Morningglory species are among the most troublesome weeds in cotton. Their presence at harvest often results in lint staining and increased leaf trash, thereby causing dramatic reductions in cotton quality. Nine treatments, including a untreated check and a weed-free check, defoliants and herbicide/defoliant combinations were evaluated for their efficacy on defoliation and desiccation of pitted morningglory Ipomoea lacunosa L., in cotton. Additionally, the effects of pitted morningglory on fiber properties and lint quality were quantified.

The experiment was established at the Pee Dee Research and Education Center, Florence, S.C., on a Goldsboro loamy sand with a naturally occurring pitted morningglory infestation. Plots were four rows wide, 30 ft long, and were arranged in a randomized complete block design with four replications. The row spacing was 38 inches. Treatments were applied Sept. 14, 1988 and visual ratings of percent pitted morningglory defoliation and desiccation were recorded two weeks later. The aboveground portion of pitted morningglory plants was harvested from two square meters of a center row in each plot Sept. 27 & 28. Leaves and vines were separated and fresh weights were recorded. Dry weights were recorded after drying for two weeks at 150 F. The two center rows of each plot were harvested with a spindle picker on Oct. 4 and ginned on a laboratory gin to obtain lint for quality determinations.

Roundup(RU)+Folex(F)+Surfactant(S)@32+16+14 oz/ac and RU+Harvade(HAR)+S @ 32+8+14 oz/ac were more effective in defoliating pitted morningglory (83 and 98%, respectively) than the other harvest aids evaluated [F @ 24 oz/ac (0%), HAR+Crop Oil Concentrate(COC) @ 8+16 oz/ac (50%), Gramoxone Super(GS)+F+S @ 11+12+14 oz/ac (40%), GS+HAR+S @ 11+8+14 oz/ac (56%), GS+Prep(P)+S @ 11+21+14 (51%)], and the untreated check (0%) and the weed-free check [defoliated with F+Dropp(D)+P @ 16 oz+o.l lb+21 oz/ac].

Satisfactory desiccation of pitted morningglory vines was not provided by any treatment evaluated. RU+HAR+S had a visual rating of-85%, which was almost twice the rating of any other treatment. However, ratios of vine fresh wt/dry wt indicated no desiccation of vines with any treatment except RU+F+S. Vine desiccation with RU+F+S may be due to greater translocation of RU by pitted morningglory leaves when F was used and no defoliation occurred.

Slight variations in fiber properties were observed, but were attributed to variations in weed populations rather than treatments. Trash content as measured by high volume instrumentation (HVI) was similar in the weed-free check (F+D+P) and where cotton was treated with RU+HAR+S, reflecting the excellent (98%) defoliation of pitted morningglory. The trash content for other treatments was greater than that observed in weed-free cotton. Fiber color as measured by HVI indicated no difference between the weed-free check (F+D+P) and RU+HAR+S. However, the reflectance of the weed-free cotton was significantly higher than the other treatments.

Evidently, RU+HAR+S is more effective in defoliating pitted morningglory than the other treatments evaluated. However, this conclusion is based on preliminary data and the experiment will be repeated in 1989.