Identify foliar corn diseases

<p>SCOUT NOW: Disease lesions are apparent on this corn leaf in the middle of the plant at tasseling. If weather projections favor disease, experts suggest considering a fungicide application.</p>

<p>MAJOR YIELD ROBBER: Gray leaf spot is prevalent across much of the Corn Belt. Lesions are typically 1.25 to 2 inches long, rectangular, and pale brown, tan or gray. They expand between leaf veins, starting off small and elongating.</p>

<p>LIKES COOLER WEATHER: You’re more likely to see these large,&nbsp;tan lesions of northern corn leaf blight in seasons with cooler temperatures. Under humid conditions, lesions become olive green due to spore production. The Purdue Corn &amp; Soybean Field Guide notes that if lesions form on resistant plants, they may be large with a yellow, transparent, irregular border, and produce fewer spores.</p>

<p>TROUBLESOME NEWCOMER: Tar spot raised eyebrows in 2018 and is still raising them. Look for small, black, raised spots on one or both sides of the leaf. You may find them on green or dead tissue. Leaves may feel bumpy, but the bumps are fungal structures that won’t rub off.</p>

<p>FLIES IN: Southern rust doesn’t overwinter in the Corn Belt but moves northward on storm fronts. Light brown to orange pustules occur mostly on upper leaf surfaces. Initially, surrounding tissue is green, but over time it turns yellow and then brown; then the leaf dies prematurely. When an infection takes hold and conditions favor quick spread, untreated fields can suffer large yield losses.</p>

<p>RIDES IN ON AIR CURRENTS: Common rust also needs help getting into the Corn Belt each year. Look for small, 1/16-inch lesions that are elliptical and brown. Find them on both upper and lower leaf surfaces. Common rust tends to come in earlier than southern rust. Most hybrids have resistance that limits severity of the disease.</p>

<p>CAN HURT INBREDS: Northern corn leaf spot may appear on hybrids, but it is more of a threat to certain inbreds in seed production. Look for small, elliptical lesions that may line up on leaves, resembling a string of pearls, according to the Purdue Corn &amp; Soybean Field Guide. Race 1 can produce tan, oval lesions, but Race 3 is most common in the Corn Belt.</p>

<p>BE AWARE: Anthracnose occurs in both a leaf blight and stalk rot phase. The leaf blight phase is less common. When it occurs, you will see small round or oval lesions about 1.25 to 1.5 inches in size on lower leaves. Warm, wet, humid conditions favor the disease.</p>

<p>SEE THE SHINE: Dark brown to shiny black shoe-polish-like lesions form on the stalk in the stalk rot phase of anthracnose. The disease tends to be worse when stress conditions set in after a favorable start to&nbsp;the year.</p>

<p>SPLIT AND SEE: Stalk rots tend to produce discoloration inside the stalk. This stalk was split to show discoloration starting inside the pith. In some cases, the inside can turn black</p>

<p>RAISING ITS UGLY HEAD: Physoderma brown spot seems to be more common over the past couple of seasons, says Betsy Bower of Ceres Solutions. Small brown to yellow spots develop across the leaf. Banding across the leaf can occur. Infection usually occurs earlier in the season. If you see this disease, be ready to scout corn early and spray early in 2021.</p>