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ABSTRACT
Role of some entomopathogenic fungi against some economic insect pests under laboratory and field conditions was evaluated. Results showed that, the pink bollworm (PBW) Pectinophora gossypiella (Saund.) and the cotton leaf worm (CLW) Spodoptera littoralis (Boisd.) were susceptible to the fungi; Beauvaria bassiana (B.b.), Metarhizium anisopilae (M.a.), Paecilomyces fumosoroseus (P.f.) and Verticillium lecanii (V.l.). LC^sub 50^ values obtained were; 154x10^sup 4^, 159x10^sup 4^, 179x10^sup 4^ and 157x10^sup 4^ spores/ml for PBW larvae treated with different concentrations of (B.b.); (M.a.); (P.f.) and (V.l.) fungi, respectively. Respective LC^sub 50^ values for CLW were: 163x10^sup 4^, 175x10^sup 4^, 199x10^sup 4^ and 187x10^sup 4^ spores/ml. Under field conditions, the tested fungi showed significant infestations' decrease in the plots treated with B. bassiana, followed by M. anisopliae. In general, PDA was the best medium for the growth of B. bassiana and 30°C was the optimum temperature, followed by 25°C. Concerning R.H., the growth of B. bassiana was much enhanced by high R.H., as it increased. Linear growth increased also to reach its maximum (88.25 mm) at 100% R.H. Results revealed that the isolate of B. bassiana was able to grow and to utilize any carbohydrate added to the growth medium. Sucrose was the best substrate for supporting growth (87.25 mm) and followed by glucose (56.25 mm). Calcium nitrate was generally the best suitable nitrogen source, followed by glycin, sodium nitrate and then ammonium nitrate. Meanwhile, ammonium phosphate was found to be the lowest one. Benlate was the most toxic fungicide to B. bassiana, even at lower concentrations. Growth of the fungus was completely inhibited (100%) at 6.25 ppm. Thymol was the most destructive insecticide, followed by Pyrethrum with a significant difference (p<0.05), while Cylone was the least one against B. bassiana.
Key words: Environmental factors, nutritional factors, fungi, insect pests, insecticides, fungicides.
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INTRODUCTION
The entomopathogenic fungus, Beauvaria bassiana is one of several fungi that are of particular research interest due to its potential as commercial bioinsecticides. Some studies had focused on identifying nutrient substrates that B. bassiana can utilize with application to industrial production, while others focused on the pathogenic processes of B. bassiana and interactions with insect cuticle (Bidochia et al., 1990).
Entomopathogenic fungi are found worldwide associated with insects and phytophagous...