Prodiamine Suppresses Spreading Dayflower (Commelina diffusa) Facilitating Hand-Weeding in Leatherleaf Fern (Rumohra adiantiformis) Ground Beds

Plots in a leatherleaf fernery uniformly infested with spreading dayflower were treated with prodiamine at 0, 2.2, 4.5 or 6.7 kg ai/ha (0, 2, 4 or 6 lb ai/A) to determine if it would suppress spreading dayflower and make weeding easier without adversely affecting leatherleaf fern. Dayflower suppression was determined by visually estimating weed coverage and by measurement of fresh weight, surface area, leaf number and root length. Morphological changes related to ease of removing dayflower were noted by counting the numbers of normal and stubby roots. By 120 days after prodiamine treatment, spreading dayflower coverage was reduced by at least 66%. Also spreading dayflower fresh weight, leaf number, surface area and root length were reduced by prodiamine and were positively correlated with the force required to remove stem segments from the soil. This weeding force declined logarithmically as prodiamine rate increased and was negatively correlated with the number of stubby roots. Less than 18% of the roots were normal in the prodiamine-treated plots and vine breakage during stem segment removal tests occurred only in the untreated plots. Leatherleaf fern frond color, vigor, and vase life were not affected by treatments.