Effect of nutrition on growth and virulence of the entomopathogenic fungus Beauveria bassiana.

Three isolates of the entomopathogen Beauveria bassiana along with one strain of Metarhizium anisopliae were cultured on seven media with different carbon/nitrogen (C/N) ratios. The effect of nutrition on virulence of the isolates was evaluated via measurement of colony growth, spore yield, germination speed, conidial C/N ratio and Pr1 (a serine protease) activity. 'Osmotic stress' medium produced the lowest colony growth with low numbers of conidia in all isolates. However, these conidia showed a high germination rate and virulence. However, conidial Pr1 activity was low in some isolates. In most but not in all cases conidia from 1% yeast extract, 2% peptone and low (10 : 1) C/N medium had higher Pr1 activity compared with conidia from other media. However, in some instances we could not conclude that there was a relationship among germination rate, conidial Pr1 activity and virulence. C/N ratio of conidia was statistically different among various media and fungal isolates. Conidia with lower C/N ratio generally produced lower LT(50) (lowest median lethal time) values (more virulent). Insect-passaged conidia from different media had lower C/N ratio compared with similar conidia from artificial cultures. Therefore, they should be more virulent than in vitro produced conidia. As germination rate, conidial Pr1 activity and C/N ratio are independent of host, it seems that host-related determinants such as insect cuticle and physiology and environmental conditions may influence host susceptibility and therefore fungal isolate virulence towards host insects.

The fauna of cynipid oak gall wasps and their parasitoids in Lorestan province, Iran.

This study was carried out in the period 2003-2005 to collect and identify gall wasps and their parasitoids on oak species in Lorestan province. There are two oak species, Quercus brantii and Q. infectoria, with different dispersion patterns in the province. Thus, 3 study sampling sites were selected to cover distributional pattern of oak forests. Collected galls maintained in the laboratory condition. Based on results obtained, overall, 26 different galls-formed on various plant parts (catkins, buds, fruits, leaves) were collected on two oak species; of which, 11 gall wasps are active on Q. brantii and 13 gall wasps on Q. infectoria. 19 parasitoid wasps of 12 genera and 6 families belong to Chalcidoidea superfamily with various frequency and dispersal were collected from mentioned galls.

Sublethal effects of imidacloprid and pymetrozine on the life table parameters of Aphis gossypii Glover (Homoptera: Aphididae).

In this study we report the sublethal effects of recommended concentrations of imidacloprid and pymetrozine on cotton aphid's reproduction. Fecundity life table parameters for AG were studied on cucumber under conditions of 25+/-1 degrees C, 70+/-5% RH and photoperiod of 16:8 (L:D). Leaf discs of cucumber immersed in the recommended concentrations of the above mentioned insecticides and controls and the new born female was released on the lower surface of leaf discs. Values of parameters such as adult longevity and daily fecundity rate were recorded. Standard error of population growth parameter was calculated using the Jacknife method. The results show that these two insecticides significantly reduce life table parameters compared with control.

Pathogenicity of the fungus, Verticillium lecanii, to the green peach aphid, Myzus persicae (Hom.: Aphididae).

Pathogenicity of the hyphomycete, Verticillium lecanii (DAOM 198499), was investigated to aphid, Myzus persicae under laboratory conditions. Analysis of lethal effect of six various concentrations 0, 10(4), 10(5), 10(6), 10(7) and 10(8) conidia/ml of V. lecanii against third nymphal stage of M. persicae, indicated significant mortality on aphids. Mean comparisons showed that there was significant difference between treatments. Three days after treatment, aphid mortality observed and after 12 days minimal mortality was 17.77 in control and maximum was 100 percent related to 10(7) and 10(8) conidia/ml. LC50 and LT50 values were estimated by probit analysis and life test. LC50 value for aphid mortality was 1.4 x 10(4) conidia/ml, LT50 values for concentrations 10(4), 10(6), 10(6), 10(7) and 10(8) conidla/ml was 10, 10, 9, 8 and 6 days, respectively. In this experiment, net reproduction rate of aphid's (R0) decreased significantly when concentration increased. These observations showed that V. lecanii (DAOM 198499) can be an active biological agent against aphids.