Individual and Combined Effects of Certain Pesticides on Rhizoctonia solani, Sheath Blight Pathogen of Rice

Abstract

The effect of different pesticides (fungicide, herbicide and insecticide) on the mycelial growth and formation and germination of sclerotia of sheath blight pathogen of rice, Rhizoctonia solani Kiihn was studied in nutrient medium and in natural soil. Among the herbicides and insecticides, fenitrothion (insecticide) and thiobencarb (herbicide) were the most effective in inhibiting the myceliai growth and sclerotial formation. These pesticides effected significant inhibition of both mycelial growth and sclerotial formation at 7.5 to lO/^g/ml concentration while fungicides carbendazim and tolclofosmethyl effected almost complete inhibition at 2.5 |Ug/ml. Interestingly, a synergistic increase in the toxicity to mycelial growth, sclerotial formation and sclerotial germination was noticed when the fungicide, mancozeb and the herbicide, thiobencarb were applied at subtoxic concentration in combination. Such synergistic interactions between pesticides in a combination leading to increased toxicity suggest that under the current practice of applying fungicides, herbicides and insecticides either simultaneously or in rotation, certain combinations may help in reducing the dose of a fungicide in disease control. ZusammenfassungEinzelne und gemeinsame Einfliisse bestimmter Pestizide gegen Rhizoctonia solani, dem Reis-Sheat-Blight-Pathogen Der Einflufi verschiedener Pestizide (Fungizide, Herbizide und Insektizide) auf das Myzelwachstum, die Bildung und die Keimung von Skleroden des Reis-Sheat-Bhght-Pathogens, Rhizoctonia solani Kiihn, wurde in Nahrmedien und natiirlicher Erde untersucht. Unter den Herbiziden und Insektiziden zeigten sich Fenitrothion (Insektizid) und Thiobencarb (Herbizid) als effektivste Inhibitoren des Myzeiwachstums und der Sklerotienbildung. Diese Pestizide bewirkten eine signifikante Inhibition des Myzeiwachstums und der Sklerotienbildung bei Konzentrationen von 7,5 bis 10 ^g/ml, wogegen die Fungizide Carbendazim und Tolclofosmethyl eine fast vollige Inhibition schon bei 2,5 jug/ml verursachten. Erwahnenswert ist der synergistische Effekt, der die Mischung Mancozeb, einem Fungizid, und Thiobencarb, einem Herbizid, bei subtoxischen Konzentrationen in dessen U.S.

Comparative Effectiveness of Some Novel Fungicides Against Soil-Borne Pathogens of Chili

“…For more comprehensive analysis, these fungal colonies were subjected to purification through hyphal tip transfer onto fresh PDA plates. The identification of isolated fungi was accomplished by assessing their morphological characteristics, utilizing identification keys provided by Booth (1971), Ellis (1971), Barnett andHunter (1972), andSingh (1982).…”

“…Root rot and damping-off caused by R. solani is a significant threat to nursery and young chili plants. R. solani is soil and seedborne pathogen (Sivalingam et al, 2006). The pathogen is challenging to control because of its ability to survive long-term in the soil and organic debris and cause disease incidence of 33.2% in seedlings and 40.2% in the field (Varma et al, 2020).…”