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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #108681
Title: SPATIAL AND TEMPORAL EXPANSION PATTERNS OF APOCYNUM CANNABINUM (HEMP DOGBANE) PATCHES.

Author
item Webster, Theodore
item CARDINA, J - OHIO STATE UNIVERSITY
item WOODS, S - OHIO STATE UNIVERSITY

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2000
Publication Date: 11/1/2000
Citation: Webster, T.M., Cardina, J., Woods, S.J. 2000. Spatial and temporal expansion patterns of Apocynum cannabinum (hemp dogbane) patches. Weed Science. 48:728-733.

Interpretive Summary: Most agronomic systems have been focused on managing annual weeds, however perennial weeds are becoming a large problem in areas where reduced tillage has been adopted. Hemp dogbane is a native creeping perennial that grows in patches and is becoming more common throughout the Midwest U.S. Studies were conducted to evaluate changes in hemp dogbane patches over two growing gseasons. We found that patches increased in size between 1996 and 1997. Patches less than 20 m2 in 1996 increased by more than 100% in 1997. However, this growth was not observed between 1997 and 1998; patches decreased in size 6 to 51% over this time period. We suspect that a late-season mowing of the A. cannabinum patches contributed to the decline in patch size between 1997 and 1998. We also found a relation between patch size and growing degree units and patch size and percent of final emerged shoots. Patches were at 50% of their final size on May 27, 1997 and May 14, 1998, a time when only 22% of the A. cannabinum population had emerged. Knowledge of patch size and expansion could help growers time weed scouting to account for the later emergence patterns of this species as well as assist in timing appropriate weed management efforts. This information could also be used in conjunction with aerial photographs to project potential patch size for site specific management of this weed.

Technical Abstract: Apocynum cannabinum is a native creeping perennial that is an increasing problem in reduced tillage crop rotations throughout the Midwest U.S. Studies were conducted to measure the inter-season and intra-season expansion patterns of natural A. cannabinum patches over two growing seasons. Regression analysis indicated strong relations between patch sizes in consecutive years 1996 to 1997 (r2 = 0.81) and 1997 to 1998 (r2 = 0.76). Patches less than 20 m2 in 1996 increased by more than 100% in 1997. However, this growth was not observed between 1997 and 1998; patches decreased in size 6 to 51% over this time period. We suspect that a late- season mowing of the A. cannabinum patches contributed to the decline in patch size between 1997 and 1998. The relations between patch size and growing degree units (r2 = 0.97) and patch size and percent of final emerged shoots (r2 = 0.99) were described by hyperbolic functions. Patches swere at 50% of their final size on May 27, 1997 and May 14, 1998, a time when only 22% of the A. cannabinum population had emerged. Knowledge of patch size and expansion could help growers time weed scouting to account for the later emergence patterns of this species as well as assist in timing appropriate weed management efforts. This information could also be used in conjunction with aerial photographs to project potential patch size for site specific management of this weed.