Thumbnail Image

Theses

Browse

1998 - 19994
Reset filters
Subject: Agricultural Entomology × End date: 1999 × Start date: 1998 × Type: Thesis × Thesis Type: Ph.D ×
Reset filters

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    ThesisItemOpen Access
    Monitoring and management of the pest complex of bitter gourd (Momordica Charantia L.)
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 1999) Nandakumar, C; KAU; Saradamma, K
    Surveys were conducted in 1995-96 among one hundred bitter gourd farmers in Thiruvananthapuram district. Information on the personal and socio- economic characteristics of the farmers was gathered. Field visits indicated that among the pests at flowering, the jassid, H.phycitis and leaf feeder, D. indica were important. At early harvest, the jassid and fruitfly B. cucurbitae were the major pests. Among the natural enemies observed, the potential ones were Cjohnsoni (parasite on Hseptima), I.scutellare, Msexmaculatus and Snubilis . (predators on A.gossypii). Mosaic was severe in 12 per cent of the plots. Sixty two per cent of the farmers used a combination of mechanical, cultural and chemical measures against pests. Most common pesticides used belonged to the organophosphate group. Farmers in general adopted injudicious methods of chemical control. Seventy per cent farmers relied on mass media and interpersonal cosmopolites for information on plant protection. The most important constraint perceived by farmers was the high cost of inputs viz., plant protection chemicals, manures and fertilizers. Monitoring of fruit fly incidence using Biosense stikatrap (lure) indicated the maximum catch at eleven weeks after sowing. Ten carbofuran smeared banana fruit traps (in yellow coloured coconut shell) were found to be more efficient than one Biosense trap in trapping the fruit fly. 2 Studies on seasonal incidence of the pests and their natural enemies from 1995 to 1996 indicated that they were more from November '95 to April '96. In studies on the assessment of potential natural enemies of pests, the biology and efficacy of Cjohnsoni against epilachna beetle was observed. Among the predators viz., Iscutellare, Msexmaculatus and S.nubilis whose biology and feeding potential was studied, Msexmaculatus was observed as the most efficient predator of aphids. In another set of experiments, the effects of botanicals and chemical pesticides on pests and their natural enemies were studied. The antifeedant effect of botanicals on third instar Hseptima grubs indicated that neem seed oil (three per cent) and nimbecidine (0.40 per cent) were effective. Estimation of the comparative effect of chemical pesticides against the fourth instar Hseptima grubs showed that carbaryl and dimethoate were more effective than quinalphos and malathion. Toxicity studies of botanicals and chemical pesticides to Msexmaculatus grubs and Cjohnsoni adults as well as parasite emergence from treated larval! pupal Hseptima hosts indicated that botanicals were safe whereas, the chemicals were toxic to the natural enemies. Based on the above experiments, the botanicals viz., neem seed oil three per cent, nimbecidine 0.40 per cent and the chemical pesticides,carbaryl 0.15 per cent and dimethoate 0.05 per cent were selected for the pest management trial in bitter gourd. The reaction of five bitter gourd varieties viz., Priya, Arka Harit, Preethi, Priyanka and local to pests was tested in a field trial. Based on pest infestation and yield, Preethi was selected for the pest management trial. 3 The pest management trial was conducted for two seasons (January to April, 1996 and 1997). The results indicated that combination of botanical with chemical pesticide was the best in pest control. Based on the results the following recommendations were suggested as part of IPM strategies in bitter gourd. 1. Use variety 'Preethi' (MC-84) for planting 2. Basal drenching of combination of nee m seed oil three per cent soap emulsion with either dimethoate (0.025 per cent) or carbaryl (0.075 per cent) prior to seeding. This is recommended in areas where pests like pumpkin beetles are endemic. 3. Need based application of above till fruit set to control pests. 4. Apply fungicide (Mancozeb) to control foliar disease (downy mildew). 5. Monitor fruit fly incidence using lure trap. Set yellow painted coconut shell trap's containing carbofuran smeared banana (palayankodan) alternated with carbofuran poisoned ocimum I jaggery (2m spacing) at flowering till final harvest. 6. After fruit set, use (need based) a combination of neem seed oil three per cent soap emulsion and dimethoate 0.025 per cent.
  • Thumbnail Image
    ThesisItemOpen Access
    Insect pest natural enemy- host plant interaction studies with special reference to the brown planthoper nilaparvata lugens(Stal.)
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1999) Haseena, Bhaskar; KAU; Joy, P J
    Field surveys were conducted in Kole land and Kuttanad to assess the population of rice BPH, Nilaparvata lugens (Stal) and its natural enemies. Field investigations on the population dynamics of BPH and its natural enemies were carried out on susceptible (Jaya), moderately resistant (Jyothi) and resistant (Kanakom) rice varieties at the rice fields of Rice Research Station, Moncompu during 1997-98. The influence of these varieties on the biology of the pest, the biocontrol efficiency of the major natural enemies and the biology of the mirid predator Cyrtorhinus lividipennis Reuter was studied in the laboratory. Histological and chemical investigations were undertaken to evaluate the factors that contribute to the resistance/susceptibility in them. Results of field survey in Kole land revealed that the population of BPH was far below the economic threshold level (ETL). In Kuttanad, in kayal area during Rabi season and in karappadam tract during Kharif season outbreaks of BPH occurred in some localities due to the indiscriminate use of insecticides resulting in the mortality of natural enemies. The results of the study on population dynamics revealed that the BPH population was significantly high on the susceptible J aya and low on the resistant Kanakom with the population reaching a peak from February to March. The predatory complex of the BPH comprised of the rnirid Cyrtorhinus lividipennis, Lycosa pseudoannulata, Tetragnatha maxillosa, Atypena formosana, Microvelia douglasi atrolineata, Pseudogonatopus sp. and Ophionea nigrofasciata. C. lividipennis was the most predominant predator regulating the hopper population and there exists a density dependent host-predator relationship. The population of the mirid predator on Jaya and Kanakom did not differ significantly. The prey-predator ratio was lowest on the resistant variety and highest on the susceptible variety. Of the weather parameters studied, the minimum -. temperature showed a highly significant negative correlation with the population of N. lugens in all the varieties. BPH reared on the resistant variety recorded longer nymphal duration, decreased nymphal survival and shorter adult longevity indicating the prevalence of antibiosis in the variety. Lesser number of eggs laid, longer pre-oviposition period and shorter oviposition period recorded on Kanakom indicate the antixenosis factor in it. Macrpterous forms of BPH did not develop on the variety . The predator C. lividipennis and Micraspis sp. fed more BPH when reared on the resistant variety. The veliid bug M. d. atrolineata, the spider L. pseudoannulata and the dryinid Pseudogonatopus sp. predated significantly more BPH nymphs on resistant variety at a higher prey density only. However, the dryinid parasitoid consumed significantly fewer number of hoppers on Kanakom at the higher host density. C. lividipennis recorded longer nymphal duration, shorter adult longevity and low fecundity when fed on BPH reared on Kanakom which can be attributed to the low fecundity of N. lugens on Kanakom leading to less availability of food to the mirid. Nymphal duration and adult longevity of C. lividipennis did not vary between the varieties Jaya and Jyothi. Well developed bundle sheath with more frequently distributed schlerenchyma tissue in the culm of the resistant variety seemed to impart resistance in Kanakom along with thicker cuticle. Higher amounts of silica, Zn and Mn and lower amounts of N, K, Ca and Mg were recorded in the culm of the resistant variety compared to moderately resistant and susceptible varieties. The findings strongly suggest the mechanism of antibiosis and antixenosis in the resistant variety Kanakom.
  • Thumbnail Image
    ThesisItemOpen Access
    Influence of weather and rearing techniques on mulberry silk worm crops in Kerala
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 1998) Krishnakumar, R; KAU; Sasidharan Pillai, K
    Investigations were conducted on the effect of weather parameters on the mulberry silkworm crops reared in different seasons and to evolve suitable rearing technology for stress seasons in order to improve the rearing during these seasons and for developing suitable package of practices recommendations for silkworm rearing in Kerala. The study was conducted during 1992-1996 at College of Agriculture, Vellayani. The experiments conducted were  Effect of climatic factors on mulberry silkworm crops in different seasons.  Identifying rearing technology for stress seasons of high temperature and humidity.  Manipulation of feeding schedule with reference to stress seasons and types of silkworm rearing houses. To study the effect of climatic conditions on the mulberry silkworm crop, the silkworms were reared during different identified seasons viz December- January, February-April, May-July, August-September and October-November in 1993-94. The mulberry silkworms used for the study were bivoltine NB4Dz and crossbreed PM x NB4D2. Three brushing were done in each season at fortnightly intervals and fifteen continuous rearings were conducted. The important weather parameters recorded were maximum temperature, minimum temperature, maximum humidity and minimum humidity inside and outside the rearing house. The rearing characters like instarwise larval duration, moulting duration, larval weight, leaf consumption, silk gland weight, disease incidences, missing larval percentage and economic traits like cocoon weight, shell weight, shell ratio, effective rearing rate, filament length, reelability and computed parameters like growth index and growth rate were also recorded. Among the different seasons, August-September and December-January were identified as the favourable seasons. October-November, February-April and May-July seasons were found to be the stress seasons as the biological and economic traits of the different silkworm races during these seasons were not compromising in comparison with other seasons. Maximum temperature and minimum temperature show direct correlations whereas maximum humidity indirectly showed negative correlations with the economic traits like larval weight, silkgland weight, shell ratio, cocoon weight and yield. Second and third experiments were conducted to identify suitable cost effective and efficient rearing house for these stress seasons and also to evolve rearing technology so as to reduce cost of production. The treatments for the second experiment were five different rearing houses along with three different larval spacings. The rearings were conducted by using the same crossbreed and bivoltine race used in the first experiment. The rearings were carried out during 1995 and 1996 in the three stress seasons viz May-July, October-November and February-March. The observations were recorded in terms of the larval characters and economic traits of the silkworms NB4D2 and PM x NB4D2 in these seasons. The results revealed that wider spacing was superior to medium and close spacings in both races. The rearing houses made of mud brick and thatched roof and burnt brick and thatched roof were found superior to other rearing houses in all the three stress seasons during the two year period. Among the different feeding schedules studied in the third experiment, three feeding a day was mostly on par with four feeding a day but was advantageous in terms of convenience of feeding time over other feeding schedules though four feedings recorded higher values for some biological and economic traits in the different silkworm types during different seasons. The incorporation of new techniques of rearing the crossbreed silkworm types in thatched mud wall rearing house, medium spacing of worms and three feeding a day was found to be an ideal profitable package during unfavourable seasons as comparable to that of favourable seasons.
  • Thumbnail Image
    ThesisItemOpen Access
    Pathogenesity of thai sacbrood virus to the ecotypes of Apis cerana indica Fab. in Kerala
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 1998) Devanesan S; KAU; Abraham, Jacob
    Identification of ecotypes of the Indian bee A. cerana indica Fab. in different ecological niche in Kerala adopting statistical analysis of the morphometric data was attempted in the investigation. Sixty worker bees each were collected from 18 locations distributed throughout Kerala and data on 50 selected characters were collected. Univariate analysis showed significant variations in the data with reference to all the fifty characters indicating the desirability of a multivariate analysis for identifying sub groups of A. cerana indica available in the state. A comparison of the honeybee population of the three topographic divisions of the state viz., highrange, highland and midland, with reference to each morphometric character revealed that the bees from highrange were distinct from those of highland and midland. There was less distinction between the bees of the latter two divisions. It also indicated that the highrange bees possessed longer proboscis, antennae, wings and legs. The abdominal size also showed an increasing trend in highland and highrange bees. Eleven morphometric characters were positively correlated with altitude while seven characters showed negative correlation. Multivariate(discriminant) analysis of the morphometric data revealed the existence of four different clusters / ecotypes in A. cerana indica populations of Kerala. Cluster I included all the six locations of midland and four locations of highland. Two locations of highland at higher altitude formed cluster 11. Pampadumpara of the highest altitude in highrange came in cluster IV and remaining locations of the highrange constituted cluster Ill. Contribution of each morphometric character towards divergence of the clusters was also assessed. Seventeen characters contributing 2.5 to 6.4 per cent of divergence were thus identified. Bees from all the four clusters / ecotypes showed susceptibility to Thai Sacbrood Virus (TSBV) infection. Studies on the pathogenicity of TSBV showed that all four larval instars of A. cerana indica were susceptible to TSBV. One day old larvae were highly susceptible recording 100 per cent mortality closely followed by 2 and 3 day old larvae showing 84 to 92 and 82 to 96 per cent mortality respectively, with an incubation period of 3-4 days. Four day old larvae were comparatively less susceptible recording 72 to 74 per cent mortality with an incubation period of 3 to 5 days. The infected larvae were seen lying on the floor of the brood cells on their back with the head directed outwards and turned upwards like the prow of a boat. In later stages they became plumbier than healthy larvae. After death each larva showed a sac like appearance when lifted up and it was filled with a milky fluid formed probably by the histolysis of the tissues. In 10 to 15 days the sac got shrunk into a small browinish black scale \ " loosely lying at the floor of the' cell. The presence of diseased larvae was found to upset the behaviour of workers and queen. These resulted in the fast dwindling of the population and cessation of cleaning activities in the hive. The hive lost the desired qualities of a bee abode and hence the surviving bees deserted the same causing total loss to apiary.