High soybean prices might shift the economic threshold for treating pests to a lower level. If you spray more often, take steps to prevent resistance from developing.
Insect and disease control is a game you can win
One of the most rewarding—yet challenging—aspects of farming is that you’re always learning. In 2011, higher soybean prices put a twist on soybean insect and disease control.
"With $14 soybeans, versus $6, you have to look at things differently," advises Farm Journal Field Agronomist Ken Ferrie.
First, higher soybean prices lower the economic threshold for treatment, which makes scouting and quick response pay dividends. Second, more frequent treatment increases the need to manage pesticides to protect the environment and prevent resistance from developing. Third, scouting must continue late into the season.
"It will pay to treat for pests at a lower level of infestation," Ferrie says. "Soybean prices held at $4 to $6 for so long that some growers—who were trying to be responsible and avoid preventive applications—might not have taken the new economic thresholds into account the past couple seasons."
What makes the process challenging is that resistance is on the rise. "We must be stewards of the tools we have," Ferrie continues. "We can’t throw integrated pest management out the
window just because it requires fewer bushels to pay for treatment. Applying products when we don’t actually need them will speed up that process."
Preventive treatment backfires. This past year, Ferrie saw several poorly thought-out treatments backfire.
"Some growers made a preventive fungicide application for disease and included a pyrethroid insecticide for bean leaf beetles," he explains.
"As it turned out, the fungicide and insecticide, which might not have been needed in the first place, eliminated spider mite predators, so mite populations exploded and then they had to spray for mites," he says.
There are two concerns with increasing the number of pesticide applications, says Phil Sloderbeck, a Kansas State University (KSU) Extension entomologist before becoming KSU Southwest Area Extension director. "One is resistance—the more pesticide applications you make, the greater the chance of developing resistance in the target pest," he says. "The second is the impact on other organisms in the system. You might kill parasites and predators in the system. That can release other pests to become problems, or it can allow more rapid resurgence of the target pest, once the initial treatment wears off."
Appoint a pest boss. To effectively manage soybean pests in an environmentally sound fashion in 2012, start by appointing yourself, a family member or an employee as pest boss, Ferrie says. "Equip him with manuals and access to pest management websites, and let him make scouting a priority task. If you don’t have a pest boss available, hire a profess-ional," he advises.
Weather conditions and moisture influence pest problems and will help your pest boss determine if a particular pest is developing to economic levels.
Understand the current economic thresholds for treatment, Ferrie continues. Most land-grant universities publish economic thresholds for various pests, such as the bean leaf beetles table on page 62 from Iowa State University.
"To be responsible and economically efficient, base your treatment decision on the contracted price for your crop, not the price of the day at the local elevator," cautions Anne Dorrance, Ohio State University plant pathologist.
Late-season threats. Don’t ease up on scouting midway through the season. You could be blindsided by late-developing pests, such as bean leaf beetles, aphids and spider mites.
- January 2012