Submitted to: Illinois Agricultural Pesticides Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 18, 1996
Publication Date: N/A
Technical Abstract: Waterhemp, a member of the pigweed family of weeds, has increased greatly in importance in the Corn Belt in recent years and is causing substantial losses in quantity and quality of yields in corn and soybeans. Nine species of pigweeds infest the Corn Belt area and vary in their ability to cause losses to crops. Two species of these are called waterhemps, and these appear to be expanding their area of importance more rapidly than the other species. Misidentification of these species has been common in the past, but correct identification is now more common as a result of a color identification guide we have published in cooperation with weed scientists from Kansas. Waterhemp species have long infested fields in the Corn Belt, but are now increasing rapidly in importance because of several factors, including changing cultural and chemical usage patterns, and the development of biotypes of these weeds that are resistant to the ALS(acetolactate synthase enzyme)-inhibiting herbicides. Waterhemp plants are abundant seed producers, are rather diverse genetically and in appearance, and have the capability to germinate and emerge over a wide time frame within a growing season, whenever hot and moist conditions occur. The increase spread of this species also tends to correlate with increased no-tillage acreage, reduced use of soil-applied herbicides, and in general a variable response to current herbicides.