Browsing by Author "Suma Paulose"

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Eco-friendly insecticides for the management of major pests of amaranths
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2001) Leena, M K; Suma Paulose
There has been increasing reports on health hazards in human beings from the unscientific and intensive use of pesticides in crops, especially vegetables. It was in this backdrop, a scientific investigation was designed to evolve safer and eco-friendly methods in pesticide use to control the major pests of the popular leafy vegetable amaranths. Field experiments were conducted at the college of Horticulture, Vellanikkara during 2000-2001 to identify the safer, eco-friendly insecticides. For the first experiment, thirteen different commercial formulations of neem, microbial and chemical pesticides were evaluated for the control of amaranths leaf webbers viz., H. recurvalis, P. basalis, weevil H. truncatulus and grasshopper A. crenulata. The best six effective components were further screened at lower doses, so as to identify the most promising one in the second experiment. The effect of the tested components on the natural enemies and other bio control agents were also studied.. Organoleptic quality evaluation of cooked amaranths leaves was done to know, whether the applied insecticides have any effect on the taste, appearance, colour, flavour, texture and bitterness. Of the insecticides tested in the first experiment, Econeem, N eem Azal, Halt, Dipel, Delfin and Nuvan were the most effective in controlling the pest population. The results of the second experiment indicated that the plots treated with Dipel @ 0.7 ml r' gave better control of both the leaf webbers. Halt @ 0.7 g r' gave comparably good results for the control of weevil. All the microbial insecticides tested were found ineffective to grasshopper. No disease symptom or deformities were observed in any of the natural enemies and other bio control agents. In the field, though Nuvan was found to control the pests, it was not effective in the long run. All the microbial products were found to protect the crop for a longer period of time. The crop sprayed with Delfin @ O.7g r' gave an yield of 5481 kg green leaves per acre compared to untreated control (2963 kg). Organoleptic quality evaluation of cooked amaranths leaves revealed that, there was no significant difference in qualities of cooked amaranths due to treatments compared to untreated control.
Host-specificity, patho-physiology and transmission of the baculovirus (Kerala isolate) infecting Oryctes rhinoceros Linn. (Scarabaeidae:Coleoptera)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1995) Suma Paulose; Abraham, C C
The Baculovirus oryctes has been recognized as one of the most promising pathogens against oryctes rhinoceros. Laboratory studies were conducted to evaluate the virus in respect of its patho-physiology, histopathology, mode of transmission, cross-infectivity, effect of physical factors on the virulence of the virus and safety to non –target organisms. The oral inoculation technique has been found to be more effective than the swim method. For long term storage of the virus, the freeze drying method was found to be ideal as it retained viability for more than sixteen months. The viral particles have been found to be bacilliform , measuring 210 to 250nm in length and 75 to 105 nm in width. The main symptoms observed in grubs due to viral infection are loss of appetite, lethargy, pallor, migration to the top of the breeding medium, disintegration of the fat bodies and development of diarrhoea. Adults did not show any pronounced external symptoms. Infected adults refused to take food and they eventually developed diarrhea. All instars of grubs and adults were susceptible to the viral infection .The susceptibility to infection was maximum in the first instar followed by third instar, second instar and the adults in that order. The mean lethal concentration of the viru required to cause fifty per cent mortalities were 0.377 x10-4 , 14.417x10-4, 0.297x10-4 and 1.137x10-4 gut equivalent for the first, second and third instar grubs and adults respectively. The cytology of the midgut contents showed desquamated epithelial cells with nuclear and cytoplasmic vacuolation, nuclear hypertrophy and ring stages nucleus. The midgut and fat bodies have been identified as the major sites of viral multiplication. Transovum and transovarial transmission studies have shown that the virus was not transmitted by any of these method. The studies on transtadial transmission established that the disease was transmitted from first to second and from second to third instar, but not from the third instar to the pupae. The predator platymerus laevicollis did not transmit the disease. The reproductive potential of oryctes was found to be significantly impaired due to viral infection. When both the mating partners were infected, the number of eggs laid was only 19 to 20 as compared to the output of 209 to 219 in the healthy pairs. The cross-infectivity studies have clearly established that the virus was not infective to other important pests of coconut such as Rhyncophorus ferrugineus, Leucopholis coneophora, opisina arenosella and the predator’s p.laevicollis. In studies on the effect of temperature on the viability of the virus, it was found that above fifty per cent mortality took place on incubation of the virus for 21/2 hours at 370c and that the viability was totally lost as a result of exposure for 4 1/2 hours. The number of adults required for release in to the breeding pits of size of 30cmx30cmx30cm to kill fifty per cent of the Rhinoceros grubs at different time intervals were 4.440, 3.668, 3.016 and 2.889. Safety studies have revealed that the virus was absolutely safe to the silkworm Bombyx mori, chick embryo, white mice and white rat.
Indigenous natural organic materials for the management of major insect pests of rice
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2005) Smitha Revi, D; Suma Paulose