Effect of temperature and host plant on the efficacy of different entomopathogenic fungi from Thailand against Frankliniella occidentalis (Pergande) and Thrips tabaci Lindeman (Thysanoptera: Thripidae) in the laboratory

Abstract

The current study is focusing on the effect of temperature and host plant on the efficacy of different entomopathogenic fungi from Thailand against western flower thrips, Frankliniella occidentalis (Pergande) and onion thrips, Thrips tabaci Linde-man (Thysanoptera: Thripidae). The results showed that the efficacy of five entomopathogenic fungi, i.e. two isolates of Beauveria bassiana (Balsamo) Vuillemin (Bb. 4591 and Bb. 5335), two isolates of Metarhizium anisopliae var. anisopliae (Metsch) Sorokin (Ma. 6079 and Ma. 7965) as well as one isolate of Paecilomyces fumosoroseus (Wize) Brown & Smith (Pfu. 5338) varied depending on the temperature and the fungal isolate in both thrips species. The Lc50 values decreased with increasing temperature. All fungal isolates showed a significantly higher efficacy against both thrips species at 25 and 30°C than at 16°C. Among five isolates, B. bassiana Bb. 5335 and M. anisopliae Ma. 7965 were superior in terms of efficacy against both thrips species within a broader range of temperature. The effect of host plants on the efficacy of B. bassiana (Bb. 5335) and M. anisopliae (Ma. 7965) was tested against first instar larvae of F. occidentalis and T. tabaci. The results revealed that the efficacy of these two fungi against F. occidentalis and T. tabaci varied with to the host plant, whether on crop or on ornamental plants. Both thrips species reared on bean, cucumber, leek and swan river daisy were highly susceptible to fungal infection but significantly less susceptible when reared on cotton and saintpaulia.