The virulence and proteolytic activity of some entomopathogenic fungi isolates, viz., Metarhizium anisopliae, Beauveria bassiana, Verticillium lecanii, and Trichoderma harzianum, against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), were evaluated. Common maize plants (Zea mays L.) infested with females of T. urticae were treated in vivo by spraying with suspensions of 1 × 10 8 conidia ml −1 concentration of selected isolates. Lethal effects of fungal isolates were assessed as percentages of daily mortalities of mites, compared to the mortality in control. Virulence of the fungi isolates was estimated based on the LC 50 values calculated by probit analysis for the individuals treated by 1 × 10 5 conidia ml −1 concentration. Proteolytic activity of isolates was assayed on casein substrate to reflect their virulence towards T. urticae. The mite mortality rates increased with increasing conidial concentrations as well as days after treatment. The mortality rate caused by M. anisopliae isolate varied from 18.75 to 85%, with LC 50 value of 4.6 × 10 5 conidia/ml and LC 90 value of 2.4 × 10 8 conidia/ml during 7 days, respectively. The isolate of B. bassiana caused 15 to 70% mortality, and its LC 50 and LC 90 values estimated 3.3 × 10 6 and 7.8 × 10 9 conidia/ml, respectively. However, V. lecanii isolate caused 11.25 to 72.50% mortality with LC 50 of 5.2 × 10 6 conidia/ml, while T. harzianum was potentially less virulent than other isolates causing 8.75 to 63.75% mortality rate to T. urticae with LC 50 of 9.4 × 10 6 conidia/ml. M. anisopliae showed the highest proteolytic activity at all concentrations, followed by B. bassiana in 3rd, 5th, and 7th day post treatment. These findings recommend the selection of virulent fungal isolates for use as natural and environmentally safe agents in biological control programs to combat mite pests.

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Seventeen pathogenic isolates of brown rot pathogen were collected from field soil, potato tubers, weeds and irrigation water at major potato districts in Egypt. Isolates recovered produced pink, or light red, colour with whitish margin on tetrazolium chloride medium (TZC) indicated possible virulent Ralstonia solanacearum pathogenic isolates. Pathogenicity test revealed the ability of the isolates to cause wilt symptoms in potted potato plant and three leaved tomato seedlings. Morphological, physiological and biochemical tests were used in identification. The biovar determination was made using for oxidization of disaccharides (maltose, lactose, and cellobiose) and confirmed the identity to R. solanacearum, race 3, biovar II equivalent to phylotype II, sequevar 1. A polymerase chain reaction (PCR) confirmed the identity of highest virulent isolates from tuber (T6) and from water (W11) to R. solanacearum. The application of biological agents Pseudomonas fluorescens, Bacillus subtilis, Pseudomonas aeruginosa and Trichoderma spp. decreased R. solanacearum infected plants and caused greater decrease in severity.