Lecanicillium enhances kidney bean growth and confers resistance against Frankliniella occidentalis (Thysanoptera: Thripidae) infestation

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), also known as western flower thrips, is a globally distributed insect pest infesting a wide range of crops. We have previously identified Lecanicillium attenuatum and L. cauligalbarum as effective entomopathogenic fungi (EPF) against F. occidentalis. In addition, studies have reported that EPF can colonize plants, promoting plant growth and resisting pests. Therefore, this study aimed to investigate whether these two Lecanicillium species can colonize plants and confer sustained resistance against F. occidentalis. We found that treating kidney beans with 5 × 107 conidia/mL L. attenuatum resulted in fungal colonization in all plant tissues. Significant enhancements in plant height, fresh weight, taproot biomass, and taproot length were observed after 20 d of treatment with L. attenuatum or L. cauligalbarum. Behavioral tests and developmental bioassays with F. occidentalis were performed to assess the effects of 15-day treatment with 5 × 107 conidia/mL L. attenuatum or L. cauligalbarum on kidney bean plants. Behavioral tests indicated that Lecanicillium-inoculated plants repelled adult F. occidentalis, and developmental bioassays revealed that both L. attenuatum and L. cauligalbarum negatively affected the growth, development, and reproduction of F. occidentalis. Compared with newly eclosed nymphs that fed on control plants, those that fed on L. attenuatum- or L. cauligalbarum-inoculated plants had substantially shorter survival, with only 57.8 % or 53.3 % of the nymphs developing to the adult stage, respectively. Oviposition of female thrips reared on L. attenuatum- or L. cauligalbarum-inoculated plants was significantly lower (16 and 17 eggs/female, respectively) than that of those reared on uninoculated plants (93 eggs/female). These findings indicate that the endophytes L. attenuatum and L. cauligalbarum are potential biological agents for the control and management of F. occidentalis.