The polyphagous, ubiquitous, destructive pest, Spodoptera litura(F.) affects 150 host plant species and notably their larval forms arenotorious. Extensive feeding and rapid reproduction cycles led ...the farmers andindustrialists to seek the effective chemical and synthetic pesticides. Randomand inappropriate usages of pesticides imposed a negative impact on non-targetorganisms, environment and abiotic factors and also pest resurgence to theparticular pesticides. To overcome this unnatural incidence, biopesticides arepracticed as an alternative source. Plant botanicals play a huge role as insectgrowth regulators (IGRs) by inhibiting the regular moulting cycle, developmentand survival of insect pests. Also, the silverback fern, Pityrogramma calomelanosare reported with several secondary metabolites which are known for theirpesticidal properties. Hence, the present work was framed to study the dietaryresponses as well as nutritional indices of S. litura treated with crudeextract of P. calomelanos. The treated larvae showed dietary andpost ingestion responses prior to moulting and death. On the 4th day oftreatment, reduction in food intake (522.89 mg), larval weight gain (41.02 mg),ECI (56.25 %), ECD (46.30 %), AD (47.21 %) and RGR (3.06 mg/mg/day) wasobserved as dose dependent manner except the feacal production (378.18 mg) ascompared to control. Therefore, the ethanolic extract of a fern, P. calomelanoscan be recommended as a biopesticides for its post ingestion andanti-nutritional effects on S. litura larvae.
Entomopathogenic fungi play an important role in the biological control of the insect pest population in an agroecosystem. Metarhizium anisopliae is one such entomopathogenic fungus, proved to be an ...effective biocontrol agent against different insect pests. However, different strains of entomopathogens show variations in their pathogenicity and host specificity. Hence the present study is aimed to determine the bioefficacy of local isolates of the entomopathogenic fungus M. anisopliae to control Dysdercus cingulatus. Fungal strains were isolated from cotton fields in Tirunelveli, Thoothukudi, Thenkasi, and Viruthunagar districts of Tamil Nadu following standard protocols. Four different isolates were identified and used for the bioassay. Bioefficacy trials were carried out in all the five nymphal instars and the adults of D. cingulatus and were treated with eight different concentrations of M. anisopliae (101,102,103,104,105,106,107and 108 spores/mL). The formulations were evaluated for their pathogenicity and efficiency against D. cingulatusnymphal instars and adults which resulted in 70% to 100% mortality. A 100% mortality rate was observed in four isolates of M. anisopliae at higher concentrations (120 hrs) after treatment. Lethal concentration (LC50) values of M. anisopliae isolates against D. cingulatus were calculated as 5.94×107(ERUM1), 6.09×107(ERUM2), 2.62×107(ERUM3), 2.69×107(ERUM4). Approaching biocontrol agents instead of chemical pesticides seems to be very promising in the march towards more sustainable, eco-friendly agricultural pest management practices and protecting the environment
Lepidopteran insect pests voraciously feed the vegetable crops and causes yield loss every year. Chemical insecticides widely used to control the destructive pest incidence which heavily affects the ...beneficial and non-target organisms and in the mean time, pests developed resistance. Biopesticides are being developed to minimize these ill effects. Plants synthesize secondary metabolites to prevent from biotic and abiotic stresses. More than 27 families of pteridophyta (ferns) are reported with phytoecdysteroids (PEs). PEs are analogues of insect moulting hormone and acts as insect growth regulators (IGRs). The present study aimed to isolate the phytoecdysteroid fraction from the fern, Pityrogramma calomelanos, preliminary screening of phytochemicals using standard protocols including UV-Visible spectrophotometric analysis and survival, growth and developmental periods of Spodoptera litura treated with phytoecdysteroid fraction. Steroids and phenolic compounds were present in the fraction and six prominent peaks were recorded between the wavelength of 200-800nm. Spodoptera litura larvae treated with phytoecdysteroid fraction showed maximum larval mortality (68%) in 2000ppm (LC50 = 1473ppm; F = 48.65; p = 0.049). Pupation, pupal weight and adult emergence were decreased in higher concentrations. Pupal mortality was relatively high in treated group than control (2.04%). Larvae treated with minimal concentrations exhibited developmental deformities includes larval - pupal, pupal -adult intermediates, deformed pupae, ecdysial failure, adultoids, early/late developmental periods and it may due to the interaction of phytoecdysteroid fraction to the insect endocrine system. Therefore, phytoecdysteroid mediated biopesticide formulation could be the better alternative to commercial chemical insecticides under IPM programme.
