Abstract:
Detailed investigations were made on the entomogenous fungus Fusarium pallidoroseum (cooke) Sacc infecting cowpea aphid Aphis cracclvora koch. Field studies showed that spore suspension and wettable powder formulations were equally effective in controlling the pea aphid. 7 x 106 spores per ml suspension in water or a similar suspension of a wettable powder or quinalphos 0.05 per cent were found to be equally effective in controlling the aphids under field conditions. Spore suspension containing 3.5 x 106 spores per ml have shown similar results during the later half of the experimental period. Pot culture studies conducted to assess the influence of host plants of aphid on the efficacy of the pathogen revealed that there was no influence of host plant on the pathogenecity of F. pallidoroseum. The germination and viability of F. pallidoroseum in formulation was found to decrease with increase in storage period and the formulations retained its capacity for germination and viability for more than ten months under refrigeration. The fungus was found nonpathogenic to vegetables viz. as bhindi, brinjal, amaranths, tomato, chillies, snakegourd, bittergourd and medicinal plants, viz., adathoda, ocimum and notchi under field conditions. Besides it was found safe to natural enemies of aphids viz., Coccinella septumpunctata, Menochilus sexmaculata and Scymnus sp. The productive insects, honey bees and silkworms were not at all affected by this fungus. Cross inoculation studies using this pathogen showed that three species of aphids, viz., Toxoptera aurantii, Aphis gossypii and Aphis malvae were not infected. A strain of F. Pallidoroseum isolated from a weed plant water hyacinth(Eichhornia crassipes) was found to be non pathogenic to the aphid Aphis Crassivora. Similarly F. Pallidoroseum was observed non pathogenic to water hyacinth. These observations indicated that the above two strains of F. Pallidorosem are entirely different.
