Abstract: An experiment was conducted in 1998 and 1999 in southeastern Pennsylvania to examine the effect of tillage and soybean row spacing on burcucumber emergence and growth. A second experiment evaluated postemergence (POST) soybean herbicides on burcucumber control. In the tillage and row spacing study, a glyphosate-resistant soybean variety was planted in no-till and reduced-tillage systems in 38- and 76-cm row spacings. In the POST herbicide experiment, chlorimuron, glyphosate, CGA-277476, thifensulfuron, and several combinations of these herbicides were applied at two different POST application timings in 38-cm row soybean planted in a reduced-tillage system. In the tillage and row spacing study, burcucumber emergence was greatest starting in late May through mid-June and mostly ceased by early July, regardless of tillage system or row spacing. Although there was no difference in germination period in either tillage system, preplant tillage increased the number of emerged plants by 110% in 1997 and 70% in 1998 compared to the no-till system. Row spacing had no effect on burcucumber emergence or biomass production. In general, most POST herbicide programs controlled burcucumber, and there was no difference between early POST and mid-POST application timings. Chlorimuron at 13 g ai/ha, chlorimuron plus thifensulfuron, glyphosate, glyphosate plus chlorimuron, and glyphosate plus CGA-277476 provided 87% or greater control of burcucumber 12 wk after planting. These herbicides reduced burcucumber density and biomass by more than 56% in 1997 and 96% in 1998.
Nomenclature: CGA-277476 (proposed name, oxasulfuron), 2-[[[[[4,6-dimethyl-3-pyrimidinyl]amino]carbonyl]amino] sulfonyl]benzoic acid, 3-oxetanyl-ester; chlorimuron; glyphosate; thifensulfuron; burcucumber, Sicyos angulatus L. #3 SIYAN; soybean, Glycine max (L.) Merr.
Additional index words: Cultural control, emergence period, herbicide application timing, herbicide-resistant crops.
Abbreviations: EPOST, early postemergence; GDD, growing degree days; LPOST, late postemergence; MPOST, mid-postemergence; POST, postemergence; WAP, weeks after planting.
