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Production and Evaluation of the Fungus Fusarium Pallidorosium (coooke)Saac. As A Biopesticide AgainstPea Aphid Apphis Craccivora Koch.
Investigations on "Production and evaluation of the fungus Fusarium pallidoroseum (Cooke) Sacc. as a biopesticide against the pea aphid Aphis craccivora Koch." were carried out at the College of Agriculture, Vellayani. A. craccivora infected by F pallidoroseum naturally or artificially,...
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| 格式: | Ph.D Thesis |
| 語言: | Undetermined |
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Vellayani
Department of Agricultural Entomology, College of Agriculture
2001
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| 總結: | Investigations on "Production and evaluation of the fungus Fusarium
pallidoroseum (Cooke) Sacc. as a biopesticide against the pea aphid Aphis
craccivora Koch." were carried out at the College of Agriculture, Vellayani. A.
craccivora infected by F pallidoroseum naturally or artificially, died within two
days. The fungus on repeated sub culturing showed variation in morphology. Number
of macroconidia got reduced and the mycelia turned more white with every
subculture which resulted in a gradual reduction of virulence. Virulence was
completely suppressed by seventh subculture.
Evaluation of different naturally available substrates for mass production
of Fpallidoroseum revealed that among the solid substrates tried, leafy substrates,
bran and oil seed-cakes supported maximum biomass and macroconidia. Among
the liquid substrates tested mature coconut water was found to support maximum
biomass and macroconidia. Increased virulence of spore suspensions prepared
from these media was found to be due to the abundance of macroconida in them.
Aphids were killed faster when spore suspensions containing more macro conidia
were sprayed.
Assessment of shelf life of the fungus for a period of twelve months
revealed that for storing spores of Fpallidoroseum semidry cadaver of the host
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insect (A.craccivora), diatomaceous earth, fine charcoal powder and leaf mold
were found to be the best carrier material with substantial retention of virulence
than viability when compared to other materials tested viz. bran, saw dust,
vermicompost and peat.
Storage under refrigeration was found to double the shelf life of the fungus
compared to storage under room temperature. Spores retained 24 to 58 per cent
virulence after 12 months storage at room temperature, while it retained 77 to 97
per cent virulence when kept in a refrigerator. Viability of the fungus was also
found to be doubled and virulence well conserved till the end of twelve months
(experimental period) when stored in a refrigerator.
Material for packaging the spore formulations did not make any
significant difference till the end of six months of storage. Thereafter glass vial
was found to extend the shelf life of Epallidoroseum spores by one month
compared to polypropylene and aluminium foil when the spore packings were kept
at room temperature while under refrigeration the effect of packing materials were
not reflected even after 12 months of storage.
Studies conducted to evaluate the compatibility of Fpallidoroseum with
commonly used botanicals revealed that mycelial growth of the fungus was not
adversely affected by none of the botanicals while seed 011 emulsions of nee m and
marotti highly inhibited the sporulating ability of the fungus. Leaf extracts of thevetia
was moderately inhibitory while that of neem, bougainvillea and hyptis were found
to enhance spourulation. Commonly used insecticide quinalphos at 0.05 per cent
concentration did not suppress growth and sporulation of the fungus completely.
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Field experiments conducted to evaluate the time and method of
application of the fungus to control A. craccivora using different spore formulations
revealed that carrier materials like diatomaceous earth, charcoal powder, semi
dry cadaver and leaf mold were effective in controlling aphids. Fpallidoroseum
spores applied by spraying as well as braodcasting were equally effective when
applied at six weeks after planting as a curative control measure which could
exert cent per cent control of the pest. Prophylactic application of the fungal
spores on cowpea plants prior to aphid infestation was not at all effective in
controlling the pest. Negligible reinfestation in Fusarium treated plants reflected
the capability of the fungal spores to survive in the cadaver of the host insect.
Management of pea aphid using Fpallidoroseum was found to significantly increase
the yeild of cowpea by 17 to 37 per cent.
F pallidoroseum was found to be nonpathoenic to the crop plants like
Amaranthus sp., Ananas comosus, Moringa ol ifer a, Morus albus, Musa
paradasiaca, Passiflora edulis, and Sesamum indicum which have been
reported to be diseased by another strain of Fpallidoroseum (plant pathogenic).
Epallidoroseum was found to be noninfectious to the common predators
of A. craccivora viz. the coccinellids, Menochiles sexmaculata, Coccinella
septumpunctata, and Micraspis crocea; syrphids, Ischiodon scutellare and
Is c h io do n sp., hemerobid; dragon flies; spiders like Par a d o s a
pseudoannulata, Tetragnatha maxillosa and Oxyopus sp. Besides it was found
to be safe to the stingless bee Trigona iridipennis and the common pollinators
like Bombus sp., Camponotus sp., Syrphus sp. and Xylocopa sp.
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The fungal spores at a concentration of 7 x 107 sporeslml was found to
be nonpathogenic to New Zealand White rabbits. The spores administered orally,
dermally, subcutaneously, intranasally and intravenously did not produce any
symptoms of acute or chronic toxicity.
The toxin fusaric acid was isolated from seven day old Czapek's liquid
culture of the fungus. The toxin yield was at the rate of 112.7 mg litre ". It caused
death of A. craccivora at 500 and 1000 ppm with a mortality rate of 46 and
100 per cent respectively at the end of 72 h after treatment. The speed of action
of fusaric acid was found to be slow when compared to the entomopathogen
Fpallidoroseum. The mortality of aphids treated with F pallidoroseum might be
not only due to the properties of fusaric acid but also due to the action of some
other toxins as well as the biological activity of the fungus.
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