AMES, Iowa – With the current drought conditions for U.S. growers in the Midwest and the Appalachians this spring planting season, “this is a tale of two areas,” said Dennis Todey, agricultural meteorologist, and director of the USDA Midwest Climate Hub in Ames, Iowa. 

“Southern areas of the Corn Belt into most of Pennsylvania, West Virginia, and Virginia, are outside of drought categories now,” Todey said. “Conditions range from slightly dry to slightly wet. In most of these areas, soils are in pretty good condition for starting planting. 

“For northern areas of the Midwest (Interstate 80 is a decent dividing line), drought conditions are a little worse,” he added. “Soils are drier and drought categories are abnormally dry to moderate drought. These are still not too problematic at this point in the season.”  

He said the serious areas for drought are from northwest Iowa into the Dakotas.  

“Northwest Iowa has carry-over problems from last year,” he said. “The Dakotas have carry-over problems, but have missed out most of the storms since last fall. Temperatures have been warm, along with windy conditions, and some very dry air, which has dried soils quickly even after rains.”

According to Michael Santos, account executive for G&S Business Communications in Raleigh, N.C., the recent weather will go down as the driest end to March in six years for the Corn Belt, which could create issues for U.S. soybean growers such as the plant pest soybean cyst nematode as they begin to plant this spring.

According to Iowa State University, soybean cyst nematodes are microscopic, parasitic worms that burrow through soybean cells, injecting foreign compounds through hypodermic needle-like mouthparts, altering the basic biology of the cells on which they feed. 

In fact, these shape-shifting worms grow so large, they burst out of the tissues within which they reside. 

“First off, soil moisture is needed to allow pre-emergence herbicides to work,” said Greg Tylka, Iowa State University professor of plant pathology. “Farmers will need to be on the lookout for possible poor early season weed control, and adjust post-emergence herbicide applications accordingly if pre-emergent herbicides turn out to be less effective than normal.

“Soil moisture also is needed for seed germination,” he added. “Soybeans might need to be planted a little deeper this year than normal to reach moisture in the soil. But great care should be taken to not plant so deep that it compromises the emergence of the soybean seedlings.”

He said his concern at this time of year with soybean cyst nematodes is whether the dry soil conditions will persist throughout the growing season. 

“Soybean cyst nematodes feeding on soybean roots stunt the root systems, and having smaller-than-normal roots is a bad thing during drought conditions,” he said. “Smaller root systems explore less soil for water, and so the effects of drought on a soybean crop are magnified in soybean cyst nematode-infested fields. 

“But additionally, soybean cyst nematode reproduction in dry soils is greater than in soils with adequate moisture,” he added. “The biological basis of this phenomenon is not known, but the phenomenon is very consistent. Soybean cyst nematodes (are) most damaging in drought years, and soybean cyst nematode management is more important than ever in such years.”

Virgil Schmitt, Iowa State University field agronomist in southeast Iowa, said the counties he covers do not have soils dry enough now to be of concern. 

“However, in areas of dry soils, soil moisture stress will exacerbate yield losses due to injury from soybean cyst nematodes,” he said.

He said the key to soybean cyst nematode management is to plant varieties with excellent resistance. 

“There are nematicides that can help a little, but genetics is the key,” he said. “I know most seed has already been purchased, but if the varieties selected do not have excellent resistance to soybean cyst nematodes, they can still be replaced by varieties that do have excellent resistance to soybean cyst nematode.”

Tylka said soybean cyst nematode management is all accomplished before planting. 

“Farmers should review or double check their soybean cyst nematode management plan for 2021, if time permits,” he said. “A drought year is no time to ‘roll the dice’ with soybean cyst nematode. 

“The nematode definitely will reproduce well, and cause increased damage and yield loss in dry years,” he added. “Farmers should be growing soybean varieties that are known to have good resistance to soybean cyst nematode.” 

He said a great majority of soybean varieties have soybean cyst nematode resistance from a breeding line named PI88788.

As a result of use of this resistance for decades, soybean cyst nematode populations in many Iowa fields, for example, have developed increased ability to reproduce on PI88788 resistance. 

“So if at all possible, farmers should seek out and plant soybean varieties with the uncommon ‘Peking’ soybean cyst nematode resistance,” he said. “But such major changes in planting plans may not be possible at this late date.  

“Finally, there are seed treatments available that offer some added protection against soybean cyst nematode,” he added. “Farmers should consider using one of these seed treatment products on soybean seeds as a way to bolster protection against soybean cyst nematodes.”