Growers who practice integrated pest management (IPM) can positively impact their crop production and bottom lines. 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.
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 potentially devastating weather events—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 IPM a success.
Growers should consider the following best practices for a successful IPM program.
1. Combat Pest 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 pH of 4.8 to 5.5
- Water management issues
- Any diseases, nematodes, weeds or insects
- 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. “When you hit multiple generations with the same mode of action, you increase the likelihood of resistance developing. 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.”
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.
2. Seed Stock
Don’t just rely on your own samples of seed from each field. Gudmestad recommends getting a North American Certified Seed Potato Plant Health Certificate for your seed lot.
This is especially critical as new strains of disease—such as have been seen with PVY and blackleg Dickeya—appear.
It’s essential to know where your seed is coming from. If you haven’t used a particular seed supplier before, visit the farm and visually inspect the seed potatoes and the general sanitation conditions of the operation, recommends North Dakota State University plant pathologist Neil Gudmestad.
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, blackspot, 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.
Growers also must note any pests or diseases found not only in potatoes, but in any crop planted in that field. This helps accurately determine what pre-planting soil treatment may be necessary.
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 a 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 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.
5. Water Management
Analyze water management strategies. 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:
- Creating field diagrams to note low spots or tree lines where moisture may be more prominent.
- Studying water runoff patterns to pinpoint places where diseases and weeds are most likely to emerge.
- Considering 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.