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Kerala Agricultural University, Thrissur
The history of agricultural education in Kerala can be traced back to the year 1896 when a scheme was evolved in the erstwhile Travancore State to train a few young men in scientific agriculture at the Demonstration Farm, Karamana, Thiruvananthapuram, presently, the Cropping Systems Research Centre under Kerala Agricultural University. Agriculture was introduced as an optional subject in the middle school classes in the State in 1922 when an Agricultural Middle School was started at Aluva, Ernakulam District. The popularity and usefulness of this school led to the starting of similar institutions at Kottarakkara and Konni in 1928 and 1931 respectively.
Agriculture was later introduced as an optional subject for Intermediate Course in 1953. In 1955, the erstwhile Government of Travancore-Cochin started the Agricultural College and Research Institute at Vellayani, Thiruvananthapuram and the College of Veterinary and Animal Sciences at Mannuthy, Thrissur for imparting higher education in agricultural and veterinary sciences, respectively. These institutions were brought under the direct administrative control of the Department of Agriculture and the Department of Animal Husbandry, respectively. With the formation of Kerala State in 1956, these two colleges were affiliated to the University of Kerala. The post-graduate programmes leading to M.Sc. (Ag), M.V.Sc. and Ph.D. degrees were started in 1961, 1962 and 1965 respectively.
On the recommendation of the Second National Education Commission (1964-66) headed by Dr. D.S. Kothari, the then Chairman of the University Grants Commission, one Agricultural University in each State was established. The State Agricultural Universities (SAUs) were established in India as an integral part of the National Agricultural Research System to give the much needed impetus to Agriculture Education and Research in the Country. As a result the Kerala Agricultural University (KAU) was established on 24th February 1971 by virtue of the Act 33 of 1971 and started functioning on 1st February 1972. The Kerala Agricultural University is the 15th in the series of the SAUs.
In accordance with the provisions of KAU Act of 1971, the Agricultural College and Research Institute at Vellayani, and the College of Veterinary and Animal Sciences, Mannuthy, were brought under the Kerala Agricultural University. In addition, twenty one agricultural and animal husbandry research stations were also transferred to the KAU for taking up research and extension programmes on various crops, animals, birds, etc.
During 2011, Kerala Agricultural University was trifurcated into Kerala Veterinary and Animal Sciences University (KVASU), Kerala University of Fisheries and Ocean Studies (KUFOS) and Kerala Agricultural University (KAU).
Now the University has seven colleges (four Agriculture, one Agricultural Engineering, one Forestry, one Co-operation Banking & Management), six RARSs, seven KVKs, 15 Research Stations and 16 Research and Extension Units under the faculties of Agriculture, Agricultural Engineering and Forestry. In addition, one Academy on Climate Change Adaptation and one Institute of Agricultural Technology offering M.Sc. (Integrated) Climate Change Adaptation and Diploma in Agricultural Sciences respectively are also functioning in Kerala Agricultural University.
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ThesisItem Open Access Biology and biometry of Neochetine elchhorniae warner (Curculionidae: Coleoptera) and the nature of damage caused by it on Eichhornia crassipes (mart)(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1990) Sreekumar, K M; KAU; Joseph, DThe biology, morphology, biometrics and dispersal pattern of the weevil Neochetina eichhorniae Warner and the nature and extent of damage caused by it on water hyacinth (Eichhornia crassipes (Mart.) were studied. An indirect method of estimating the field population was also attempted. The insect laid the eggs beneath the epidermis of plant parts. Incubation period was 6.6 days and the hatching percentage was 93.2. The larvae fed by tunnelling, and the first, second and third larval instars were completed in 8-10, 13-16 and 13-17 days, respectively. The cocoon was attached to the live roots of the plant and the pupation was just below the water surface. The pupal period was 16.6 days. Adult female longevity was 75.3 days while that of the male was 172.3 days. Pre-oviposit iona I period was 49 days and the total number of eggs produced during the whole life period was 462.5. The head capsule width of first, second and third instar larvae were 0.3, 0.488 and 0.693 mm respectively. In adult males, the average distance between the antennal socket and the tip of the rostrum was 0.259 mm and it was 0.487 mm in females. This character helps in the identification of sexes. No microbes or mites were recorded as natural enemies. The predators were the common non-specific aquatic insects like dytiscid beetle, giant water bug, dragon fly naiads and back swimmers.ThesisItem Open Access Biology and Population Build up of the Rice Whitebacked Planthopper, Sogatella furcifera (Horvath) on Different Rice Varieties(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1990) Ajith, P P; KAU; Madhavan Nair, GInvestigations were carried out in the College of Agriculture, Vellayani during 1988 to identify cultivars resistant to the white backed planthopper, S. furcifera from among the high yielding rice varities commonly cultivated in Kerala. The rice cultivars Cul 126, Cul 93, Ptb 33, Karthika, Pavizham, Jyothi, Triveni and TN-1 were chosen for preliminary screening by seed box screening, free-choice and no-choice tests and by tests on orientation and settling response and population build up. In the seed box screening and free choice and no choice tests, the cultivar Cul 126 recorded the lowest damage and the cultivar TN-1 showed the highest damage, indicating resistance in the former and susceptibility in the latter. The cultivar Jyothi did not differ from Cul 126 and the cultivars Cul 93, Ptb 33, Pavizham and Karthika showed intermediate levels of resistance. In the orientation and settling response test the highest number of S. furcifera nymphs were seen settled on TN-1, where as it was the lowest on Cul 126 and it was followed by Jyothi, indicating a clear preference to the susceptible TN-1. The insect multiplied faster and in greater number on TN-1 and the total count was about thirty times more on TN-1 as compared to that on Cul 126 at 60 days after release. Based on the results of the preliminary screening trials, the cultivar Cul 126 and Jyothi (resistant), Pavizham and Karthika (moderately resistant) and TN-1 (susceptible check) were selected for studying the mechanisms of resistance. In the experiment to study the ovipositional preference of the insects it was found that the susceptible TN – 1 and the resistant Cul 126 received the highest and lowest number of eggs respectively. It was also revealed that the leaf sheath received more eggs than the leaf blade. The antibiosis factor in the cultivars was investigated in terms of nymphal duration, nymphal survival, sex ratio of emerging adults, adult longevity, fecundity and hatching percentage of eggs in three growth stages of plants, namely, seedling, tillering and booting stages. The insects from the susceptible TN – 1 had the shortest nymphal duration and the longest adult longevity. The percentage of nymphal survival, fecundity and female/male ratio of the emerging adults were also the highest on TN -1. However, the insects from Cul 126, and Jyothi had longer nymphal duration and shorter adult longevity. The survival, fecundity and female/male ratio of the emerging adults from these cultivars were also lower as compared to TN – 1. The results were uniform in all the three growth stages of the crop. No difference could be observed in the hatching percentage of eggs in the test cultivars in the seedling stage, but in the tillering and booting stages the eggs on TN – 1 showed higher hatching percentage. The results indicated the presence of antibiosis factor in the resistant cultivars, Cul 126 and Jyothi. These results were further confirmed in the experiment on the feeding rate of the insect on the test cultivars. Insects on TN-1 produced the largest area of honey dew spots as compared to others in all the three growth stages showing significantly higher feeding rates. The feeding rate in Cul 126 was the lowest. The effect of crowing of first instar nymphs was more pronounced on the insects on TN-1. The survival percentage was the maximum in crowing at the rate of 25 and it dwindled substantially in the susceptible and resistant cultivars alike in crowding at the rate of 100. Crowding did not have any effect on the sex ratio and brachyptery of emerging adults. When S. furcifera and N. lugens were released together in different proportions, the latter surpassed the former in total number in all the cultivars when counts were taken at 60 days after release of the insects. The result indicated that in cultivars resistant or susceptible to both the insects, N. lugens established a numerical superiority over S. furcifera. In studies to identify the wet land weeds which serve as alternate hosts to S. furcifera, it was found that the insects oviposited in none of the weed plants tested. The nymphs could survive only on Echinochloa colona and Panicum repens.ThesisItem Open Access Effect of chitin synthesis inhibitors on rice swarming caterpillar spodoptera mauritia and rice moth corcyra cephalonica and a larval parasitoid bracon brevicornis(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1991) Prathapan, K D; KAU; Dale, DEffects of four chitin synthesis inhibitors viz. diflubenzuron, chlorfluazuron, PH 70-23 and BASF LAB 153 959 I were assessed on two insect pests, the rice swarming caterpillar Spodoptera mauritia ( Boisduval) and rice moth Corcyra cephalonica (Stainton) and on its larval parasitoid Bracon brevicornis (Wesmael). Ovicidal action was assessed by treating one and two-day old eggs of S. mauritia in aqueous and mathanilic media. It was low in aqueous medium. But in methanolic medium diflubenzuron and the highest doses of the other three compounds showed enhanced action. In general, high ovicidal action was observed in methanolic medium. There was no significant difference between one and two-day old eggs in their susceptibility to chitin synthesis inhibitors. Chlorfluazuron was the most toxic causing cent per cent mortality at doses as low as 2 x 10 -5% when treated on second and fifth instar larvae of S. mauritia. Diflubenzuron, PH 70-23 and BASF LAB 153 959 I were also highly effective. Second instar larvae were more susceptible than fifth instar ones. Besides stomach action, a high degree of contact action was also observed. Final instar larvae of S. mauritia when treated with the test chemicals, produced larval-pupal intermediates and caused pupal mortality and emergence of deformed adults. All the four moult inhibitors were highly active during larval – pupal transformations. Pupae were less susceptible to chitin synthesis inhibitors. Yet, some treatments caused mortality and emergence of deformed adults. Chlorfluazuron was the most toxic to pupae. Fecundity, hatchability of eggs and longevity were reduced when the male moths of S. mauritia were fed on sugar solution containing the moult inhibitors. Antifeedant action of the chitin synthesis inhibitors was found to be less pronounced. Residual effect of all the four compounds persisted on the treated rice foliage throughout a study period of 36 days. But the efficacy of residues exposed to sunlight and rain was very low. Ovicidal action of the moult inhibitors was low to moderate on one and four-day old eggs of C. cephalonica in aqueous medium. In methanolic medium diflubenzuron at 2 x 10 -1 %, 2 x 10 -2 % and 2 x 10 -3 % and PH 70-23 and BASF LAB 153 959 I at 2 x 10 -1 % caused enhanced ovicidal action. In general there was no significant difference between the susceptibility of one and four-day old eggs. Chlorfluazuron was found to be the most toxic compound against larvae of C. cephalonica followed by BASF LAB 153 959 I. Diflubenzuron and PH 70-23 were less effective. Early larval instars were more susceptible. Contact action of compounds other than chlorfluazuron was low. Larval – pupal intermediates, pupal mortality and emergence of deformed adults were resulted when the last instar larvae of C. cephalonica were treated with the chemicals. Chlorfluazuron was found to be the most toxic compound. Prepupal treatment also caused the above juvenomimetic effects. But treatments other than chlorfluazuron 2 x 10 – 2% were less effective. Treatment of pupae of C. cephalonica resulted in pupal mortality and emergence of deformed adults. But pupae were less susceptible to the moult inhibitors as compared to the larval stages. External application of Chitin synthesis inhibitors to moths of C. cephalonica had no adverse had no adverse effect on fecundity, hatchability of eggs and longevity of the treated moths. Chlorfluazuron was found to inhibit the emergence of adult parasites from treated hosts and adversely affect the progeny production of B. brevicornis. Diflubenzuron, PH 70-23 and BASF LAB 153 959 I were non-toxic or only slightly toxic to the parasite.ThesisItem Open Access Nature and extent of damage caused by insect pests on stored pepper, cardamom, ginger and turmeric(Department of Agricultural Entomology, College of Agriculture, 1992) Jijy Joseph, KAU; Nalinakumari, TThe occurrence and distribution of insect pests in stored ginger, turmeric, pepper and cardamom in five districts of Kerala were assessed in a survey conducted at bimonthly intervals for a period of six months. In stored ginger, the major pests recorded were L. serricorne and A. fasciculatus and in turmeric, L. serricorne. Low infestation Of S. paniceum occurred in pepper. Cardamom was relatively free of insect infestation. Both adult and larval stages of these pests damaged these produces. Besides these, damages by T. castaneum, L. minutes, O. surinamensis and R. dominica in ginger and turmeric were observed in a few samples. Stray samples of turmeric also showed infestation by adults and grubs of S. paniceum. Caterpillars of P. manihotalis, E. zebrine and S. ruttella were seen infesting neglected stocks of ginger and P. manihotalis and E. zebrine in neglected stocks of turmeric and pepper respectively. Quantitative loss studies revealed a loss of 13.01 per cent and 17.97 per cent respectively in ginger and turmeric by L. serricorne in six months, where as A. fasciculatus caused 11.58 per cent loss in ginger. Pepper exposed to S. paniceum caused only 1.2 per cent loss over a period of six months. While the volatile oil content of ginger infested by L. serricorne and A. fasciculatus reduced significantly after five months, the non volatile acetone extract reduced significantly in the sixth month compared to the fixed quality standards. In turmeric L. serricorne infestation resulted in a significant decrease in volatile oil content after three months of storage and non volatile acetone extract after five months. Significant positive correlation existed between the population build up and weight loss in ginger infested by L. serricorne and A. fasciculatus and turmeric by L. serricorne. In pepper exposed to S. paniceum the correlation was not significant. Significant negative correlation existed between the population build up of L. serricorne and A. fascicultus and volatile oil content and non volatile acetone extract of ginger and L. serricorne and volatile oil content of turmeric. The correlation between the population build up of L. serricorne and non volatile acetone extract in turmeric was not significant. Significantly high incubation period of L. serricorne was recorded in ginger compared to turmeric and only insignificant differences were noticed in larval and pupal duration and adult longevity. S. paniceum showed significantly high incubation and pupal period in pepper compared to that in turmeric where as the adult longevity was significantly higher in turmeric. Compared to L. serricorne, A. fasciculatus took longer period to complete its development in ginger.ThesisItem Open 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 ThomasThe 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.ThesisItem Open 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 KAn 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.ThesisItem Open Access Resurgence potential of the rice leaf folder. Cnaphalocrocis.medinalis Guen. as influenced by the soil application of carbofuran granules(Department of Agricultural Entomology , College of Horticulture, Vellanikkara, 1991) Baby, P Skaria; KAU; Abraham, C CIn investigations on the changes taking place in the extent of feeding, growth and development of the rice leaf folder, Cnaphalocrocis medinalis Guen. on rice plants receiving soil application of carbofuran granules at 0.50, 0.75 and 1.00 kg ai/ha/application at 20, 50 and 20 and 50 days after transplanting, the extent of larval feeding on leaves did not show any variations as a result of carbofuran treatments. In the third, fourth and fifth larval instars and pupae, carbofuran treatments led to their weight gain due to possible enhancement of the digestibility and more effective conversion of ingested food into body matter, under .influence of factors mediated by the metabolites of carbofuran in leaf tissues. In respect of mean larval and pupal mortality, the insecticidal treatments did not show any impact, but the metabolites showed a negative correlation with the mortality levels thereby indicating the favourable influence of the metabolites on the development of C. medinalis. There was improvement in female emergence as a result of treatment with 1.00 kg ai/ha of carbofuran applied at 20 as well as 50 DAT as compared to untreated control, but the sex-ratio variations as a result of treatments were not pronounced. The first instar larval emergence (F1 generation) showed a positive influence by different metabolites of carbofuran. Carbofuran treated plants showed distinctly positive orientational stimulus to C. medinalis adults due to positive olfactory stimuli probably due to emission of vapour-phase admixture of carbofuran metabolites, but there was no improvement in fecundity under such treatments. There was distinct improvement in progeny production from females developing from carbofuran treated rice plants. This is mainly due to the ingress of more female moths and the resultant increase in overall ovipositional output rather than increase in fecundity'. Carbofuran treatments caused increase in the density of leaf hairs in a dose-dependent manner, but such variations were not significant as compared to untreated control. The positive relationship between ovipositional preference on the one hand and leaf hair density of treated plants .on the other brings to focus the role of tactile stimuli provided by leaf hairs in the acceptance of host plants for oviposition. The residues and metabolites of carbofuran in leaves favourably influenced most of the growth and developmental attributes of the rice leaf folder. None of the plant biochemicals showed any changes under influence of carbofuran treatments.ThesisItem Open Access Distribution of spindle bug of Arecanut, Carvaholia arecae Miller and China in Kerala.Its broecology, suspected role as the vector of yellow leaf disease and control(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1990) Stanley, Jacob A; KAU; Mohan, Das NA state wide survey was conducted in Kerala during 1988 with a view to ascertaining the distribution and severity of incidence of C. arecae and yellow leaf disease on arecanut. The pest enjoyed a state wide distribution while the disease was present only in 40 per cent of the locations covered in the survey. Based on the percentage of the infested palms and on adult popula tion of the insect, the southern zone was found as most affected and the nymphal population was more in the northern zone. Based on total population northern and southern zone came on par. The leaf injury caused by the bug was higher in the northern zone and other zones came on par and less effected. Thus on different criteria the severity of the pest infestation in different agroclimatic zone did not show consistency .Vadakkanchery and Palghat in the middle zone were identified for the first time as the only pest free locations in Kerala. In southern zone, Pandianpara, Kattakkada and Ettiruthi had high pest incidence while at Theviyode, Vithura and palode the infestations were found comparatively lower. A consecutive monthly monitoring of the populations in five of the above locations during 1987-89 revealed that places found less affected in the single state wide survey were seen badly affected and vice versa in repeated assessment. In the problem zone Moncompu, Vytilla and Chengannur were much more affected than Karthikaplly, Kumarakom and Karunagapally. In the middle zone, Alwaye, Pattikkad and Peechy were more affected than Vadakkanchery, Palghat and Mukundapuram. In the hill zone Peringamala, Vythiri and Ernadu had much higher population than Vaduvanchal and Kottapady. In northern zone Calicut, Taliparamba, Madhur and Koipady were more infested than Kumbla, Tellichery and Koothuparamba. Since repeated survey over two years reversed the relative position of the locations based on single survey, the latter did not appear conclusive thus suggesting the need for resorting to control measures throughout the state for tackling the pest problem. A new spot of high incidence of yellow leaf disease in north Kerala was detected at Irrikkur near Cannanore. Incidence of C.arecae and yellow leaf disease did not show any association in different agroclimatic zones in Kerala or among different locations within each zone. Continuous monitoring of the population over 24months revealed that the occurrence of immature stages and adults overlapped, indicating continuous breeding of the pest. Period of high/low incidence of pest could not be identified consistently. The occurrence of the symptoms of yellow leaf disease did not coincide with the levels of fluctuating pest population. Maximum temperature and minimum relative humidity showed negative and positive correlation with the pest population respectively. C.arecae fed and multiplied on its alternate hosts A. triandra, C. lutescens and pinanga sp.as favourable as on A catechu. E.guineensis also was found a suitable host since the immature and adult stages of the pest on the host showed more favourable attributes when compared to those on A. catechu. The feeding behavior of the insect relating to the ‘plant surface exploration ‘,’exploratory probes ‘ and ‘imbibing food ‘ agreed with the behavior of other ‘Cimico-morphs’ described by earlier workers. The feeding suppressed the emergence of spindle leaf partly or fully depending on the period of the damage. Total suppression of spindle leaf emergence even choked further growth of the palm. Injury caused by oviposition was observed in detail for the first time .Characteristic ‘pot marks’ made on the rachis of the leaf and the internal damage also were noted in detail for the first time. Histological observations of the leaf along the feeding marks showed that the bug resorted to ‘lacerate and flush’ feeding .Formation of water soaked areas soon after stylet insertion , continuance of plasmolysis after the removal of the insect from the feeding spot and later discolourations and collapse of cells indicated that the action of the saliva would have caused the injury . Histochemical studies of the injured leaf lamina showed accumulation of proteins and lipids in the portion . The above host reactions were detected for the first time . A new technique of warding off C. arecae from the crown of areca palms by keeping phorate /carbofuran granules in perforated polythene sachets , at the leaf axil, was developed and standardized . The technique was evaluated at field level in comparison with the recommended methods of spraying insecticides on the crown or keeping granules directly in leaf axils. On the basis of cost and bioefficacy, the new technique was found far superior to the recommended practices. Salivary glands of C.arecae , exposed on yellow leaf disease affected palms for 20 to 33 days (ensuring acquisi-tion and incubation periods for MLO), were excised , processed , stained and examined under electron microscope for locating mycoplasma like organisms in the acini of the anterior, posterior and lateral lobes, if any . The haemolymph drawn from such insects also was examined under electron microscope . MLOs were absent in all the preparations. This finding in conjunction with the absence of correlations between the pest population and disease incidence ruled out the possibility of the insect being a vector of the disease.ThesisItem Open Access Nematodes associated with the tuber crops In Kerala(Department of Agricultural Entomology, College of Agriculture, Vellayani, 1991) Remesh, Kumar V; Ravindaran, Nair K KA survey of plant parasitic nematodes of tuber crops, cassava, sweet potato, coleus, colocasia/xanthosoma and diascorea in twenty five panchayats representing five agroclimatic zones of Kerala was conducted during December, 1988. This was the first attempt in this line of investigation. Meloidogyne sp. and Rotylenchulus sp. were more widespread with all the five tuber crops in the five agroclimatic zones of Kerala. These two genera were seen in soil and root samples. Rotylenchulus sp. was more predominant than Meloidogyne sp. in tapioca, sweet potato and diascorea than in colocasia /xanthoma and coleus. The two genera of nematodes are potential threat to cultivation of all the five tuber crops in Kerala. Pratylenchus sp. was also observed in soil samples associated with all crops but it could be collected from the root samples of diascorea and colocasia/xanthosoma only. In high population the genera may become a potent meance to both the crops since its pathogenecity on these crops have already been established. Helicotylenchus sp. and Radopholus sp. could be seen in soil samples associated with all the crops, Helicotylenchus sp. was more predominant in distribution and intensity in the tuber crops in all the agroclimatic zones. Hoplolaimus sp. was seen associated with diascorea alone in soil samples among the five crops in most cases. Tylenchorynchus sp. could be obtained from soil samples associated with all crops except diascorea. Heterodera sp. and Tylenchus sp. were recorded from colocasia/xanthosoma and sweet potato very sparsely. The effect of varying levels of M. incognita on the growth parameters and yield of C. esculenta was assessed in a pot culture experiment. A population of 500 larvae per plant found causing 12 per cent yield reduction over control. With an increase in the initial population of the pest a progressive suppression in plant height, number of leaves, shoot weight, root weight and weight of tubers and an increase in trend in pest population, root knot and percentage of galls (weight basis) were observed. But these were not linear. Apparently healthy tubers harvested from the nematode inoculated treatments suffered spoilage in storage. Histopathological observation of M. incognita infested colocasia roots showed that the damage was similar to those reported in colocasia roots showed that the damage was similar to those reported in coleus and sweet potato. A pot culture experiment revealed that the extent of adverse effect on the tuber crops did not show wide variations at the normal and water stress conditions. In coleus the adverse effect on the growth of the plant by nematodes was more with higher levels of irrigation. Less frequent irrigation in sweet potato and coleus caused higher reduction in the population of the pests compared to that in dioscorea. Even with lesser population of nematodes more damage can occur in a crop under stress and the response was found to vary with crops.