Warm winter poses unique crop threats
It's been a warm winter in much of where the nation's corn, soybean and wheat crops are grown. And, it's been dry...a lot of farmers are heading into spring with a lot less soil moisture than a year ago.
In addition to the risks those conditions alone pose to potential crop output this year, other risks, like increased pest pressures, could eat into yield potential.
Warmer winter temperatures alone don't exclusively mean more bugs. A lot depends on how much snow cover there's been throughout winter, as well as the intended crops and when they'll be planted this spring, according to Ohio State University Extension field crop entomologist Ron Hammond.
"The area where warmer temperatures can, and probably will, impact field crop insects concerns when the pests might show up and require scouting," Hammond says, adding much depends on the number of heat units accumulated. "The time for scouting will probably come earlier in the season. We would recommend sampling to determine the actual need for treatment. Then, there are the many insects that migrate from southern areas, so their development is affected by weather conditions further south, e.g., black cutworm, true armyworm, potato leafhopper. Whether they migrate earlier or not into Ohio will depend on the weather conditions later this spring."
Then, there are the insects that can overwinter in the Corn Belt. The warmer winter weather could have 1 of 2 distinct outcomes. First, if the pest -- like the corn flea beetle, for example -- start to actively feed before the crop's planted or mature enough to offer enough of a feedstock, it could mean an early demise. If the crop is off and running, though, potential crop damage could be worse than normal.
"A few years ago, we saw soybean aphids hatch earlier on buckthorn, their overwintering host, because of warmer temperatures, but suffer significant mortality because of a late spring freeze," Hammond says. "There is one crop pest that we specifically tie into winter temperatures, corn flea beetles and their ability to vector Stewart’s bacterial wilt. Because of the warmer temperatures during December, January and February, more corn flea beetles are expected, and thus, the potential for greater Stewart’s bacterial wilt."
Dry soils & pest damage
Now, add in drier-than-normal soils. If some insect pests get an early start on account of the warm winter and spring, any shortage of soil moisture could worsen potential damage, says Iowa State University Extension agronomist Mark Licht.
"If we go into planting dry, what does that do to insect pressures? Corn rootworm pressure tends to be more damaging when it's dry. Any damage is potentially higher when it's dry," he says. "With corn aphids and soybean aphids, if we stay dry into July and August, they can be more damaging because they're sucking moisture out of the plant."