Persistence and efficacy of Beauveria brongniartii strains applied as biocontrol agents against Melolontha melolontha in the Valley of Aosta (northwest Italy).

AIMS

To monitor and select genetically characterized strains of Beauveria brongniartii to be used as microbiological control agents against Melolontha melolontha in different climatic conditions of the Valley of Aosta (northwest Italy).

METHODS AND RESULTS

Molecular random amplified polymorphic DNA markers allowed monitoring of five B. brongniartii strains (C2, F, K2, N3 and W2) in field trials. Ten sites were chosen at Jovençan, Saint-Pierre and Quart areas, where a mixture of the five strains colonizing rye kernels was applied to the soil of each M. melolontha infested site. Growth, persistence and virulence on M. melolontha larvae of five fungal strains were evaluated in two subsequent 24-month studies. Beauveria brongniartii grew best at the Jovençan sites. Not only did strain F persist better than the other strains in most soil samples but it was also the most virulent strain. Strain F was isolated the most frequently from infected M. melolontha larvae recovered from the test sites. A general decrease in the larvae rate was detected in the test field soil.

CONCLUSIONS

Strain F of B. brongniartii was better than other strains in growth, persistence and virulence against M. melolontha larvae in the test site soil.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results obtained from preliminary field trials support the use of strain F as a biological control agent against M. melolontha in the Valley of Aosta even if further targeted studies are still necessary.