The function of an MBC-releasing deposit of benomyl and thiophanates in plant roots and soil

Abstract

A comparative study has been made on the effects of short-term treatment versus long-term treatment with benomyl and three thiophanates with regard to distribution of fungitoxicant (MBC, or EBC) within plants and their protection against fungal diseases. In both treatments, plants were exposed to the fungicides for two days and then transplanted to garden soil; long-term treated plants received an additional supply of fungicide as a daily drench for one week.Results of short-term treatment of cucumber seedlings and tomato plants provided additional proof for the hypothesis, that MBC derivatives, substituted at N-1 in the benzimidazole nucleus, are retained to some extent on or in the roots, and gradually converted to MBC which then moves into the aerial parts of the plant. Correlation of infection with concentration of fungitoxicant within leaves showed 0.35 vg/g fresh weight to be the limiting concentration for symptom expression of cucumber powdery mildew. Only with benomyl was MBC to be released long enough into the aerial parts of the plant to protect leaves, unfolding after termination of the treatment, for some weeks.With long-term treatment, a concentration of MBC (or EBC) suff• for protection was found with all fungicides in all above-ground parts of the plant until the end of the experiment. Thus, a reservoir of fungicide in the planting medium guarantees a continuous supply of fungicide only then may new growth be efficaciously protected.

Influence of MBC on some physiological processes in the leaves of gherkin

“…The differences observed between the effects of the two fungicides might be due to a different ability of MBC and thiophanate-methyl (or an intermediate conversion product; Fuchs et al, 1972) to function as an MBC-releasing deposit in plant roots and soil (Fuchs et al, 1974).…”

Isolation of a benomyl-resistant strain of Sphaerotheca fuliginea (Schlecht.) Poll. in Greece and the effectiveness of other systemic fungicides

“…In the first tests, The effectiveness of triforine and imazalil against the benomyl-resistant strain can best be explained by their different mode of action. Benomyl and its breakdown product MBC~ the compound mainly responsible for the fungitoxicity of this fungicide (Clemons and Sisler, 1969;Sims et al, 1969;Fuchs et al, 1972Fuchs et al, , 1974Petsikos-Panayotarou, 1972), have been found to inhibit mitosis in different fungi (Davidse, 1973;Hammerschlag and Sisler, 1973;Richmond and Phillips, 1975). iOn the contrary, triforine has been found to inhibit sterol biosynthesis (Sherald et al, 1973;Sherald and Sisler, 1975).…”

Duration of effects of benomyl on growth and wilt (Verticillium dahliae) development in the strawberry, cv. Cambridge Vigour, in relation to time of inoculation

“…The long-term effects of benzimidazole fungicides deposited in the soil on the control of plant diseases have been discussed in detail by Fuchs, Fernandes & de Vries (1974). The long-term effects of benzimidazole fungicides deposited in the soil on the control of plant diseases have been discussed in detail by Fuchs, Fernandes & de Vries (1974).…”