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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 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 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.ThesisItem Open Access Control of cashew stem borer (Plocaederus ferrugineus L.) by the DD. 136 nematode (Nevaplectana earpocapsae Weiser 1955)(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1989) Madhu, S; KAU; Venkitesan, T SAn experiment was conducted at the Department of Agricultural Entomology, College of Horticulture, Vellanikkara to evaluate the possibility of utilisation of the DD-136 nematode, Neoaplectana carpocapsae Weiser to control the grub popoulations of stem borer of cashew Plocaederus ferrugineus L. The grubs belonging to different insters were treated with different doses of the nematode under simulated field conditions. The results of the study indicated that the nematode is incepable of inducing mortality of the grubs of cashew stem borer, even under conditions favourable for the nematode. Detailed , in depth studies on the various aspects of host nematode parasite relationships were warrented. Also it will be worthwhile to examine the possibilities of using other bio-control agents against the cashew stem borer.ThesisItem Open Access Bio-ecology of the cyst nematode infecting banana(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1989) Job Sathyakumar, Charles; KAU; Venkitesan, T SPathogenicity of the cyst nematode on banana cv. Nendran carried out revealed that the nematode can affect crop growth and yield at lowest initial inoculum of 100 cyst3 per plant. However, the threshold level of initial inoculum of 800 to 1,000 cysts per plant the growth, yield and quality of fruits were considerably reduced. An initial inoculum of 100 to 1,000 viable cysts per plant at planting time could reduce bunch weight by 20.5?£ to 56.6?4. The nematode Infection was observed to affect quality of fruits by increasing acidity and reducing total sugars. This nematode attacks the minute tertiary feeder roots and not observed to attack the fleshy roots and rhizome portions. The attacked feeder roots turn black in colour and detach easily. The final nematode population revealed that there was significant build up in the density of population. The increase ranged from 15*59 to 35.18 per gram root and from 1,168 to 3,188 in 100 gram soil. A significant negative correlation was found to exist with plant growth parameters, bunch characteristics and root weight with the initial inoculum levels of cyst nematode population.ThesisItem Open Access Bioefficiency persistence and residue dynamics of carbofuran in bittergourd (Momordica charantia L.)(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1989) Cherian Thomas; KAU; Sosamma JacobStudies were undertaken to assess the bioefficiency, persistence and residue dynamics of carbofuran in bittergourd (Momordica eharantia L.). Carbofuran was applied at two doses, 0.75 and 1.5 kg ai/ha at different growth stages, namely sowing, vining, flowering and at all the above three stages of the bittergourd crop. An untreated control was also maintained to compare the effects of various treatments. All the treatments recorded lower population of epilachna beetle (Henosepilachna 28 punctata Fab.) than control. But the treatment wherein carbofuran ® 1.5 kg ai/ha applied at the time of sowing, vining and flowering was found to be the most effective one in controlling the epilachna beetles with 95,79 per cent reduction over control 80 days after sowing. In controlling the red pumpkin beetle Raphidopalpa feveicollis Lucus. and melon fruit fly Dacus cucurbitae Coq. also the same above treatment was found to be the most effective one. The percentage of reduction in incidence of fruit fly was of the order of 79.72 over control in terms of fruit damage by number and 83.35 by weight. The treatment in which carbofuran Q 0.75 kg ai/ha applied at the time of sowing was found to be least effective in controlling the above pests.
