Phytoparasitica (2001) 29, 247-248
E. Shlevin, S. Saguy, Y. Mahrer and J. Katan (2001)
Utilization of the Weibull model to quantify survival of soilborne pathogens under dynamic conditions during structural solarization
Phytoparasitica 29 (3), 247-248
22nd Congress of the Israeli Phytopathological Society, February 12-13, 2001, Bet Dagan, Israel, lecture
Abstract: Disinfestation of soil or media is an essential procedure in greenhouse management. However, it is difficult to eradicate inocula of plant pathogens adhering to the greenhouse structure, which is a potential source of reinfestation. Sanitation of the greenhouse structure is usually done by applying toxic chemicals such as formaldehyde. Structural (space) solarization is carried out by closing the greenhouse during the hot period between crops. Consequently, air temperatures can reach up to 55-65° C and is accompanied by relative humidity (r.h.) decreases. Although this method utilizes dry heating, typically less effective than wet heating, it can be used as a nonchemical approach for structural sanitation. Most models describing thermal inactivation have considered constant temperature conditions, and fluctuating conditions of temperature and humidity, that could play a significant role, were hardly considered. Our objective was to assess the effectiveness of structural solarization for sanitation and to develop a dynamic model, using dynamic climatic conditions, namely, fluctuating temperatures and r.h., prevailing during the process. Such a model could be utilized for optimization of pathogen inactivation. Inocula of two pathogens were tested: Sclerotium rolfsii sclerotia and soil naturally infected with Fusarium oxysporum f.sp. radicis-lycopersici (Forl). Survival curves could not be described by the classic first-order reaction, and were characterized by a dynamic approach using microorganism survival distribution known as the Weibull model. The model is defined by two parameters, n and b. The relationship found between the model coefficient, b, and temperature was exponential and Fermi equation for Forl and S. rolfsii, respectively. Utilizing the Weibull model for estimation of the survival curves under fluctuating temperatures and constant moisture conditions showed complete inactivation of the two fungi in ca 3 days. In practice, this was reached for Forl and S. rolfsii after 25-30 and 15-20 days, respectively. Including fluctuating greenhouse moisture data of the inocula, showed close agreement between the actual and calculated values, with a high coefficient of determination in nine of 12 experiments. In this work we have proven that even under climatic conditions of a closed greenhouse, which are apparently dry conditions, wetting and drying processes are occurring at a micro level, contributing to enhanced thermal resistance of the inoculum.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Jaacov Katan
Research topic(s) for pests/diseases/weeds:
control - general
environment - cropping system/rotation
Pest and/or beneficial records:
| Beneficial | Pest/Disease/Weed | Crop/Product | Country | Quarant.
|
|---|---|---|---|---|
| Athelia rolfsii | ||||
| Fusarium crown and root rot | ||||
| Fusarium oxysporum |
