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
Bionomics and ecological management of coconut eriophyid mite
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2001) Vidya, CV; KAU; Ranjith, A M
The bionomics and ecological management of coconut eriophyid mite, Aceria guerreronis (Keifer) was studied under the Department of Entomology, College of Horticulture, Vellanikkara. The preference of mites to bunches of different maturity, symptoms of damage, population dynamics, relationship of mite population with weather factors and the distribution pattern of mites based on plant morphology were considered for the study. Some ecological management practices were also tried along with this. The experiment was laid out as completely randomised design. Mites were absent in male and female flowers and also on buttons of first bunch. Initiation of infestation starts from buttons of second bunch and population increases further and maximum population is noticed in buttons of third and fourth bunches and thereafter it decreases. This is because after fourth bunch, the meristematic tissue becomes necrotic due to feeding of mites and hence mites cannot feed further easily. Traces of population were noticed even on nuts of ninth bunch. Predatory mites were also seen along with eriophyid mites even though they are very negligible. Symptoms of damage were seen outside from second bunch onwards. The symptom initially appears as whitish streak or triangular patch and it increases further in length and breadth and becomes brownish and later necrotic. In some cases, cracks, cuts and gummosis can be seen on the husk. The relationship between surface damage and mite population was worked out. Maximum mite population was noticed when the surface damage was 1-3 and 3-6 cm2 before and after the removal of perianth respectively and the percentage of damage was 1-3 per cent. Mite population was found to vary with different weather parameters. Minimum temperature of current week, current, -1 and -2 fortnights and maximum temperature of -2 fortnight were positively related with mite population. Morning humidity is also positively related with mite population. Mite population was negatively related with wind speed of zero current, current, -I and -2 fortnights. There is no direct relation between mite population and rainfall, number of rainy days, evening humidity and sunshine hours. Mite infestation was irrespective of the height of the palm, crown shape and perianth arrangement. The intensity of infestation varies between each inner tepals. Maximum infestation was under fourth tepal followed by fifth and sixth tepa\. The preference of mites to different portions under each tepal also varies with maximum entry through the 'outer edge' of fourth tepal followed by 'outer edge' of fifth tepal, 'middle' portion of sixth tepal, 'middle' portion of fifth and fourth tepal, and 'inner edge' of sixth and fifth tepa\. Infestation was found to be less in round shaped nuts compared to oval and oblong nuts. Maximum incidence was in green coloured nuts followed by greenish yellow and orange coloured nuts. There was no reduction in mite damage by different water regimes (rainfed, channel and drip irrigated) fertilizer regimes (0.34:0.17:0.68 kg NPK/palm, 0.5:0.32:1.2 kg NPKlpalm and 0.25:0.32:1.2 kg NPKlpalm) micronutrients (MgS04, ZnS04, MnS04, Borax and Micronutrient mixture) and crown cleaning (once and twice in an year).
Open Access
Management of stingless bee Trigona iridipennis Smith (Meliponinae: Apidae) in the homesteads of Kerala
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2002) Nisha, M M; KAU; Devanesan, S
With the objective of studying the management of stingless bees, Trigona iridipennis Smith in the homesteads of Kerala, studies were conducted at the College of Agriculture, Vellayani during 2000-2001. Different management practices were tried. Division of the• bee colony could be successfully carried out by transferring equal amount of brood cells, pollen and honey pots along with queen to the different hives VIZ., wooden, bamboo and earthen pot with different capacities. Bamboo hive with capacity 1500cc was found to be more suitable for hiving T. iridipennis since the brood development, pollen storage, population buildup and honey storage were superior in this type of hive. Observations on handling of bees indicated that wooden hives were easy to handle compared to bamboo and earthen pot. Brood development and pollen storage were shown maximum during the month of February, while maximum honey storage was noticed during the month of April. Bee strength increased as the colony got established well. Presence of queen cells and drones were noticed from November to March during which population build up existed. The bee strength was also found to be . maximum in bamboo hive which had maximum brood, pollen and honey storage. Investigation on the reuse of emptied honey pots by the bees indicated that the bees reused it for reconstruction of worn off honey pot parts beneath and nearby. Investigations on the foraging activity of T. iridipennis showed two peak periods of activity one at 1200h and the other at 1500h and with maximum activity during July. It was observed in the present study that 76 plants were visited by the stingless bees for nectar or pollen or both. Of this twenty plants provided both nectar and pollen. Thirty five plants provided nectar only and 20 plants provided pollen only. The Trigona honeys collected from different tracts around Kerala varied widely in colour from light yellow to dark amber colour with all intermediate shades. The percentage of moisture varied from 18.96 to 20.48 in different districts of the state and pH ranged from 3.76-4.4. In all the honey samples the acidity ranged from 0.17-0.29 while the ash content varied from 0.17-0.19 per cent. The specific gravity also ranged from 1.3507-1.3775. The observations of reducing sugar indicated that it ranged from 77.12-69.85 per cent. The refractive index value also indicated variation from 1.4855 to 1.4891. The values on glucose and fructose per cent varied from 35.92-33.53 and 38.16-39.74 respectively. The glucose fructose ratio observed indicated variation from l.17 -1. 05. The sucrose per cent also seen varied from 1.23-l.81 and the values on specific heat varied slightly from 60.50-60.9. A dipteran fly Hermetia illucens L., a mite, Amblyscius sp. and Megachile disjuncta was newly identified as pest of T. iridipennis. Solenopsis geminata was also observed to attack weak colonies. No disease incidence was noticed.
Open Access
Eco-friendly insecticides for the management of major pests of amaranths
(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2001) Leena, M K; KAU; Suma Paulose
There has been increasing reports on health hazards in human beings from the unscientific and intensive use of pesticides in crops, especially vegetables. It was in this backdrop, a scientific investigation was designed to evolve safer and eco-friendly methods in pesticide use to control the major pests of the popular leafy vegetable amaranths. Field experiments were conducted at the college of Horticulture, Vellanikkara during 2000-2001 to identify the safer, eco-friendly insecticides. For the first experiment, thirteen different commercial formulations of neem, microbial and chemical pesticides were evaluated for the control of amaranths leaf webbers viz., H. recurvalis, P. basalis, weevil H. truncatulus and grasshopper A. crenulata. The best six effective components were further screened at lower doses, so as to identify the most promising one in the second experiment. The effect of the tested components on the natural enemies and other bio control agents were also studied.. Organoleptic quality evaluation of cooked amaranths leaves was done to know, whether the applied insecticides have any effect on the taste, appearance, colour, flavour, texture and bitterness. Of the insecticides tested in the first experiment, Econeem, N eem Azal, Halt, Dipel, Delfin and Nuvan were the most effective in controlling the pest population. The results of the second experiment indicated that the plots treated with Dipel @ 0.7 ml r' gave better control of both the leaf webbers. Halt @ 0.7 g r' gave comparably good results for the control of weevil. All the microbial insecticides tested were found ineffective to grasshopper. No disease symptom or deformities were observed in any of the natural enemies and other bio control agents. In the field, though Nuvan was found to control the pests, it was not effective in the long run. All the microbial products were found to protect the crop for a longer period of time. The crop sprayed with Delfin @ O.7g r' gave an yield of 5481 kg green leaves per acre compared to untreated control (2963 kg). Organoleptic quality evaluation of cooked amaranths leaves revealed that, there was no significant difference in qualities of cooked amaranths due to treatments compared to untreated control.
Open Access
Effect of entomopathogenic fungi on sucking pests and leaf feeders of vegetables under in vitro conditions
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2002) Jincy, Simon; KAU; Susamma, Mathai
Investigation on "Effect of entomopathogenic fungi on sucking pests and leaf feeders of vegetables under in vitro conditions" was carried out II1 the Insect Pathology Laboratory, Department of Agricultural Entomology. College of Agriculture, Vellayani. Among the seven entomopathogenic fungi tested, Be auver ia r a l it ura and Peri call ia ricini, an aphid isolate of Fusarium pallidoroseum infected aphids Aphis craccivora and Myzus pers icae while Rhizop us oryzae caused mortality of Dysdercus cingula/us. The LCso values for B. bassiana were calculated as S.75 x 108. 6.99 X J08 and 2.72 x 105 spores m]"1 against S. derogat a. S. l it ura and P. rici ni respectively. F. pallidoroseum caused SO per cent mortality of A. cracci vora and M. persicae at 3.86 x 106 and 0.72 x 106 spores 111]"1 respectively. R. oryz ae caused 50 per cent mortality of D. cingula/us at 4.15 x 106 spores mrl. Evaluation of different naturally available substrates for mass multiplication of B. bassiana. F. p all i dor o se um and R. oryz ae revealed that both rice bran and gingelly oil cake were suitable for the mass multiplication of these fungi.'Among the liquid substrates. coconut water produced maximum mycelial growth of all the fungi. At room temperature. B. bassiana retained the vi.ulerice up to five months after inoculation in rice bran and gingelly oil cake. hut the vi rulence of the fungus was drastically reduced after two months or storage. F. p al lidorosetnn retained the virulence upto six months in rice bran and gingelly oil cake but R. oryzae lost the virulence after two months of storage. Coconut water and starch solution could not retain the \ i a h i lit y all d vir u I e n c e 0 f the fu n g i a ft e r t w 0 III 0 nth s 0 f s tor age. l-, p allidoroseum and R. OITZ(/(! with different pesticides revealed that two per cent neem oil emulsion could be incorporated with B. bassiana and R. oryzae without any inhibitory effect while sporultio n of F. pallidoroseum was inhibited by nee m oil. Mancozeb, dimethoate malathion, quinalphos and chlorpyriphos greatly inhibited the growth and sporulation of the three fungi tested.
Open Access
Management of the american serpentine leaf miner Liriomyza trifolii (Burgess) Dietars on cowpea, Vigna unguiculata (L.) Walp
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2002) Reji, G V; KAU; Hebsy Bai
Survey conducted in Kailiyoor panchayat of Thiruvananthapuram district revealed that Liriomyza trifol ii caused maximum damage to cowpea at the reproductive phase of the crop III summer. Raising susceptible varieties, applying high doses of nitrogen and frequent use of insecticides were noted to intensify the pest incidence. The weeds, Achyranthus aspera, Amaranthus viridis, Cleome viscosa, Cleome monophylfa, Heliotropium indicum, Physalis minima and Desmodium gyrans were identified as host plants of the pest. Seven larval parasitoids were recorded of which Chrysonotomyia rexia and Asecodes sp. were predominant. Twenty accessions of ccwpea including trailing and bush types were screened in the laboratory for resistance to L. trifolii. Accessions of trailing type were more susceptible to the pest. VU-12 was least susceptible among the trailing type while Sharika and Vyjayanthi were highly susceptible. Among the bush type, VU-4, VU-6, VU-3 and Arka Garima were less susceptible. Four plant oils and four synthetic insecticides when evaluated in the laboratory at two doses along with neem oil (2.5 per cent) and dimethoate (0.05 per cent) showed no significant diffe. ence in efficacy between the doses. Neem oil, marotti oil and ilIupai oil at 2.5 per cent and abamectin, 0.003 per cent, thiamethoxam, 0.02 per cent and profenophos, 0.025 per cent were found to be effective in controlling the pest. All the treatments reduced the pest infestation significantly in the field. Abamectin, 0.003 per cent was significantly superior. Neem oil, marotti oil and illupai oil 2.5 per cent also reduced pest infestation. Considering the cost and safety to the natural enemies, the oils were found more advantageous to the farmers. Based on the results, cultivation of the tolerant accession VU -12 111 endemic areas, destruction of weed host plants, judicious application of nitrogen and need based application of neem oil / marotti oil / illupai oil at 2.5 per cent can be recommended for inclusion in rPM strategies of L. trifolii.
Open Access
Eco-friendly management of root-knot and burrowing nematodes associated with kacholam (Kaempferia galanga Linn.)
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2001) Nisha, M S; KAU; Sheela, M S
Field experiments were conducted to evaluate the efficacy of bioagents (Pseudomonas fluorescens, arbuscular mycorrhizal fungi, Trichoderma vir i dae (3 per cent w/w) plant products (nee m oil (2%), neem leaf extract (S%), neem oil + garlic (2%), neem leaf extract (4%)+ garlic (l %), botanical pesticide, nimbecidine (0.2%), hot water treatment (SSoC) and organic amendments (neem cake (200g/m2), coir pith (SOOg 1m2), sawdust (SOOg/m2), neem leaf (7S0 g/rn ") as rhizome and main field treatments for working out an eco-friendly management strategy against the nematodes (Meloidogyne inco gnit a and Radopholus si milisi in the medicinal plant, kacholam, Kaempfer ia galanga Linn. The efficacy of green leaf mulching was also tested using locally available green leaves (neem, glyricidia, mangium, clerodendron, calotropis, chromolaena) @ Skg 1m2 as mulch, to maximise the natural resource utilization in the context of low cost farmer friendly technology. To establish the potential of rhizome treatment with bioagents, botanicals, plant products and hot water treatment a micro plot study (2 m x 2 m) was conducted at College of Agriculture, Vellayani in sick plots having an initial population range of 100 to 160 M. incognita and 4S-6S R. similis per 100 g soil. The effect of the above treatments were compared with the chemical, dimethoate (0.1 %) and untreated. The results showed that maximum improvement in biometric characters like fresh plant weight and root weight of kacholam plants was observed in rhizome treatment with P. fluorescens. Next best treatments were AMF and hot water treatment and the effect of these two were significantly better than the chemical, dimethoate. The improvement in biometric characters due to above three treatments increased the yield of kacholam to the tune of 87 to cent per cent. Regarding the reduction in nematode population in root (root-knot count and number of females), P. jluorescens and AMF were the best treatments. Next effective ones the hot water treatment and T. viride were also better than the chemical, dimethoate. There was no significant variation in the R. similis population in soil due to rhizome treatments. The results on the effect of application of bioagents and organic amendments in soil at the time of planting revealed that neem cake (200 g I m2) and AMF (300 g inoculum I m") were on par in leaf production and nee m cake established its superiority in improving the shoot weight also. Neem cake, AMF, sawdust and coir pith were statistically on par in improving the fresh weight of plant. In all these cases effect of the above treatments were on par with the chemical, carbofuran (lkg a.i.lha). Regarding the improvement in yield also the best treatments (neem cake, AMF, sawdust, P. jluorescens and coir pith) were on par with the chemical, carbofuran. The superiority of carbofuran was maintained in reduction of nematode population only in root (number of females and larvae). In all other cases (nematode population in soil at different periods) the effect of nee m cake, AMF, neem leaf were on par with the chemical. The results on the. effect of mulching with green leaves revealed that neem and chromolaena leaves improved the fresh plant weight and yield of kacholam. Reduction in nematode population in soil was observed 111 glyricidia leaves also along with neem and chromolaena. The effect of nee m and chromolaena @ Skg 1m2 leaves were on par in reducing the root-knot count and number of larvae in root. There was no significant variation in population of R. similis due to mulching with different leaves but minimum population was recorded in neem leaf (4 MAP). Even the application of mangium @ 5 kg/rn ' significantly reduced the nematode population in soil, but the effect was inferior to other leaves, but superior to the untreated.
Open Access
Impact of botanicals on pests and defenders in rice ecosystem
(Department of Entomology, College of Agriculture, Vellayani, 2000) Ajaya Kumar, C; KAU; Nalina Kumari, T
The magnitude and intensity of insect pest and their defenders at different growth stages of rice were assessed in a survey during the virippu season of 1998, adopting random sampling technique, in three taluks of Thiruvananthapuram district. The survey revealed that the occurrence and distribution of the population of pests and defenders were same in the various locations, where the tolerant variety Jyothi was cultivated. The total population of pests and defenders observed at different growth stages of the crop followed a definite pattern in the three locations. Different concentrations of the leaf extracts of A. indica, and C. infortunatum and nimbecidine were evaluated in the laboratory for their antifeedant and deterrent activity and contact toxicity against important pests of rice and their defenders. Based on the percentage of leaf protection, the plant products tested were superior to control against C. medinalis. The same effect was noticed with N. depunctalis, only with the highest dose of leaf extracts of A. indica and nimbecidine. Seventy five per cent deterrent effect was observed to N. lugens at the highest dose of the plant products. None of the plant products showed any deterrent action against L. acuta or exhibited contact toxicity to L. acuta, C. medinalis. N. depunctalis andN. lugens. Both the defenders tested CL. pseudoannulata and O. nigrofasciatay; were safe with the plant products. 2 Replicated experiment was conducted on rice to evaluate the efficacy of plant products in suppressing the pests as well as in augmenting the defenders under field conditions. The leaf extract of C. infortunatum was found to be efficient in suppressing the population of C. medinalis. The effect was same as that with insecticides. The population of N. depunctalis was reduced by the leaf extracts of A. indica and C. infortunatum as observed in treatment with carbaryl. The suppressing effect observed on N. lugens was same with both the leaf extracts and insecticides, whereas, none of the treatments showed reduction in the population of L. acuta. The total population of the pests in general, showed a varying effect of plant products at different growth stages of the crop. Leaf extracts of C. infortunatum resulted in an immediate suppression of the total population of the pest at 20 DAT, whereas, A. indica gave significant reduction at 40 DAT. The treatments didnot show any effect on the total pest population at 60 DAT. The effect of plant products on spider population revealed that they were found to be safe. The leaf extract of A. indica increased the spider population at 20 DAT and C. infortunatum at 60 DAT, whereas, insecticides showed harmful effect up to three days after application. Adverse effect with plant products on the population of 0. nigrofasciata was not observed in any of the treatments. An increase in the population of the predator was observed with leaf extracts of A. indica at 20 DAT and with C. infortunatum at 40 and 60 DAT. Significant reduction in the population of Agriocnemis spp. was recorded in treatment with leaf extract of C. infortunatum, whereas, significantly higher population was observed in treatment with leaf extract of A. indica. The population of M crocea was reduced due to the application of plant products and the effect was retained up to three days after application. 3 The influence of plant products on the total population of defenders has clearly indicated that the leaf extracts of A. indica and C. infortunatum were safe to the defenders. Based on the P:D ratio, these products were found to have the best effect in augmenting the population of defenders and suppressing the population of pests. Significant differences in the grain and straw yield was not recorded either in treatments with plant products or with insecticides when compared with control. Overall assessment of the results obtained revealed that A. indica and C. infortunatum can be effectively and safely used for the management of important pests of rice with out much adverse effect on non target organisms in the rice ecosystem. Just like A. indica, C. infortunatum could also be utilised for developing effective plant protection chemicals for replacing undesirable synthetic insecticides in integrated pest management.
Open Access
Eco-friendly pest management in snakegourd
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2001) Sivakumar, T; KAU; Jiji, T
A study was conducted to document farmers' practices for pest control, record the population of pests of snakegourd and their natural enemy complex in farmers' field, as well as to evolve an eco - friendly package of practices for pest management. The survey conducted in the farmers' field revealed that the farmers were resorting to indiscriminate use of pesticides. The recommended pesticide/ fertilizer dosage was not practised by the farmers. Quinalphos was the most widely used pesticide followed by carbaryl. The frequency of spraying was the highest at fruiting stage. The major pests observed in the field were B. cucurbitae, A.peponis, D. indica, E. septima, Aulacophora sp. A. gossypii and L. trifolii. A very low population of pests and their natural enemies were present in the farmers' fields compared to untreated plot maintained in the Instructional Farm, Vellayani. In the untreated plot there was ten fold population of natural enemies compared to farmers' field. Fruit flies were found to be serious pests causing 63.63 per cent loss in unprotected field and this emphasised the importance and necessity for fruit fly management in snakegourd fields. Three fruit fly traps viz., were tested to assess their efficacy in catching fruit flies. Among the three traps tested, banana traps consisting of palayamkodan fruit pieces and carbofuran were the best. Three snakegourd varieties viz., Kaumudi, T.A. -19 and Local, were tested against insect infestation. Kaumudi had the lowest infestation by pests like pumpkin beetle (Aulacophora sp.), leaf eating caterpillar (Diaphania indicas, snakegourd semilooper (Anadevidia peponis) and fruit fly (Bactrocera cucurbitae). Kaumudi recorded the minimum fruit fly damage and consequently, the highest yield. Field evaluation of fourteen treatments was carried out at the Instructional Farm, Vellayani during 1999-2000. Chemical insecticides were found to be very . effective in controlling the pests of snakegourd at vegetative and flowering period, but the pest population build up was the highest with them. Neem oil - garlic emulsion was the best in controlling the pest menace with the least impact on natural enemies. Population build up of pests was also low in case of neem oil - garlic emulsion. The practice of covering fruits was very effective in preventing the flies from attacking the fruits. Covering the fruits and setting up of banana traps at the rate of two traps for three plants gave the best protection against the fruit flies. The treatments involving neem oil - garlic 2.5 per cent spray at vegetative stages + covering the fruits and banana trap setting at flowering and fruiting stages gave the highest yield and benefit - cost ratio (1.938). Spraying neem oil -garlic emulsion 2.5 per cent, on need basis, at vegetative stages and setting up of banana fruit fly traps and covering the fruits with reusable polythene covers was found to be the best eco- friendly and economical package for the management of major pests affecting snakegourd.
Open Access
Bio-ecology of coconut eriophyid mite, aceria guerreronis keifer and yield loss due to its infestation on popular coconut cultivars
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2001) Ambily Paul Thomas; KAU; Biju Mathew
Studies were conducted to understand the biology, ecology, population dynamics and rr .te-host interactions of A. guerreronis and to assess the yield loss on popular cultivars of coconut as influenced by nut characters and weather parameters. An abstract of the work done and the results are given below. Biology of A. guerreronis was studied under both laboratory and field conditions. The study indicated that a total period of 9.8 days was required for completing one generation under laboratory condition. Population dynamics of A. guerreronis in young buttons of susceptible and tolerant palms of variety WeT and Komadan was studied from February 2000 to January 2001. Population of mites under each tepal was counted by using cello tape embedding method. The results revealed that the population was the highest in nuts sampled from fifth bunch followed by fourth and sixth bunches in both susceptible and tolerant palms. The present study indicated that age of developing nut was the most critical factor in the study of population dynamics. Monthly mean population of A. guerreronis was correlated with weather parameters viz., temperature, relative humidity and rainfall prevailed during the time of sampling, probable time of mite entry and the total duration of critical age of the bunch. The results indicated that the relative humidity prevailed at the probable time ofmite entry alone had a positive correlation with population in the susceptible type of Ko mad an. The length to circumference ratio of young nuts and its influence on mite injury was observed. The results showed that round nuts having a length to circumference ratio of 1 :1.90 to 1 :2.29 suffered less damage. The study gave an indication that elongated nuts were more susceptible to mite attack than round ones. The expansion of feeding scar on coconut husk due to mite injury in relation to growth of nuts was studied in young nuts with different degree of injury in terms of number of triangular lesions. The study indicated that the age of buttons / nuts at which the colonization started w~ the most critical factor in deciding whether the nut will finally become economically damaged (category 4 and 5) or not. Yield loss studies were carried out from the nuts obtained from ten consecutive harvests by categorizing them into five damaged categories and the yield loss was calculated by deducting actual yield from potential yield. No significant variation was observed among the five varieties studied, viz. WeT, Komadan, T X YD, Laccadive Ordinary and Dwarf Orange Yield loss in terms of reduction in weight ofcopra ranged from 11 to 39 percentage and reduction in weight of husk ranged from 12 to 40 percentage. Additional labour requirement for de husking infested nuts was studied in a separate experiment. Study revealed that an extra time of 25.05 to 41.75 minutes was required to dehusk 100 damaged nuts over healthy nuts. Another experiment was conducted to assess the effect of mite injury on the quality and quantity of fibre and coir. Husk obtained from fifty harvested nuts representing the damage categories 1 to 5 were subjected to natural retting practices. Fibre obtained from nuts coming under damage category 4 and 5 resulted in 47-53 per cent reduction in length.

Kerala Agricultural University, Thrissur

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