Skip to main content
ARS Home » Research » Publications at this Location » Publication #70874
Title: RESPONSE OF AN ALS-RESISTANT BIOTYPE OF AMARANTHUS RUDIS TO SELECTED ALS-INHIBITING AND ALTERNATIVE HERBICIDES

Author
item SPRAGUE, CHRISTY - UNIV OF ILLINOIS
item Stoller, Edward
item Wax, Loyd

Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The use of herbicides that kill weeds by inhibiting the plant enzyme acetolaclate synthase (ALS) has increased rapidly in recent years. In some areas in the cornbelt, some pigweeds are no longer controlled with ALS-inhibiting herbicides. Infestations of waterhemp species that are resistant to ALS-inhibiting herbicides have recently increased across the corn belt in fields with a history of several consecutive years use ALS- inhibiting herbicides. We studied both resistant and susceptible common waterhemp (Amaranthus rudis) and found that the resistant plants were not killed with application rates up to 2000 times greater than the normal use rates of chlorimuron. The resistant plants were not killed with high rates of other ALS-inhibiting herbicides such as primisulfuron, halosulfuron, or imazethapyr. The resistant plants withstand the excessive herbicide applications rates because they have an altered ALS enzyme that is not affected by these herbicides. The resistant plants were adequately controlled with normal rates of premixes containing atrazine or dicamba. This information will be very useful to all personnel involved in developing and implementing weed management programs such as growers, crop consultants, researchers, industry personnel, and extension specialists.

Technical Abstract: An Amaranthus rudis Sauer biotype from a field treated for two consecutive years with a chlorimuron + metribuzin (1:6 ratio) premixture was tested in greenhouse and laboratory studies to determine the magnitude of resistance and cross-resistance to four acetolactate synthase (ALS)-inhibiting herbicides. This A. rudis biotype demonstrated >1,920-fold resistance at the whole plant level, and >850-fold resistance at the enzyme level to chlorimuron. This chlorimuron-resistant biotype also demonstrated resistance to two other sulfonylurea herbicides primisulfuron and halosulfuron and was cross-resistant to imazethapyr, an imidazolinone. Additional greenhouse studies were then done to determine if herbicides with other modes of action would control this resistant biotype of A. rudis. Atrazine alone or in combination with ALS-inhibiting herbicides provided excellent control of the resistant biotype of A. rudis. Combinations of dicamba and ALS-inhibitors also provided adequate control. Additionally, premixtures of flumetsulam + metolachlor and dicamba + atrazi furnished excellent control of this chlorimuron-resistant A. rudis biotype.