Managing purple nutsedge (Cyperus rotundus) populations utilizing herbicide strategies and crop rotation sequences

Field experiments were conducted in North Carolina hom 1994 through 1998 to evaluate the effects of five weed management strategies and four corn (Zea mays)-peanut: (Aratchis hypogaea) rotation sequences on purple nutsedge (C yperus rotundus) population development. Effects of these weed management p rograms on cotton (Gossypium hirsutum) and peanut production in following y ears were also investigated. Herbicide programs included a nontreated contr ol, a carbamothioate preplant incorporated (PPI) combination treatment util izing vernolate in peanut and butylate in corn, an early postemergence (EPO ST) acetolactate synthase (ALS) inhibitor combination treatment utilizing i mazapic in peanut and halosulfuron in corn, and EPOST treatments of imazapi c and imazethapyr in both peanut and imidazolinone-resistant corn. Crop rot ation sequences for the 3 yr included continuous corn (CCC), peanut-corn (C PC), peanut-corn-peanut (PCP), and continuous peanut (PPP). The imazapic an d ALS inhibitor combination treatments both provided excellent shoot and tu ber control, After 3 yr, imaaapic and the ALS inhibitor combination treatme nt reduced shoot and tuber population densities to less than 10% of the non treated control. Imazethapyr provided variable but better control than the carbamothioate treatment; with tuber densities (measured from 0 to 15 cm so il depth) and shoot densities increasing from 733 to 2,901 tubers/m(3) of s on and 16 to 43 shoots/m(2), respectively, after 3 yr, Tuber densities incr eased in the nontreated control from 626 to 9,145 tubers/m(3) of soil and f rom 962 to SfC64 tubers/m(3) of soil in the carbamothioate treatment during this same period. Also, shoot densities increased in the nontreated contro l from 22 to 159 shoots/m(2) and from 8 to 92 shoots/m(2) in the carbamothi oate treatment. There was a 31% peanut yield reduction from 1994 to 1996 wh en peanut was continuously planted or rotated to corn for only 1 yr. Herbic ide carryover effects were not observed in cotton during 1997.