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Subject: Agricultural Entomology × Author: KAU × End date: 1992 × Start date: 1992 × Type: Thesis ×
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    ThesisItemOpen Access
    Biology of banana pseudostem weevil Odoiporus longicollis Oliv. (Coleoptera : Curculionidae)
    (Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1992) Jayasree, T V; KAU; Jim Thomas
    The Banana Pseudostem Weevil, Odoiporus longicollis Oliv., considered as one of the destructive pests in North and North East India is very recently found to be causing wide spread damage in the banana growing tracts of Ernakulam and Trissur districts of Kerala. The present investigation was envisaged to properly understand about the nature of attack, symptomatology, bio-ecology, morphology and the preliminary control measures of the pest species under both field and laboratory conditions. The insect pest is associated with the banana plants throughout the year in Kerala in overlapping generations with its maximum population during both the monsoon periods. This insect has a very congenial condition in Kerala for their survival and multiplication in general and its hot spots of infestation were identified to be around Alwaye-Perumbavoor regions in Ernakulam District. Of late the infestation was observed to be spreading to other Districts also. The banana varieties more susceptible to its attack were found to be Nendran, Palayankodan and Poovan while; Njalipoovan was relatively tolerant. The adult weevils preferred to oviposit on the outersheaths on 3-4 months old plants coinciding with the peduncle formation at a height ranging from 3-4 meter above ground level. The weevil grubs bored into the pseudostem portions and cause extensive tunnelling and riddling leading to weakening of growth, delayed flower emergence, smalling of bunches and finally breakage and lodging leading to partial or complete loss of the crop. The biology, morphology and biomorphometrics of the insect under laboratory conditions were worked out in detail. Because of the peculiar nature of the plant and the fruit produce, as well as the type and nature of the pest species, chemical means of control by spray impregnation of natural products, injection of systemic insecticide through root, rhizome and pseudostem portions and padding technique with fumigant insecticide gave inconclusive results. Bio-control with the parasitic nematode, DD-136, Steinernema sp. eventhough showed good in vitro mortality under lab conditions, it was not successful under field condition. From the above studies, it was found that, to contain the pseudostem weevil infestation effectively, an integrated pest management strategy with special emphasis on cultural techniques on a community basis should be evolved and practiced.
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    ThesisItemOpen Access
    Host resistance in cowpea ( Vigna unguiculata (L .) Walp) to the pod borer Maruca testulalis (Geyer) (PyralidaeiLepidoptera)
    (Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1992) Anitha Kumari, V; KAU; Sheila, M K
    An investigation on the host resistance in cowpea ( Vigna unguiculata (L.) Walp) to the pod borer Maruca testulalis (Geyer) was carried out by screening 100 varieties of cowpea during 1990 - 91. These were classified into highly susceptible, moderately susceptible and moderately resistant classes. This study rules out the chance of any of the varieties screened to be resistant to this particular pest. Selected accessions from the three different classes based on the field evaluation, were subjected to artificial infestation by the first instar larvae of M. testulalis on caged plants in the green house. Here too, the susceptibility spectrum was found to be similar to the trend observed in the field trial. The accession V30 was identified to be the most moderately resistant type and V100 as the most susceptible one. In the studies on antibiosis it was found that the larvae reared on moderately resistant type took longer durations of development as compared to the susceptible ones. The larval survival as well- as the adult emergence was lower in the resistant types The highly susceptible accessions produced more females than the resistant lines. The fecundity of F females was adversely affected when the larvae were reared on the moderately resistant accessions. Among the biophysical components, though the pod wall thickness and pubescence of the pods did not show any correlation with the level of borer infestation, the length of flower stalks, disposition of corolla, calyx and seeds and the nature of seed testa, had a positive influence on its distribution. Positive correlations were also detected between the mean percentage of total sugars, crude protein, amino acids and nitrogen in the pods on the one hand and pod damage on the other.
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    ThesisItemOpen Access
    Studies on the entomogenous fungus associated with cowpea aphid
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 1992) Faizal, MH; KAU; Susamma Mathai
    Studies were conducted on the entomogenous fungus Fusarium pallidoroseum (Cooks) Sacc. infecting cowpea aphid Aphis craccivora Koch. The infected aphids turned pale and assumed brownish black discolouration. Death occurred in 24 to 72 hours after infection and mycelial growth appeared on the cadavers 24 to 48 hours after death. For mass production of the fungus, wheat bran and rice bran appeared to be comparatively suitable as they recorded maximum growth, sporulation and virulence of the pathogen. Maximum sporulation was noticed 8 days after inoculation. Culture substrates subjected to full heat sterilization produced maximum growth and sporulation of the fungus followed by those subjected to full solarization. A mortality per cent of 99.57 was observed when aphids were sprayed with culture filtrate of F. pallidoroseum grown in Richard’s medium indicating the presence of toxins. Studies on the effect of pesticides on the growth of the fungus showed that mercaptothion and monocrotophos were the least inhibitory. Fenthion showed the least inhibition of sporulation. HCH, captan and zineb completely inhibited the growth. Sporulation was completely inhibited in all the fungicidal treatments. Under laboratory conditions spore suspension of the fungus in water was found to be superior to the spore formulations tried. Among the formulations wettable powder with diatomaceous earth as inert material was found to cause more mortality followed by wettable powder with talc as inert material. Dust using talc as inert material was found to be the least effective. Spore suspension in water, wettable powder formulation of fungal spores with diatomaceoue earth as inert material and quinalphos 0.05 per cent were found to be equally effective in bringing down the population of aphids under field conditions. The virulence of spores of F. pallidoroseum in formulation was found to decrease with increase in storage period and it retained substantial virulence up to four days of storage.