Toxic and Antifeedant Effects of Different Pesticidal Plant Extracts against Beet Armyworm (Spodoptera exigua)

The beet armyworm(BAW),Spodoptera exigua(Lepidoptera:Noctuidae)is a highly destructive pest of vegetables and field crops.Management of beet armyworm primarily relies on synthetic pesticides,which is threatening the beneficial community and environment.Most importantly,the BAW developed resistance to synthetic pesticides with making it difficult to manage.Therefore,alternative and environment-friendly pest management tactics are urgently required.The use of pesticidal plant extracts provides an effective way for a sustainable pest management program.To evaluate the use of pesticidal plant extracts against BAW,we selected six plant species(Lantana camara,Aloe vera,Azadirachta indica,Cymbopogon citratus,Nicotiana tabacum,and Ocimum basilicum)for initial screening experiment.Four out of six plant species such as A.indica,N.tabacum,C.citratus and O.basilicum showed promising mortality of more than 50%.Therefore,we selected these four plant extracts for the subsequent experiments.Through contact bioassay,A.indica showed high mortality 66.63%,followed by the N.tabacum 53.33%,at 10%w/v concentration.Similarly,N.tabacum showed the highest mortality rate,66%at 10%w/v concentration,followed by the A.indica 46%through feeding bioassay.Furthermore,the feeding deterrence assay showed that C.citratus had a high antifeedant index(−50)followed by A.indica(−39),and N.tabacum(−28).In living plant assay,the N.tabacum extract showed a low mean damage score 3.6 on living cotton plant followed by C.citratus 4.5 and A.indica 5.5.Hence,extracts of three plant species provided promising results against the BAW,which can minimize the use of synthetic chemicals,particularly for small landholding farmers.Further studies are also required to evaluate the effects of these plant extract against BAW on cotton plants under field conditions to optimize the further use.

Response of Contrasting Rice Genotypes to Zinc Sources under Saline Condition

Abiotic stresses are among the major limiting factors for plant growth and crop productivity.Among these,salinity is one of the major risk factors for plant growth and development in arid to semi-arid regions.Cultivation of salt tolerant crop genotypes is one of the imperative approaches to meet the food demand for increasing population.The current experiment was carried out to access the performance of different rice genotypes under salinity stress and Zinc(Zn)sources.Four rice genotypes were grown in a pot experiment and were exposed to salinity stress(7 dS m^(−1)),and Zn(15 mg kg^(-1)soil)was applied from two sources,ZnSO4 and Zn-EDTA.A control of both salinity and Zn was kept for comparison.Results showed that based on the biomass accumulation and K^(+)/Na^(+)ratio,KSK-133 and BAS-198 emerged as salt tolerant and salt sensitive,respectively.Similarly,based on the Zn concentration,BAS-2000 was reported as Zn-in-efficient while IR-6 was a Zn-efficient genotype.Our results also revealed that plant growth,relative water content(RWC),physiological attributes including chlorophyll contents,ionic concentrations in straw and grains of all rice genotypes were decreased under salinity stress.However,salt tolerant and Zn-in-efficient rice genotypes showed significantly higher shoot K^(+)and Zn concentrations under saline conditions.Zinc application significantly alleviates the harmful effects of salinity by improving morpho-physiological attributes and enhancing antioxidant enzyme activities,and the uptake of K and Zn.The beneficial effect of Zn was more pronounced in salt-tolerant and Zn in-efficient rice genotypes as compared with salt-sensitive and Zn-efficient genotypes.In sum,our results confirmed that Zn application increased overall plant’s performance under saline conditions,particularly in Zn in-efficient and tolerant genotypes as compared with salt-sensitive and Zn efficient rice genotypes.