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Dry conditions have impacted corn

By Staff | Aug 11, 2017

Corn in eastern Sac County shows signs of stress.



The cool down in temperatures and those areas that have received some recent rains have been welcomed by producers, but until the combines roll, no one will know exactly what the lasting effects of the dry and hot weather in July has had on the crops.

Angie Rieck-Hinz, field agronomist with Iowa State University Extension and Outreach, said the corn yields have already been impacted for this year’s growing season, but soybeans could still have a chance.

“For soybeans, moisture in August is crucial,” she said. “If conditions improve, soybeans will continue to flower and new pods will set. However, seeds per pod and seed weight may still be impacted.”

Rieck-Hinz said the Aug. 1 U.S. Drought Monitor showed 67 percent of the state of Iowa was considered abnormally dry, 36 percent ranked as being in a moderate drought and 7 percent of the state placed in a severe drought.

In her region, Rieck-Hinz said, all of Calhoun and Webster, most of Hamilton and parts of Humboldt and Wright are considered to be moderate drought conditions. The next drought monitor report scheduled for Aug. 10 could show some changes.

“With the continued spotty rains cross this area, I would anticipate the dry conditions to creep further east and may even worsen in severity,” she said.

Yield projections

Rieck-Hinz said at this time, it is too early to begin checking yields, especially as dry conditions continue.

“Even though pollination was not too bad during the hot and dry July time period, yield is being compromised now by reduced grain fill, causing kernel abortion near the ear tip and smaller, lighter kernels,” she said. “As we continue in corn development stages, through the dough and dent stage, we continue with decreased kernel weight and premature physiological maturity.”

In corn, she explained, there is stress for four or more consecutive days, that could bring an estimated yield loss of 3 to 9 percent at pollination to blister stage; 3 to 6 percent at the milk stage; 3 to 5 percent at the dough stage and 2 to 4 percent at the dent stage.


Along with the dry conditions, Rieck-Hinz said typically comes insects.

“One pest to scout for during dry conditions is two spotted spider mites in both soybeans and corn,” she said.

Spider mites are small and can be hard to detect. They generally cause small yellow spots on lower leaves of plants and, if severe enough, will cause the leaf to die. You may find webbing on the underside of the leaves.”

Rieck-Hinz suggested consulting a local agronomist for infestation level information and potential treatment options.

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