Progress in bioherbicide development has been hindered by the strict moisture and temperature requirements of the living active ingredient. Application of a jute fabric to areas treated with a Sclerotinia minor granular bioherbicide improved broadleaf weed control and broadened the effective application period to include the warm summer season. When turfgrass plots treated with the bioherbicide were covered with burlap fabric for 3 d, broadleaf weed (dandelion, white clover, broadleaf plantain, buckhorn plantain, ground ivy, and prostrate knotweed) control was greatly enhanced. The cover was made of natural jute fibers that retained water but had sufficient transparency to allow 33% light penetration for continued growth of the grass. Virulence of the bioherbicide was maintained under elevated temperatures that would otherwise reduce efficacy. The bioherbicide was ineffective in the summer unless covered, but dandelion density, broadleaf weed ground cover, and dandelion survival were all reduced by the bioherbicide when plots were covered, even if applications were made in July. The efficacy of the bioherbicide was also enhanced under favorable conditions, and covering permitted reduced application rates without loss of efficacy. When applied at a rate of 20 g/m² and covered, S. minor granules exerted significantly greater biocontrol of dandelion than 40 g/m² without covering. Covering for up to 5 d did not cause any adverse effects on the turfgrass. This approach may overcome one obstacle to the commercialization of the Sclerotinia minor bioherbicide, permitting its deployment under challenging environmental conditions.

Nomenclature: Broadleaf plantain, Plantago major L. PLAMA; buckhorn plantain, Plantago lanceolata L. PLALA; dandelion, Taraxacum officinale G. H. Weber ex Wiggers TAROF; ground ivy, Glechoma hederacea L. GLEHE; prostrate knotweed, Polygonum aviculare L. POLAV; white clover, Trifolium repens L. TRFRE.