Diplodia ear rot this fall has occurred at a lower incidence rate than in the past couple of years in part due to the lack of rainfall/cloudy weather during pollination! Corn on corn is usually the most severely affected, although many 1st year corn fields have an unacceptable level of Diplodia (especially along the edge of the fields).
If an insecticide was added to the fungicide application at pollination time, the incidence of Diplodia was greatly reduced or eliminated. Corn field management this summer that reduced or eliminated Diplodia was correlated with the Japanese beetle feeding on pollinated silks. Japanese beetle feeding in the silks opened up the husk of the ear enough to allow the Diplodia fungus spore into the ear where it could infect the ear at the tip. In most cases, the pollination of the kernels was complete and the length of silk or amount of feeding on the silks did not trigger an insecticide application.
In the photo, the edge of this field has ears with kernels missing from silk clipping and many of the ears infected with Diplodia. The rest of this corn on corn field had an insecticide added to the fungicide application and had an acceptable level of Diplodia.
Japanese beetles live a very mobile life style that moves them from feeding primarily on tender soybean leaves until the first pollinating corn in the area begins to pull them into the corn to feed on the nutrient rich silks. Once the corn silks have dried up, the beetles move back to the soybean fields for more nutritious bean leaves.
Diplodia pressure also tended to be associated with early flowering corn fields in our area in 2011. Early planted corn with early flowering hybrids should be monitored for Japanese beetle pressure, especially if the fields in the area have a history of Diplodia.
To properly manage Diplodia in the future I believe we should now add insect feeding of silks to the disease triangle of host, environment and disease presence.
Did Smart Trio make a yield difference in soybeans?
The yield comparisons in side by side field trials has ranged from 2 to 6 bu. per acre as the harvest numbers are coming in off the weigh wagons.
Yellow soybean flash was the norm whenever Smart Trio was not added to the post herbicide application this summer. This is what I heard from producers, manufacturer reps, and retailers throughout the Midwest as the summer progressed. Soybean metabolism this spring was reduced by spring seasonal stresses of cool and damp coupled with low nutrient concentrations verified by tissue tests.
As herbicides were post applied to the soybeans, the beans displayed a bright yellow flash as the herbicide was metabolized slowly by the soybean. The flash lasted anywhere from a few days to as much as a week depending on the rate, maturity stage, and the amount of sunshine after application. When Smart Trio was added to the post application, the flash was minimized or eliminated allowing the soybean to continue to mature at a normal rate.
Another visual sign was evident in many fields this fall as the beans matured and the leaves began to drop. The areas where the yellow flash was heavy on the end rows of a field and overlapped sprayed point rows did not mature as fast as the rest of the field. This is more evidence that the maturity of the soybean is delayed during a yellow flash event. Yield trials continue to demonstrate the value of reducing crop stress through foliar nutrient applications.
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