A number of insects could be on producers' and retailers' radar for the 2009 soybean growing season. However, predicting which ones will be the season's key pest and which won't is like betting on a blackjack hand. Only the right combination of weather will create the winners and losers.

The closest to a sure bet though, will likely be the soybean aphid. This invasive pest has become the biggest insect threat to soybeans since its discovery in the U.S. in 2000. The challenge for 2009 will be determining how big of a threat these aphids could become.

"If the alternating boom/bust trend of soybean aphid infestations holds to the trend of the past few years, we could expect a heavier infestation in 2009," said Christian Krupke, Purdue Extension field crop entomologist.

However, it is believed that the soybean aphids' pattern may have been interrupted last year. "We thought 2008 was going to be a quiet year for soybean aphids, but it turned out to not be so quiet. And we're not 100 percent sure why," said Matt O'Neal, assistant professor, Department of Entomology, Iowa State University. "Iowa had a wet, cold spring followed by delayed planting and more insecticide sprays were made than ever before. We think the spraying affected the soybean aphids' natural enemies. As we go into 2009, the natural enemies may not have been able to recover. Then what used to be an on/off cycle could be switched to 'on' all the time."

Krupke agrees that this year could break the normal pattern. "Any organism that is introduced to an environment eventually reaches equilibrium with its environment and establishes a more consistent pattern. We are still within the first decade of understanding soybean aphids. 2008 may have been the tipping point year for them."

Kevin Steffey, Extension entomologist, University of Illinois, agrees that 2009 looks to be difficult for predicting soybean aphids. "The cycle could have been broken in 2008," he said. "Many acres were infested in 2008. We used to be able to predict their movements broadly based on the number of winged aphids captured in suction traps in the fall. However, very few were captured in 2007 yet we saw a major outbreak in a year when we weren't supposed to.

"In the fall of 2008, there were large numbers of winged aphids in traps. Few aphids have been found on buckthorn, their overwintering host plant. It is suspected that a fungal disease may have significantly reduced their numbers."

Bean Leaf Beetles and Japanese Beetles
Although soybean aphids are the insect most people will be watching for, it's important not to forget a few other pests that may still pose a problem for soybeans in 2009.

Bean leaf beetles are one pest to watch. Like the soybean aphid, bean leaf beetles have typically had an on/off pattern, said O'Neal.

"We never take bean leaf beetles off our radar," Steffey said. "Typically we expect their populations to be down after a particularly cold winter because they overwinter above ground. We had a cold winter in Illinois this year so there should be fewer bean leaf beetles to start off the season. However, early-planted soybeans are particularly attractive to bean leaf beetles when they come out of hibernation."

In addition to bean leaf beetles, Japanese beetles are becoming an increasing nuisance to producers. Iowa had more Japanese beetles in 2008 than the state had ever seen before. O'Neal said 30 counties were added to the state's roster of infested areas.

"In the past, Iowans have not had to budget an insecticide for this pest, but as this pest spreads throughout Iowa, more producers may need to consider a treatment," O'Neal said.

Japanese beetles are expected to continue spreading west, but entomologists have discovered that the beetles do not do well in sandy soils. Those types of soils will prevent the spread of the beetles.

Japanese beetles have been problematic in Illinois for the past several years and are expected to pose problems in some areas again in 2009. Steffey indicated that Japanese beetles overwinter as grubs and soil temperatures below 20 degrees F increased grub mortality. However, even though it was considered a cold winter in Illinois, soil temperatures may not have dipped as low as above-ground temperatures because of the snow cover.

"We had a lot of snow this year," Steffey said. "And snow tends to insulate the ground. So we won't know whether they survived well until they begin to emerge in June."

Two-Spotted Spider Mites and More
If the weather turns dry for three to four weeks in mid- to late summer, it could lead to an outbreak of two-spotted spider mites. O'Neal reminds retailers and producers that timing is important because the eggs of these mites are not affected by insecticides, but only by ovicides. These mites can cause major problems if not treated, but they can't be predicted ahead of time.

In addition to two-spotted spider mites, stink bugs could be a problem for more southern states. Although they are not a huge threat to most Midwestern states, Louisiana has seen up to five applications in a season to control them, said O'Neal.

Another pest, Steffey said to keep an eye on is called the Dectes stem borer, also known as the soybean stem borer.

"This pest has always been around, but it's starting to get noticed more by researchers in Kansas," Steffey said. "Recently researchers have noticed an upsurge in their numbers, but are unsure why these pests are increasing."

Steffey said this pest isn't expected to be a huge problem in 2009, but considers it to be a pest of interest for the future.

Ultimately no one can predict the next big threat to soybeans. Soybean aphids were a complete surprise when they arrived. The key is to scout early and often for pests so they can be controlled if necessary.