Alabama farmers are expected to harvest about half a million acres of soybeans this year, and while many producers were bracing for the worst in terms of pest control -- especially from kudzu bugs and rust -- luckily for them the worst didn’t happen.

After what seemed like a kudzu bug infestation of plague proportions in 2013, the pest appears to have been staved off for the most part thanks to cold winter temperatures and a parasitic wasp.

“We’ve had a pretty light insect year on soybeans for the most part across the state,” said Tim Reed, Auburn University Extension entomologist, speaking at the recent Central Alabama Crops Field Day. “A cold winter appears to have knocked back the kudzu bug really hard. We haven’t sprayed that many acres, but we did get call recently from Cullman County that some growers there had about 60 acres in four different fields that were severely infested. It was along the Interstate, and that’s what we expect. They tend to be worst where they were initially spread, and they started along the Interstate hitching a ride on cars.”

In late August, Alabama growers were dealing with mixed populations of caterpillars, kudzu bugs and stink bugs. “Those are the main pests we’re seeing out there now. It makes for a difficult treatment decision, but you want to look for 20-percent defoliation and caterpillars being present along with other insects,” says Reed.

If you have a pretty good yield outlook, Reed advises to go ahead and spray your soybeans. “If you spray now, you won’t have a resurgence of your kudzu bugs, but you may have caterpillar problems to come in after you spray. We’ve been fighting soybean loopers at the Fairhope Substation in Baldwin County for about two weeks. We started out with a lot of them, but the beneficial insects took them out. At Brewton, we’ve had a lot of kudzu bugs at the station. We sprayed an insecticide over some soybeans and created a problem with loopers and green clover worms where we’re conducting a trial.”

Thankfully, insect overall insect pressure has been low on soybeans this year, says Reed. Next year might be different, depending on winter weather conditions and how the parasitoid wasp performs on kudzu bugs.

“The parasitic wasps also were slowed down by the severe winter. They started off slow, with less than 1 percent parasitized kudzu bug eggs in June. By July, it had picked up to about 10. Now, we’re seeing about 20 to 25 percent parasitization of egg masses in the field.

“What I’ve observed in the plot work I’ve done is that if you start spraying these kudzu bugs early before you begin picking up immatures, subsequent numbers of immatures will be reduced. Knocking those numbers down in mid to late June really helps.”

At Brewton this year on June 18, Reed says he was running seven adult kudzu bugs per sweep. At Prattville, it was about the same as in 2013, with 16 adult kudzu bugs per sweep across two rows.

“We’ll see if we get a yield reduction. We’re looking at spraying different numbers of times during the year and at different times at Brewton and Prattville to see how that affects the yields.”

Light year for soybean rust

Alabama soybean producers have seen a mixed bag of weather conditions this year, with a wet, cool spring followed by hot, dry conditions in mid-summer, says Dennis Delaney, Auburn University Extension agronomist.

“We had a lot of frogeye leaf spot early on,” says Delaney. “With enough rain, even resistant varieties will be affected by the disease. Growers with frogeye susceptible to moderately tolerant varieties should strongly consider applying a tank-mix fungicide combination at the R3 growth stage before the disease appears in the field. Applying a fungicide after frogeye is observed in a field is not an effective method of controlling this disease. We’ve found that a lot of the disease in the Southeast is resistant to strobilurin fungicides. So we’re recommending that our growers use a mixture of the different chemistries to control it.”

A constant check continues for the presence of soybean rust disease in the state, he says.

“The hard freeze we had during the winter pushed the disease back into central Florida. It has slowly been moving back and was found first in Baldwin County and has since been found in central Alabama. With hot, dry weather in mid-summer, it just didn’t move very much. We have sentinel plots that we check once each week just to stay on top of the disease.”

Looking at soybean seeding rates

Researchers have been taking a closer look at soybean population rates, says Delaney.

“We can start with seeding rate, but we’re interested in the final plant population. Soybean seed costs have been increasing, and where we once paid about $20 for a bag, we’re now paying $55 to $75 per bag. At several locations around the state, we’ve got different seeding rates, and we’re counting plant populations to see what we end up with. In Shorter, we planted in 15 inch rows, plugging every other hole in the drill, and we planted in 7-inch rows. We went all the way from 60,000 seed per acre to 210,000 seed per acre,” he says.

Plant population is the most important thing, says Delaney, and knowing your soil conditions and machinery capability is as important as the actual seeding rate.

“If you’ve got good soil and good moisture, you can cut back quite a bit on your seeding rate. If you’re using one of the older, less precise drills, then you need to bump up the seeding rate to get the desired plant population. And uniformity is probably more critical than actual population. If you have skips in the field, it’ll hurt you more than having fewer plants.

“What we’ve found in the last few years is that with 30-inch rows, we usually can get down to 80,000 plants per acre and still have maximum yields. Sometimes, in dry weather, we need 120,000 plants. You’ve been buying seed with 140,000 seeds per bag. If it’s really uniform, planting in good conditions and in good ground, you certainly can drop it back some. Some drills are very precise like row planters and some are not.”

Because stands were skippy last year, Delaney says he needed between 120,000 to 150,000 plants per acre to get maximum yields.

“We’re trying to refine those recommendations and see how many seed we really need to plant. With seed costs what they are, it would help if we could cut back just 5 to 10 percent.”