Application Variables that Affect Efficacy of Disinfestants Sprayed on Different Substrate Materials to Control <i>Colletotrichum siamense</i>

Disinfestants are an important sanitation tool used to eliminate plant pathogens. Disinfestant product labels, as well as university and company literature, provide instructions and guidance for the proper usage of disinfestants, yet recent research reviews have shown that inconsistencies in efficacy occur even when these information sources are followed. The efficacy of hypochlorite, isopropyl alcohol, quaternary ammonium, and peroxygen compounds against Colletotrichum siamense was evaluated relative to substrate porosity, contact time, and disinfestant wettability properties in a series of in vitro studies in which disinfestants were sprayed on six substrates (concrete, galvanized metal, polypropylene ground fabric, polyethylene plastic sheet, pressure-treated pine, and twin-wall clear polycarbonate) commonly found in ornamental plant production systems. Bayesian generalized linear mixed models were used to calculate posterior distributions of the median point estimate and 95% equal-tailed credible intervals representing uncertainty about the means. Control of C. siamense was consistently achieved on the nonporous surfaces with all six disinfestants, but the level of control was variable when treating porous surfaces. The natural duration of evaporatively declining coverage over 1 to 20 min after disinfestants were sprayed on surfaces and the initial coverage from disinfestants that innately spread out or bead up on surfaces were not prominent factors that affected efficacy. Control outcomes were improved on porous substrates by making two sequential applications of a label dose or one application of a high dose, although two applications of a label dose, which does not violate disinfestant product label guidance, more consistently achieved the lowest recovery of C. siamense. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2025.