Loading...
Theses
Browse
1 results
Search Results
ThesisItem Open Access Evaluation of potential botanical pesticides gainst tobacco cutworm(Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2002) Suresh, S; KAU; Jim Thomas (Guide), Thomas (Guide)Investigations were carried out on the "Evaluation of potential botanical pesticides against tobacco cutworm, Spodoptera litura (Fab.)" in the Department of Entomology, College of Horticulture, Vellanikkara during 2000-2001. The objectives of this study were to screen the botanicals with biological resources such as ovipositional deterrency, ovicidal action, antifeedancy, morphogenic disruptions, insecticidal properties, etc. on the enigmatic and polyphagous caterpillar pests such as S. litura. Ovipositional deterrency test was conducted with aqueous plant extracts and essential oils. Azadirachta indica and Hyptis sauveolens aqueous extracts allowed lower rate of oviposition (as evidenced by their lower average score values of 3 to 6) on the treated surface at five and ten per cent strengths. Similarly, the essential oils viz., Cinnamomum zeylanicum and Cymbopogon martinii showed pronounced ovipositional deterrency even at 0.5 per cent level. Aqueous extract of Azadirachta indica gave higher ovicidal action as high as 61.43 and 88.39 per cent hatching inhibitions at five and ten per cent concentrations respectively. Among" the six tested essential oils, Cinnamomum zeylanicum and Cymbopogon martinii exhibited cent per cent egg mortality at 0.5 per cent strength each. Citronella winterianus oil, Kaempferia galanga oil and :4. indica aqueous extract exhibited higher leaf protection of 62 to 77 per cent at three per cent concentration each. Oils of Kaempferia galanga and Cymbopogon martinii and aqueous extract of Azadirachta indica induced larval starvation of 56 to 70 per cent at the same concentration of three per cent each. Among the solvent extracts of the botanicals tested, acetone extract of Andrographis paniculata exhibited larval starvation of 63 per cent at its two per" cent concentration, while, dichloromethane extract of the same produced 63 per cent leaf protection at the same strength. Vitex negundo extract in methanol afforded leaf protection to the level of 64.31 per cent and larval starvation of 55.99 per cent at its five per cent level. Chloroform extract of Azadirachta indica at four per cent level produced more than 70 per cent leaf protection as well as larval starvation. The Approximate Digestibility (AD) was lower in aqueous extracts of Andrographis panicufata, Thevetia nerifolia, Clerodendron infortunatum and Strychnos nux-vomica at one and three per cent strengths on the treated insects, highlighting their inhibitory action during digestion process, whereas, the essential oils viz., Citronella winterianus, Cymbopogon martinii and Kaempferia galanga treatments at three and five per cent inhibited the assimilation of ingested and digested food into body matter as indicated by their lower ECl and ECD values. The third instar larvae when fed on host leaves treated with oils of Cymbopogon flexuosus and Kaempferia galanga and aqueous extracts of Strychnos nux-vomica, Vitex negundo, Azadirachta indica and Andrographis paniculata (@ 1, 3 and 5% levels each) were found to be inducing pupal and adult malformations (7.53 to 16.67% total malformations). The chloroform extract of Azadirachta indica and acetone extract of Vitex negundo on exposure on host plants, induced higher rate of deformities at the time of pupation and eclosion to the extent of up to 30.8 per cent. Cymbopogon martinii oil had the lowest LCso value of 178 ppm as compared to other oils viz., Mentha piperita, Cymbopogon flexuosus and Citronella winterianus (with- their respective LCso values of 273, 311 and 370 pp m) indicating its significant insecticidal and insectistatic properties and offer their scope for lPM strategies.