Purdue News
Purdue News
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June 7, 2001 Cornfields may show problems due cool weatherWEST LAFAYETTE, Ind. – Cool, wet weather has hung over Indiana for the past two weeks, slowing growth and development of the state's corn crop, says a Purdue University Extension agronomist. Bob Nielsen says surface soil moisture has been replenished after the dry beginning this spring. However, some areas have received excessive rainfall and cooler than normal temperatures, causing problems, such as purpling in corn. "Certain hybrids exhibit a genetic response to this combination of factors by turning purple," Nielsen says. "The purpling results from the accumulation of a purple pigment called anthocyanin. Hybrids with more anthocyanin-producing genes will show more purple." The purpling will slowly disappear as temperatures warm, Nielsen says. Nielsen also says slowed root growth in early corn development restricts photosynthetic plant sugars from being used, which causes an excess of sugar in the leaves. This higher sugar level can cause anthocyanin to produce as well. Nielsen says the cause of leaf purpling, not the purpling itself, determines if there will be yield loss. "If the cause of root restriction is temporary, such as cool temperatures, then purpling should disappear as the plants develop, and yield losses should be minimal, if any," he says. "If the cause affects the plant's roots for some time, such as soil compaction, purpling may continue, and yield loss may result if plants become stunted." Once dry, warm weather returns to the state, producers need to be on the lookout for twisted growth of corn whorls, where new leaves emerge. Nielsen says cool growing conditions followed by warm weather and ample moisture sometimes causes corn to show unusual, twisted growth. Whorls of the affected plants are tightly twisted, severely bent and don't unfurl correctly, Nielsen says. If this stage of the problem isn't noticed, the whorls will later unroll, and yellow tops may then be visible across the field. Nielsen says younger leaves trapped inside the twisted upper leaves will be yellow because they were shaded for a long period of time. "In addition to being fairly yellow, the leaves will exhibit a crinkly surface caused by restricted expansion inside the twisted whorl," Nielsen says. "Another day or two will green the plants and the problem will no longer be visible." In the long run, Nielsen says yield effects from twisted growth due to weather-related causes are minimal. Nielsen also is concerned about uneven stands of corn. He says fields that emerged and developed uniformly are now uneven in color and size because of cool temperatures and excessive rainfall. "Uneven stands lead to unfair competition among adjacent corn plants and lower yield potential for the field," he says. "If stand establishment is uneven this year, there is little that can be done about it now. "Any time that germination, emergence or stand establishment are delayed significantly, the developing crop is simply exposed to a lengthier period of stresses." Source: Bob Nielsen, (765) 494-4802, rnielsen@purdue.edu Writer: Jennifer Doup, (765) 494-6682, jdoup@aes.purdue.edu Purdue News Service: (765) 494-2096; purduenews@purdue.edu Related Web site:
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