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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Open Access
Evaluation of multi x bi bivoltine hybrids of silkworm
(1998) Rajeni, Narayanan; KAU; Ranjith, A M
In a study undertaken to evaluate the region and season specific multi x bi and bivoltine hybrids of silkworm Bombyx mori, for commercial exploitation in Kerala, six hybrids of silkworm were reared using K-2 and S-36 mulberry varieties under Vellanikkara condition. The crosses used were PM x NB18, PM X NB4D2 and their reciprocals, NB4D2 x NB18 and its reciprocal and PM as check. The evaluation was carried out based on characters like leaf consumption, larval duration and weight, cocoon and shell weights, shell ratio percentage, average filament length, denier, reelability and renditta. The climatic factors were also correlated with major economic characters of silkworm. The present study confirms the superiority of bivoItine silkworm hybrids like NB4D2 x NBI8 and NB18 x NB4D2 justifying their wide acceptance in states other than Kerala. It is evident that if rearing is done in a systematic way, by strictly adhering to the brushing period in correlation with the seasons and if the use of high quality mulberry varieties is advocated these crosses will yield good returns in Veil ani kkara. Though the various economic parameters reflected a variable trend, ultimately when the average filament length/g cocoon, shell ratio percentage and cocoon weight were considered, the bivoltine hybrids performed superior to the others.
Open Access
Mass trapping of the sweet potato weevil (Coleoptera: Curculionidae) males using sex pheromone
(Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 1993) Mini, E S; KAU; Sitarama Rao, S
The efficacy of the synthetic pheromone of C. formicarius elegantulus in attracting the males of C. formicarius formicarius was tested in the field. The effect of continuous mass trapping of adult males on the population build up of the pest in the field was assessed. The effect of different doses of pheromone as influenced by the trap designs was also assessed. Low cost traps designed and fabricated out of locally available materials were tested in the field and incremental benefit of treatments was worked out. The range of attraction of pheromone doses was assessed by analysing the recapture data of marked males released at different distances from the pheromone baited traps. The results indicated that the weevils were most active during the night as is evidenced by higher capture of weevils at morning observations than those in the evening observations. The weevil catch was not significantly influenced by the higher doses of pheromone. Day light affected the flight pattern of weevils while the moon phases have no significant effect. continued attraction of males towards the pheromone baited traps indicated their effectiveness inspite of the presence of virgin females in the field. The pheromone doses were effective in checking the rapid build up of the pest in the field as evidenced by the non reduction in vine weight. Among the three trap designs polythene bag trap was the cheapest one to install and resulted in the most favourable C : B ratio. The attraction of the pheromone doses decreased with increase in the distance of release from the pheromone source. A distance of 25 m was found to be ideal for placement of traps in the field. The cheapness of traps facilitate installation of large number of traps at reasonable increase in cost.
Open Access
Bioecology of orthogalumna terebrants wallwork on waterhyacinth
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1994) Babykala, P; KAU; Joy, P J
The mite biology, morphology, nature of extent of damage and interaction with N. eichhorniae were studied. The might laid solitary eggs sideways to the oviposition holes, deeply embedded in the aerenchyma cells. The incubation period was 5.8 days. The larvae and nymphs fed by making galleries. The larvae, proto and deuto nymphal stages were completed in 3 days each, while that of tritonymph took 4 days. The duration of inactive stages from larva to proto, proto to deuto and deuto to tritonymphal stage were 1.6 days each, whereas from tritonymph to adult, it was 3 days. Adult longevity was 57.3 days. pre-ovipositional period was 4 days and the total number of eggs produced during the whole life period was 41.5 eggs. The larvae have three pairs of legs but no genital opening. The nymphal stages have four pairs of legs, ending in single claws. The proto, deuto and tritonymphal stages, have one, two and three pairs of genital papillae respectively. This character helps in identification of larval and nymphal stages. The adults are pteromorphs and sexual dimorphism is absent. Sensillus is relatively short with curved stem and globular roughened head. Terminally the tarsus of the leg has three claws on a short peduncle the lateral claws more slender than the median and sharply angled. The larval and nymphal feeding produces galleries on leaves of waterrhyacinth resulting in brown streaks on the leaf lamina. Such brown streaks later coalesce to form large brown areas, leading to drying up of the entire leaf. As the mite load increased from ten to eighty the number of plants and number of leaves showed significant reduction 90 days after release. The extent of damage caused by O. terebrantis with or without weevil under open and partially shaded conditions of waterhyacinth plants was experimented upon, and it showed that, the root length, petiole length ( in open condition), laminar width and length, number of leaves and number of plants under both light intensities (partially shaded and open condition), in general showed a decreasing trend. The plants in tanks having ten weevils alone per tank and 10 weevils plus 100 mites per tank under partially shaded conditions collapsed within 60 days, whereas in open condition of that having 10 weevils plus 100 mites per tank, all the plants collapsed by the 75th day. In the treatment with ten weevils alone per tank in open condition the collapse occurred only at 105 days. In the treatment with 100 mites alone per tank, there was no collapse of plants upto 105 days (in both conditions). The number of mite galleries and mite population per leaf with Neochetina feeding marks was comparatively more in the presence of weevils than in their absence. Fungi like Fusarium, Aspergillus and Rhizopus were isolated and also the spider mite and insects like aphids and grasshoppers were noticed.
Open Access
Isolation of the bioactive pinciples of thevetia nerlifolia juss.(Apocynaceae) and determination of their biological activities
(Department of Entomology, College of Agriculture, Vellayani, 1996) Hebsi, Bai; KAU; George, Koshy
Fresh and dried leaves and seeds of Thevetia neriifolia were evaluated for their antifeedant activity against Henosepilachna vigintioctopunctata, using acetone, benzene, ethanol, hexane, methanol and water as extractants. Based on the percentage of leaf protection, seed extracts were superior to the leaf extracts. Fresh leaf and dried leaf extracts were on par. Among the solvents, ethanol and methanol gave maximum leaf protection closely followed by water. Based on larval starvation, seed extracts were superior to leaf extracts and fresh leaf extracts were significantly better than dried leaf extracts. Water, methanol and ethanol were on par for extracting plant tissues. Soaking of powered plant material well in solvents for 48 hours and filteration was found as effective as soxhlet method for extracting antifeedant components from leaves and seeds of T. neriifolia. Leaves and seeds of the plant showed conspicuous hormonal/sterilant activity on Dysdercus cingulatus and the response was dose dependent. This was evident in post treatment larval mortality, prolonged preovipositional period, emergence of malformed adults and reduced fecundity. Adult longevity, incubation period and hatching percentage of eggs were not affected. Forty per cent and ten per cent of leaf and seed extracts as well as 20 and 5 per cent extracts of the same came on par in juvenomimetic effect. The results showed that seeds were four times more effective than the leaves in their juvenomimetic effect on D. cingulatus. The length of ovary, number of oocytes per ovariole and size of basal, penultimate and antepenultimate oocytes were significantly lower in seed and leaf extract treated females of D. cingulatus. Closer examination of the data revealed that growth of ovary was delayed rather than suppressed by the plant extracts. Levels of protein, glycogen and lipid contents observed on ovary, fat body and haemolymph of treated and untreated insects from first to fifth day after emergence indicated a delay in vitellogenesis and oocyte development in treated insects. Consequently previposition period was prolonged. The effect observed is similar to the effect of chemosterilants reported on some insects earlier. Results indicated that reduction in fecundity of D. cingulatus may be due to the chemosterilant action of T. neriifolia extracts. Bioassay studies in the laboratory revealed the low contact toxicity of leaf and seed extracts of T. neriifolia to S. litura and H. vigintioctopunctata. Chromatographic isolation of different fractions of ethanol extracts of fresh leaf and seed yielded six bioactive fractions from the leaf and four from the seed. Fractions III and IV were absent in seeds. Fractions IV, V and VI obtained from leaves and V and VI from seeds had far higher activity than the remaining fractions and they were on par in their antifeedant effect and larval starvation on H. vigintioctopunctata. Available active fractions were more concentrated in seeds than in leaves. Laboratory studies showed the safety of leaf and seed extracts of T. neriifolia at field doses to Chrysocharis johnsoni, the most important parasite of H. vigintioctopunctata in Kerala. Toxicological studies in albino mice and rats revealed that 400 mg/kg body weight was the LD50 dose of seed extract of T.neriifolia while doses upto 1000mg/kg body weight of leaf extract was not toxic to the animals. Haematological picture of animals chronically exposed to the extracts showed marginal deviations in the haemoglobin content, RBC count, serum cholesterol, SGOT levels in seed extract treated animals from the permissible safe range. Leaf extract treatment caused deviations in SGOT and serum cholesterol. Vacuolation, cytoplasmic acidophilia and degenerative changes in the liver and heart tissues and inflammation of kidney were observed in animals treated with seed extract. Adverse effects of leaf extract were negligible. Replicated field experiments were conducted for two seasons on bittergourd and amaranthus to evaluate the efficacy of crude extracts of T. neriifolia in controlling their major pests. All the extracts viz., ethanol and water extracts of dried and fresh leaves and seed reduced the pest population and the extent of leaf damage. Seed extract was on par with the insecticide check, carbary 1 (0.15 per cent) in bittergourd and malathion (0.1 per cent) in amaranthus. Fresh leaf extract was on par with the seed extract and was superior to extracts of dried leaf in reducing pest population and increasing yield of both the crops. Water extracts of leaves and seed were found equally good for checking the pest population and increasing yield. On cost benefit basis water extracts were found more advantageous to the farmer. Parasitization of egg masses, grubs and pupae in treated plots were on par with control while they were totally missing in the insecticide treated plots. Extracts of T.neriifolia were thus found to be safe to the non – target organisms too. An overall assessment of the results obtained revealed that water extracts of fresh leaf and seed in appropriate doses can be effectively and safely used for the control of important pests of bittergourd and amaranthus without any health hazards and adverse effect on the non target organisms in the agroecosystem. T. neriifolia can be considered as a plant suited for developing effective plant protection chemicals for replacing undersirable synthetic insecticides, especially in integrated pest control calendar.
Open Access
Evaluation of neem triterpenes as ovipositional and feeding deterrents to the tea mosquito bug, Helopeltis antonii Sign. on cashew
(Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 1995) Angaiah, K; KAU; Sitarama Rao, D
Experiments were conducted at the Department of Entomology, College of Horticulture, Vellanikkara, to ascertain the feasibility of utilizing the commercially available neem products for the management of populations of tea mosquito bug, Helopeltis antonii Sign. On cashew, Anacardium occidentale L. The effects of three neem products in altering the ovipositional behaviour and the feeding behaviour of H. antonii through contact and translaminar effects and the number of feeding punctures as affected by the contact and translaminar effects, were tested in comparison with NKS. Radio labelling of cashew seedlings prior to application of treatments and quantification of feeding based on the quantum of radio activity in the bodies of test insects fed on the treated seedlings was developed as a new technique. The study resulted in the following findings. 1. Godrej Achook at 1.6 and 3.2 per cent doses and Rakshak at all the tested doses significantly reduced the number of egg laying sites. 2. Duration of egg laying was significantly reduced by Godrej Achook and Rakshak at 1.6 and 3.2 per cent doses. 3. Significant reduction in the total number of eggs laid was brought about by Rakshak 1.6 per cent and Godrej Achook at 1.6 and 3.2 per cent doses. 4. Rakshak at all doses and Godrej Achhok at 1.6 and 3.2 per cent doses significantly reduced the nymphal duration. The nymphs failed to reach adult hood. 5. Feeding deterrency through contact action was exhibited by the treatments. Nimbecidine and Godrej Achook at higher doses were better. 6. The number of feeding punctures was influenced by the treatments through translaminar effects. 7. Development of feeding punctures was affected by the treatments through contact action also. Higher doses of Godrej Achook and Nimbecidine were better than the other treatments. In conclusion it can be stated that the commercially available neem products showed a high degree of effectiveness in reducing the feeding and oviposition by H. antonii, eventhough the neem tree is an alternate host of the tea mosquito bug. The neem products can be included as candidates for the management of population of H. antonii on cashew.
Open Access
Bionomics of pareuchaetes pseudoinsulata rego barros (lepidoptera:arctiidae) and its interaction with the siam weed chromolaena odorata king and robinson (asteraceae)
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1995) Lyla, K R; KAU; Abraham, C C
Studies were undertaken on the biology, morphometrics, feeding habits, factors affecting fecundity and fertility of Pareuchaetes pseudoinsulata King and Robinson (Arctiidae : Lepidoptera) and also the plant response of the weed host Chromolaena odorata L. at the College of Horticulture, Vellanikkara during 1990 – 1993. The morphometrics and morphology of the various immature stages and adults have been described. The total life-cycle of P. pseudoinsulata took a total of 46.75 days and the various developmental stages lasted for 5.5 days in eggs, 21.30 days for larvae (seven instars) 1.5 days for pre-pupa and 10.15 days for pupae at a mean ambient temperature of 28.40 C. In feeding trials to assess the relative preference of tender, mature, semi yellow and yellow leaves of C. odorata, it was found that the I instar larvae showed district preference to tender leaves as compared to mature leaves. The I and II instar larvae did not feed on semi-yellow and yellow leaves and they died of starvation when these types of leaves were offered for feeding. Consumption indices decreased as the age of larvae advanced and thus early instars consuming all the types of leaves recorded high indices. The rate of increase in larval weight gain was higher in later instars (VI and VII). Caterpillars feeding on mature, semi-yellow and yellow leaves showed higher Relative Growth Rate during IV to V stage, but during I to II stage, a high RGR was seen on larvae which fed tender leaves. Yellow. leaf diet for late instar larvae adversely affected their development and adult emergence. Highest fecundity was recorded when the parental sex-ratio of moths was kept at 1:1 level followed by 1:2 ratio and 2:1 in that order. Egg production and viability were significantly higher at 250 C and 75 per cent RH as compared to 300 C and 60 per cent RH. Adult food did not show any influence on fecundity but in respect of improvement of egg viability the treatments were advantageous. Total nitrogen content in leaves was maximum on the sixth day of release of four larvae per cage. Leaf nitrogen showed a declining trend when the larval load per plant was increased from the eighth day of release onwards. Soluble nitrogen content in leaves showed an increasing trend with increase in larval load per plant, but this however failed to reach significant levels. Chlorophyll content in leaves got reduced significantly at increased larval population loads and with passage of time of confinement. The natural enemies of P. pseudoinsulata consisted of avian fauna, spiders and ants and parasitoids. Predatory species of ants recorded in association with the insect included Lioponera sp. Oecophylla smaragdina Fabr. Solenopsis sp.and Monomorium sp. Occasionally NPV infection occurred in the laboratory as well as in field cultures causing substantial mortality. The implications of the various findings in reorienting the biocontrol strategies involving P. pseudoinsulata against C. odorata have been discussed.
Open Access
Phytochemicals and vam for management of nematodes in brinjal
(Department of Entomology, College of Agriculture, Vellayani, 1997) Asha, John; KAU; Hebsy, Bai
Aqueous neem leaf extract, neem oil and marotti oil at different concentrations were tested as bare root-dip treatments for their efficacy in containing root-knot nematode infestation in brinjal. Root-dip in neem leaf extract for one hour resulted in significantly better height and number of leaves in the treated plants than nee m oil and marotti oil. Among the different concentrations of neem leaf extract tested, 6.25 and 25 per cent extracts proved more effective. Significant reduction in gall index was also seen in neem leaf extract treated plants. Higher concentrations of the extract (50 and 25 per cent) significantly reduced the number of egg masses produced. But none of the phytochemicals had any adverse effect on the hatching of the egg masses. All the three phytochemicals irrespective of the doses reduced population of the nematode in the soil. An overall assessment of the result established the superiority of neem leaf extract (25 per cent) among the different phytochemicals tested in checking nematode infestation. Different isolates of V AM fungi like, G. fasciculatum, G. etunicatum, G. mosseae, G. constrictum G. monosporum and A. morroweae did not show any significant difference in the growth parameters of brinjal plants (height and number of leaves) at transplanting and one month after transplanting irrespective of the pot size. Later (45 and 60 days after transplanting) significant increase in height and number of leaves were observed in plants raised in soil inoculated with G.etunicatum and G. fasciculatum. Higher percentage of V A mycorrhizal colonisation was observed in plants artificially inoculated with V AM. Plants raised in G. etunicatum G. fasciculatum and G. monosporum recorded significantly lower root-knot indices. The fecundity of the nematode and the number of larvae hatching per eggmass was also significantly reduced in mycorrhizae treated plants. Irrespective of the pot size, G.fasciculatum registered the lowest population per gram root while G. fasciculatum and G. constrictum significantly lowered the nematode population in the soil. Overall assessment of the results revealed G. fasciculatum as the most effective mycorrhizae among the isolates tested for protecting brinjal plants from root-knot infestation. Field trial with bare-root dip in 25 per cent neem leaf extract and insecticides monocrotophos (500 and 250 ppm) and carbosulfan (500 and 250 ppm) nursery treatment with G. fasciculatum and root-dip of the mycorrhizal seedlings in neem leaf extract and nematicides did not show any significant effect on growth parameters of the plant like height, number of leaves and root weight But the . bare-root dip treatment in neem leaf extract and mycorrhizal nursery treatment and bare-root dip treatment in monocrotophos 500 ppm resulted in significant increase in shoot weight. Root-dip in nematicides was definitely superior to root- dip in neem leaf extract and nursery treatment with G. fasciculatum in increasing yield significantly. Bare-root dip in neem leaf extract, nursery treatment with G.fasciculatum also registered significantly higher yield. Root-dip of mycorrhizal seedlings in monocrotophos and carbosulfan were far more superior than the individual treatments in increasing the yield of brinjal. During the early stage (45 DAT) no significant difference was seen in the gall index, number of egg mass per plant and mycorrhizal colonization percentage. Later, as the plant matured a significant difference was seen in these parameters. Root -dip in neither nematicide nor neem leaf extract showed any deleterious effect on mycorrhizal colonisation.
Open 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.
Open 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.

Kerala Agricultural University, Thrissur

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