1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Population dynamics, intensity of damage and management of the coreid bug, paradasynus rostratus dist.(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2006) Ambily Paul; Nandakumar, CExperiments were conducted to study the influence of alternate hosts on the population dynamics of the coreid bug, Paradasynus rostratus Dist. and consequent damage to coconut and to evolve an eco-friendly management strategy to the pest. An abstract of the work done and the results are given below. A survey conducted in Thiruvananthapuram district to study the incidence and intensity of coreid bug infestation on coconut revealed that the infestation was the highest in the coastal region. The incidence was lower in the upland and midland regions. Among the variety of crops seen in the coconut based homesteads, guava, cashew, cocoa and neem were recorded as potential hosts of the pest. Studies on the influence of alternate hosts on the population build up of coreid bug revealed that the alternate hosts were a major determinant in the extent of infestation of coreid bug on coconut. The pest multiplied on the alternate hosts during flushing, flowering and fruit formation stages of the crops and subsequently shifted to the base crop, coconut in multiple cropping systems. The changes in size and yield parameters of nut due to the infestation of P.rostratus were assessed. Nuts with negligible damage (category II) did not show any significant difference in nut shape, nut characters, copra and oil content. Significant reduction in copra and oil was observed in moderately (category IV) and , heavily (category V) damaged nuts. The endosperm was not at all formed in severely damaged (category VI) nuts. The changes in the biochemical constituents of coconut buttons due to feeding of coreid bug were studied. The phenol content in young infested nuts recorded an increase compared to healthy nuts. A progressive reduction in starch and fibre content of young nuts was obtained with increase in degree of infestation The study on the effect of infestation of P.rostratus on germination and vigour of seedlings revealed that though all the nuts in damage category II (negligible damage) to IV (moderate damage) germinated within six months, only seedlings from nuts with negligible damage (category II) had the qualities of good seedlings. The antifeedant effect of neem based botanicals and efficacy of synthetic chemical pesticides were evaluated against coreid bug. Among the botanical and chemical pesticides, neem seed oil- garlic emulsion 2 per cent and profenophos 0.05 per cent proved most effective against the coreid bug. A field experiment was conducted to evaluate the effect of selected treatments on alternate hosts for control of coreid bug in coconut. The study revealed that the combined application of neem seed oil- garlic emulsion 2 per cent + profenophos 0.025 per cent was the most effective in reducing the extent of coreid bug infestation in the surrounding coconut palms. The present study could establish the role of alternate hosts on the population buildup of coreid bug. Plant protection operations in alternate hosts against coreid bug are more effective, economical and viable options compared to those in coconut. Based on the results of the study, a package involving regular monitoring of the alternate hosts in the homesteads, removal and destruction of the egg masses and early instars of the pest and giving a need based spray with an insecticide formulation like neem oil- garlic emulsion 2 per cent + profenophos 0.025 per cent on the alternate host would be a practical and cost effective approach for reducing the damage of P.rostratus on coconut in the homesteads.Item 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 Biju MathewStudies 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.