July 10, 2009

Illinois corn crops in the silking stage of development are far fewer than the five-year average at this time of year, but the silks of many of the hybrids grown now emerge early and grow aggressively, a University of Illinois report said Thursday (July 9).

The silking stage is when corn crops are ready for pollination, which is when plant yields are set. Under weather stress release of silk tissue can be delayed which can inhibit yields.

The US Department of Agriculture said 5 percent of Illinois corn was silking by July 5. The number is greater than last year's 1 percent of crops silking at this time, but far less than the five-year average of 31 percent. The USDA also said by this time in 2008, 63 percent of the Illinois corn crop was rated good-to-excellent, while currently, only 57 percent of the crop holds that rating.

"This early silk emergence is likely a result of selection in newer hybrids for reduced "silking interval" the period between the time pollen shed begins and first silks emerge," said Emerson Nafzinger, extension agronomist. "So it stands to reason that selection for the ability to pollinate under stress means earlier appearance of silks.... But when we have good pollination conditions, as we have had the past three years, silking can seem early and aggressive."

Corn crops planted at two intervals in April at University of Illinois' test fields have reached silking already and it's expected much of the crop in the rest of the state will reach this stage in the next two weeks.

The early emergence of silks doesn't offer a downside, as rapid silk growth could reduce the effect of insect feeding. "As long as some intact silk is exposed when pollen grains land, the pollination process should proceed normally," the report said.

Leaf disease development is possible with wetness, and Illinois has seen a wet June continuing into July. Still, "when we say that "rain makes grain" we usually refer to rain in July," the report said, offering a positive outlook. Because late planting of the crop means later pollination than normal in many areas, the report said rain will ideally continue into August.