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aTreatment at 4 kg/3 m2 plot size bNematode population per 250 g soil sample.

aTreatment at 4 kg/3 m2 plot size bNematode population per 250 g soil sample.

seed cakes in the field. The amendments also increased the yield (Sadanandan and Iyer, 1986). Rhizome rots caused by F. solani and P. aphanidermatum are also reduced by amendments using oil cakes made from Azadiracta indica (Table 8.6), Calophyllum ino-phyllum, or Pongamia glabra (Thakore et al., 1987). Lee et al. (1990) studied the properties of suppressive and conducive soils on ginger rhizome rot in Korea.

Biological Control: Thomas (1939) suggested biological control of Pythium sp. using Trichoderma lignorum as an antagonist. He observed that the increased acidity of the medium resulting by the antibiosis effect of T. lignorum might be responsible for reduced growth of Pythium. Antagonism studies of Trichoderma sp. to P. aphanidermatum, F. equiseti, F. solani, Cladosporium cladosporioides, and Mucor hiemalis also have been studied in vitro (Bhardwaj and Gupta, 1987). T. harzianum and Gliocladium virens are also known to inhibit the growth of F. oxysporum f. sp. zingiberi when it caused rhizome rot in ginger (Sharma and Dohroo, 1991).

Bhardwaj et al. (1988a) treated the rhizomes by steeping in a spore suspension of T. viride or smearing with T. hamatum and found effective inhibition against P. aphani-dermatum. Prestorage steeping of rhizomes in T. hamatum suspension or by smearing with T viride also showed inhibition against F equiseti. Rathore et al. (1992) suggested that T viride produce some nonvolatile substances that inhibit the growth of P. myriotylum andF. solani. Ram (1988) reported a significant reduction in rhizome rot when Trichoderma viride was applied to soil along with sawdust. Panayanthatta (1997) has isolated a biocontrol organism from native soils, and eight such isolates were tested under field conditions for the control of rhizome rot. Infected soil was treated with Sorghum grain preparation of antagonists before planting ginger. All treatments, except Absidia, improved rhizome sprouting significantly. The incidence and severity of rhizome rot was also less, and yield increased in such treatments (Table 8.7).

Rhizome treatment with T harzianum, T. aureoviride, and Gliocladium virens and a nonresident isolate of T. viride reduced ginger rhizome rot, a rhizome- and a seed-borne disease caused by F solani or P. myriotylum or both and significantly increased the yield (Ram et al., 2000). Shanmugam et al. (2000) indicated that T harzianum and T viride are potential antagonists against P. aphanidermatum. Bhat (2000) found that Oxyspora paniculata extracts gave highest inhibition of P. aphanidermatum while Macaranga dentic-ulata extracts gave complete inhibition of Pythium sp.

Table 8.7 Effects of fungal antagonists on rhizome rot

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