Deeper Look

Nematode management primes potatoes for profit

Published online: Dec 05, 2018 Fungicide, Insecticide, New Products
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This article appears in the December 2018 issue of Potato Grower.

What a potato grower can’t see at planting can be painfully visible at harvest. Nematodes cause the kind of pain that starts with reduced yield and tuber size. The damage can extend to bumps, warts and brown spots that diminish the potatoes’ appearance and spread to the grower’s profit potential.

“Nematodes are ubiquitous, essentially,” says Kelly Luff, a Bayer potato technical representative based in Idaho. “About 30 percent of the Snake River Plain potato acreage is infested with the root-knot species, and about 90 percent has lesion nematodes of one species or the other. A grower needs to keep an eye on his populations, take soil samples and keep them monitored. If nematodes aren’t reduced, the populations can escalate until they are difficult to manage and it becomes unprofitable to raise a crop.”

Nematodes also open the door to disease, increasing the risk of early dying complex.

“Early die is caused by a fungus called Verticillium dahliae,” says Saad Hafez, a University of Idaho nematologist based at the Parma Research and Extension Center. “Root lesion nematodes facilitate disease development by feeding on potato roots and creating wounds where the fungus can enter. There is an interaction between lesion nematode and Verticillium wilt that causes early dying.”

Managing nematodes, then, not only can increase both quality and yield; it can also impact the cost of bringing the crop to harvest and decrease the risk of losing a field to disease.

The first step is learning which nematodes are putting pressure on a field and at what levels. Growers generally sample in the fall.

“Essentially, most acres have a nematode issue of one sort or the other. That doesn’t mean the population meets the threshold for treatment, but it will be there,” Luff says. “So a grower needs to keep an eye on his populations, keep them monitored.”

The economic threshold for treatment varies across states, is specific to the species of nematode, and considers the field history.

“What’s important is whether you have a history of early dying in the field,” Luff explains. “If the field had early dying in the past, the grower just about needs to be treating at any nematode level.”

Plan to Manage Nematodes

Once a grower knows what he’s up against, the next question is which option offers the most efficacious and cost-effective treatment. Many Idaho growers have the option to implement a non-fumigant treatment program, which is preferred for ease of use.

A field under low pressure from nematodes can be treated with a combination of Velum Prime and Movento. At higher nematode levels, the same treatments can be used following a kick-start from a fumigant. Any crop management plan, of course, must comply with label instructions for each material.

Luff recommends two sequential applications of Velum Prime at planting, in ½ to ¾ inches of water, at the  6- to 10-inch plant stage or at row closure, depending on the nematode species and population. Roughly 21 days after the Velum Prime application, Luff recommends treating with Movento, then making a second sequential Movento application 14 days later.

Luff offers an example of a fumigation-based program for both Columbia and northern root-knot nematodes.

“For root-knot nematodes, typically what you want to do is start with a fall fumigation, then apply Velum Prime at planting,” he says. “Depending on the situation, you may want to make another application of Velum Prime at your first irrigation or at row closure.”

Velum Prime and Movento can also be used to augment an oxamyl program. Application timings are flexible depending on nematode and disease pressure in a given field.

Luff also recommends applying a protectant fungicide between Velum Prime applications and ending the season with additional protectant applications. Those fungicides can add disease protection and help with resistance management.

Reaching the Goal: Higher Yield & Quality

“The big advantage of using Velum Prime is the nematode management plus the disease management,” Luff says. “We talk a lot about early dying complex, but we can’t forget early blight and white mold. Velum Prime offers suppression of these diseases.”

Data shows a Velum Prime-plus-Movento program increases yield up to 82 hundredweight per acre. With systemic activity, Movento offers sustained in-season nematode protection and prevents juvenile nematodes from developing. The disease and nematode control offered by Velum Prime add to the return on investment. Velum Prime offers wide-spectrum nematicidal activity and is an excellent management tool for root-knot and root lesion nematodes. Velum Prime also suppresses early blight and white mold. The overall impact of improved root health helps create a healthy bottom line.

Whichever direction a grower takes, the goal is efficient, effective nematode management to improve root health, and thus yield and quality.