Corn, beans and the pests that came to the party
• Do your corn seedlings show potential herbicide injury? Illinois weed specialist Aaron Hager says there is an increasing number of such reports, but says there may be several reasons:
- Corn hybrids can vary in their sensitivity to certain herbicides although labeled for corn. ALS-inhibiting products are prone to injuring corn, along with other post-emergent ones.
- High air temperatures and relative humidity can favor rapid absorption of foliar-applied herbicides; and environmental stresses can interrupt herbicide metabolization by the corn.
- Rates of herbicide absorption by the corn plant can be increased with spray additives, but those additives should carry labels that indicate potential problems.
- Contaminated spray tanks, containing residues from prior applications such as soybean herbicides from the prior year, can be the cause of herbicide injury to corn.
- Herbicide persistence in the soil, carried over from the prior cropping season, is another source of injury. Those are blamed on insufficient chemical and microbial degradation.
- A high soil pH will tend to slow the degradation of certain chemicals by the process known as hydrolysis. Triazines and sulfonylurea herbicides are particularly susceptible.
- Soil moisture is often the most critical factor in carryover, since many herbicides are degraded by microbial action and such action can be limited in soils lacking moisture.
- With the dry soils of the late 2011 growing season, some herbicides did not fully degrade and the early planting of 2012 may have hurt seedlings before the rotational interval expired.
Numerous insects have the potential to reduce yields this year, and fields throughout the Cornbelt need to be scouted for problems. Although weed issues can be yield-reducers also, there are many problems that might crop up as you prepare to battle weeds. Among those are herbicide injuries, and many farmers are finding that corn plant symptoms are reminiscent of herbicide injury. But it may be in the way that the herbicide was applied and when it was applied.
Source: FarmGate blog