Reji Rani, O PDevi, Balakrishnan.KAU2021-07-132021-07-132020174974https://krishikosh.egranth.ac.in/handle/1/5810170449PGThe study entitled “Bioefficacy of capsule formulations of Beauveria and Metarhizium in managing banana weevils” was conducted at Instruction Farm, College of Agriculture, Vellayani, Thiruvananathapuram and in the farmers field at Venganoor panchayath, Peringamala, Thiruvananathapuram during 2018-2020. The objective of the study was to validate the efficacy of biocapsules of Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin for the management of banana weevils. The study intended to standardize the dosage and method of application of the Beauveria capsules against the pseudostem weevil, Odoiporus longicollis Oliver and rhizome weevil, Cosmopolites sordidus Germer. The capsules were formulated at a higher spore load of 1010 with HPMC coating and chitosan as carrier following the protocol developed by Remya and Reji (2019). There were three sets of field experiments (1) Efficacy of biocapsules (both Beauveria and Metarhizium) applied as prophylactic treatment against both the weevils (2) Efficacy of Beauveria capsules in curative treatment of pseudostem weevil (3) Efficacy of Metarhizium capsule in curative treatment of rhizome weevil. For prophylactic treatment of pseudostem weevil, two methods of application were tested (1) applying one Beauveria capsule each on all four sides of the outer leaf sheath and (2) applying one capsule each in the outer four leaf axils on all four sides of the plant. The time intervals tested were (1) monthly intervals and (2) bimonthly intervals, starting from fourth month till bunch emergence. Curative management was tested by leaf axil application + bore hole application at two time intervals, weekly and fortnightly. To test the prophylactic treatment against rhizome weevil two methods were tested (1) Plugging the rhizomes at paring on all four sides @ four capsules rhizome-1, followed by pit application @ four plant-1 and (2) pit application alone @ four, plant-1. The time intervals tested were monthly and bimonthly. For curative treatment, the methods tested were pit application at fortnightly, monthly and bimonthly intervals. Results revealed that, placement of Beauveria capsules in the outer leaf sheath @ four, plant-1 at monthly intervals starting from fourth month till bunch emergence was superior with least infestation. Destructive sampling of plants done in the seventh month revealed that there was 90.9 per cent reduction in the population of grubs and adults and 83.33 per cent reduction in the pupal population. The other method, outer leaf axil application @ four, plant-1 at monthly intervals was also found to be effective with a reduction in the population of 72.2 per cent in the case of grubs and adults and 83.33 per cent in pupae. This was on par with single application of chlorpyriphos 20 EC 0.05 % @ 2 mL L-1 as leaf axil filling, where the reduction in population of grubs, pupae and adults was to the tune of 81.81, 50 and 72.72 respectively. Both the methods when applied bimonthly were observed to be less effective. For curative treatment of pseudostem weevil, weekly application of capsules was superior with 51.51, 60.8 and 61.5 per cent reduction in the population of grubs, pupae and adults respectively. This was equally effective as one time application of chlorpyriphos 20 EC 0.05 %@ 2 mL L-1 as leaf axil filling, where the population observed was 54.54, 52.17 and 53.8 per cent of grubs, pupae and adults. Plants in which fortnightly application was done exhibited less control with 24.24, 34.78 and 33.33 per cent reduction of grubs, pupae and adults,respectively. Though there was a marginal increase in yield in the best method, statistically it did not vary from those of others. In the case of rhizome weevil, for prophylactic treatment, placement of four Metarhizium capsules by plugging on the four sides, followed by pit application at monthly intervals was more effective than all other treatments. No tunneling was observed at the time of destructive sampling and the pest stages were totally absent (100 per cent control). When the same method was followed at bimonthly intervals, population reduction was 77.77 and 70 per cent of grubs and adults respectively. Pit application was also effective when applied every month, with 77.77 and 60 per cent reduction of grubs and adults respectively. For curative treatment of rhizome weevil, placement of four capsules in the planting pit at fortnightly intervals was equally effective as one time soil application of Fipronil 0.3 G @ 10g plant-1. Population assessed at the time of harvest revealed that there was 66.65 and 62.5 per cent reduction in the population of grubs and adults, compared to 66.65 and 58.325 per cent in chemical treatment. Analysis of data on yield plant-1 revealed that treatment with capsules at fortnightly and monthly interval were on par with that of chemical treatment and the treatment at bimonthly intervals was equivalent to the yield from untreated plants. It is concluded that for prophylactic management of pseudostem weevil, Beauveria capsules placed in the outer leaf sheath at monthly intervals @ four plant-1, starting from fourth month till bunch emergence is effective, while for curative treatment placement of capsules in the outer four leaf axils @ four plant-1 and one each in the bore hole at weekly intervals is as effective as one time application of chlorpyriphos 20 EC 0.05 % @ 2 mL L-1 treatment. For rhizome weevil, placement of Metarhizium capsules @ four plant-1 by plugging the rhizome at the time of paring, followed by pit application at monthly intervals @ four plant-1 is effective as prophylactic measure and for curative treatment, pit application of capsules at fortnightly intervals @ four plant-1 is effective and equivalent to single application of Fipronil 0.3 G @ 10g plant-1. Therefore the biocapsules of Beauveria can be recommended for the management of pseudostem weevil and those of Metarhizium can be recommended for the management of rhizome weevil.EnglishThesis