Effects of nutrients on germination of Verticillium lecanii (=Lecanicillium sp.) conidia and infection of greenhouse whitefly, (Trialeurodes vaporariorum)

Laboratory experiments were conducted to assess effects of nutrients on germination of Verticillium lecanii (=Lecanicillium sp.) conidia and infection of the greenhouse whitefly, Trialeurodes vaporariorum. Suspensions of V. lecanii conidia were prepared in four nutrient solutions: 2% glucose, 2% sucrose, 2% maltose, and 2% peptone. Suspensions in de-mineralized water served as the control. At 23°C the germination rate was highest in the 2% glucose solution, followed by sucrose, maltose, demineralized water, and peptone, respectively. Germ tube growth was greatest at 23°C in the 2% glucose solution after 10 h incubation. Results of the bioassays indicated that the nutrients influenced whitefly infection. Infection levels were highest for conidial suspensions (1×10⁶ conidia/mL) prepared in 2% glucose, and were significantly greater than for peptone, demineralized water and maltose. Infection levels at 1×10⁸ conidia/mL were not significantly different from each other for all materials tested. The potential use of nutrients in a spray formulation as a means of enhancing field efficacy are discussed.