Low thermotolerance in entomopathogenic fungi is the main impediment to their industrialization. This research, for the first time, describes the generation of a thermotolerant colony by pairing and subculturing two Beauveria bassiana isolates without sexual reproduction. A mixture of B. bassiana ERL1578 and ERL1576 was inoculated on 1/4SDAY. The paired culture was subcultured three times, followed by a heat treatment as a selection pressure. Two morphologically different colonies (BbHet1 and BbHet2) were isolated from the pairing. BbHet2 had the most rapid mycelial growth and produced sponge-like mycelial masses (the others were flat), and its conidia were darker than the non-paired colonies under a microscope. BbHet2 conidia had 60.7% germination after exposure to 45°C for 60 min (the others had <15%) without significant loss of virulence against western flower thrips, but a slight decrease in conidial yield was found. Sequencing of Bloc locus and 2-D electrophoresis were done to further clarify the phenomenon. The new phenotypes formed suggested that a genetic variation happened as a result of heterokaryosis and/or recombination, more than environmental adaptation, when mixing different conidia. This methodology seems to be very useful for enhancing thermotolerance in fungi.

Reported herein is the use of mycotized millet grains with entomopathogenic fungi applied to soil to control western flower thrips (WFT), Franklinella occidentalis. The majority of mature larvae move from plants to soil for pupation. Mycotized millet grains with Beauveria bassiana ERL1170 and Metarhizium anisopliae ERL1171 were mixed in the upper layer of potting soil containing a blossomed marigold as a banker plant. B. bassiana GHA, a commercial isolate, served as a control. One week post applicaion 3 mated WFT females were added per plant. At 8 wks post infestation WFT mortality in pots with ERL1170 and ERL1171 treatments was 90% and 81% respectively compared to GHA with 15% mortality. Plants in the two ERL treatments had lower levels of damage. The insecticidal activities were positively associated with the fungal soil colonization. No significant release of fungal innoculum from the potting medium was observed. These results suggest that soil applications of entomopathogenic fungi can reduce WFT populations to significantly low levels by targeting pupae. Application timing and the life cycle of WFT are important considerations.