Some factors affecting the control of Rhizoctonia solani by systemic and non‐systemic fungicides

Abstract

In laboratory tests, Rhizoctmia solani grew best on agar at 30 "C and pH 5-5. Mycelial growth was strongly inhibited by benomyl, chloroneb and quintozene, less so by thiophanate-methyl. The optimum temperature for inhibition was 25 "C for quintozene; the other three fungicides gave greatest inhibition at the lowest temperature tested (20 "C). Benomyl and thiophanate-methyl were most inhibitory at pH 7-8, chloroneb and quintozene at pH 5-6.In pot trials using mung bean, long melon, egg-plant, common pea and sugar beet, R . solani caused maximum disease at 20 "C and in wet and alkaline soils. As seed treatments, benomyl and thiophanate-methyl gave optimum control at 20 "C and pH 7-6; chloroneb and quintozene were most effective at 30 "C and pH 5-4. All four fungicides gave maximum control on plants growing in wet sandy loam. Comparisons of host effects showed that, on all the four hosts tested, thiophanate-methyl wettable powder at 0.25 % (0.175 % a.i.) gave 90 % control, chloroneb w.p. at 0.3 yo (0.195 yo a.i.) gave 80 yo control on mung bean and sugar beet, benomyl w.p. at 0-3 % (0-15 % a.i.) was satisfactory on mung bean, egg-plant and sugar beet but not on long melon, quintozene w.p. at 0.3 % (0.225 % a.i.) gave effective control on sugar beet only. I N T R O D U C T I O NRhixoctonia solani Kuhn, a soil-borne plant pathogen of world-wide distribution, causing root rot and damping-off of a variety of plants, can be controlled by fungicides applied as seed treatments or soil drenches. There is some evidence that control by the commonly recommended fungicides is affected by host plant, seasons and locations. R. K. Grover & B. L. Chopra (unpublished) found that the control of R. solani rot of Phaseolus mungo by seed treatment with carboxin varied at different times of the year. Grover (1973) indicated the effect of environmental soil factors in determining the toxicity of five systemic fungicides to R. solmi Studies were therefore initiated to investigate the reasons for discrepancies in control of R . solani on different hosts and under different environmental conditions, using three systemic fungicides (benomyl, chloroneb and thiophanate-methyl) and one non-systemic (quintozene).

Influence of fungicidal seed treatments and soil type on severity of root disease caused by Rhizoctonia solani AG-8 on wheat

“…Rancona Dimension at the high rate showed the strongest fungitoxic activity against R. solani, not only reducing the severity of root disease but also providing significantly greater protection for dry shoot and root weight and also root and shoot lengths from reductions. While this fungicide showed high efficacy in both river sand and Gingin loam soil, its effect was overall greatest in river sand compared with the loam soil, a similar finding as reported with earlier studies on R. solani by Blair (1943), Kataria and Grover (1976) and Rushdi and Jeffers (1956). Such differences could be a consequence of the lesser absorptive and cation exchange capacity of a sand compared with a loam soil, as demonstrated in past studies relating to the effect of various factors on the degree of control of R. solani with fungicides (e.g., Rushdi and Jeffers, 1956).…”

“…It is noteworthy that there was a significant interaction between the efficacies of fungicides with soil type, highlighting that the greatest potential for new fungicides is particularly likely to be in wheat growing areas where sandy soils rather than sandy loam soils predominate. It is well known that efficacy of fungicides is affected by soil type (Kataria and Grover, 1976;Rushdi and Jeffers, 1956) and specifically so in relation to fungicides affecting root diseases caused by R. solani (e.g., Bateman, 1984;Bateman andNichols, 1982: Bateman et al, 2008;Cook et al, 1987;Ebbels, 1969). In particular, the study of Kataria and Grover (1976) observed that the fungicides benomyl, thiophanate-methyl, chloroneb and quintozene were more effective in a sandy loam than in a loam or clay loam soil, despite approximately similar disease incidence/severity in these three soil types.…”

“…It is well known that efficacy of fungicides is affected by soil type (Kataria and Grover, 1976;Rushdi and Jeffers, 1956) and specifically so in relation to fungicides affecting root diseases caused by R. solani (e.g., Bateman, 1984;Bateman andNichols, 1982: Bateman et al, 2008;Cook et al, 1987;Ebbels, 1969). In particular, the study of Kataria and Grover (1976) observed that the fungicides benomyl, thiophanate-methyl, chloroneb and quintozene were more effective in a sandy loam than in a loam or clay loam soil, despite approximately similar disease incidence/severity in these three soil types. Their findings are in agreement with the current study where, while reductions of disease severity from the tested fungicides were overall not effected by soil types, the efficacy of Rancona Dimension was greater in river sand compared with Gingin loam, particularly at the high rate.…”

Linkages of Farmers' Operations with Rhizoctonia Root Rot Spread in Bean Crops on a Regional Basis

“…Although severe RRR in beans has been often observed in wet soils (Kataria and Grover ; Kobriger and Hagedorn ; Allen and Lenné ), there are a few reports on the best growth of R. solani at low soil moisture content (Blair ; Sneh et al. ).…”

Fungitoxicity of mineral oils against Rhizoctonia solani causing damping‐off of mung bean (Phaseolus aureus)

“…The method for inoculating the soil (autoclaved) was the same as reported earlier (Kataria & Grover, 1976). One kg soil was packed into a 15 cm diameter earthenware pot into which seeds were sown.…”