This past week we were able to visit the Lake Preston L.E.A.P. plot and Blunt L.E.A.P. plot. A recent storm event passed through Blunt, SD and we were very lucky to still have the Blunt L.E.A.P. plot as areas near this location had received baseball size hail and strong winds.
As we walked through the plots, we found common smut. Common smut is common where corn is grown, but does not cause significant economic losses. Common smut has galls which are abnormal growths that appear anytime and anywhere on the corn plant that is above ground. Young growing tissue is especially prone. Galls commonly develop on ears, tassels, stalks or leaves. In Figure 1, these galls are developing on the ear which will result in a greater yield loss than if the galls developed in a different location on the plant. The galls are covered with a white to silvery tissue. Later, dark masses develop on the inside of the galls and resembles a wet soil type look. Common smut is most severe when plants are wounded by wind, hail, or by mechanical damage. Rainy, wet conditions may enhance this disease, just like poor pollination and excessive nitrogen fertilization. Common smut can be managed with resistant hybrids, crop rotation, and by maintaining proper soil fertility.
Figure 1: Common Smut
Corn Leaf Aphid
We also found corn leaf aphids at the Blunt L.E.A.P. location. Corn leaf aphids have a green to gray color to their bodies and are small, usually 1/8 inch or less (see Figure 2). They are soft-bodied, and pear-shaped. All aphids have piercing and sucking mouth parts and feed on the sap from the plant. They produce a honeydew type sap that can cover the above ground portion of plants. The honeydew can promote a sooty mold that interferes with plant photosynthesis.
Aphids are not as detrimental to yield in corn as they are in soybean. The biggest impact to yield happens when corn leaf aphids start feeding on the top of the plant and the tassel before pollination starts. After pollination, there is very little effect on yield from damage caused by corn leaf aphids. However, if corn plants are under stress after pollination, damage from corn leaf aphids will affect yield. Knowing how to scout for corn leaf aphids is necessary in order to know your economical threshold and figure out if it is necessary to spray. The best time to start looking for aphids would be just before VT.
Corn Growth Stages: Subdivisions of the V stages are designated numerically as V1, V2, V3, etc. through V(n), where (n) represents the last leaf stage before VT for the specific hybrid under consideration. The first and last V stages are designated as VE (emergence) and VT (tasseling).
The best location to find aphids would be in the whorl of the plant where the tassel is present. A foliar insecticide may be applied in drought stressed fields if 80 percent of the plants have 100 or more aphids present per corn plant when the plants are at VT. After VT, there isn’t much that can be done unless the honeydew is interfering with corn growth.
LEGEND ELITE ADVANCEMENT PROJECTLegend Elite Advancement Project (L.E.A.P.) is our proprietary, in-house research program. It validates data on hybrid genetic performance over time and agronomic placement. Our L.E.A.P. plots are used for product evaluation, selection, and positioning on the right soil type and in the right geography to consistently deliver high value products to growers. Since 2014, we've conducted 85,890 replicated corn trials across 68 locations. As a result of our rigorous testing, we advance only the elite hybrids into our line-up, averaging 19 new products per year out of the thousands we tested.