The Potato's Bat-phone

Blight Hotline an Important Tool

Published in the June 2013 Issue Published online: Jun 14, 2013
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A boundary in a test plot infected with late blight, where fungacide application ended
A boundary in a test plot infected with late blight, where fungacide application ended


Late blight remains an ever-present threat in all of America's potato-growing areas, so when conditions are right for Phythophthora infestans to take hold and cause a late blight outbreak, it's vital for growers to know whether the disease is in their area-and whether or not to spray.

The Late Blight Hotline has long been a 24-hour-a-day resource for growers in Idaho, Michigan, North Dakota, Oregon and Washington.

"I think it's a really important tool," says Phil Nolte, Extension Seed Potato Specialist at the University of Idaho. "It's a source of information that's as close as your cell phone-and it's information you can trust. We're able to share the latest information that can be updated within a matter of hours."

After several years of low pressure from late blight, growers have lost the fear of the disease that grew in the wake of devastating outbreaks in the 1990s, notes Phil Hamm, Professor Emeritus at Oregon State University. But that doesn't diminish the need for the Hotline, he adds.

"We've seen over the last few years fewer folks concerned about late blight, but that's because we haven't had what I call a `late blight year,' with conditions that favor the pathogen," he says. "If late blight becomes a problem, the Hotline becomes very important. When late blight starts to appear, the Hotline is used quite heavily by growers throughout the region."

In North Dakota, University Distinguished Professor Neil Gudmestad points out that the Late Blight Hotline can deliver a great deal of vital information in a single call.

"Most important, it helps growers understand the dynamics of the disease as it develops over the season," Gudmestad says. "It also gives them guidance as to when they should initiate a fungicide program, whether they should go out with a protectant product like Bravo or, if it's intensifying, if they should move to a more active fungicide like Revus Top. We can recommend whether they should be decreasing their interval from a seven-day schedule to five days, or if they can increase the interval to 10 days. Growers need to know if they're in a hotspot for late blight development when the disease is developing."

At this stage, knowledge is vital to keeping late blight in check, adds Dennis Johnson, Extension Plant Pathologist at Washington State University.

"Late blight is a disease that can be spread very rapidly with the right weather conditions, so it is best managed on a regional basis. It's important to know whether it's present and where it is. Then people in an area with the disease need to intensify their sprays, be monitoring more and probably shorten the intervals in their spray applications."


Commitment to the Industry

Since the 1990s, Syngenta and its legacy companies have sponsored the Late Blight Hotline to keep growers and fieldmen advised on the latest in late blight model results and on-the-ground tracking. It's part of the company's commitment to the potato industry, says Crop Specialist Kiran Shetty at Syngenta Specialty Crops.

"It's a commitment we made to help keep growers informed," he says. "We also learn from what's happening out there and make adjustments in our research and recommendations based on what we hear back from the field."

Johnson agrees that the Hotline has been a great source of insight for research into late blight.

"We have been able to collect some epidemiological data from this, and increase our knowledge and understanding of the disease," Johnson says. "Things like this don't happen unless there's funding."

Gudmestad agrees. "If it weren't for Syngenta's support, the Hotline wouldn't exist," he says.

Hamm adds that the Hotline, though sponsored by Syngenta, is very even-handed about which fungicides it recommends. "This is really a service to the industry by Syngenta," he says. "If they didn't do these things, it just wouldn't get done."


Model and Scouting

Between June and September, state extension teams use the BlightCast model, which takes into account temperatures, relative humidity, leaf wetness and stage of crop development to predict the chance of a late blight outbreak. The states also scout fields and confirm reports of late blight in the field-an important role in helping growers spend their crop protection dollars wisely, Nolte points out.

"It's information you can trust," he says. "We're not going to set off any false alarms. We're not going to call late blight `till we confirm it. It's happened in the past that rumors spread and people sprayed when they didn't need to. That can have a profound effect on how much money you spend, and you're also using a product that isn't appropriate."

Johnson says he's seen the same thing in Washington.

"The only thing that spreads faster than late blight is a rumor about late blight," he quips. "That can cause a big problem with people putting on chemicals when they don't need to."

In Michigan, the Late Blight Hotline augments online tracking and Twitter updates on the disease, notes William Kirk, Associate Professor of Plant Pathology at Michigan State University. Telephone access helps keep growers apprised of the status of the disease whether or not they typically use the Internet.

"What we try to get is 100 percent saturation in the potato market," says Kirk. "The Late Blight Hotline is another tool to help us achieve that. What we'd also like to do is get tomato growers to tune into the Hotline as well."


Late blight begins to appear in potato leaves
Late blight begins to appear in potato leaves.

One-Stop Shop

In Idaho, Nolte says, the Late Blight Hotline covers more than just late blight. "We're calling it the Late Blight Hotline, but it's really a pest hotline," he says. "It's one-stop-shopping in Idaho for green peach aphid reports and other plant disease like zebra chip."

The North Dakota Hotline takes a similar approach, says Gudmestad. He, Gary Secor and their team post scouting reports on early blight, green peach aphid and leafhopper on the Hotline as well as news on late blight.

Late blight control starts with a good seed treatment labeled for control of the pathogen, notes Shetty, because the disease can be spread by infected seed. Cull pile management and volunteer potato control are also vital to minimizing the pathogen load. Fields with a history of soil-borne late blight should receive a protectant, and if the disease appears on newly emerged vines, a curative program is in order. If BlightCast predicts an outbreak or scouts find late blight in the field, alerts are posted on the Late Blight Hotline and growers in affected areas can initiate their programs.

In addition to making timely applications, selecting the right fungicides for control of late blight is key, adds Shetty. A late blight program should consider application of an appropriate seed treatment to protect against seed-borne infection. This is good insurance to start with. Thereafter, the growers should access the Hotline information for their respective areas or consult with local experts in the industry. It is mandatory that a strict resistance management program must be implemented against this disease. It is now incumbent upon people to read the label of each product carefully and abide by rotation guidelines."

The Late Blight Hotlines can measure their success in the number of acres that didn't suffer outbreaks of the disease, notes Johnson in Washington.

"Outbreaks the last couple of years have been moderate-the potential was high, but because we were on top of things, we were able to manage it," he says.

As online resources build, scouts tweet via Twitter and alert growers to keep late blight from boiling over into a huge problem. Shetty says the industry still needs to keep a close eye on the disease using every tool at its disposal.

"The pathogen is evolving in front of us-we can't get complacent about it," warns Shetty. "But growers are well-equipped and informed. With due diligence, we can keep late blight in check." PG

A tuber infected with late blight
A tuber infected with late blight