Weather plays a big role in when and if volunteer wheat appears, but no matter what the weather, growers should vigilantly watch for it, said Kansas State University agronomist Jim Shroyer.
"In some years, it may seem like there will be little or no problem with volunteer wheat at first. But keep watching for it all summer," said Shroyer, who is the agronomy state leader for K-State Research and Extension. "That´s because volunteer sometimes emerges more slowly than in normal years."
Dry soil can be a factor in delayed emergence, but that´s not the case this year in most of the state. High moisture content of wheat seed at maturity can be another factor, which may be a problem in northwest Kansas.
Research on Kentucky bluegrass has shown that the higher the moisture content of seed when it is harvested, the longer the period of post-harvest dormancy. That probably applies to wheat, too, Shroyer said. Post-harvest dormancy is the period after physiological maturity during which seed won´t germinate because of germination inhibitors within the seed. Germination inhibitor activity dissipates with time, and germination promoters become more active. This period of post-harvest dormancy in wheat may last one to two months, depending on variety and environmental factors.
If the grain had high moisture content at maturity and for quite awhile after, volunteer wheat seed can take longer than normal to germinate, he said. The post-harvest dormancy period is longer than usual under these conditions.
"In most cases, however, volunteer may start emerging soon, if it hasn't already," Shroyer said. "Producers sometimes question whether early flushes of volunteer need to be controlled. Volunteer wheat that emerges soon after harvest (as occurs when heads are shattered by hail) is actually a more serious threat than later-emerging volunteer because it permits pests to move directly from maturingwheat to the new volunteer. Moisture loss is also greatest with early volunteer. Therefore, early destruction of volunteer is often beneficial."
In any case, he said, it is critical that all volunteer wheat within a half-mile be completely dead at least two weeks prior to planting. Destroying volunteer after the new wheat emerges is too late.
"Give yourself enough time to have a second chance if control is incomplete," Shroyer added.
More information is available in the K-State Extension publication MF- 1004 "Be a Good Neighbor: Control Your Volunteer Wheat" at: www.oznet.ksu.edu/library/crpsl2/Mf1004.pdf.
Source: Kansas State University news services