All of the corn fields that I have seen this week look very similar to this one. I am seeing very little (if any) disease pressure.
SO … Do I spray or not? This is literally the same decision that we had to make with our wheat crop this year.
A fungicide application will cost will cost in the neighborhood of $20 – $25 per acre. At the current corn growth stage will this application pay?
Most corn studies have found the greatest yield benefit from a fungicide application to be at the VT (Tasseling) to R1 (Silking) growth stages. Intuitively, this makes sense since this is typically a time of high disease pressure, and the tissues we want to protect most are present and active. The ear leaf and those leaves that are younger are the solar panels that generate the sugars that then fill the grain. These later applications take us further into the season with the protection of this foliage.
Continued scouting is needed, especially in fields with susceptible hybrids and a history of foliar diseases. These 3 diseases are the most prevalent this time of year.
Gray leaf spot: symptoms of GLS include tan, rectangular lesions up to 2-4 inches long that first appear on lower leaves. Lesions are bordered by leaf veins and can turn gray later in season. Infection requires dew or foggy conditions and high relative humidity in the canopy.
Tar spot: this relatively new foliar disease prefers wet weather and moderate temperatures and can progress rapidly under the right conditions. The main signs of tar spot are raised, black spots called stroma that cannot be rubbed off and appear on both upper and lower leaf surfaces. In general, fungicides with multiple active ingredients (AI) are more effective against tar spot and should be applied between VT and R3 in a high disease environment (>5% severity).
Northern corn leaf blight: keep an eye out for tan, “cigar-shaped” lesions (Figure 3) that will expand up to six inches in length across leaf veins. NCLB is favored by high relative humidity and wet, but slightly cooler conditions than those that favor the development of GLS.
Seedling leaves are oar shaped, first true leaves appear lance-shaped and have a minute notch at the tip of the leaf.
Corn growth varies greatly throughout the county, but, more fields are beginning to tassel. As corn begins to tassel, nutrient (K > N > P) and water (0.30 inch per day) demands for the crop are close to maximum. Heat and drought will affect potential number of kernels. Scout for insects (e.g., corn leaf aphid, western bean cutworm, corn earworm, fall armyworm) and diseases (e.g., gray leaf spot, southern rust, northern leaf
VT (Tasseling) – Stage VT occurs two to three days before silking, when the last branch of the tassel is completely visible but silks have not emerged yet from the ear shoot. The plant has reached full height and the pollen shed begins. The time between VT and R1 can vary with different hybrids and due to environmental conditions.
Postemergence herbicide applications – Don’t forget the preharvest intervals (PHI) for grazing or harvest. 
Caused many fields to turn yellow in late June and July. A dry spring delayed nodulation, then heavy rainfall saturated soils just as plants required large amount of N during the rapid growth phase. There is often a lag phase when nodulation and N fixation is insufficient to supply enough N for the plants demands early in the season.
The soybean aphid, a native of Asia, has been in the Midwest since 2000 and has quickly become a serious pest of soybeans in parts of the Midwest.
As with many aphids, the soybean aphid has a complicated life cycle, that requires the presence of its overwintering host, buckthorn. One important feature of the lifecycle is the ability of female soybean aphid to reproduce live, female offspring (clones) parthenogenically during the summer months. This means that soybean aphid numbers can often increase rapidly when conditions are favorable in a soybean field. Soybean aphid are usually found in soybeans from late May through August.
Seedlings: Hairy, often red in color, especially near the base. Cotyledons are narrow and green to reddish in color on the upper surface. Lower surfaces of cotyledons have a reddish tint. First true leaves are alternate, ovate in shape, and are slightly notched at the tip of the leaf blade (apex). Hairs may occur on the leaf margins and along veins, especially along the lower leaf surfaces.
Stem: Stout, erect, branched, and reaching 6 1/2 feet in height. Stems usually have short hairs, especially near the upper portions of the plant.
Leaves: Alternate, ovate in outline, with petioles that reach 1/2 inch in length. Leaves have wavy margins and hairs that occur along the veins of the lower leaf surfaces.
2nd cutting is well underway. Potato leafhoppers are very active. If you haven’t cut yet, continue to monitor, where damage is increasing, cut as soon as weather permits.
Our corn growth varies greatly throughout the county. Some fields are beginning to tassel and some field are at V8.
Soybeans are starting to look a little bit better, however, there are still a lot of “yellow” beans throughout the county. Two possible reasons are 
Wheat harvest has come to an end and most of the straw is in the barn. From what I hear, wheat yields were pretty good with little to no disease issues.
