Submitted to: Integrated Crop Management Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 20, 1995
Publication Date: N/A
Technical Abstract: The common pigweeds of the Midwest can be placed in three distinct groups: 1) redroot pigweed, smooth pigweed and Powell Amaranth, 2) common waterhemp, tall waterhemp and Palmer amaranth, and 3) spiny amaranth, tumble pigweed and prostrate pigweed. The first group has been somewhat more important than the second, and the last group seems to dominate only in specialized niches. The second group has become much more important in the last few years, as it appears that biotypes of these species have evolved resistance to a class of herbicides that inhibit the acetolactate synthase enzyme system (ALS). These herbicides are used on a majority of the soybeans grown in the Midwest at this time and an increasing acreage of corn also is being treated with this same class of herbicides. We are locating these resistant biotypes and developing resistance management strategies for these species. We have also prepared publications about identification of these species, as correct identification among the pigweeds is difficult, but essential. Proper management of these species involves putting together the correct combinations of chemical and non-chemical methods of control and persistently attacking the problem year after year.