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Selective Broadleaf Weed Control in Turfgrass with the Bioherbicides Phoma macrostoma and Thaxtomin A

Wolfe, Joseph C., Neal, Joseph C., Harlow, Christopher D.
Weed technology 2015 v.30 no.3 pp. 688-700
Cardamine, Festuca arundinacea subsp. arundinacea, Galinsoga quadriradiata, Lamium amplexicaule, Oxalis, Passeriformes, Phoma, Poa annua, Rorippa, Rubia, Stellaria media, Taraxacum officinale, Trifolium, Veronica hederifolia, Vicia, auxins, biopesticides, broadleaf weeds, marshes, pendimethalin, recreation areas, turf grasses, weed control
Both regulatory and consumer forces have increased the demand for biopesticides, particularly in amenity areas such as turfgrass. Unfortunately, few natural products are available for selective weed control in turfgrass. Two bioherbicides reported to control broadleaf weeds without injuring turfgrass are Phoma macrostoma and thaxtomin A. Field and container experiments were conducted to evaluate PRE and POST efficacy of P. macrostoma and thaxtomin A on regionally important broadleaf weeds. In container experiments, PRE applications of P. macrostoma provided 65 to 100% control of dandelion, marsh yellowcress, and flexuous bittercress, equivalent to that of pendimethalin. Control of yellow woodsorrel, henbit, hairy galinsoga, common chickweed, or annual bluegrass was less than with pendimethalin. In contrast, POST applications did not control any species as well as an industry-standard synthetic auxin herbicide. PRE or POST applications of thaxtomin A controlled six of the eight species tested as well as the industry-standard PRE or POST herbicides. In field tests, overall PRE broadleaf weed control with P. macrostoma and thaxtomin A peaked 4 wk after treatment at 64 and 72%, respectively, and declined afterward, suggesting that these bioherbicides possess short residuals and therefore must be reapplied for season-long control. Overall POST broadleaf weed control using P. macrostoma and thaxtomin A was only 41 and 25%, respectively. PRE followed by early-POST applications of thaxtomin A provided ≥ 86% henbit control. These results suggest that both P. macrostoma and thaxtomin A are capable of controlling certain broadleaf weeds in turfgrass. However, both lack efficacy on some important weed species, particularly chickweed. Thaxtomin A efficacy on henbit was improved by increased dose and by PRE followed by early-POST applications.Nomenclature: Phoma macrostoma; thaxtomin A; hairy galinsoga (Galinsoga quadriradiata); dandelion, Taraxacum officinale G.H. Weber ex Wiggers, TAROF; yellow woodsorrel, Oxalis stricta L., OXAST; marsh yellowcress, Rorippa palustris (L.) Bess., RORIS; ivyleaf speedwell, Veronica hederifolia L., VERHE; annual bluegrass (Poa annua); flexuous bittercress, Cardamine flexuosa With., CARFL; henbit, Lamium amplexicaule L., LAMAM; common chickweed, Stellaria media (L.) Vill., STEME; large hop clover, Trifolium campestre Schreb., TRFCA; sparrow vetch, Vicia tetrasperma (L.) Schreb., VICTE; field madder, Sherardia arvensis L., SHRAR; tall fescue, Lolium arundinaceum (Schreb.) S.J. Darbyshire, ‘The Rebels', ‘Top Choice'.