Bob Nielsen characterizes your yellow, stunted corn, which results from a variety of issues. Among them: excessive rainfall and ponded fields; compacted soil from heavy equipment; light soil color which warms more slowly than dark soil resulting in fewer GDDs; damage from parasitic corn nematodes; seedling blights and fungal issues that erupt when seed treatments wear off, and the shortage of N uptake when wet soils stunt root development.Crop scouting #1. “Crappy looking corn,” is how Purdue’s
Erin Hodgson says consider a foliar insecticide during tasseling and silking if: there are 3 or more beetles per ear, silks have been clipped to less than 1/2 inch, AND pollination is less than 50% complete. If they are in your beans, the treatment threshold is 30% defoliation before bloom and 20% defoliation after bloom.Crop scouting #2. Japanese beetles are hungry and awaiting your corn silks to emerge. They have emerged from the grub stage you noticed while looking for corn rootworms. IA St. entomologist
IA St. specialists say it does not need to be managed, and is different from anthracnose stalk rot. Corn will rapidly grow out of the disease, and the affected lower leaves, which do not contribute to yield, will die and fall off the plant within a couple of weeks.Crop scouting #5. Anthracnose leaf blight is being found on lower leaves, and that is common for a wet spring.
common rust in corn. Most hybrids have resistance, but in-breds do not have resistance and seed production fields should be scouted and a fungicide applied if the disease is present. Common rust is only seen rarely in commercial corn fields, but may be found in seed fields.Crop scouting #6. Producers with seed corn fields should be vigilant for
Soil testing to measuring the concentration of NO3-N and NH4-N remaining in the rootzone is an alternative to guesstimating how much N was lost, say Purdue agronomists.Crop scouting #9. Excessive rainfall and the resulting ponding, flooding, or saturated soils have likely caused some loss of applied and soil-derived nitrogen (N). Nitrate-N (NO3-N) is the form of N most likely to be lost from the crop root zone. Unfortunately, no matter what forms of N are added to the soil, all of them eventually convert to NO3-N.
Crop scouting #12. Do you have more broadleaf weeds that you used to? Are you using less atrazine? Are you using more glyphosate? If you answered “yes” to each, the reason comes from WI researchers, who investigated that long term trend. “The weed community composition consisted of more broadleaf weeds in fields where atrazine has not been used in the recent decade coupled with greater glyphosate use. These results provide evidence of negative long-term implications for glyphosate resistance where growers increased reliance on glyphosate in place of atrazine.”
KS St. researchers have achieved improved control on 8-12” Palmer with mesotrione (Callisto or Tenacity) when sprayed at lower temperatures, such as less than 80° with nighttime lows under 60°. At higher temperatures the plant more easily metabolizes the herbicide and resists the HPPD enzyme inhibitor. That was not the case at lower temperatures. You have to get up early in the morning to beat Palmer amaranth.Crop scouting #13. The magic bullet to controlling Palmer amaranth may be the air temperature at which you spray it.
Mike Marshall. “It all boils down to timing. If you wait a week to ten days to spray emerged weeds, your expected control can drop off significantly, especially with Palmer amaranth. It can take control of a field in a matter of days because of its ability to produce up to 1 mil. seeds per plant. Waiting to address a Palmer amaranth problem, even for a few days, could mean the difference between a clean field and one overrun with weeds.”Crop scouting #14. If you have Palmer amaranth, address that issue immediately, says Clemson weed specialist
get ahead of it before it takes over your fields completely. Control all growing Palmer with tillage or a grammoxone burndown. Consider planting LibertyLink beans until it is controlled. Use a soil applied pre-emergent herbicide such as Valor or Fierce prior to or immediately after soybean planting. Post emergent herbicides such as Liberty must be applied before Palmer is 3” tall. Tank mix that with a residual such as Dual II, Magnum, Warrant, Outlook or Zidua. Follow with additional post-emergent applications.Crop scouting #15. If Palmer amaranth is becoming an issue for you,
MO researchers have worked with genes on 19,000 specimens to get some with flood tolerance.Crop scouting #17. What you need this year is a flood tolerant soybean. It is coming, and will be ready for the next flood, should you know when that will happen. Actually it is a soybean that does better than others on flat land, with heavy soil that drains slowly.