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Title: SPATIAL AND TEMPORAL EXPANSION PATTERNS OF HEMP DOGBANE (APOCYNUM CANNABINUM) PATCHES.

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

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/1999
Publication Date: 2/1/2000
Citation: Webster, T.M., Cardina, J., Woods, S.J. 2000. Spatial and temporal expansion patterns of hemp dogbane (Apocynum cannabinum) patches [abstract]. Proceedings of Southern Weed Science Society. 48(6):728-733.

Interpretive Summary:

Technical Abstract: Hemp dogbane is a native creeping perennial in corn and soybean rotations in the Midwest U.S that relies on vegetative reproduction. Field studies determined the inter-season and intra-season expansion patterns of natural patches of hemp dogbane in 1996 through 1998 in Wooster, OH. The field was planted to soybean in 1996 and 1998 and fallow in 1997. Inter-season expansion was measured using a global positioning system with real time differential correction. Intra-season expansion was determined by monitoring emergence weekly. At the conclusion of the season, each patch was divided into 1 m2 quadrats and all shoots were spatially quantified by emergence date. Regression analysis indicated strong relationships among patch size in 1996 and 1997 (r2 = 0.81) and patch size in 1997 and 1998 (r2 = 0.76). Patches less than 20 m2 in 1996 increased by more than 100% in 1997. A regression of the square root of patch radius in 1997 against that tin 1996 indicated that there was an exponential increase in patch size ove this time period (r2 = 0.89). However, patches decreased in size 6 to 51% between 1997 and 1998. Analysis indicated an exponential reduction in patch size from 1997 to 1998 (r2 = 0.95), likely due to a mid-August mowing in 1997. This late season mowing corresponded to the late flower to early fruit stage of this weed, a time when carbohydrate levels have been shown to be the lowest in the root system. The relationship between patch size and growing degree units (r2 = 0.97) and patch size and emerged percentage of the final hemp dogbane population (r2 = 0.99) were described by a rectangular hyperbole function. Knowledge of patch size could help growers time weed scouting and(or) weed management practices to account for the later emergence patterns of this species.