Sclerotinia sclerotiorum: Epidemiological Factors Affecting Infection of Greenhouse Aubergine Crops

Abstract

A series of greenhouse cultivations of Aubergine plants were studied for a three‐year period which included the 1981—1982, 1984—1985 and 1985—1986 growing seasons to determine the number of infections produced by S. sclerotiorum and the plant organs infected. A time‐phase difference was detected between the discharge of air‐borne spores and the appearance of infections. The appearance of flowers, the plant organ most susceptible to infection, appeared to mark the end of the latent period and the beginning of infections. The distribution of the infections within the greenhouse was random for two of the three seasons studied and fitted a Poisson distribution (p < 0.01). Analysis of the tendencies of the number of infections and numbers of infected plants revealed a sigmoidal curve that was a function of the accumulated hours in which relative humidity was 80 % or more.

A Model for Sclerotinia sclerotiorum Infection and Disease Development in Lettuce, Based on the Effects of Temperature, Relative Humidity and Ascospore Density

“…In addition, duration of high relative humidity (RH) has also been shown to be an important factor for infection and disease development in aubergine and oilseed rape [16], [17]. However, the effect of temperature, and particularly RH on S. sclerotiorum infection and disease development, has not been analysed systematically, nor has this information been implemented in a forecasting model.…”

“…Previous work has demonstrated the importance of leaf wetness for S. sclerotiorum ascospore germination and infection [12] , [13] and a relationship between leaf wetness duration and infection levels has been demonstrated for soybean, white bean and dry bean [9] , [14] , [15] . In addition, duration of high relative humidity (RH) has also been shown to be an important factor for infection and disease development in aubergine and oilseed rape [16] , [17] . However, the effect of temperature, and particularly RH on S. sclerotiorum infection and disease development, has not been analysed systematically, nor has this information been implemented in a forecasting model.…”

Environmental conditions influencing Sclerotinia sclerotiorum infection and disease development in lettuce

“…Disease incidence also varied inconsistently with RH value or duration of 98% RH, so it is possible that controlling ambient RH did not modify conditions in the stem base enough to prevent infection. Since ascospores of S. sclerotiorum can survive for long periods at RH < 80% (Clarkson et al ., 2003) and high humidity periods potentially conducive to Sclerotinia infection may often occur in glasshouses despite plants being watered from below (Tores & Moreno, 1991), infections may have occurred on lettuce plants in the glasshouse after the period in CE cabinets. Wetness or high humidity conditions conducive to infection may therefore always be found at the lettuce stem base, irrespective of leaf wetness or ambient air RH.…”

“…Boland & Hall (1987, 1988) found a relationship between plant surface wetness and S. sclerotiorum infection of white bean and soybean with durations of at least 54 h (15–25°C) and 70–120 h (20°C) required, respectively. In addition, Tores & Moreno (1991) reported that the incidence of sclerotinia disease on aubergine in the glasshouse was related to accumulated hours of RH > 80%. Hannusch & Boland (1996) showed that bean plants inoculated with S. sclerotiorum ascospore suspensions developed disease at RH > 90% at 20–28°C.…”

“…Previous work on ascospore infection by S. sclerotiorum has shown similarities in the infection process on various crops. Leaf wetness is required for infection of beans (Abawi & Grogan, 1979; Tu, 1989), and Tores & Moreno (1991) reported that duration of high humidity is an important factor for infection and disease development on aubergine ( Solanum melongena ). A wide range of temperatures at which infection occurs has been reported, with no infection at 5 or 30°C, and optimum infection at 20–25°C for beans (Abawi & Grogan, 1979; Phillips, 1994).…”