Late-Planted Beans Face Bug Attacks

Late-Planted Beans Face Bug Attacks

With the significance of Ohio's wet spring fresh in farmers' minds, an Ohio State University expert recommends extra vigilance when scouting fields for soybean pests this summer.

Ron Hammond, an entomologist with OSU Extension, recommends producers be especially mindful of two particular insects this season: bean leaf beetle and soybean aphid.

"Scouting for the bean leaf beetle is more for the growers that happened to get in early this year, where they're the only ones who have an early-planted field in a fairly large area, like a county or township," Hammond says.

Those early-planted fields served as trap crops, playing host to the overwintering beetles that came out in spring. While the beetles normally might spread across several fields in the same area, absent the normal planting progress, the overwintering insects gathered instead in the few fields where farmers planted in the typical timeframe.

"If farmers went into those early fields a month ago, they'd have seen a lot of feeding," Hammond says. "Those growers need to be cautious now because the first true generation is just starting to come out, and some of those fields may have a large population feeding."

Bean leaf beetle pressure would not normally worry Ohio farmers because they would not cause enough feeding to be of economic concern. This year, however, affected fields could be riddled throughout the entire canopy because of the unusually late planting.

But perhaps a larger looming concern is soybean aphid appearance later this month and early next. Aphids were not a major issue in Ohio last year, but Hammond expects a more significant showing for the 2011 crop.

"I've tended to believe in Ohio in the two-year cycle for aphids and it looks like that will hold true again this year," Hammond says. "We're starting to see fields in Ohio where aphids are already emerging."

He acknowledges, however, that not every area of the state, nor any given field in a region, will be affected by an aphid infestation. Farmers, he says, must be vigilant in late July and early August to avoid economic impact of aphid pressure on a plant population.

Because plants are later developing than normal due to later planting, they are physically smaller than at this point in a normal growing season, and potentially more susceptible to damage.

"With the kind of insects we're going to deal with this year, if the plants stay relatively short and we get a lot of beetles, they'll be more susceptible to feeding simply because they don't have as much leaf area for feeding," Hammond says. "The same is probably true of aphids, too."

Most areas of the state could use an inch of rain to boost plant growth. Most areas of Ohio are experiencing soil dryness in the root zone, holding back plant potential.

With some timely rains, Hamond says, plants will really start growing, belaying some of his concerns for insect feeding in the latter part of the season.

"The insects will come out at their normal time, most likely, but we'd like to see more plant growth to handle that insect pressure. On the other hand luckily, the early-planted fields where we'll likely see bean leaf beetles have a lot more leaf area than do most of the soybean fields across the state."

 

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