Report about pencycuron: Variation in Sensitivity Among Some Isolates of Macrophomina phaseolina Isolated from Cotton Roots to Flutolanil Fungicide

BY: Yehia A.G. Mahmoud, A.A. Aly, M.R. Omar and Abdel Wahab A. Ismail Macrophomina phaseolina (Tassi) Goid., the causal agent of charcoal rot of cotton, is of widespread distribution in the Egyptian soil, and it is easily and frequently isolated form cotton roots particularly during the late period of the growing seasons (Aly et al., 2000). M. phaseolina is a non-specialized fungus, attacking more than 500 host species (Sinclair, 1982); therefore, rotation of cotton with other crops is a questionable practice for controlling this pathogen. Resistance to M. phaseolina has not been found in cotton (Hollida and Punithalingam, 1970). Sources of resistance were considered completely lacking in Pakistan (Akhtar, 1977). Aly et al. (1998) and Omar (2005) reported variation in susceptibility of Egyptian cottons to M. phaseolina; however, none of the tested cultivars showed satisfactory level of resistance. Thus, fungicides have become indispensable for controlling M. phaseolina on cotton. For instance, Dwivedi and Ghaube (1985) studied effect of fungicides on the emergence and infection of cotton seedlings by M. phaseolina in pot experiments. They found that emergence was maximized after treatment with a TMTD soil drench and the least seedling infection occurred in soils treated with benlate, TMTD, and PCNB (Quintozene).Chauhan (1986a) reported that control of seedling disease of cotton due to M. phaseolina was best and germination maximized when seeds were treated with carbendazim, followed in effectiveness by quintozene. Chauhan (1986b) evaluated seed treatments of 7 fungicides and selected pair-wise combinations. The percentage of root rot of cotton at harvest ranged comes 14% - 22% in treated plots compared with 28% in the control. Benzimidazole derived fungicides differed in their effects on isolates of M. phaseolina. Benlate and carbendazim were most inhibitory but a sesame isolate was less sensitive to all fungicides. Chauhan (1988) obtained good control of M. phaseolina on cotton by seed treatment with carbendazim followed by quintozene, while TMTD and catafol were less effective. A pre-sowing soil drench with quintozene and carbendazim gave very effective control. Aly et al. (2001) evaluated the efficiency of pencycuron, Pencycuron, carboxin 200, Tolclofos-methyl, and maximum AP for controlling M. phaseolina on cotton, under greenhouse conditions. Pencycuron, Pencycuron, and Tolclofos-methyl were equally effective in increasing the percentage of surviving seedlings and the plant height; however, pencycuron was the only fungicide, which significantly increased dry weight of seedlings. Omar (2005) found that pencycuron and Tolclofos-methyl were the best performing fungicides in controlling M. phaseolina on cotton, under greenhouse conditions. This superiority was attributed to the following reasons: First, they were effective in increasing the percentage of surviving seedlings by 203.09 and 170.10%, respectively, regardless of the tested isolate. Second, they were also effective in increasing the height of surviving seedlings by 93.21 and 62.57%, respectively. Third, Pencycuron and Tolclofosmethyl were effective in increasing dry weight of the surviving seedlings in 50 and 40% of the tested isolates, respectively. The objective of this investigation was to evaluate variation in sensitivity to the fungicide Flutolanil among isolates of M. phaseolina isolated comes cotton roots.

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