Abstract. Effects of two concentrations (200 and 2000 l*g g-t soil) of two heavy metals (copper and zinc as sulphates) applied to clay or sandy soil for 12 weeks on the total counts of fungi, bateria and actinomycetes were studied. Activities of three soil enzymes (urease, nitrate reductase and amidase) were also investigated. Application of heavy metals to the clay soil reduced the microbial populations. However, although neither heavy metal showed any significant increasing effect on microorganisms populations in clay soil samples, some stimulatory effects were noted in sandy soil. Activities of urease and nitrate reductase were inhibited by heavy metal application in both soils. Amidase activity was inhibited only with the higher application rate after some experimental periods.

The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is occasionally found in beehives and is a major pest of stored wax. Entomopathogenic fungi have recently received attention as possible biocontrol elements for certain insect pests. In this study, 90 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae were screened for proteases and lipases production. The results showed significant variations in the enzymatic action between the isolates. In the bioassay, the selected isolates evinced high virulence against the 4th instar of the G. mellonella larvae. The isolates BbaAUMC3076, BbaAUMC3263 and ManA-UMC3085 realized 100% mortality at concentrations of 5.5×10 6 conidia ml −1 , 5.86×10 5 conidia ml −1 , and 4.8×10 6 conidia ml −1 , respectively. Strong enzymatic activities in vitro did not necessarily indicate high virulence against the tested insect pest. The cuticle of the infected larvae became dark and black-spotted, indicating direct attack of fungus on the defense system of the insects. The LC 50 values were 1.43× 10 3 , 1.04×10 5 and 5.06×10 4 for Bba3263AUMC, Bba3076AUMC and Man3085AUMC, respectively, and their slopes were determined by computerized probit analysis program as 0.738±0.008, 0.635± 0.007 and 1.120±0.024, respectively.

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Among 39 fungal species and one variety belonging to 16 genera isolated from 116 healthy tomato fruits collected from markets in Assiut, Egypt, during 1994, Aspergillus niger was found to be the most prevalent, being isolated from 84.6% of the samples. Of 11 species recovered from 156 diseased tomatoes, Alternaria alternata, Rhizopus stolonifer and A. niger were the most common and isolated from 52.7%, 35.9% and 25.0% of the samples, respectively. Experiments for comparison of the effects of medium containing tomato juice with synthetic medium on the mycelial growth of nine fungal species indicated that, the tomato juice medium was more suitable for growth of all fungal species. The effect of five commercial fungicides and sodium hypochlorite when applied as post-harvest dips after inoculation was studied in laboratory against A. alternata, A. niger and R. stolonifer. At 10 and 100 micrograms ml-1, neither of the fungicide caused a noticeable inhibition of Alternaria rot. At 1000 micrograms ml-1 benlate, rovral and sumisclex completely prevented Alternaria and Aspergillus rot, whereas cuprosan and ridomil were ineffective against rotting caused by A. niger. Rhizopus rot development was inhibited by over 50% with one treatment only (rovral at 1000 micrograms ml-1). Sodium hypochlorite has good curative properties against fruit rots especially those caused by A. alternata and A. niger.

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