Field experiments were established to evaluate weed control with AC 263,222 alone and in combination with imazaquin or imazethapyr. Addition of AC 263,222 to either imazaquin or imazethapyr resulted in additive or synergistic increases in control of johnsongrass, pitted morningglory, and entireleaf morningglory. Reducing the rate of imazaquin from 140 to 18 g ai ha−1 did not reduce control of johnsongrass or pitted morningglory when AC 263,222 was added at 18 g ai ha−1 and above, compared to 140 g ha−1 imazaquin alone, through 8 weeks after treatment (WAT). When 9 g ha−1 or more AC 263,222 was added to imazethapyr, reducing imazethapyr rate from 70 to 9 g ai ha−1 did not reduce control of johnsongrass or pitted morningglory through 8 WAT. Adding 9 g ha−1 or more AC 263,222 to various rates of imazaquin or imazethapyr 2 and 8 WAT additively or synergistically increased control of johnsongrass, pitted morningglory, entireleaf morningglory, and tall waterhemp compared to those herbicides applied alone. Soybean injury increased 2 WAT when 35 or 70 g ha−1 AC 263,222 was added to most rates of imazaquin or imazethapyr, but was less than 15% in all treatments by 8 WAT. Visual soybean injury did not translate into a yield loss, and an increase in weed control often resulted in increased yield.

Experiments were conducted at the Lacombe and Lethbridge Research Stations to determine tralkoxydim activity at two leaf stages of green foxtail and wild oat and to determine tralkoxydim activity in tank mixtures with bromoxynil and thifensulfuron. Green foxtail and wild oat control was usually better when tralkoxydim was applied at the 2- to 3-leaf stage. However, tralkoxydim applied at the 4- to 5-leaf stage of the weeds often led to less weed topgrowth at harvest because later flushes of green foxtail and wild oat often occurred after the early applications. Nevertheless, wheat and barley yields usually indicated the importance of early weed removal. In greenhouse and field tank mixture studies, thifensulfuron antagonized tralkoxydim activity on green foxtail more than wild oat. Bromoxynil was less antagonistic than thifensulfuron, but significant reductions in green foxtail and wild oat control were detected in tralkoxydim tank mixtures with bromoxynil. In field studies, control of false cleavers with thifensulfuron or bromoxynil was not reduced in tank mixtures with tralkoxydim.

Four-year cropping sequences of continuous cotton, cotton-soybeans-soybeans-cotton, continuous soybeans, soybeans-grain sorghum-soybeans-grain sorghum, and cotton-rice-cotton-rice were treated each year with high and low levels of herbicides to control johnsongrass. High levels of herbicide were necessary to control johnsongrass in continuous cotton, cotton-soybeans-soybeans-cotton, continuous soybeans, and the soybeans-grain sorghum rotation. Johnsongrass was not eradicated, however, after 4 years of cropping sequences with high herbicide inputs. Both low and high levels of herbicide coupled with water management required for rice production controlled johnsongrass and prevented rice yield reductions.

Interactions of water-soluble soil organic matter (WSSOM) with the herbicides bromacil, metribuzin, alachlor, diquat, and paraquat were examined to determine if these interactions can improve predictions of herbicide leaching potential. A high-performance liquid chromatography gel filtration column was used to separate WSSOM extracts from four mineral agricultural soils into fractions with approximate log molecular weights of 4.96 to 6.82. WSSOM fractions were predominantly anionic in nature with some hydrophobic character. The amount of paraquat bound by WSSOM ranged from 1.1 to 2.1 mmol g−1DOC−1 with KDOC (partition coefficient for dissolved organic carbon) values from 0.050 to 0.187 L kg−1. Diquat was bound at 0.9 to 1.5 mmol g−1DOC−1 by the extracts with KDOC values from 0.044 to 0.143 L kg−1. Bromacil, metribuzin, and alachlor did not bind to the extracts tested. WSSOM did not increase paraquat solubility in the presence of soil. Binding of these herbicides to WSSOM in the soils used in this study would not be a significant mechanism for increased mobility and groundwater contamination potential.

An isolate of Fusarium moniliforme (Sheldon) (JW #1) was discovered on greenhouse-grown jimsonweed in Mississippi, U.S.A., in 1990. Applications of aqueous suspensions of spores/mycelia (>1 × 107 propagules ml−1) grown on potato-dextrose agar to the potted soil in which 2- to 4-wk-old jimsonweed plants were grown caused local lesions or mosaic-like patterns on the leaves and inhibited growth. Application of lesser doses to the leaves only produced no visual effects. When the fungal suspensions were applied at higher dosages (>1 × 107 propagules ml−1) either by soil drench or subirrigation, symptoms such as local lesions or a mosaic-like pattern on the leaves appeared and plant growth was inhibited. When the fungus was grown on an autoclaved rice medium and the ground mixture applied to jimsonweed plants, the plants wilted within 24 h and died after 48 h. Crude and cell-free filtrates of the fungal-rice culture also killed 1- to 2- and 3- to 4-week-old plants after 24 to 72 h. A major toxin identified was fumonisin B1, isolated from fermented rice at 400 μg g−1. Fumonisin B1 applied in water at 2.5 μg 100 μl−1 to excised jimsonweed leaves caused the same symptomology (i.e., soft rot diffusing along leaf veins) within 24 h as the cell-free extract or the crude culture filtrates. Similar damage occurred to intact plants treated with crude or cell-free filtrates or purified aqueous fumonisin B1 solutions.

In field experiments conducted from 1985 to 1987 in Mississippi and Arkansas, jimsonweed was successfully controlled with the fungus Alternaria crassa (Sacc.) Rands. Conidial applications of the fungus provided an average of 96% control in Mississippi, and 87% control in Arkansas. Mycelial formulations were less effective than conidial applications overall, but during periods of favorable environmental conditions, weed control provided by the mycelial formulations was similar to that provided by conidial preparations. These results indicate that Alternaria crassa has potential as a mycoherbicide for controlling jimsonweed.