How can one farmer clear 60-bu. beans when another, planting on the same day, only gets yields of 50 bu.? Often, the difference comes from small things like variety selection and careful scouting.
Looking back to the 2006 growing season, we lost some “easy” bushels to soybean cyst nematodes (SCN) because of wrong variety selection. Another source of yield loss in Central and Southern Iowa was from bean leaf beetles. Many farmers struggled to clear 50 bu./acre. It wasn't the dry conditions and high temperatures, it was SCN, bean leaf beetles and bean pod mottle virus in Central Iowa in 2006.
Bean leaf beetles were at their highest level since 2002. Some fields near Ames had to be treated twice since the background beetle levels were so high.
Besides significant yield loss, bean leaf beetles also cause tremendous seed quality issues from the high incidence of bean pod mottle virus they transmit. This will be a huge problem for seed companies this year.
In addition to the virus-infected seed, the pod feeding from the second generation of beetles caused moldy seed since seed was vulnerable in August and September from wet weather.
A warm winter with little or no snow cover will lead to high bean leaf beetle counts this year, too. Delayed planting to avoid the over-wintering generation of beetles may help. In 2006, the problem was that even late May-planted soybeans went above the beetle threshold in Central Iowa. And delayed planting lowers yield potential.
However, we can manage them easily by scouting. Just because soybean aphids may not be in your area does not mean you shouldn't scout. Bean leaf beetles cannot reproduce as fast as soybean aphids, but timing is critical, as it is with soybean aphids. It's all about scouting.
For more information on soybean management practices including bean leaf beetles, please visit www.soybeanmanagement.info.