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2020 - 20232
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Subject: Entomology × End date: 2023 × Start date: 2020 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Bioefficacy studies of biorational approaches against Leucinodes orbonalis Guenee on brinjal in Himachal Pradesh
    (CSK HPKV, Palampur, 2023-01-16) Negi, Nitika; Sharma, Prem Chand
    Studies were carried out to know the incidence of Leucinodes orbonalis on brinjal in agro-climatic zone I and II of Himachal Pradesh and data on the incidence of L. orbonalis were recorded at monthly interval during 2019 and 2021. The crop was found to be infested with L. orbonalis at all the locations during both the years. Incidence of L. orbonalis appeared early in the month of May and remained up to the end of the season. The peak incidence of L. orbonalis was recorded in the month of July and August on shoots and fruits of brinjal during both the years. Among all the locations, Una district had a maximum shoot and fruit infestation (25.33 and 28.83%, respectively) during 2019, while in 2021 the maximum shoot infestation was recorded in Hamirpur district (26.50%) and fruit infestation in Kangra district (28.64%). The intrinsic toxicity studies against neonate larvae of L. orbonalis revealed emamectin benzoate as most toxic with LC50 value of 0.0043 ppm followed by spinosad (0.0303 ppm), Bacillus thuringiensis (3.989 ppm), azadirachtin (8.847 ppm), Brahmastra (24203.194 ppm) and Agniastra (29795.95 ppm). The field experiments were undertaken during the kharif season of 2020 and 2021 at the Experimental Farm of the Department of Entomology, CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur. For the management of L. orbonalis, different approaches were evaluated under three modules, cultural & mechanical methods (M1), natural products & biopesticides (M2) and insecticides (M3). In Module 1, amongst seven treatments, minimum mean shoot infestation (9.33%) and fruit infestation (number as well as weight basis i.e., 12.68 and 13.86%) was recorded in neem cake (NC) + clipping of shoots. In Module 2, out of nine treatments, application of Bt resulted in least mean shoot infestation (13.56%), whereas fruit infestation on the number basis was minimum in neem cake + Azadirachtin; on the weight basis, neem cake + Bt recorded lowest per cent fruit infestation (15.27%). In case of Module 3, shoot infestation was minimum (6.40 %) in emamectin benzoate followed by neem cake + emamectin benzoate (6.70%) and spinosad (6.87%). On the basis of fruit infestation (number and weight), neem cake + application of emamectin benzoate resulted in lowest fruit infestation (9.39 and 8.85%) followed by emamectin benzoate (9.61 and 8.88%). On the basis of incremental output input ratio of two years, emamectin benzoate (27.27) was the most economically viable treatment followed by spinosad (10.82). After two applications of insecticides, the average initial deposits of emamectin benzoate (@10 g a.i./ha) were 0.307 ppm, whereas the average initial deposits of spinosad (@75 g a.i./ha) were 0.489 ppm. A waiting period of 4 days for emamectin benzoate and 2 days for spinosad was suggested for safe consumption of brinjal fruits.
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    ThesisItemOpen Access
    STUDIES ON NATURAL ENEMY COMPLEX OF APHIDS INFESTING OILSEED BRASSICAS
    (CSKHPKV. Palampur, 2020-01-30) SONI, SAURBH; Surjeet, Kumar
    Studies on natural enemy complex of aphids infesting oilseed Brassicas were carried out to find the distribution and abundance of aphid species and associated natural enemies in different parts of the state. The field experiments were undertaken during the rabi season of 2015-16, 2016-17 and 2017-18 at the Experimental Farm of the Department of Entomology, CSK Himachal Pradesh Krishi Vishvavidyalaya, Palampur on mustard variety RCC-4 and the data on the population build-up of aphids and their associated natural enemies were recorded at weekly interval. At other locations of the state, the observations were recorded at fortnightly interval during rabi 2016-17 and 2017-18. The crop was found to be infested with all the three aphid species viz. mustard aphid, Lipaphis erysimi (Kaltenbach), cabbage aphid, Brevicoryne brassicae (Linnaeus) and green peach aphid, Myzus persicae (Sulzer). L. erysimi appeared early in the season and remained active for a longer duration. B. brassicae activity started late in the season and reached the peak towards the maturity of the crop. M. persicae appeared for a shorter duration and its population was scarce at all the locations. Three natural enemies i.e. coccinellids, syrphids and one parasitoid, Diaeretiella rapae M‟Intosh were found to be associated with the aphid species. They appeared late in the season and their peak population did not synchronize with peaks of aphid population and thus were unable to check the aphid population. Correlation coefficients indicated that the temperature favoured the build-up of aphid population and their natural enemies while rainfall exerted negative impact. The population of coccinellids was negatively correlated with the population of L. erysimi and M. persicae while, positive correlation with B. brassicae was observed. On the other hand, population of syrphids was found to be positively correlated with aphid population. Regression analysis revealed that none of the weather parameter alone was responsible for the population build-up of aphids and associated natural enemies. In order to know the biological control potential of the aphid parasitoid D. rapae, biological and behavioural characteristics were studied in the laboratory using M. persicae, B. brassicae and L. erysimi as host. The parasitoid successfully completed its life cycle on different instars in all the aphid hosts. It was longer in early instars compared to that in later instars. Oviposition period, post-oviposition period, fecundity (number of eggs laid/female/day) and total fecundity (total number of eggs laid/female) of D. rapae parasitizing nymphs of different age groups (1-2 days and 4-5 days old) of M. persicae, B. brassicae and L. erysimi were studied and the results showed that age of the host at the time of oviposition by the parasitoid significantly affected the duration of oviposition and fecundity of the parasitoid. Older nymphs (4-5 days old) of the aphids were able to defend themselves against ovipositing females of the parasitoid more effectively than the younger nymphs (1-2 days old). Immature survival of the parasitoid, D. rapae was found to be highestxii in the third instar (85.81+10.31%) of M. persicae, B. brassicae (83.70+5.62) and fourth instar (87.67+14.48) of L. erysimi. Highest survival was observed in older instars than in younger instars. A female-biased sex ratio was found for the parasitoid with mean values of 79.99, 73.38 and 79.32 per cent for M. persicae, B. brassicae and L. erysimi, respectively. Adult longevity of D. rapae was found to be significantly longer for females in comparison to that of males in all the aphid hosts. Mean longevity of adult females of D. rapae was significantly longer while parasitizing nymphs of younger age groups (1-2 days) in comparison to older age groups (4-5 days). Among different host plants tested, M. persicae reared on capsicum, B. brassicae reared on cabbage and L. erysimi reared on mustard was found to be the best host for D. rapae on the basis of high mean fecundity, high parasitization (%), female biased sex ratio and the shortest time required by the parasitoid for completion of total developmental period. Host and parasitoid sizes were determined based on the length of their hind tibia and it was longest in M. persicae, followed by B. brassicae and L. erysimi. The adults of D. rapae emerged from M. persicae were the largest (males= 0.626 mm and females= 0.689 mm), followed by adults emerged from B. brassicae (males= 0.539 mm and females= 0.565 mm) and L. erysimi (males= 0.516 mm and females= 0.521 mm), respectively. Host stage preference of D. rapae on different instars of three aphids was studied in choice and nochoice preference tests. Second instar of M. persicae was the most preferred in both choice and no-choice tests. The parasitoid showed higher preference towards third instar nymphs of B. brassicae and second instar of L. erysimi in both choice and no-choice tests, respectively. D. rapae exhibited type II functional response to all the three aphids. The per capita parasitization and search efficiency of the parasitoid were observed to decrease with increase in parasitoid density. Similarly, the search efficiency of the parasitoid gradually decreased with the increase in the parasitoid density. It was concluded from the study that D. rapae is effective biological control agent which can be mass produced on aphids infesting oilseed Brassicas for utilization in augmentative biological control. The study can be helpful in further standardizing the protocols for mass rearing of the parasitoid.