Evaluation of certain botanicals against cowpea aphid, Aphis craccivora Koch

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dc.contributor.advisorGogoi, Inee
dc.contributor.authorMohapatra, Swapnalisha
dc.date.accessioned2023-10-06T15:49:23Z
dc.date.available2023-10-06T15:49:23Z
dc.date.issued2018
dc.description.abstractField and laboratory experiments were conducted in the experimental farm, Department of Horticulture, Assam Agricultural University, Jorhat and Department of Entomology, Assam Agricultural University, Jorhat during 2017-18 to evaluate the efficacy of few botanicals in reducing aphid population and to study the natural enemy complex associated with the cowpea aphid. A preliminary laboratory bioassay was carried out to determine the LC50 and relative toxicity of some botanicals (leaf extracts) viz., Pongamia pinnata, Polygonum hydropiper, Ocimum sanctum, Ageratum conyzoides, Lantana camara and Murraya koenigii along with check imidacloprid 17.8 SL and control. From the present work on bioassay, the order of toxicity to Aphis craccivora with respect to LC50 values was as imidacloprid (0.045%) > O. sanctum (0.828%) > P. hydropiper (1.158%) > M. koenigii (2.100%) > A. conyzoides (4.664%) > L. camara (5.779%) > P. pinnata (6.011%) after 24 hours, imidacloprid (0.036%) > O. sanctum (0.480%) > P. hydropiper (0.576%) > M. koenigii (1.209%) > A. conyzoides (3.188%) > L. camara (4.201%) > P. pinnata (4.328%) after 48 hours exposure period and imidacloprid (0.031%) > O. sanctum (0.316%) > P. hydropiper (0.341%) > M. koenigii (0.707%) > A. conyzoides (2.381%) > L. camara (3.200%) > P. pinnata (3.357%) after 72 hours. The order of relative toxicity was imidacloprid > O. sanctum > P. hydropiper > M. koenigii > A. conyzoides > L. camara > P. pinnata for the exposure period of 24, 48 and 72 hours, respectively. On the basis of LC50 values the most effective ones i.e., O. sanctum, P. hydropiper and M. koenigii each @ 5% were taken for further study on bio-efficacy along with neem oil @ 1%, river sand + neem leaf powder @ 10kg/ha (3: 1 ratio), ash @ 10kg/ha, ash + river sand @ 10kg/ha (5: 1 ratio), check imidacloprid 20gm a.i/ha and control. In the bio-efficacy study of the botanicals P. hydropiper leaf extract @ 5% was found to be most effective in reducing the aphid population up to 77.48% followed by neem oil @ 1% (74.11%), O. sanctum leaf extract @ 5% (74.00%), M. koenigii extract @ 5% (70.96%), ash @ 10kg/ha (68.04%), river sand + neem leaf powder @ 10kg/ha (3:1 ratio) (44.48%) and ash + river sand @ 10kg/ha (5:1 ratio) (42.53%) after seven days of spraying. All together five coccinellid predators viz., Coccinella transversalis, Cheilomenes sexmaculata, Harmonia dimidiata, Micraspis discolor and Brumoides suturalis were recorded as natural enemies feeding on aphids. From the correlation studies with weather parameters, aphids showed a significant negative correlation with average relative humidity (r = -0.515) and rainfall (r = -0.514). Among the coccinellid predators, Coccinella transversalis (r = -0.517) and Harmonia dimidiata (r = -0.505) showed significant negative correlation with average relative humidity. All the predators found viz., Coccinella transversalis (r = 0.883), Cheilomenes sexmaculata (r = 0.611), Harmonia dimidiata (r = 0.584), Micraspis discolor (r = 0.770) and Brumoides suturalis (r = 0.605) showed significant positive correlation with their prey i.e aphid, Aphis craccivora.
dc.identifier.urihttps://krishikosh.egranth.ac.in/handle/1/5810198521
dc.language.isoEnglish
dc.subEntomology
dc.themeEvaluation of certain botanicals against cowpea aphid, Aphis craccivora Koch
dc.these.typeM.Sc
dc.titleEvaluation of certain botanicals against cowpea aphid, Aphis craccivora Koch
dc.typeThesis
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