Efficacy of Spray Applications of Entomopathogenic Fungi Against Western Flower Thrips Infesting Greenhouse Impatiens Under Variable Moisture Conditions

Publication date: Available online 26 February 2016 Source:Biological Control Author(s): S.P. Wraight, T.A. Ugine, M.E. Ramos, J.P. Sanderson Laboratory bioassays of three entomopathogenic fungi (Beauveria bassiana strain GHA, Metarhizium brunneum strain F52, and Metarhizium anisopliae s.l. strain ESC-1) were conducted against 2nd-instar nymphs of Frankliniella occidentalis. All three fungi were highly virulent, with respective LC50s of 193, 140, and 72 conidia/mm2 of treated leaf surface. Efficacy tests were conducted against thrips infesting small plots of Impatiens walleriana on open greenhouse benches under variable moisture conditions. Multiple spray applications of fungal conidia suspended in 0.01% Silwet® were made at a high rate of 2 x 1014 conidia/ha at 3–5-day intervals, and efficacy was assessed from twice-weekly samples of both flowers and foliage. During tests, moisture conditions were modified via controlled sprays of water onto the concrete floor beneath the greenhouse benches for a period of ca. 40 h (from the evening through the second night) following each application (post-spray period). Efficacy of the pathogens expressed as percent reduction of the combined populations of thrips nymphs and adults relative to spray-carrier controls was ultimately correlated to greenhouse environmental conditions. Mean relative humidity (RH) over all test days was a strong predictor of thrips control on foliage (R2 = 0.820) and flowers (R2 = 0.756). Fungal ef...
Source: Biological Control - Category: Biology Source Type: research