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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #106185
Title: APOCYNUM CANNABINUM (HEMP DOGBANE) INTERFERENCE IN NO-TILL GLYCINE MAX (SOYBEAN).

Author
item Webster, Theodore
item CARDINA, JOHN - OHIO STATE UNIVERSITY
item WOODS, SAMUEL - OHIO STATE UNIVERSITY

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2000
Publication Date: 10/1/2000
Citation: Webster, T.M., Cardina, J., Woods, S.J. 2000. Apocynum cannabinum (hemp dogbane) interference in no-till glycine max (soybean). Weed Science. 48:716-719.

Interpretive Summary: Perennial weeds are becoming more common in reduced tillage systems throughout the Midwest U.S. due to a reduction in tillage, reduced rates of atrazine, and the reliance on herbicides with a low efficacy against perennial weeds. As a result, many growers are facing these new weeds for the first time and are unfamiliar with the overall importance of these weeds in terms of crop yield reduction. The second most troublesome broadleaf perennial weed in Ohio corn-soybean rotations is hemp dogbane (Apocynum cannabinum). To provide some answers to the importance of perennial weeds on crop yields, field studies were conducted at two locations to measure no-till soybean yield loss in relation to hemp dogbane vegetative shoot density. Maximum soybean yield loss approached 69, 58, and 75% from densities of 40, 32, and 28 hemp dogbane shoots m-2, respectively. Differences between locations were attributed to rainfall and temperatures with delayed soybean canopy closure and higher yield loss where rainfall was heavy and temperatures were relatively cool. Application of these predictive soybean yield loss equations to field populations of hemp dogbane showed that between 19 and 36% soybean yield loss could be expected from within hemp dogbane patches. These results also challenge the appropriateness of the use of rectangular hyperbole regression for clonal perennial species. Interference studies conducted with annual weed species are appropriately analyzed using this type of regression. However, our results indicate that the biological basis for the use of the rectangular hyperbolic model for perennial weeds is questionable.

Technical Abstract: Field studies were conducted at two locations to measure no-till Glycine max yield loss in relation to Apocynum cannabinum vegetative shoot density. Rectangular hyperbolic functions adequately described the data (r2 > 0.80). Maximum G. max yield loss approached 69, 58, and 75% from densities of 40, 32, and 28 A. cannabinum shoots m-2, respectively. Differences between locations were attibuted to rainfall and temperatures with delayed G. max canopy closure and higher yield loss where rainfall was heavy and temperatures were relatively cool. Application of these predictive G. max yield loss equations to field populations of A. cannabinum showed that between 19 and 36% G. max yield loss could be expected from within A. cannabinum patches. The biological basis for the use of the rectangular hyperbolic model for perennial weeds is questionable.