Soil treatment with Botanigard®WP22 (Beauveria bassiana GHA): ON and OFF-season biocontrol tool of Ceratitis capitata

Abstract

Control of fruit flies (Diptera: Tephritidae) is mainly based on insecticide treatments targeting the adults. Targeting the soil-dwelling stages by soil treatment with an entomopathogenic fungus is a strategy to consider. Botanigard®WP22 is a commercially mycoinsecticide based on the Beauveria bassiana for use as a spray. The objective of this study was to examine the efficacy of the Botanigard®WP22 as soil treatment in orchards, targeting the soil-living stages of Ceratitis capitate.

Two sets of experiments were carried out on late L3 larvae. The first consisted in testing a high dose of 10⁷ conidia/g of soil of Botanigard®WP22 in apple orchards in Italy. The second was carried out to test in the laboratory doses (10⁵, 10⁶, and 10⁷ conidia/g of soil) of Botanigard®WP22 and temperature (10, 15, 20, 25^oC) effects. The fungus was able to maintain itself in the soils of apple orchards reducing significantly the emergence of flies for at least one year. Laboratory experiments demonstrated i/ that Botanigard®WP22 soil treatments significantly reduced emergence and increased mortality of emerged adults of C. capitata whatever the dose and temperature tested. C. capitata mortality positively correlated with the dose of Botanigard®WP22 and that 2/ mortality was negatively correlated with the temperature, which demonstrated that it can provide an OFF-season control of C. capitata. At low temperature, the fungus remained active while the insect developed slowly or did not.
This biocontrol strategy could be suitable to target the first and the latest generations of C.capitata produced in spring and in autumn.