161 Journal of Biopesticides, 4 (2): 161-168 (2011) Effect of different concentrations of Beauveria bassiana on development and reproductive potential of Spodoptera litura (Fabricius) Sanehdeep Kaur a , Harminder Preet Kaur a , Kirandeep Kaur a and Amarjeet Kaur b ABSTRACT Beauveria bassiana, the most common and ubiquitous fungal entomopathogen is known to be highly potent for the control of insects belonging to various orders. The virulence of B. bassiana was tested against second, third and 4 th instar larvae of S. litura using three concentrations i.e. 2.03 × 10 8 , 4.03 × 10 6 and 1.47 × 10 5 spores/ml. All the treatments resulted in significantly higher mortality than control. Besides mortality, sublethal effects were also evaluated on larvae that survived fungal infection. Significant decrease in larval period was observed due to infection as compared to control. The life span of females emerging from treated larvae was half that of the control females. In addition to this, inhibitory effects were also manifested as reduced reproductive potential. The eggs descended from treated larvae showed significant decrease in hatchability. B. bassiana also induced pupal and adult deformities. A significantly higher number of deformed adults were observed at lower concentrations as compared to the highest concentration. Key words: Entomopathogenic fungi, biological control, susceptibility, sublethal effects INTRODUCTION Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), commonly known as tobacco caterpillar, is one of the most destructive pest of cauliflower, groundnut, cotton, tomato, cabbage and other cruciferous crops (Anand et al., 2009). It passes through 5-6 overlapping generations annually (Sasidharan and Varma, 2005; Kumar and Chapman, 2006) and if not controlled timely, it may result in huge crop losses ranging from 25.8-100 percent in various parts of India (Ahmad et al., 2005). For the management of this pest, insecticide use is the most widely practiced. Although effective in reducing pest population in short term, these chemicals have little long term regulatory impact on pest population and often cause unwanted environmental side effects. The development of physiological resistance is one of the main reasons for this insect to become the key pest of many vegetable and field crops. Biological control of insect pests using microorganisms is highly specific, of relatively low cost and low risk to ecosystem (Castillo et al., 2000). Among these microorganisms, entomopathogenic fungi (EPF) play a significant role in controlling various crop pests. Unlike bacteria or viruses, EPF directly infect through insect cuticle and do not require ingestion for infection. Although 700 to 750 species of EPF have been reported as pathogenic to insects but only about a dozen have been exploited for insect control (Stark and Banks, 2003). Among these Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hyphocreales) is a facultative pathogen with wide host range (Armes et al., 1997; Sahayaraj et al., 2007). This fungus has potential to control over 70 insect pests belonging to different orders particularly lepidopteran pests, infesting various crops and appears to be innocuous to most non target organisms. Another important factor to be considered in favor of EPF is that, to date there has been no report of development of resistance. Effectiveness of control agents has been measured typically by percent mortality of treated population. However, these might affect various developmental stages, fecundity, longevity and reproductive potential of adults with potentially strong impacts on population growth and future abundance. Although sublethal effects of insecticides have been well documented by many workers but few references are available on EPF. Deleterious effects of the EPF Aschersonia aleyrodis (Deuteromycosina: Coelomycetes) were documented by Vargas et al. (1995) and Fransen (1987), when applied to Trialeurodes vaporariorum (Westwood). Changes in locomotion, excretion and food seeking behavior have also been observed in other species. Torrado - León et al. (2006) reported the sublethal effects of B. bassiana on Bemisia tabaci (Genadius). Reduced fecundity, preoviposition, oviposition and incubation period have been documented when ticks were treated with Metarhizium anisopliae (Metschnikoff) (Kaaya and Hassan, 2000). Such adverse effects on development of an insect, ultimately affect the 161 © JBiopest. 257 Beauveria bassiana on Spodoptera litura biology