Effect of Microclimate on Leveillula taurica Powdery Mildew of Sweet Pepper

Abstract

Sweet pepper-Leveillula taurica microclimate relations were studied under controlled conditions and in commercial greenhouses. Conidial germination occurred at 10 to 37 degrees C and was optimal at 20 degrees C. Conidial viability declined as temperatures increased to 40 degrees C for 6 h. Leaf colonization was optimal at 15 to 25 degrees C. Severe leaf infections occurred at 15 to 20 degrees C and conidiation was suppressed at 20 to 25 degrees C. Highest germination rates were observed at 75 to 85% relative humidity (RH). Severity of leaf coverage by symptoms was high for plants which were subjected to longer periods of temperatures between 10 to 15 degrees C and daytime RH between 85 to 95%, and positively correlated with nighttime RH. Disease severity was negatively correlated with lengthy periods of temperatures >25 degrees C, day and night average temperatures, and average daytime RH. Conversely, leaf shedding was relatively high under conditions characterized by long periods of temperatures >20 degrees C and <13 degrees C, and positively correlated with average daytime temperatures and periods of RH <75%. Increasing nighttime temperatures by heating and daytime temperatures by closing the greenhouse side walls reduced disease in two commercial greenhouse experiments. A midseason shift from a cooler greenhouse climate to warm daytime climate halted epidemic development. Flower number and yield were reduced in infected crops.

Spray treatments combined with climate modification for the management of Leveillula taurica in sweet pepper

“…Unlike earlier results (data not shown here, see Elad et al 2007), no cultivar effect was noticed, except for one evaluation of leaf coverage. Night-time temperature significantly affected the disease leaf coverage and shedding.…”

“…Sweet pepper (Capsicum anuum) is an important crop in Israel (2240 ha in greenhouses and net houses) (Elad et al 2007). Powdery mildew, caused by Leveillula taurica is a major problem in this crop; it attacks pepper in all cropping regions; farmers treat plants by spraying intensively, sometimes with low control efficacy.…”

“…In Israel, this disease has been known for several decades. The disease first appears early in the growing season and control becomes increasingly difficult over the course of the season (Elad et al 2007). L. taurica in pepper develops differently than the 'classical' powdery mildew fungi.…”

“…Increasing night-time temperatures by heating and day-time temperatures by closing the greenhouse side walls reduced disease in commercial greenhouse experiments (Elad et al 2007). In this work, we tested potential control agents for powdery mildew of pepper under different climatic conditions and in combination with cultural methods of control such as greenhouse day-time passive heating for optimising disease suppression.…”

Effects of field bindweed (Convolvulus arvensis L.) and powdery mildew [Leveillula taurica (Lev.) Arn.] on pepper growth and yield - Short communication

“…Two azoxystrobin applications restricted the disease progress on field bindweed and pepper plants (Tables 2 and 3). In contrast, Elad et al (2007) reported that the current recommendation for powdery mildew control is frequent fungicide applications beginning early in the season. Concerning the disease severity in the prevent study, there were no significant differences between the weed-free control and field bindweed treatment.…”