Modeling the Survival of Two Soilborne Pathogens Under Dry Structural Solarization

Abstract

Structural (space) solarization of a closed, empty greenhouse for sanitation involves dry heating to 60 degrees C and higher and low relative humidity (RH), under a fluctuating temperature and RH regime. Survival of inocula of Fusarium oxysporum f. sp. radicis-lycopersici and Sclerotium rolfsii during structural solarization was studied for 4 years (total of 12 experiments) in an attempt to develop a dynamic model for expressing the thermal inactivation of the pathogens. After 20 days of exposure, the populations of F. oxysporum f. sp. radicis-lycopersici and S. rolfsii were reduced by 69 to 95% and by 47.5 to 100%, respectively. The Weibull distribution model was applied to describe pathogen survival. The Weibull rate parameter, b, was found to follow an exponential (for F. oxysporum f. sp. radicis-lycopersici) and the Fermi (for S. rolfsii) functions at constant temperatures. To improve the applicability of the model, fluctuating conditions of both temperature and RH were utilized. The Weibull distribution derivative, expressed as a function of temperature and moisture, was numerically integrated to estimate survival of inocula exposed to structural solarization. Deviations between experimental and calculated values derived from the model were quite small and the coefficient of determination (R (2)) values ranged from 0.83 to 0.99 in 9 of 12 experiments, indicating that ambient RH data should be considered. Structural solarization for sanitation could be a viable component in integrated pest management programs.

Greenhouse soil solarization: effect on weeds, nematodes and yield of tomato and melon

“…Soil temperature increase caused by solarization must be sufficiently high and prolonged to cause irreversible damage to most soil-borne pathogens (Nico et al, 2003). Therefore, this technique is particularly suitable for the Mediterranean climate, where the occurrence of high summer temperatures can ensure an effective control of fungi, nematodes and weeds (Shlevin et al, 2003;Oka et al, 2007;Roe et al, 2004).…”

Control of Plant Disease through Soil Solarization

“…A logarithmic relationship was indeed found between time and temperature (at constant temperatures) for the thermal inactivation of four soil-borne plant pathogens (Pullman et al, 1981). Studies on thermal inactivation under fl uctuating temperatures, such as those naturally prevailing in the fi eld, are much more complicated to perform, because the partial effects of varying temperatures on pathogens are diffi cult to weigh, and they require numerical integration to account for their complexity (Shlevin et al, 2003). There are other approaches to simulating and modelling pathogen control by solarization, for example by plotting the level of mortality versus accumulated hours above a certain temperature, that is the degree-hours (DH) (Chellemi et al, 1994).…”

“…There are other approaches to simulating and modelling pathogen control by solarization, for example by plotting the level of mortality versus accumulated hours above a certain temperature, that is the degree-hours (DH) (Chellemi et al, 1994). Shlevin et al (2003) developed a model describing the process of pathogen control with time under structural (dry) solarization. In an other study on modelling regular (wet) SH, the common DH approach for predicting the rate of heat inactivation was further improved by giving different weights to the different temperatures, thus refi ning the correlation between temperature data and pathogen survival from R 2 = 0.324 to R 2 = 0.86 (Shlevin et al, 2005).…”

“…This is achieved by closing the greenhouse during the summer time, thereby elevating the temperatures (dry heating) to 60, and even close to 70 o C (Figure 10.5). Structural solarization is carried out under dry conditions and is considered solar sanitation (Shlevin et al, 2003).…”

Efecto de la biofumigación y biosolarización en el control de agentes fitopatógenos.

“…En otros estudios adicionales acerca de lo que ocurre al producirse este fenómeno, diversos autores apoyan la teoría de que tiene lugar cuando no se detectan en el suelo nemátodos ni patógenos superiores, entre los que se encuentran los hongos y las bacterias del suelo (Chen y Katan, 1980;Katan, 1981;Stapleton y DeVay, 1982b;Stapleton y DeVay, 1983 (Shlevin et al, 2003;Shlevin et al, 2004-b;Stapleton, 2000).…”