tubers form dark stripes when they are cut and fried—the zebra-like appearance that inspired the disease’s name—and render the chips unsellable. No health risks have been connected to the consumption of potato chips infected with the disease. If fields are infected, there are foliar signs to watch for, such as chlorosis, leaf scorching, swollen nodes, vascular tissue browning and curled leaves. However, U.S. researchers are trying to find ways to detect and monitor potato psyllids well before they infect the fields.

At North Dakota State University, Neil Gudmestad, distinguished professor in the Department of Plant Pathology, is part of a team of researchers that is making inroads in monitoring psyllid movement across various states. Their ultimate goal is to provide producers with improved control methods. “The name of the disease, zebra chip, is an unfortunate misnomer,” explains Gudmestad. “It is more appropriate to refer to the disease as the zebra complex.

“The Specialty Crop Research Initiative grant that we obtained through the United States Department of Agriculture’s-National Institute of Food and Agriculture in 2009 has helped us develop a very sophisticated monitoring network,” he says. The network involves sticky traps in native vegetation, he explains, “to monitor the buildup of potato psyllids before the potato crop has emerged, and then to monitor the movement of adult psyllids into fields and the establishment of a population in a potato field by detecting nymphs and eggs.”

This trapping network, which is managed by SCRI participants John Goolsby and Don Henne, helps monitor the network from Texas through to North Dakota. “They also test the adults for the presence of zebra chip bacterium so we know the frequency of adults carrying the pathogen,” adds Gudmestad.

Preventative Measures

Gudmestad admits that zebra chip disease isn’t preventable, but that it has become more manageable thanks to the ongoing research and knowledge-gathering over the last three years since the team received the SCRI grant. “Control measures include [delaying] planting to avoid psyllid populations coming off the overwintering hosts that usually have a high level of bacterium in them, [avoiding] the most susceptible potato cultivars and [using] reduced-risk insecticides to manage the psyllid populations,” says Gudmestad.

Zebra chip has become more of an issue in the United States since it was found at damaging levels in Washington, Oregon and Idaho in 2011. “This region is the largest and arguably the most important potato region in the United States,” emphasizes Gudmestad.

Research is Critical

The SCRI research group has published 96 peer-reviewed research papers on the potato psyllid and the zebra chip bacterium in the past three years. “The research group has also written literally hundreds of other technical bulletins,” says Gudmestad. “Insecticide is only one of a number of management options and the SCRI research group is investigating many others.”

As the spread of zebra chip widens, researchers will continue to intensify their efforts. The team is applying to extend their funding through the USDA-NIFA grant system. “Its continuation is critical to the long-term health of the potato industry and in our continued development of disease management strategies,” says Gudmestad.

Management Tips

  • Scout fields regularly
  • Look for chlorosis, leaf scorching, swollen nodes, vascular tissue browning, curled leaves
  • Remove all volunteer plants
  • Use traps to monitor for psyllids at egg, nymph and adult stages
  • Leaf sampling for eggs, nymphs and adults
  • Sticky cards for adults
  • Sweep nets for adults
  • Use proper chemical controls
  • Neonicotinoid insecticide
  • Foliar insecticide
  • Observe proper timing for planting and applying chemicals
  • Avoid planting susceptible cultivars

The Specialty Crop Research Initiative was established to solve critical industry issues through research and extension activities. Visit  http://www.nifa.usda.gov/fo/specialtycropresearchinitiative.cfm for more information.