Physiological characteristics of herbicides and management of Old World climbing fern (Lygodium microphyllum)

Absorption and translocation patterns were determined in Old World climbing fern [Lygodium microphyllum (Cav.) R. Br.; OWCF] using the three herbicides most commonly used for management of this plant by land managers in Florida. Using 14C-labeled herbicides, absorption and translocation were evaluated for glyphosate, metsulfuron, and triclopyr in OWCF using five different application scenarios (cut and spray, basal spray, 25% foliar spray, 50% foliar spray, and 100% foliar spray). Triclopyr was absorbed to the greatest extent (60.3%) of applied radioactively compared to glyphosate (31.2%) and metsulfuron (19.8%). The majority of radioactivity remained in treated leaves for all herbicides with only small percentages of the absorbed radioactivity being detected in other plant parts. All three herbicides translocated acropetally and basipitally to some extent. Radioactivity, for the most part, translocated evenly throughout the plants but the greatest amount of radioactivity derived from triclopyr occurred in rhizomes when the cut and spray and basal applications were used. The radioactivity in rhizomes derived from glyphosate was greater in those treated using cut and spray. Based on autoradiographs, there was limited horizontal movement of any herbicide in the rhizomes of OWCF which may explain why re-sprouts are observed several weeks following treatment.;OWCF gametophytes were highly susceptible to metsulfuron with ≤ 1.4% survival at concentration ≥ 27 mg a.i./l. Inhibition concentrations of OWCF gametophytes exposed to metsulfuron were 6.1 and 26.4 mg a.i./l for the I50 and I95 values, respectively. Survival of treated gametophytes that developed into sporophytes was ≤ 0.014% at concentration ≥ 27 mg a.i./l, but no sporophytes developed at concentrations ≥ 432 mg a.i./l. Inhibition concentrations of OWCF sporophytes were 5.6 and 24.1 mg a.i./l for the I50 and I95 values, respectively. Based on the total number of OWCF gametophytes treated that developed into sporophytes, the tolerance level for a concentration of 216 mg a.i./l metsulfuron is 2.0 x 10-5. This indicates that the potential for tolerant OWCF populations is high using lower concentrations as no gametophytes developed into sporophytes at the standard field treatment concentration of 432 mg a.i./l. Spores of OWCF were highly susceptible to metsulfuron, but exhibited tolerance to imazapyr, glyphosate, fluroxypyr, asulam, and triclopyr exposed in bathing solution. Spore germination rates were 0.4% for spores exposed to 0.1 g a.i./l of metsulfuron, but 0% for rates ≥ 0.2 g a.i./l. Reduction in spore germination was observed with all other concentrations of herbicides tested, ranging from 10.4% with triclopyr (40.0 g a.i./l) to 42.6% with asulam (4.2 g a.i./l) compared to 47.9% germination for untreated checks. Metsulfuron also exhibited residual activity on OWCF gametophyte development, growth and survival on agar containing a concentration of 0.4 g a.i./l of metsulfuron compared to untreated checks. These results may explain why greater control has been achieved with metsulfuron for control of OWCF.;Aerial and ground applications of metsulfuron on Everglades tree islands were more effective in reducing OWCF cover than aerial and ground application of glyphosate. Both herbicides resulted in significant non-target damage to ground cover. There was a reduction in native climax species ground cover and an increase in ruderal species ground cover at the end of the study. High tree survival and limited reductions in canopy cover were observed on tree islands treated with metsulfuron, while low tree survival and large decreases in canopy cover were observed on tree islands treated with glyphosate. Based on the results of this study, metsulfuron should be aerially applied to for initial control of OWCF and followed up with ground treatments using glyphosate or herbicides with other modes of action.