As we approach a potential late harvest, the effects of drought on the corn crop in southern Iowa, South Dakota, and other areas in the Midwest are evident. Concerns include ear tip back and potential stalk lodging. On the positive side, many areas of East Central and NE Iowa, N. Illinois, Wisconsin and Michigan have gotten enough rain and crops are excellent, assuming we get enough time to mature the crop before frost. Corn rootworm beetles have been a concern in some fields, especially in continuous corn fields, while Japanese Beetles were troublesome in many areas in both corn and soybean fields. Refuge and conventional corn showed some European Corn Borer damage, but generally less than 2016. This may be a bad year for earworm, unless protected by the Agrisure Viptera® trait.
This year Common Rust is present in many fields, and we have seen the start of Grey Leaf Spot (GLS). Northern Corn Leaf Blight (NCLB) has been slow to develop in Southern and Central Iowa, partially due to warmer temperatures, however I have seen some NCLB in Northern Illinois, where it was cooler and wetter. Due to the recent moisture and humidity, I expect this will be a year with a high incidence of disease, including GLS. It also is a year where leaf tissue is at a premium, due to smaller total leaf area than normal. I am inclined to apply Headline AMP® or a similar fungicide in most corn and bean fields this year. I especially would consider applying fungicides to fields with high residue, fields following cover crops, corn-on-corn fields, low lying fields, or poorly drained fields. I also would apply fungicide to hybrids which are more fungicide responsive for yield and standability. A greater economic advantage exists for fungicide application, if you already need to apply an insecticide. We feel the ideal time to spray a fungicide on corn is around the first brown silk. However if CRW or Japanese Beetle clipping of corn silk occurs, I would apply the fungicide with an insecticide during flowering. Avoid using an adjuvant if applying fungicide before full silk.
Soybean diseases could be prevalent this year in areas with excess rain and fungicidal control may be justified, because we must preserve the limited soybean leaf area in 2017. White mold (WM) could be a problem in wetter fields, but WM may be reduced this year, as it appears soybeans could breathe better since soybeans are generally not be as big as normal.. Due to the high level of SDS last year, continue to monitor fields that are wet during early flower for SDS. SDS management involves seed treatments (Clariva® and ILevo®), improved drainage, and planting highly tolerant varieties such as 3155CRR2 and 2659CLL. We focus heavily on launching improved SDS and white mold soybean varieties.
Insects in corn and soybeans are considerable in some fields this year due to the mild winter. Many Japanese Beetles, and in corn-on-corn fields, a lot of Corn Rootworm (CRW) beetles have been observed this year. Be sure to scout at silk emergence in later planted or variable emerging fields to determine if there is a need to spray insecticide to prevent silk clipping and pollen feeding. If an insecticide is needed, we suggest combining it with a fungicide application due to the current ideal conditions for disease development. This is also a key timeframe for Western Bean Cutworm (WBC) flights. WBC can be quite damaging to the yield and grain quality unless you spray or have genetic control, such as Agrisure Viptera.
We are concerned about the high number of Japanese Beetles feeding in soybean fields as well, especially since many beans are smaller than normal because they struggled with a slow start due to often being too wet around planting and then before roots were well established it often turned off dry.
It also is a good time to do root digs to observe any rootworm feeding. Let us know by the end of July, if you planted Miller Hybrids corn containing a rootworm trait that did not adequately control corn rootworms, as there may be credit given to you from the genetic trait provider.
Thoughts from Ph. D. Corn Breeder and Miller Hybrids Owner, Bob Miller.
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