IPM is a Powerful Tool for Potato Growers

Growers who practice Integrated Pest Management (IPM) can positively impact their crop production and their bottom line.

Integrated strategies offer the strongest protection for potato growers, who need a complete plan for combating every element that threatens their crop. Managing obvious threats like insects, nematodes, diseases, and weeds are often at the forefront of IPM tactics, but taking steps to monitor water management and crop rotation are also important in keeping potatoes healthy and in maximizing yield and quality. Additional components like knowing field history and developing a successful treatment plan help to fortify a successful IPM plan.

As growers work at managing everything—timing and mixing modes or sites of action in chemical applications, selecting healthy seed stock, scouting for weeds and live pests, and even identifying weather events that can have potentially devastating results—they take the power of new technology and put it to work with age-old growing practices. It’s the careful orchestration of each of these things that makes Integrated Pest Management a success. Growers should consider the following best practices for a successful IPM program:

Best Practices for an Effective IPM Program for Potatoes

1. Develop a pest management plan that combats resistance

Prevention is key with potato crops, as many growers know. Plan for the worst, and hope for the best. To do this, collect data from previous years to develop an educated plan for insecticide, herbicide, nematicide and fungicide usage. That data should include:

• soil nutrient condition, with optimal pH of 4.8-5.5 and well drained
• water management issues
• any diseases, nematodes, weeds or insects present
• weather conditions
• previous year’s pest problems and spray program

Part of the plan should employ different modes of action as one way to combat resistance.

“The idea is you’re hitting different generations of the different insects with different modes of action,” says Erik Wenninger, associate professor of entomology for the University of Idaho in Kimberly, Idaho. “When you hit multiple generations with the same mode of action, that increases the likelihood of resistance developing.”

He recommends clustering modes of action. “If you do six sprays per season, do the first and second spray using one mode of action, then for sprays three and four, use another mode of action.”

• Early Season
  
  An important first step involves soil fumigation—a way of ensuring soil health by pretreating the field for soil diseases like Verticillium wilt, pink rot, and others. Fumigation before planting also helps to control nematodes and other parasites.
  
  Use soil sampling to help determine treatment options, looking for things like nematodes. A good month before planting, watch for wireworms, which tend to be present in the soil, Wenninger says. He recommends putting food bait like germinated cereal seed in a trap in the soil to attract these pests. Applying a fumigant can inhibit the growth of powdery scab or Sclerotium stem rot and unwanted nematodes.
  
  If a plant health certificate reveals that there was late blight in the field previously, it’s safe to assume that you have that infection in that seed and need to use a seed treatment fungicide as well.
  
  At planting, apply an in-furrow pesticide based on soil conditions and past diseases. Neil Gudmestad, University Distinguished Professor from North Dakota State University in Fargo, N.D., recommends applying one to four preventative controls to target foliar infections early in the season. “If you’re an irrigated producer, you really need to get some kinds of fungicide on the lower canopy before row closure...in order to establish residue on lower leaves to protect the crop,” he says.
  
  
• In Season
  
  Treat potatoes on a cultivar-by-cultivar basis, depending on their susceptibility to major threats like early blight or late blight. Some cultivars require extra care, and it’s important to make sure you have a good program that includes specialty fungicides for those cultivars to keep disease management under control, Gudmestad says. “If you had a lot of late blight pressure the previous year, and/or an area where there were substantial volunteer potatoes planted right next door, target those areas with specialty fungicides,” he says.
  
  Scouting efforts can help dictate your course of action. As the season progresses, if you find a poor stand with rows that won’t close, you will have a bigger weed problem and will need to adjust your herbicide program accordingly. If you find significant stand loss and can’t replant, other decisions downstream about crop management will need to be made.
  
  Be sure to apply treatments under good weather conditions. For maximum effectiveness, apply herbicides or insecticides under optimum conditions, and water in herbicides promptly when directed. Windy conditions can result in poor spray coverage and/or drift.
  
  
• Post-harvest treatment/storage
  
  As part of your disease resistance management plan, follow a similar approach to pre-planting by testing seed tubers for infections at harvest time, Gudmestad says. Send samples to a lab to identify any diseases present. Post-harvest testing of the seed is definitely something being done more. “In 39 years, we’ve gone through eight or nine major epidemics of bacterial ring rot, which causes wilt and can rot tubers,” he says.
  
  Consider phosphorous acid treatment as potatoes are going into storage, particularly if you suspect that a crop has been exposed to late blight or pink rot, says Trent Taysom, agronomist and research trial manager at Miller Research in Rupert, Idaho. “If you spray that on as potatoes are going into storage, you can prevent breakdown in storage.”
  
  Also be sure to follow proper harvest sanitation techniques, especially if you suspect pests or diseases. The longer tubers remain unharvested after vine kill, the longer the time period available for moths to move into cracks in the soil and lay eggs on and near tubers, Wenninger notes. Be sure to maintain relatively moist soil conditions in such situations to reduce soil cracking, which provides easier tuber access to the moths and larvae.

2. Seed stock

Don’t just rely on your own samples of seed from each field. Get a North American Certified Seed Potato Plant Health Certificate for your seed lot, Gudmestad says.

This is especially critical as new strains of disease appear. “The emergence of Potato Virus Y, which causes tuber necrotic ringspot disease (TNRD) in susceptible varieties, and the emergence of blackleg Dickeya, both serious seedborne diseases, are very important reasons why you need to get a copy of the North American Certified Seed Potato Health Certificate (NACSPHC) for each lot of potato seed you buy,” warns Cornell University’s Cooperative Extension Vegetable Program website.¹

It’s essential to know where your seed is coming from. If you’ve not used a particular seed supplier before, visit the farm and visually inspect the seed potatoes and the general sanitation conditions of the operation, Gudmestad recommends. It’s critical to be sure you’re starting with the healthiest seed, as many diseases can be traced back to seed pieces.

3. Scouting

Hire professionals to scout for insects, diseases, weeds and nematodes. Scouts in the field should set traps and look for aphids, Colorado potato beetle, wireworm, psyllids and other pests and closely examine plants for key diseases like Verticillium wilt, early blight, late blight, black spot, black dot, and white mold.

First, focus on field history. Know the history of your fields and document what previous crops were planted; this helps determine which nutrients might be present (or lacking) in the soil and which diseases, pests and weeds were present.

“When it comes to your own fields, all growers should sample their fields to know what the fertility is—to plan for the crop based on residual nutrients in the soil,” Gudmestad says. Growers also must note any pests or diseases found in ANY crop planted in that field (not just potatoes). This helps accurately determine what pre-planting soil treatment may be necessary.

• Scouting for Pests
  
  WHEN: A good month before planting, watch for wireworms, which tend to be present in the soil, Wenninger says. He recommends putting food bait like germinated cereal seed in a trap in the soil to attract these pests. Then, based on the count of pests, decide whether you could apply an insecticide before planting. By emergence, scout for small pests like the potato psyllid by using sticky traps, ideally on a weekly basis.
  
  “You should be walking the fields, getting a good idea of what’s going and whether populations are increasing or decreasing,” Wenninger says.
  
  Scout for larger pests like the Colorado potato beetle by observing them directly on the plant. You’ll want to note what life stage the pest is in as the season progresses. Treat fields based on pest activity. For instance, with the Colorado potato beetle, you’d apply sprays when most if not all of eggs have hatched. The egg stage provides some protection from insecticides, so the larval stage is more vulnerable than the egg stage.
  
  HOW OFTEN: On a weekly basis, or as often as you can, once plants emerge.
  
  
• Scouting for Diseases
  
  WHEN: On live plants, start scouting as soon as plants begin to emerge from the soil. Pay attention to how uniform emergence is and make note of any stand loss or slow emergence. Symptoms like this can indicate diseases like soft rot or Dickeya blackleg. These diseases can emerge if seed was mishandled in shipping or if seed was planted in colder than recommended temperatures (or sandy soil that heated up too quickly). If you have more than a 10-degree differential between seed temperature and soil temperature, you can get sweating, which can cause rot.
  
  HOW OFTEN: Start within a day or two of plant emergence; continue several times weekly.
  
  
• Scouting for Weeds
  
  WHEN: Before planting, note which weeds are present in the fields, in borders and ditches surrounding the fields, and in adjacent fields. When rows are full, watch for patches within fields that can be spot treated.
  
  HOW OFTEN: Ongoing as plants emerge, particularly before row closure.

4. Crop rotation

Crop rotation is widely used already, but growers may implement a shorter rotation than would be optimal.

“Growers might grow potatoes (in one field) and come back three years later and plant potatoes again when it might be better to come back five or seven years later,” Wenninger says. “Yields can suffer a bit without proper rotation.”

Log previous crops in current fields (and adjacent fields, if possible) to help determine what pests and diseases might be present and to develop a crop rotation plan. Whether you own or rent your land, document and consult planting data back several years (up to a decade) to determine crop history.

Rotating potatoes with other crops, like sugar beets for example, can provide an added benefit. By exposing them to fungicides in the soil that wouldn’t be used on potatoes, they’re exposed to a different mode of action that can combat diseases and weeds while helping to prevent resistance, says plant pathologist Jeff Miller, president and CEO of Miller Research, a firm that conducts scientific research for the improvement of crop production.

5. Water management

Analyze water management strategies; too much water (even just in isolated spots) encourages weed growth and can promote a variety of diseases. Carefully controlling moisture can make the difference between a low-disease/low-pest crop and one that requires additional chemical treatments.

“Growers need to use the ‘checkbook’ method—write down the amount of water you use, figure evapotranspiration rates, and be sure the irrigation can meet that demand without overdoing it,” Gudmestad advises. Factor in predicted precipitation before watering, too. Other helpful factors include:

• Field diagrams. Create field diagrams to note low spots or tree lines where moisture may be more prominent.
• Runoff. Study water runoff patterns to pinpoint places where diseases and weeds are most likely to emerge.
• Irrigation. Consider irrigation methods. Crops should have enough water but not too much; high moisture increases the likelihood of diseases like late blight. Also, monitor chemical mixing and application of fungicides, herbicides and insecticides—to be effective, treatments must be mixed correctly and spread accurately. Doing so maximizes the effectiveness of the treatments and minimizes resistance issues.

6. Post-harvest data

Gather post-harvest data to create next year’s IPM plan. Use data from previous years that includes:

• soil nutrient content
• water management issues
• any weeds, diseases or insects present
• weather conditions like low wind-prone or high moisture-prone areas
• previous year’s pest control program

This provides powerful insight into crop success. Use this data to target insect-, disease- and weed-prone areas with specialized treatments instead of treating the entire field, where possible.

A Look Ahead: What’s on the Horizon

IPM is a melting pot of strategies and statistics. As growers go about their everyday duties of scouting for pests and diseases, they should also watch for new strategies that are on the forefront. Advances in the field that are ones to watch include biotechnology, using a flexible schedule for treatment application, and row spacing.

Biotechnology

Boise, Idaho-based J.R. Simplot Co. has pioneered gene manipulation in the Innate Generation 2 tuber, which is bred for late blight resistance. The Innate Generation 2 potato currently offers a single gene for late blight resistance, but genes can be stacked, so the next generation will have more than one gene for resistance, making it more durable, Gudmestad says.

Flexible Schedule for Treatment

As we move forward, growers will be challenged to reduce the amount of chemicals on their crops because of environmental protection issues and public perception, Taysom notes. It’s about working smarter, not harder, to combat resistance. Targeted treatments based on regional climatic conditions, coupled with fine-tuning treatments via different modes of action will be key.

Row Spacing

Any non-chemical method to balance integrated pest management is worth a look. Some Idaho growers are experimenting with decreasing the space between rows from 34-36 inches to 32 inches, Taysom says. Narrower rows allow for quicker row closure, which helps control weeds in the fields. Large-scale trials of this are not yet happening.

Treatment Options

Applications of Luna Tranquility^® combat potato diseases as part of an integrated pest management program. Luna^® systemically moves into new tissue, including buds and blossoms, to help combat a wide variety of diseases.

Designed to protect against the effects of soil and foliar bacterial and fungal diseases, Serenade^® ASO activates the plant’s natural defenses and results in higher yields. Serenade Opti fungicide and bactericide fights disease-causing pathogens using multiple sites of action—it stops spores from germinating, disrupts cell membrane growth and works to keep harmful pathogens from attaching to the leaf. This three-pronged approach is effective in its effort to combat the disease in multiple stages, and it helps to avoid resistance.

To target nematodes, consider a combination program of Velum^® Prime fungicide and Movento^® insecticide, which together combat these roundworms in the soil, resulting in improved root health and crop quality. These products can be used separately but also make an effective solution as a team.

Seed piece treatment of Emesto^® Silver fungicide helps to ensure healthy potato plants thanks to its focus on building strong plants by targeting seed and soilborne diseases.

Work Cited

¹ MacNeil, Carol. “Cornell Cooperative Extension Cornell Vegetable Program.” How Copper Sprays Work and Avoiding Phytotoxicity - Cornell Vegetable Program - Cornell University - Cornell Cooperative Extension, 31 Aug. 2016, cvp.cce.cornell.edu/submission.php?id=253.