Volunteer wheat is worse than normal this year, due to hail damage and abandoned wheat fields, according to Jim Shroyer, agronomist for K-State Research and Extension.
With wheat planting occurring now, volunteer wheat should be destroyed as soon as possible, because it exacerbates the following problems, he says:
- Wheat streak mosaic and associated viruses - Volunteer wheat is often infested with wheat curl mite, which serves as a vector for wheat streak mosaic and High Plains Virus. After planted wheat has emerged, the wheat curl mite populations on volunteer wheat can move onto the planted wheat.
- Hessian fly - Hessian fly pupae (or flaxseed) live through the summer on the stubble and crown of the previous season's wheat crop. The pupae emerge as adults in late summer and early fall, and look for wheat on which to lay eggs. If volunteer is close by, the Hessian fly adults will lay eggs on this wheat, thus maintaining their populations in that area and possibly infesting nearby planted wheat with the next generation.
- Barley yellow dwarf - As with the wheat curl mite, greenbugs and bird cherry oat aphids can infest volunteer during the summer, and move onto planted wheat in the fall. These insects serve as a vector for barley yellow dwarf virus, and spread the disease to nearby fields.
- Russian wheat aphid - This aphid can also infest volunteer wheat during the summer and move onto planted wheat in the fall.
For these reasons, all nearby volunteer wheat should be controlled before planting wheat. If the planted wheat has already emerged and volunteer has not been controlled, caution should be taken.
"In this case, spraying the nearby volunteer with glyphosate will cause the volunteer to die slowly over the course of several days, and wheat curl mites (and other pests) will simply migrate off the volunteer onto the emerged wheat during that time. Where planted wheat has already emerged, it is best not to spray the nearby volunteer with glyphosate to kill it. If conservation compliance regulations permit, volunteer could be destroyed with deep tillage in this situation, however, with minimal impact on mite movement," Shroyer says.
The volunteer could also be left uncontrolled if necessary, but grazed heavily. "Grazing will remove most of the green tissue and help lower the mite and aphid populations. Grazing would likely have only minimal impact on Hessian fly populations, however, because those insects are usually in the lower leaf sheaths or crowns, or below the soil surface," Shroyer explains.
On fields with volunteer, the best option is to control it, then plant a new crop of wheat two weeks later rather than leave the volunteer for harvest, he says. Producers could gain an extra 20 to 40 bushels or more of yield by planting a new crop of wheat instead of leaving the volunteer for harvest.
"Not only that, but they would also help their neighbors out by helping to reduce the chances of wheat streak mosaic, barley yellow dwarf, or Russian wheat aphid on their wheat as well," Shroyer says.
More information on volunteer wheat control is available in the K-State publication MF-1004 "Be a Good Neighbor: Control Your Volunteer Wheat." It is available at county and district K-State Research and Extension offices or on the Web at: www.oznet.ksu.edu/library/crpsl2/Mf1004.pdf.