Tillage and Herbicides Affect Burcucumber Management in Corn

and burying the seeds of large-seeded species can increase germination due to better seed-to-soil contact The effect of tillage and herbicide application timing was examined (Clements et al., 1996). In no-till systems, the majority on established populations of burcucumber (Sicyos angulatus L.) in corn (Zea mays L.). The field study consisted of three tillage regimes of weed seeds are found near the soil surface (Buhler (moldboard plow/disk, chisel plow/disk, and no-tillage) and three her- and Mester, 1991; Yenish et al., 1992). bicide treatments: atrazine (6-chloro-N-ethyl-N9-(1-methylethyl)- Field studies demonstrate that burcucumber seeds 1,3,5-triazine-2,4-diamine) plus the dimethylamine salt of dicamba; can germinate from depths of 15 cm (Mann et al., 1981). 3,6-dichloro-2-methoxybenzoic acid applied preemergence (PRE) or This suggests that vigorous tillage, such as moldboard postemergence (POST); and no atrazine plus dicamba (no broadleaf plowing, may not prevent seedling emergence. Dor- herbicide). Postemergence treatments were applied to 3- to 6-leaf mancy of burcucumber seed is common and caused pri- corn and cotyledon to 8-leaf burcucumber. In two of three field loca- marily by an impermeable seed coat (Mann et al., 1981). tions, late-season burcucumber dry weight was approximately 65% Research with velvetleaf (Abutilon theophrasti Med- less in no-tillage than in the moldboard plow treatment, while no icus), which has a similar dormancy mechanism, has difference in burcucumber dry weight was observed between chisel plow and no-tillage treatments. Regardless of tillage system, atrazine shown that germination does not readily occur on the plus dicamba applied POST was more effective than PRE applica- soil surface (Buhler and Oplinger, 1990). Under no-till tions. Corn grain yield was not affected by tillage treatment, but was conditions, burcucumber seeds could experience higher higher in both the PRE and POST treatments than in the no broadleaf mortality rates on the soil surface due to poor seed-to- herbicide treatment. Depth of burcucumber seedling emergence was soil contact, germination and subsequent desiccation, examined in the greenhouse. Pre-germinated burcucumber seeds were predators, and parasites (Fround-Williams et al., 1981; placed in the soil at 0, 1, 3, 5, 10, 15, and 20 cm deep. Percent emergence Reader, 1991; Roberts and Feast, 1972; Zorner et al., was highest in the 1 to 5 cm depth. Less burcucumber emerged from 1984). depths of 10 cm or greater or when burcucumber was placed on the Herbicides are an important component of weed man- soil surface. These data suggest that tillage and herbicide timing can agement programs. Atrazine applied PRE has been the influence burcucumber control.