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ThesisItem Open Access Control of aphis craccivora koch. with fungal pathogens and their impact on the natural enemies of the pest(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1989) Hareendranath, V; KAU; Vasudevan Nair, K PStudies were made to collect information on the population fluctuation of pea aphid Aphis craccivora Koch. a regular pest of cowpea in relation to time of planting and stage of the crop. The population fluctuation of pea aphid in relation to the prevailing weather factors and the predators were also investigated to collect information on host predator interactions and interrelations. A survey on the occurrence of fungal pathogens associated with pea aphid was conducted in the pulse crops raised at the Instructional Farm, College of Agriculture, Vellayani and adjacent farmers fields. The suspected fungi were isolated and their pathogencity tested in the laboratory. Pathogencity could be proved only in the case of Fusarium pallidoroseum (Cooke) Sacc. Detailed studies were made on its growth, sporulation and pathogenicity using different artificial culture media. It was observed that the cowpea crop planted during November recorded maximum population of pea aphid followed by crop planted during October and December. Lowest population of pea aphid was noticed in the crop planted during March. The active reproductive stage of the crop recorded maximum population of pea aphids. Correlation studies with weather factors and predator population revealed that relative humidity and predator population was positively correlated with the population of pea aphid. Regression analysis of the data obtained indicated that 84 per cent of variation of population could be accounted by the variables under study. Partial regression coefficient of the aphid population and relative humidity was found to be positive and significant. Partial regression coefficient between pea aphid population and predator population was also positive and highly significant. Studies on the pathogenicity of F. pallidoroseum showed that pea aphid infected with the fungus turned pale and assumed a brownish black discolouration. Death occurred in 48 to 72 hours after infection and white mycelial growth appeared on the cadavers 24 to 48 hours after death. Growth, sporulation and virulence of the fungus was found to be superior in Sabouraud medium followed by potato dextrose agar. Sporulation was maximum in 6 day old culture and virulence was highest in 6 day and 7 day old cultures. For mass production of the fungus broken maize grain appeared to be the most suitable media followed by tapioca chips and jack seed as they produced maximum number of spores. Studies on the safety aspects of the pathogen showed that the fungus was not pathogenic to the crop plants tested viz. rice, bhindi, chillies and tomato and also to the predator Menochilus sexmaculata. Bioassay showed that LC50 of the fungus to pea aphid was 3.408 x 10 6 spores per ml. Field experiment to test the efficacy of the fungus in controlling aphid population revealed that the fungus at the rate of 7 to 10 6 spores per ml and 3.5 x 10 6 spores per ml was as effective as the insecticide quinalphos 0.05 per cent. The fungal treatment did not show any harmful effects on predator population in the field.ThesisItem Open Access Bioecology and control of pests of rose(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1989) Vijayan Nair, V; KAU; Visalakshy, AThe distribution of the major insect and mite pests of rose in Trivandrum taluk and the damages caused by them were studied in a survey . The survey was conducted in six locations in the taluk (Kowdiar, Paruthippara, Karamana, Palkulangara, Vanchiyoor and Vellayani) at monthly intervals for a period of 13 months starting from August 1986, adopting standard sampling techniques . The results of the survey revealed that the major pests of rose in the area were the thrips, R. Syriacus, S. dorsalis, the scale A. aurantii, the leaf feeding beetles Adoretus spp and the mites, T. neocaledonicus and T.cinnabarinus. The mean levels of population /damage found during the period of the survey showed that T.neocaledonicus was the most important pest in all the locations and it caused more than 50 percent of the plants damaged in some locations. It was followed by Adoretus spp, A. aurantii, R. syriacus, S.dorsalis and T.cinnabarinus in a descending order of importance with apparent variations in pest status at different locations. An overall assessment of the seasonal incidence of the pests revealed that the thrips and mites were seen in serious proportions during the months of December to May and the beetles caused heavier damage from November to January whereas the scale insect was seen damaging the plants throughout the year. Between the population of thrips and mites and maximum temperature there was significant positive association. While the relative humidity and number of rainy days showed significant negative correlation. Rainfall also had significant negative correlation with the thrips and mites, but it was statistically insignificant in the case of T.cinnabarinus only. The nature of damage caused by various pests of rose was studied in detail. It was seen that the thrips, mites and the scales were causing serious damage to leaves causing its drying and withering. The other sucking pests and the defoliators noted were of minor importance except the leaf beetles Adoretus spp which was found to cause serious defoliation of the of the plants. The investigation on the biology of R.syriacus on the rose showed that the life cycle was completed in 16.9days. When they were reared on castor and subabul the duration and size of various stages were same as those of rose while those reared on cassava were bigger in size and the life cycle was shorter. The experiments on chemical control of pests of rose showed that monocrotophos, dimethoate or fenthion at 0.05percent spray was effective in controlling the different spices of pests . But in the case of flower bud damage caused by S.dorsalis, a higher concentration of 0.1 per cent of the insecticides was necessary for getting proper control.ThesisItem Open Access Pest complex associated with mango inflorescence and their control(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1984) Satheesan, N V; KAU; Abraham, C CIn a survey conducted during 1982-83 in the State of Kerala to study the incidence of various insect pests associated with mango inflorescence with reference to their seasonal history, a total of ten insect pests were recorded. The hoppers idioscopus niveosparaus Leth. and I. clypealis Leth. were found to be widely distributed in the State. Significant variability was not detected among the population loads of I. niveosparsus in different districts, while in the case of I. clypealis such variations were significant. The heaviest populations of the latter was recorded from the Calicut District. The seasonal changes in I. clypealis populations were recorded only in the two Districts of Calicut and Trivandrum. I. niveosparsus showed a well defined peaks in the Palghat and Wynad districts. The fluctuations I. niveosparsus and I. clypealis populations have been discussed with reference environmental conditions. Procystiphora mangiferae Felt. is reported for the first time from the State from the Wynad and Cannanore Districts. Infestations by the pest led to transformation of the floral buds to conical galls. In the Wynad District, there was a well defind population peak in March, while in the Cannanore District a district crest waslacking. The mango blister midge, Erosomyia indica grover and Prasad was recorded to occur in association with P. mangiferae in these two districts. The larvae of E. indica tunnel into inflorescence axis and cause ovate galls thereby causing losses. Bombotelia jocosatrix Gn. was recorded from the Cannanore, Palghat, Trichur and Alleppey Districts throughout the flowering season. Eublemma anguilifera Moore as well as another unidentified spp. of Eublemma were recorded to occur throughout the State, except in the wynad District. The seasonal fluctuations of this pest were significant only in the Palghat District. An unidentified species of Cacoecia was recorded for the first time as a minor pest of mango inflorescence. The larvae fed on flowers and floral buds. The other pests observed during the course of the survey were Rapala manea Hewitson, Haplothrips ganglbaueri Schmutz, Dichocrosis punctiferalis Guenee and an unidentified Geometrid. The bio-efficiency of monocrotophos applied by two methods, namely, stem injection and stem banding, against the Idiocerine hoppers infesting mango inflorescence was evaluated in a separate experiment. The relative toxicity of the insecticide was determined from the time- mortality relationship between the insecticide reaching the inflorescence of treated trees and the mortality of the fourth instar nymphs of I. niveosparsus. The LT -50 values of the nymphs following application of the insecticides by the stem injection method was found to be substantially lower than the corresponding values for the stem banding method of application. It was thus evident that the toxicant moved at a faster pace when administered by the stem injection method. The variations in the pattern of translocation of the toxicant under the two methods of administration have been discussed. The residues of monocrotophos on freshly formed mango fruit at five weeks after application by the stem injection method at 4 ml and 2 ml ai/tree were 0.3600 ppm and o.3750 ppm respectively. The corresponding residues in the mango fruit consequent on stem banding method of administration were 0.0550 ppm. The implications of the above results in formulating control methods against Idiocerine hoppers infesting mango inflorescence have been discussed.ThesisItem Open Access Taxonomic studies of leaf and plant hoppers associated with paddy in Kerala(Department of Entomology, College of Horticulture, Vellanikkara, 1984) Abdulla, K; KAU; Mammen, K VTaxonomic study on the leaf and plant hoppers of paddy was conducted to find out the various specious of leaf and plant hoppers associated with paddy in Kerala. Paddy fields from two important paddy growing tracts of Kerala viz., Trichur and Palghat were selected and weekly collections of hoppers were made. Collections were made with a fine mesh hand net for the entire cropping season from transplanting upto harvest. Fixed numbers of sweeps were taken from the same field in order to get an idea about the population fluctuations. Collections from each field for each week were separately preserved in homeopathic vials with collection data. Later insects in all vials were sorted out, number of specimens collected in each week were noted, sexes separated, and each species were preserved in separate vials. Vials were serially numbered and collection data were noted under each serially numbered species. Genitalia of males as well as general form and colouration of all species were stidied. However genitalic studies of Exitianus indicus (Dist.) and Nisia nervosa (Motsch.) could not be conducted for want of male specimens. Altogether nine species were collected viz., Nephotettix Virescens (Dist.), N. nigropictus (Stal), Recilia dorsalis (Motsch.) and Exitianus indicus (Dist.) coming under Cicadellidae, Nilaparvata lugens (Stal), Sogatella furcifera (Horv.),Matutinus pusanus (Dist.) belonging to Delphacidas and Nisia nervosa (Leth) under Meenoplidas. Among these species all but M. pusanus were reported to be occurring on paddy in India and other East Asian countries, while E. indicus and N. nervosa were not observed by earlier workers from Kerala. Apart from these, two male and two female specimens of Nephotettix showing variations in characters from N. nigropictus and N. virescens were also obtained. These may be natural hybrids between N. virescens and N. nigropictus. Certain morphometric studies were conducted using head measurements viz., eye diameter to interocular distance and /or vertical distance next to eye to median length of Vertex. It was found that there is difference between male specimens of N. virescens and N. nigropictus with regards to the ratio of vertical distance next to eye to median length of vertex; and in females of these species there is difference between the ratios of eye diameter to interocular distance. Similarly there is difference between male specimens of N. lugens and S. furcifera with regards to the ratio of eye diametor to interocular distance. Studies on the seasonal abundance of leaf and plant hoppers revealed that there is variation in the predominant species present in each area.ThesisItem Open Access Crops loss caused by root-knot nematode infesting coleus parviflours and its control(Department of Entomology, College of Agriculture, Vellayani, 1988) Sosamma, P; KAU; Ravindran Nair, K KCrop loss caused by the root-knot nematode infesting Coleus parviflorus and its control was studied in a pot culture experiment and a field experiment in the Department of Entomology, College of Agriculture, Vellayani, Trivandrum, during August to December, 1986. The number of leaves, shoot length, fresh shoot weight and weight of tubers obtained were less in inoculated plants than in control. The yield and growth parameters showed an negative correlation with the population of nematodes. A high positive correlation was noticed between the tuber weight and the number of leaves and shoot weight of coleus. The shoot length did not influence the tuber yield significantly. Roots showed profuse galling by the second month. Rotting of roots was observed by the third month, and at harvest, no healthy root was present in infected plants. Tubers when stored developed dark patches on the suface of galls and these spread inwards covering the whole of the internal tissues within nine days, and by the twelfth day the internal contents had turned into a dark brown watery liquid with a bad odour. The peel of the tubers did not show rotting. The nature of rot indicated the involvement of secondary organisms like bacterial and fungi. Histopathological studies showed that the nematodes were lodged in the cortex with head in the stellar region of the root. One month after inoculation, quadrangular giant cells (four in number) were observed in roots. There was cell proliferation in the stellar region of the infected roots. Alternate arrangement of the xylem and phloem was disturbed, though the central cylinder and cortex could be distinguished. Two months after inoculation the giant cells were seen larger and fewer in number. The cytoplasm of giant cells became granular and aggregated towards the head region of the nematode. Stele could not be easily distinguished from the cortex. The cortex was greatly enlarged due to hypertrophy and hyperplasia of cells. The development of medullary rays and secondary xylem noticed in the normal root could not be distinguished in infected roots. Infected roots showed numerous cavities formed by the disintegration of giant cells, egg masses and adult females by end of the fourth month. Necrosis of tissue was also observed. The xylem and phloem elements were not distinguishable. At five months after inoculation the tissues of the roots were completely rotten. In the field experiment application of nematicides one month after planting preceded by the burning of plant material in the field prior to planting was found better than the other treatments. Carbofuran @ 1 kg a.i./ha was more effective than phorate for the control of the nematode. No residue of carbofuran or phorate could be detected in tubers at harvest. The rotting of tubers obtained from different plots when kept in store indicated the inefficacy of the treatments for giving protection from the nematode and the need for a second application of the nematicide at tuber setting. Hot water treatments of the tubers prior to storage did not reduce the damage.ThesisItem Open Access Biology morphology nature of attack and dispersal of cytobagous salviniae calder and sands (Curculionidae coleoptera)(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1988) Leena, K T; KAU; Joy, P JIn studies on the biology and morphology of cyrtobagous salviniae calder & sands (curcullionidae: Coloeptera) a very successful agent for the bio control of the menacing weed salyinia molesta Mitchell, the females were found to insert their eggs on leaf base and rhizome scars. The egg period was 7.9 days. There are three instars, the average larva period was 23.5 days. The pupal period extended for 11.3 days. Adults showed a mean life span of 211.9 days. A pre ovipositional period of five to ten days was recorded. The three larval instars differed in respect of the relative size of head capsule and width of mandible. Adult females are slightly larger than the males. The spine like processes towards the distal end of the hind tibia are arranged in a linear manner, while in fore and midlegs these spines are arranged in a circular manner. The hind leg spur does not have a hump. Observations on the nature of damage showed that the adults were capable of arresting the growth of the weed by feeding on the buds and leaves. Occassionally they feed on rhizomes and roots. Larval scraping followed by tunneling resulted in the decay of plant parts. Weed mass showed discolouration about 15 days after initiation of feeding by the weevil and the whole weed became a black mass in about 90 days. The rate of dispersal of adult weevils was found to be very slow.ThesisItem Open Access Joint action of nuclear polyhedrosis virus of Spodoptera (Fabricius) with insecticides and its applicability in pest control(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1984) John, V Cherian; KAU; Vasudevan Nair, K PExperiments were conducted to study the joint action of nuclearpolyhedrosis virus (NPV) of Spodoptera litura (Fabricius) and five insecticides viz., quinalphos, carbaryl, BHC, monocrotophos and permethrin. The investigation carried out included bioassay of the virus and insecticideson third instar larvae of S.litura, effect of different combinations of the virus and insecticides on larval mortality and the effect of simultaneous and sequential application of virus and insecticides for the control of pest.ThesisItem Open Access Host resistance in bittergourd (Momordica charantia L.) to the infestation by the fruit fly Dacus cucurbitae Coq.(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1989) Padmanabhan, V; KAU; Madhavan Nair, GIn studies on the host plant resistance in Mamordica charantia L. to infestation by the fruit fly Dacus cucurbitae Coq. (Tephritidae: Diptera) a field trial for screening sixty six accessions of bittergourd was laid out in the summer season of 1984-85 in the Horticulture College Farm, Vellanikkara. The mean percentage of fruit infestation in the accessions ranged from 10.866 to 74.266. Based on the levels of fruit infestation , the accessions were classified as highly susceptible (more than 30 percent ) moderately susceptible (between 20 to 30 per cent) and moderately resistant (between 10 and 20 per cent)ThesisItem Open Access Pathogenicity of reniform nematode (Rotylenchulus reniformis Linford and Oliveira, 1940) on ginger (Zingiber officinale rose)(Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1989) Elizabeth John; KAU; Venkitesan, T STwo pot culture experiments were laid out (i) to study the pathogenic effect of different inoculum levels of R. reniforms on ginger comprising of seven treatments and four replications and (ii) to studythe relative pathogenic effect of root -knot and reniform nematodes singly or in combinations on the same crop comprising of five treatments and four replications. The duration of study was 120 days The result reveals that ginger is a good host for reniform nematode R. reniformis and it can cause pathogenic effect at a considerable extend at higher inoculum levels, within a period of 120 days.
