Browsing by Author "Thania Sara Varghese"

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Bioactivity of essential oil from the tea tree Melaleuca bracteata F. Muell. against stored product pests
(Department of Agricultural Entomology, College of Agriculture , Vellayani, 2023-03-16) Farzana M Sha; Thania Sara Varghese
The research work entitled “Bioactivity of essential oil from the tea tree Melaleuca bracteata F. Muell. against stored product pests” was carried out at the Department of Agricultural Entomology, College of Agriculture, Vellayani during 2020 to 2022 with an objective to isolate and characterize and evaluate the bioactivity and persistence of toxicity of M. bracteata essential oil against stored product pests viz. red flour beetle, Tribolium castaneum (Herbst) and pulse beetle, Callosobruchus chinensis (Linn.). The essential oil (EO) from M. bracteata was extracted by hydro distillation in clevenger type apparatus. Essential oil yield per 100g leaves was observed as 1.08 mL. The efficacy of tea tree essential oil was tested against the laboratorymaintained culture of T. castaneum and C. chinensis by contact, fumigant and repellent bioassays and the persistence of toxic activity of the essential oil on the test insects were also evaluated under laboratory conditions. In contact toxicity bioassay, the LC50 and LC90 values of the EO against T. castaneum were 25.16 % and 69.94 %, respectively at 24 hours after treatment (HAT). The LC50 and LC90 values of EO against C. chinensis were 0.05 % and 2.73 %, respectively at 24 HAT. In fumigant toxicity bioassay of T. castaneum, the LC50 and LC90 values of the EO were 7.7mLL-1 and 22.95mLL-1 at 24 HAT. The LC50 and LC90 values of EO against C. chinensis were 4.30 μLL-1 and 29.96 μLL-1 , respectively at 24 HAT. In the case of T. castaneum, the maximum repellency observed was 93.75 % at 5% concentration of EO. Cent per cent repellency was not observed here because of the fumigant effect at higher doses which scattered the released insects into both treated and untreated filter paper halves in Petri plates. In case of C. chinensis, the insects get repelled at a very low concentration. 100 per cent repellency was observed at 0.01% and 0.05% concentration of EO after 2 h and 45 min, respectively. The toxic effect of M. bracteata EO persisted up to 34 days on C. chinensis whereas upto 10 days for T. castaneum when exposed to LC90 values obtained from 136 fumigant bioassay. The GC-FID and GC-MS profiling of the EO showed 46 components where, methyl isoeugenol (69.64%) a phenylpropanoid was found to be major component followed by methyl cinnamate (8.73%) and methyl eugenol (7.40%), which may alone or synergistically with other constituents caused the insecticidal effects. Experiments on the effect of the EO on the detoxifying enzymes of T. castaneum and C. chinensis showed that the enzymes like cytochrome P 450, carboxyl esterase were significantly lower in essential oil treated insects, whereas the activity of glutathione S- transferase was found to be higher when compared to untreated insects. Similarly, the total protein content was also found lower in essential oil treated insects compared to the untreated insects. In the present investigation, M. bracteata was found to have a good essential oil yield of 1.08 per cent. The M. bracteata EO showed strong contact, fumigant and repellent toxicity against C. chinensis when compared to T. castaneum. Against C. chinensis, the toxic activity of the essential oil persisted up to 34 days. Methyl isoeugenol (69.53%) was found to be the major component in the essential oil, followed by methyl cinnamate (8.73%) and methyl eugenol (7.41%), which may alone or synergistically with other constituents caused the insecticidal effects. The essential oil in the present investigation has effects on the detoxification enzymes of the test insects.
Bioactivity of essential oils against insect pests of brinjal
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2022) Manoj, K; Thania Sara Varghese
The study entitled “Bioactivity of essential oils against insect pests of brinjal” was undertaken in the Department of Agricultural Entomology at College of Agriculture, Vellayani during the period 2019-2021 with an objective of evaluating the bioactivity of essential oils viz., basil oil, citronella oil, eucalyptus oil and orange oil against insect pests of brinjal and characterization of the most effective essential oils. Laboratory screening of essential oils viz., basil oil, eucalyptus oil, citronella oil and orange oil was conducted against one sucking pest (mealy bug, Coccidohystrix insolita (Green)) and one chewing pest (Hadda beetle, Henosepilachna vigintioctopunctata (Fabricius)) in brinjal. Acute toxicity of the essential oils against the test insects was determined by leaf dip bioassay. Preliminary test dose range causing 10 to 100 per cent mortality was fixed and based on these 6 doses including a control treatment was taken. Based on the results of leaf dip bioassay of essential oils against mealy bug, LC50 and LC90 of basil oil, eucalyptus oil, citronella oil and orange oil were (0.49 and 1.33), (1.86 and 4.28), (0.64 and 2.39) and (1.54 and 3.53) per cent respectively at 24 hours after treatment (HAT). The corresponding LC50 and LC90 values of the above four oils at 48 HAT were (0.29 and 0.89), (0.72 and 1.92), (0.28 and 1.22) and (1.06 and 2.17) per cent respectively. Against hadda beetle the LC50 and LC90 values of basil oil, eucalyptus oil, citronella oil and orange oil were (1.25 and 2.85), (3.35 and 5.09), (0.93 and 1.52) and (3.48 and 9.11) per cent respectively at 24 HAT. While the corresponding LC50 and LC90 values at 48 HAT were (0.85 and 1.70), (2.09 and 3.51), (0.63 and 1.14) and (2.02 and 4.05) per cent respectively. Based on toxicity bioassays, basil and citronella oil had lower LC50 and LC90 values than eucalyptus and orange oil against both mealy bug and hadda beetle at both 24 and 48 HAT and these two were selected for further lab and field evaluation. Repellent and antifeedant effect of the selected essential oils from the first experiments viz., basil oil, citronella oil were evaluated against hadda beetle by modified preference method and no choice method respectively. At 0.5 to 1 per cent 76 concentration, both basil and citronella oil showed 90-100 per cent repellence at 30 and 60 minutes of treatment. On other hand, 0.5 to 1 per cent concentration of basil and citronella oil showed antifeedant effect of 100 per cent after 24 hours of treatment. Before conducting field evaluation of essential oils, bloom test and phytotoxicity evaluation on brinjal plants were done. Bloom test was conducted to check the emulsification of essential oil and surfactant formulation in distilled water. Results were showing “Good” bloom rating for basil oil and “Excellent” bloom rating for citronella oil. Phytotoxicity evaluation of basil and citronella oil was carried on brinjal plant as per the protocols of CIBRC (Central Insecticide Board and Registration Committee). Basil oil and citronella oil at 0 to 0.7% were not showing any phytotoxic symptoms on brinjal plants while the higher doses of 1%, 1.5% and 2% were showing slight moderate and severe phytotoxic symptoms. Based on the laboratory and phytotoxicity evaluation, two doses of basil oil and citronella oil (0.5% and 0.7%) were selected for the pot culture experiment along with two chemical checks and an untreated control. The experiments were laid in completely Randomized design with three replications. In field study, spraying of basil oil and citronella oil at 0.7% showed significant reduction in aphid population and it was statistically on par with thiamethoxam 25% WG even at 14 DAT. The leaf webber population was also significantly reduced for basil and citronella oil at 0.7% and it was statistically on par with chlorantraniliprole 18.5% SC even at 14 DAT. Basil oil and citronella oil at 0.7% showed significant reduction in the shoot and fruit borer damage after 14 days of treatment and it was statistically on par with chlorantraniliprole 18.5% WG at 14 days after treatment. Basil oil and citronella oil at 0.7 per cent showed significant reduction in the lady bird beetle population. There was no statistical difference among the different treatments with regard to the biometric observations viz., total number of leaves, damaged leaves, plant 77 height after the field spraying, however the fruit yield was recorded significantly higher in chlorantraniliprole 18.5% WG. GC-FID/GC-MS studies on basil and citronella oil revealed that the predominant component of basil oil is Methyl chavicol (75.73%), followed by Linalool (18.21%) and (8) Cuprenene (1.58%). In citronella oil, Geranial (64.77%) was the most abundant component followed by Citronellyl acetate (7.92%), Geraniol (7.08%), (Z) Iso citral (5.29%) and Neral (3.60%).
Bioefficacy and safety evaluation of biorational insecticides for the management of sucking pest complex of chilli (capsicum annuum L. )
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2011) Thania Sara Varghese; Thomas Biju Mathew
Insecticide resistance management in Rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae)
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2021) Neethu, P; Thania Sara Varghese
The research work entitled "Insecticide resistance management in rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae)" was done at College of Agriculture, Vellayani during 2019 to 2021.The objectives of the study were to assess the resistance levels in rice weevil, biochemical basis of resistance and screening of new molecules for the management of S. oryzae. Different sample populations of S. oryzae were collected from the three godowns of Food Corporation of India (FCI) viz., Kollam, Valiyathura, and Thikkodi, as well as a susceptible lab culture of S. oryzae maintained without pesticide exposure, was obtained from the Division of Entomology, Indian Agricultural Research Institute (IARI). Resistance levels of the commonly used insecticides in FCI viz., malathion and deltamethrin were evaluated in the three populations collected from Kollam, Valiyathura and Thikkodi by film method of bioassay and compared it with the susceptible lab population from IARI. Kollam population showed highest resistance to both malathion and deltamethrin with resistance ratios of 14.94 and 9.03 followed by Valiyathura with resistance ratios of 11.39 and 7.79, respectively. Thikkodi population showed the least resistance to malathion and deltamethrin, with resistance ratios of 8.74 and 5.48, respectively. Malathion resistance was higher in all the three populations than the deltamethrin resistance. The most resistant population selected from the previous experiment i.e., the Kollam population was further assayed for its biochemical basis along with the susceptible IARI lab culture. The Kollam population was found significantly higher in total protein (6 mg ml-1 ) and activity of detoxifying enzymes viz., carboxylesterases (0.65 µmol min-1 mg protein-1 ), glutathioneS-transferases (0.41 µmol min-1 mg protein-1 ) and cytochrome P450 (0.74 p mol min-1mg protein-1 ) than the lab sample. The sample population collected from Kollam was again screened for their susceptibility to new generation insecticides like fipronil, indoxacarb and chlorantraniliprole by film method of bioassay. Fipronil was found to be more toxic with LC50 value of 5.86 ppm followed by indoxacarb (90.57 ppm) and chlorantraniliprole (4041.43 ppm). Fipronil and indoxacarb were 619.8- and 40.13-fold toxic to resistant population of S. oryzae with respect to malathion. The newer insecticides in the previous experiment along with malathion and deltamethrin were further screened simulating the conditions of FCI godown. The insecticides were sprayed on jute bags containing 1 kg of rice grains and 50 adult beetles of Kollam population of S. oryzae. The dosages of newer insecticides were taken 10 times more the LC50 value obtained in the laboratory bioassay and FCI recommended dosage was taken for malathion and deltamethrin. Fipronil 5% SC @ 0.006% recorded significantly higher mortality of 86.5 and 89.5 per cent at 24 and 48 h of treatment followed by indoxacarb 14.5% SC @ 0.09% and chlorantraniliprole 18.5% SC @ 4.04%. The persistence of the most effective insecticide fipronil along with malathion and deltamethrin on rice grains were further studied by recording the residue levels at different time intervals after spraying. Dosages were same as the previous experiment. Insecticides were sprayed on jute bags containing rice grains and residues were analysed at 0 (2 h after spray), 1, 3, 5, 7,10, 15, 20 and 30days intervals using the methods validated prior to residue estimation. Fipronil residues were below the limit of quantification at 2 h after spraying. The residues of deltamethrin and malathion persisted up to 3 and 5 days after spraying with a half-life of 2.48 and 2.71 days, respectively. From the present study it is revealed that S. oryzae collected from Kollam, Valiyathura and Thikkodi were resistant to the commonly used insecticides viz., malathion and deltamethrin and it is confirmed here by the presence of higher levels of detoxifying enzymes in the resistant population. Further screening of newer insecticide molecules against the resistant population of S. oryzae suggested that fipronil 5% SC @ 0.006% is highly effective and less persistent on grains when compared to malathion and deltamethrin.