Browsing by Author "Ranjith, A M"
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ThesisItem Open Access Bionomics and ecological management of coconut eriophyid mite(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2001) Vidya, CV; KAU; Ranjith, A MThe 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).ThesisItem Open Access Distribution of coconut lacewing bug Stephanitis typicus distant and its natural enemy complex and assessment of biocontrol potential of the major natural enemies(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1994) Unnimon, N K; KAU; Ranjith, A MA study on the distribution of the coconut lacewing bug Stephanitis typicus and its natural enemy complex was carried out during the period 1991-92 at four selected root (wilt) prone districts of kerala . The bio-control potential of the major identified natural enemies were also carried out during the same period . The results revealed that population of S.typicus showed a fluctuation throughout the year . The population was higher in the field during the dry seasons and it was at lower levels in rainy periods. The numbers of the pests increased from January onwards and recorded its maximum in March-April. The population started decreasing from May onwards and recorded the lowest level in June-July . From August the number of pest again started increasing and reached the second maximum in September - October. The level of population recorded was lowest in November- December. Congregation of S. typicus was observed in higher numbers on the inner whorls of coconut crown. Compared to leaves of inner whorls, the number of pest were fewer in middle and outer whorls. Natural enemy population was observed to remain stagnant throughout the year. Only a slight fluctuation was recorded in population of natural enemies , in accordance with the increased level of pest population . Generally a low level of natural enemy population was observed in the field throughout the study period . Rearing of S. typicus in glasshouse condition on different host plants like coconut , turmeric and arrowroot showed the preference by the pest to the coconut plants. Compared to other host plants the multiplication and survival of the pest was more on coconut plants. Among the natural enemies observed in the field , the mired predator S. praefectus was recorded as the important one . other natural enemies observed in the field included spiders and one pentatomid bug. It was noticed that the mired predator consumed both adults and nymphs of the pest . But in case of spiders they preferred adults of the pest to nymphs.ThesisItem Open Access Enhancing the performance of the egg parasitoid, Trichogramma.chilonis Ishii (Trichogrammatidae : Hymenoptera)(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2006) Shajna, P K; KAU; Ranjith, A MA study entitled ‘Enhancing the effectiveness of the egg parasitoid Trichogrmma chilonis Ishii (Trichogrammatidae: Hymenoptera)’ was carried out at the College of Horticulture, Vellanikkara with the objectives of increasing the effectiveness of T. chilonis and to standardize the optimum storage period of the trichocards. A prototype of an olfactometer suitable to monitor the movements of T. chilonis was at first made using polyester film for standardizing the design. The prototype was validated by keeping the kairomones in each of the four arms. As this was found to be a success, it was further fabricated in transparent acrylic sheet incorporating slight modifications. Various error factors were identified during the continued studies and they were eliminated and an improved design was standardized as uniform air inflow olfactometer. The responses of T. chilonis to different semiochemicals were studied in the uniform air inflow olfactometer. A higher response of adult parasitoids was noticed towards moth extracts of C. medinalis and Corcyra cephalonica and also moth scale extract of C. cephalonica in hexane solvent. This may be because hexane could extract more concentration or wider range of the kairomones which attract the parasitoids. The results corresponding to the response to plant volatiles emanating from the weeds in the paddy ecosystem are a clear pointer to the ecological adaptation of T. chilonis for survival. The highest attraction was towards the leaf folder damaged leaves followed by plant parts of Oryza rufipogon. Among the different semiochemicals, significant attraction was towards 10 per cent honey solution. The results thus established that a band or grid application of honey solution will increase the longevity of adults as well as the per cent parasitism. The adult moth which is the primary producer of eggs is the most preferred from among the different life stages of C. medinalis tried. A wind tunnel set up was fabricated to evaluate the olfactory responses of T. chilonis to the best semiochemicals. The distance travelled by the parasitoids was observed for every 30 minutes, for a total duration of three hours. Maximum distance travelled by the adult parasitoids was towards honey solution. The results validate the findings observed using the four arm olfactometer (free choice test) with a single source wind tunnel (no choice test). The effect of refrigerated storage on the emergence and parasitization efficiency of T. chilonis was studied. More than 50 per cent emergence was noticed up to 36 days in four day old cards which is of interest to nucleus stock of Trichogramma being maintained at the laboratories. The results of the study have shown that the Trichogramma emergence can be delayed even up to 50 days under ordinary refrigerated storage. Such cards even with around 10 per cent efficiency would be more economical than continuous rearing of Corcyra culture and production of trichogrammatids. Even for farmer situations, it may be more advisable to manage initial leaf folder populations at its first level of emergence itself. At this time the population is very low and even a 10 per cent parasitoid emergence can easily take care of first generation of leaf folder.ThesisItem Open Access Evaluation of multi x bi bivoltine hybrids of silkworm(1998) Rajeni, Narayanan; KAU; Ranjith, A MIn 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.ArticleItem Open Access Influence of food plants on the consumption of folfage and pupal characters of pericallia Ricini Fab. (Arctiidae: Lepidoptera)(Kerala Agricultural University, 1985) Ranjith, A M; Dale, D; KAUThe influence of different food plants on the growth of the arctiid caterpillar Pericallia ricini is discussed. DJe to differences in the quality of the nutrients and the nutrient balance in the different food plants, the pupal periods of caterpillars feeding on the varied food plants differed significantly. The pupal weights and the mortality of larvae and pupae differed batween the insects feeding on the different food plants. An increased consumption of food by larvae of the later instars and by females than males was also observed.ThesisItem Open Access Insect pollinators of oil palm in Kerala(Department of Agriculture, College of Horticulture, Vellanikkara, 2010) Sambath, Kumar; KAU; Ranjith, A MOil palm, Elaeis guineensis (Jacq.) (Arecaceae) is one of the most commonly available and extensively cultivated perennial trees in many parts of the world. Previously pollination was considered as a serious constraint, so manual pollination was often carried out, to sustain the yield. Wind and honey bees play an important role in pollination of many crops. But they alone can not give adequate level of pollination in all circumstances. In nature, pollination by specific insect species is vital for many crops. In this context, the present investigation on the “Insect pollinators of oil palm in Kerala” was carried out in the Plantation Corporation of Kerala, Athirappilly and Laboratory trails were conducted in the Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2009 to 2010. Fifteen different insect species were observed to visit on the inflorescence. Insect species such as, African oil palm weevil, Elaeidobius kamerunicus (Coleoptera: Curculionidae); an earwig, Forficula sp.? (Dermaptera); a moth, Pyroderces sp.? (Lepidoptera: Cosmopterigidae) and Indian honey bees, Apis cerana indica (Hymenoptera: Apidae) were main species from the collection on male and female inflorescences. Population of different insect visitors on anthesising female inflorescence was highly varied and E. kamerunicus was found to be more, among all insect species. Weevils were found to be visiting the female flowers between 10.00 a.m. to 2.00 p.m. and the peak weevil population was observed on the 1st and 2nd day of anthesis, around 12.00 noon. But, on male inflorescence weevil population was less during 10.00 to 2.00 p.m. Thereafter, it was gradually increased and attained the maximum at 4.00 p.m. Highly significant positive (r = 0.712**) correlation was observed between population of E. kamerunicus on 1st day of anthesis of female flowers and per cent pollination whereas, it was not significant (r = 0.199) on the 2nd day of anthesis which indicates that maximum amount of pollination occurred in the 1st day of anthesis. Weevils of E. kamerunicus were congregating on the male inflorescence during the entire period of anthesis and their statistical median weevil population was 48, 76, 80 and 35, 56 and 72 on top, middle and bottom portions of male inflorescence during rainy and summer seasons respectively. Adult weevils of E. kamerunicus feed on anthers of male inflorescence and multiply. Everyday, during occasional visits to female inflorescence, they would shed the pollen grains and get back to its original place of host which would cause adequate level of pollination of female flowers. The anise seed like odour (estragole 5, 4 allylanisole) attract the weevils towards both male and female inflorescences. The biology of E. kamerunicus was carried out in both rainy and summer seasons under wire cage. The female weevil laid eggs singly on the spent male inflorescence of oil palm. The fecundity ranged from 32 to 33 eggs (median = 32) in rainy and 34 to 35 eggs (median = 35) in summer seasons with an ovipositional period of 1 to 2 days during both seasons. The eggs hatched into grubs within 1 to 2 days. The grub period lasted for 8 to 10 days in rainy and 7 to 9 days in summer seasons respectively with three larval instars. The grubs pupated for 3 to 4 days in rainy and summer seasons and the adult weevils emerged out. The total life cycle from egg to adult was completed within 14 to 16 and 11 to 14 days in rainy and summer seasons respectively. The longevity of adult weevils varied with the sex and males lived longer than females. The life span of male weevils was 5 to 7 and 4 to 6 days during both rainy and summer seasons respectively. Female weevils lived for 4 to 6 days in rainy and 4 to 5 days in summer seasons. Among the duration of different life stages viz., egg, larva, pupa and adult of E. kamerunicus, the grub period was found to be longest (7 to 9 days) followed by adult longevity (male = 5 to 6 days; female = 5 days), pupa (3 to 4 days) and egg (1 to 2 days). The number of female weevils in the field was more, when compared to the male with the sex ratio (♂ : ♀) of 1 : 1.87 in rainy and 1 : 1.96 in summer seasons respectively. Morphometric study of different life stages of E. kamerunicus showed that the diameter of egg measured 0.258 mm. The freshly laid eggs were creamy white in colour. The first instar grub was pinkish yellow in colour with brown head capsule and other instars are yellow coloured. The average length of I, II and III instar grubs were 1.59, 2.73 and 3.84 mm. Similarly mean body width of corresponding instars was 0.52, 0.86 and 1.62 mm. The pupa also showed yellow colour with the length of 3.53 mm and width of 1.63 mm. The newly emerged adult weevil was light brown in colour and later on changed to dark brown. The male and female weevils could be differentiated based on their size and additional structures on their body. Males (length = 4.13 mm; width = 1.54 mm)) were bigger than female (length = 3.81 mm; width = 1.28 mm). Males also had setae on the peripheral side of elytra with some dorsal spines. Female has smaller body and absence of above mentioned structures over its body. Both male and female inflorescences were produced separately in successive whorls. Production of male inflorescence ranged from 0 to 2 from 10 different marked palm trees and at least one male inflorescence (mode = 1) could be seen in each tree from July ‘09 to Jan ‘10 except during Sep ‘09 (mode = 2). Female inflorescence production ranged from 0 to 1 during July ‘09 to Feb ‘10 except during Aug ‘09 (1 to 6) and Oct ‘09 (0 to 3). The mode value of female inflorescence production was 1 during July ‘09 and Aug ‘09 and it was zero from Sep ‘09 to Feb ‘10. Anthesis period of male inflorescence accounted for 10 to 14 days with more weevil population between 4th to 7th days which coincided with the maximum odour emission. Stigma receptivity lasted for 2 to 3 days but, insect visit was observed for only 2 days. So, assisted pollination can be done only up to 2 days of anthesis of female flowers. The bunch set was not found to be uniform in each month. The mode value of bunch set was varied in different months like 0, 1, 5, 5, 4, 6 and 2 from July ‘09 to Feb ‘10. Production pattern of male and female inflorescence with regard to different climatic factors was recorded from July ‘09 to Feb ‘10. An increasing trend of male inflorescence production was observed from July ‘09 to Sep ‘09 (mode = 2) with the maximum and minimum temperature of 29.91 and 24.28 oC, relative humidity of 94.37%, rain fall of 12.67 mm and sun shine hours of 0.52 hrs. Later on uniform production was recorded until Jan ‘10 and no inflorescence was seen during Feb ‘10. Similarly female inflorescence production was found to be uniform during July ‘09 and Aug ‘09 (mode = 1) which coincided with monthly maximum (28.4 and 29.94 oC), minimum temperature (23.45 and 24.08 oC), relative humidity (98.38 and 93.52%), rain fall (19.72 and 12.31 mm) and sun shine hours of 2.48 and 3.05 hrs. There after, it was very much reduced (mode = 0). Bunch set was low in July ‘09 which, gradually increased and reached the maximum during Jan ‘10 (mode = 6) with the weather parameters such as, maximum (32.24 oC), minimum temperature (21.7 oC), relative humidity (85.23 %), rain fall (0.18 mm) and sun shine hours (8.96 hrs). Correlation study of inflorescence production and various weather parameters showed that there was a significant positive correlation with relative humidity and rain fall and significant negative correlation with maximum temperature and sunshine hours. On the contrary, monthly bunch set showed a significant negative correlation with relative humidity. Wind could be offer only less contribution towards pollination and fruit set and, it was also not influenced by birds. Totally 336 to 800 flowers were counted from female inflorescences (mean = 596.4) and the range of fruit count was from 186 to 583 (mean = 393) with 27 to 132 partially developed fruits (mean = 73.8) per bunch. Per cent pollination was from 60.36 to 88.37 (mean = 77.13 %). It took around 145 to 161 days for the complete development of fruits (mean = 153.3) and the bunch weight was 5 to 29 kg (mean = 17.13) with a mean fruit weight of 32.52 g per bunch. Observations on period of stigma receptivity of female inflorescence and time of weevil visit to female flowers may be helpful to the farmers when they would need assisted pollination either manually or through artificial means by using E. kamerunicus. The present study showed that, they can restrict the pollination just for 2 days after anthesis which will ultimately save labour, money and time spent on this. Artificial culturing of weevils can be done with kairomones to maintain their population during summer season since, very poor inflorescence production was noticed during summer. It is also necessary to retain the male inflorescence at least for one month after anthesis. This will help for multiplication of weevils. During rainy months, the spent inflorescence must be removed within 40 to 45 days to avoid disease occurrenceThesisItem Open Access Integrated insect pest management (IIPM) and Biological Control based integrated pest management (BIPM) in rice(Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 2012) Pramod Kumar, KAU; Ranjith, A MRice is the staple food of India and most parts of the world. India has a history of pest outbreaks resulting in extensive losses in rice production, with a lot of factors contributing to it. For managing pests in rice many farmers use only the parasitoid Trichogramma (available as trichocards) and sometimes with the addition of Pseudomonas fluorescens. Trichogramma will manage only yellow stem borer and leaf folder (YSB and LF). Other lepidopteran pests and sucking pests have to be tackled by adopting other management practices. Even trichocards are wasted due to wrong application techniques. Light traps can be used to monitor the incidence of YSB and LF to aid in the placement of trichocards. Hence the present study “Integrated insect pest management (IIPM) and biological control based integrated pest management (BIPM) in rice” was taken up with the objectives of separating/fractionating the contribution of biological control based integrated pest management (BIPM), need based super imposition of integrated insect pest management(IIPM) over BIPM, synchronizing trichocard with moth emergence to explore the possibility of reducing trichocard numbers, evaluation of trichocard dispensing technologies and economic analysis of these operations. The experiment was conducted in transplanted rice and direct sown rice at State Seed Farm, Mannuthy. Both BIPM and IIPM strategies were implemented. Two light traps were installed in the field. The trichocards @ 5cc ha-1 were released four times in treated plots to suppress the yellow stem borer and leaf folder based on moth emergence. Other treatments included application of Beauveria bassiana and neem oil garlic extract 2% in BIPM plot and need based application of insecticides in IIPM plot for managing the pests. Results revealed that the relationship between light trap catches of yellow stem borer (Scirpophaga incertulas) and dead heart/white ear head damage did not differ significantly between transplanted and direct sown rice and trap catches were also low in both the cases. Considering the percentage damage, it was seen that control plot shows significantly high damage compared to other treatments. After sixth fortnight, the application of insecticides in IIPM and botanicals in BIPM plots reduced the damage and resulted in more yield. While observing the relationship between light trap catches of leaf folder (Cnaphalocrocis medinalis) and number of leaves damaged in transplanted and direct sown rice, less damage was observed in BIPM plot compared to other treatments. Considering the percentage damage, it was observed that control plot showed significantly high damage. After sixth fortnight , when other pests started infesting the crop, application of insecticides in IIPM and botanicals in BIPM plots reduced the damage and resulted in more yield. The yield data of various treatments indicate that the IIPM plot recorded highest yield i.e. 9,150 kg ha-1 in transplanted and 8,600 kg ha-1 in direct sown rice in comparison to BIPM (8,425 kg ha-1 and 7,975 kg ha-1) and control (6,115 kg ha-1 and 5,225 kg ha-1). The highest benefit cost ratio was recorded in IIPM (1.49 and 1.53:1) followed by BIPM (1.36 and 1.41:1). In the experiment to synchronize trichocard release with moth emergence for possible reduction of trichocard numbers, four releases starting from second to fifth fortnight could suppress both yellow stem borer and leaf folder. Different trichocard dispensing techniques have an important role in suppressing the yellow stem borer and leaf folder. In the cup method adults are restricted inside the cup and hence, leaf clipping method or coconut leaf method are recommended and also discourage the use of cup method. The results reveal that for minimizing pest incidence, providing protection and for phytotonic effects, seed treatments with insecticides and Pseudomonas is best suited. Major rice pests can be monitored by installing the light trap in the field and it is possible to synchronize the trichocard releases with moth emergence of yellow stem borer and leaf folder. Egg parasitoids T. japonicum and T. chilonis are effective against yellow stem borer and leaf folder only. BIPM method is best for managing leaf folder and IIPM for yellow stem borer. It is necessary to use need based application of insecticides, neem oil garlic extract and other biocontrol methods in controlling insect pests. Maximum yield is attained in IIPM plot followed by BIPM in transplanted and direct sown rice and benefit cost ratio was high in IIPM followed by BIPM method.ThesisItem Open Access Management of banana pseudostem weevil Odoiporus longicollis Olivier (Coleoptera: Curculionidae) with induced resistance and epideictic compounds(Department of Entomology, College of Horticulture, Vellanikkara, 2002) Raihana, K C; KAU; Ranjith, A MThe present investigation on management of banana pesudostem weevil Odoiporus longicollis Olivier (Coleoptera:Curculionidae) with induced resistance and epideictic compounds was undertaken in the Department of Entomology, College of Horticulture, Vellanikkara during 2000-2001. Extraction of epideictic pheromone associated with the weevil, evaluation of the resistance of the moisture stressed Nendran plants to the attack of the weevil and the resistance offered by the progenies of tissue cultured plants of infested plants were considered for the study . Females of 0. longicollis at different population intensities were released on cut pseudo stem of Nendran in the laboratory to arrive at the minimum pest load at which the concentration of epideictic pheromones would deter further oviposition. The results indicated that the weevil numbers above five per pseudostem was deterrent to conspecific emales. Pest load which would deter oviposition on banana was also be assessed by artificial confined release of females in the field. With increase in the pest loads on the plants there was a deterrency effect in the oviposition by the weevils. The maximum oviposition was observed by two weevils per plant (4.25). Even with twenty females per plant the oviposition count was very less (1.75). The oviposition deterrency was due to the deposition of the epideictic pheromone by the conspecific females after egg laying. It was seen that the acetone and ether extracts of pseudo stem pieces of 10 cm where five pairs of weevils had laid their eggs, when sprayed after air drying and dilution with water deterred the oviposition by other females. The acetone extract, air dried and diluted with water was the most effective for the extraction of the pheromone. Identification of the chemical composition of pheromones will help in their utilisation against the weevil. No-choice tests were designed to study the resistance of moisture stressed plants to the weevil attack. The weevil infestation was absent in those plants which received the minimum quantity of water though their yield was low. However, the plants which received slight reduction in the moisture (0.9 IW/CPE) •. gave a yield similar to those plants grown with normal irrigation. Only 40 per cent of these plants was infested when comparing with 90 per cent infestation in control plants. Rind-pulp ratio was also in par with control plants. The results indicated that the plants which receive a slight moisture stress from 6th month onwards at least in the outer sheaths will escape :from the attack of the weevil without affecting the yield adversely. No-choice experiment was conducted on the progemes of infested tissue cultured plants to evaluate the resistance to the weevil attack. The tissue cultured plants was found very resistant to the weevil attack. The experiment was started from the flower bud initiation stage (February). No plant was infested .upto three months after artificial infestation. Infestation was noticed during rainy period. The grades of infestation (0\ and O2) were very low in all the experimental plants.ArticleItem Open Access Natural enemy complex of coconut lacewing bug Stephanitis typicus distant and predatory potential of major natural enemies(Kerala Agricultural University, 1998) Unnimon, N K; Ranjith, A M; KAUThesisItem Open Access Resistance mechanisms against the pseudostem weevil odoiporus longicollis olivier (coleoptera : curculionidae) in banana(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 1999) Lalitha, N; KAU; Ranjith, A MThe present investigation on resistance mechanisms against pseudostem weevil Odoiporus longicollis Olivier (Coleoptera:Curculionidae) in banana was undertaken in the Department of Entomology, College of Horticulture, Vellanikkara during 1997-99. In insect-plant interactions, it is always the survival of the fittest. There is also a constant enhancement in the physiological preparedness both by the insect and the host plant to gain the upper hand. It is felt that even though the insect conqu6¥$ the resistance of the host plant in majority of cases, there may be a threshold of insect attack, which would induce plant defenses to deter the attack. It was also possible that some of these plant defenses may be triggered off by enzymes produced in the plant system consequent to the attack. These incitory enzymes or chemicals may be transferred to the offspring, which would make them resistant to attack, by the weevil. Hence, major objectives of the study were to evaluate sucker and in vitro regenerated progenies of infested Nendran (AA B) for resistance against 0. longicollis, to evolve methods for screening resistance under artificial conditions, laboratory rearing of 0. longicollis and identification of morphological, biochemical and anatomical bases of resistance using Nendran as susceptible and Njalipoovan as the resistant source. Preliminary field screening of Musa (AAB) Nendran for resistance against pseudostem weevil was done based on the number of ovipunctures/feeding holes on the pseudostem, surface area of infestation and the size of feeding holes. All of these contributed to the intensity of the attack. The multiplication product of these factors led to the development of a new 0-4 rating scale, for scoring the damage by 0. longicollis in the field. No-choice tests conducted on sucker and in vitro regenerated progenies of such graded mother plants revealed a better performance by plants having lower history of infestation. This suggested the existence of induced resistance involving triggering off of enzymatic reactions. Besides these lower grades, the plantlets of G4 exhibited better tolerance than control by exerting greater potential to stand amidst heavy winds till complete maturity of the bunch. The in vitro regenerated plants performed much better than the sucker derived treatment plants. This offers potential for mass multiplication of such in borne resistance for commercial release. The results obtained so far opens up the possibility of induced resistance that may be genetically inherited to the plantlets from its mother as an evolutionary character. Such triggering mechanism operating in vivo offers greater potential to select resistant clones. The methodology for screening banana for resistance to 0. longicollis by artificial infestation in field situations was standardized. Four adult weevils in the sex ratio 1: 1 (2!f' and 2 r:J) was found to be optimum to create moderate levels of infestation during the most favourable season (May-August). Mass rearing of 0. longicollis in laboratory conditions using natural diet was quite successful for maintaining a large-scale population throughout the year. A continuous supply of uniformly aged test insects for exposing the experimental plants at specific pest load was made possible by this. Studies involving the duration of development of the weevil revealed acute antibiosis in Njalipoovan manifested by reduced egg laying prolonged duration of life cycle, reduced hatching of eggs (39.5%) and reduced adult emergence from eggs (29.7%) in contrast to 94.9 per cent hatching of eggs and 9l.3 per cent adult emergence in Nendran. A no-choice test was designed to study the appropriate age of Nendran from which it becomes susceptible to infestation. Results indicated a distinct preference for oviposition by the adults on pseudostem of banana from seventh month onwards. This information helps to reduce the insecticidal load in the banana ecosystem by advocating pesticides from seventh month only. The existence of oviposition deterrency when more females were confined to Nendran pseudostem pieces revealed the deposition of spacing pheromones by conspecific females after egg laying. It was seen that the acetone and ether extracts of pseudostem pieces where ten females had laid their eggs, when sprayed on fresh pseudostem, deterred the oviposition by other females. Isolation and identification of such epidectic compounds will help in their utilisation in the field to prevent egg laying on banana pseudostem. The morphological, anatomical and biochemical bases of resistance were also identified. The morphological parameters associated with resistance were smaller width and breadth of the sheath coupled with more number of sheaths in the resistant variety. These increased the number of cuticular layers and cell walls the grub had to traverse before entering the central pith. The pith formation is of prime importance to the curculionid as it becomes the target site of feeding for third and fourth in stars. There are certain cues emanating from the pseudostem subsequent to maturity, which aids the adult weevils in host selection and oviposition. The lesser moisture and higher crude fibre content of Njalipoovan pseudostem exhibited greater influence on resistance by posing a mechanical barrier to egg laying and feeding of neonate larva. The information on moisture content is of practical utility in the management of the pest in endemic areas. It may be possible to artificially create moisture stress in the plant attaining flower bud initiation stage by regulating irrigation. The level of irrigation has to be adjusted so as not to induce a yield reduction but at the same time to induce moisture stress at least in the outer sheaths to prevent oviposition. The water suckers served as more conducive hosts for the pest even before sufficient maturity and this highlighted the need for removal of water suckers from endemic fields. The anatomical sections of pseudostem sheath clearly revealed a thick cuticle on epidermal cells with four to five layers of dense collenchymatous hypodermis imposing a physical barrier against oviposition in the resistant cultivar. Further, the ground tissues which constituted of compactly arranged parenchymatous cells with several starch grains offered feeding deterrency. The closely packed bigger sized lower epidermal cells along with additional parenchymal layers below the air cavity operated as a mechanical barrier which caused the failure of the neonate larva to penetrate inner tissues. Higher content of phenolics generally showed a positive correlation with resistance. However, the role of ortho dihydric phenolic substrates in resistance is greatly dependent on the enzymatic activity of polyphenol oxidase to form toxic metabolites like quinones and tannins. Hence, the oxidation factor of OD phenols clearly indicated the dominance of the resistant variety, Njalipoovan. The accelerated activity in Njalipoovan is endowed with greater potentiality to activate polyphenol aggressively effecting more production of lignin, quinone and tannins, in the event of egg laying or feeding by the pseudostem weevil.ThesisItem Open Access Studies on the consumption, digestion and utilisation of food plants by Pericallia ricini(epartment of Agricultural Entomology, College of Horticulture, Vellanikkara, 1981) Ranjith, A M; KAU; Dale, DThe present investigation was carried out in the Entomology Department of the College of Horticulture, Vellanikkara. It was aimed at working out idices relating to consumption, digestion and utilisation of eight food plants by the larvae of Pericallia ricini F., a polyphagous pest in Kerala. The study was also meant to assess the relative growth of the caterpillars on the different food plants so that a general idea can be obtained on the suitability of the food plants to the larvae. Data on the pupal and adult emergence were also collected with a view to probing further in to the identification of probable insect growth inhibitory substances among the host plants. The most preferred plants with regard to the consumption of foliage were pumpkin, castor and brinjal. Consumption index was calculated on fresh and dry weight bases. It was seen that the consumption of brinjal leaves was the maximum and the index was the least for sweet potato. The other foods did not differ among them significantly. On dry weight basis, banana-fed insects with a C.I. of 3.02 ranked first, followed by larvae fed on cotton. Larval weight gain on brinjal was the maximum followed by those grown on pumpkin. The least weight gain of 0.66 g was exhibited by larvae which were fed on banana leaves. The last instar larvae consumed the largest quantity of food during their larval period. Consumption of food was very low among the third instar larvae. Females were to consume more foliage than the corresponding male counterparts. The differences in consumption by the two sexes were statistically significant. The growth rates were calculated both on fresh and dry weight basis. On fresh weight basis, larvae reared on brinjal had the highest growth rate of 65.7 and the least growth rate of 30.7 was obtained from larvae grown on banana. On dry weight basis, it was seen that pumpkin was superior to all others in supporting larval growth of P. ricini. The approximate digestibility was calculated on the basis of fresh weight of the digestible food and the weight of the ingested food. A.D. was the maximum (91.40 per cent) with sesamum on fresh weight basis, but on dry weight basis, it was castor that the larvae digested most. Indices relating to efficiencies of converting ingested food and digested food to biomass were also calculated both on fresh and dry weight bases. The reasons for the observed values deviating from the expected ones are discussed. Utilisation of nitrogen, both ingested and digested, by the larvae varied among food plants significantly. Colocasia, sesamum and cotton had the higher values of E.C.I. (N). In the descending order. But taking into consideration of the E.C.D. (N) values, the numerical figure was the highest with castor and the least with banana. The present study has clearly indicated that the food plants have a significant effect on the pupal period, pupal weight and pupal length. It is also seen that some host plants cause larval and pupal mortalities at varying degrees. The effect of larval feeding on the sex ratio of emerging adults was also recorded. Insects fed on castor and cotton leaves showed the near best sex ratio of 1: 0.88. In the case of sweet potato and sesamum, the ratio was 1: 2. All other foods led to sex ratios ranging from 1:0.67 to 1: 2.