In vitro and in vivo responses of fungal biocontrol agents to gradient doses of UV-B and UV-A irradiation

Conidia of Beauveria bassiana and Metarhizium spp. smeared on glass slides were assayed for their responses to irradiation with weighted 312-nm UV-B and 365-nm UV-A at gradient doses of 0.005-1.1 and 1.0-18.0 J cm-2, respectively. All inverted, sigmoid dose-survival trends showed good fit to a survival model (r2 ≥ 0.97), yielding respective UV-B LD50s of 0.23-0.59 and 0.05-0.65 J cm-2 for 24 B. bassiana and 36 Metarhizium isolates, and UV-A LD50s of 2.78-10.46 J cm-2 for 24 Metarhizium isolates. Myzus persicae apterae on detached leaves were sprayed with a concentrated spore suspension of B. bassiana or M. anisopliae, followed by exposure to the UV-B doses to cause 10-90% viability losses. These doses caused aphid mortality reductions as expected but affected neither spray-to-death period nor fungal growth on cadavers. The results highlight the merits of using UV-tolerant candidates and photoprotection measures in fungal formulations for pest control. © 2010 International Organization for Biological Control (IOBC).