Phytoparasitica (1999) 27, 162-163
E. Shlevin, Y. Mahrer and J. Katan (1999)
Increased thermotolerance of pathogens during structural (space) solarization of greenhouses
Phytoparasitica 27 (2), 162-163
20th Congress of the Israeli Phytopathological Society, February 15-16, 1999, Bet Dagan, Israel, poster
Abstract: Structural (space) solarization of the greenhouse, by closing it, is a complementary method based on sanitation, to soil disinfestation for the elimination of residual pathogen inoculum surviving on greenhouse structures. Closing the greenhouse during summer time under Mediterranean conditions, raises air temperatures to as high as 55-65°C, which is accompanied by a decrease in relative humidity, resulting in dry heating. This reduces control effectiveness as compared with heating under high humidity conditions. A dynamic model for predicting rate and level of pathogen control, by analyzing climatic data measured in the closed greenhouse, was developed, based on mortality curves at constant temperatures. This model predicted complete control of inoculum of Fusarium oxysporum f.sp. radicis-lycopersici (F.o.r.l.) after 3-4 days, whereas in practice it occurred only after 25-30 days; thus the model overestimated the effect of heating. The aim of this work was to investigate the causes of the large gap between the expected and experimental data, and to examine the role of acquired thermotolerance in reducing control effectiveness. Laboratory tests showed that chlamydospores of F.o.r.l., when exposed to a sub-lethal temperature (35-38°C) at 1% soil moisture, acquire thermotolerance to higher lethal temperatures at 55°C. In greenhouse trials, under standard agricultural conditions, inoculum is exposed to fluctuation of both temperatures and relative humidity. We assume that in the earlier part of the day, when sub-lethal temperatures occur, acquired thermotolerance is developed by the inoculum, whereas later in the day, when the relative humidity of the greenhouse atmosphere drops to 20%, inoculum is desiccated. Both phenomena result in lower thermal inactivation sensitivity to lethal temperatures. Another approach for predicting pathogen survival during structural solarization is by analyzing the survival curves with segmented logarithmic regression.
(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
Pest and/or beneficial records:
| Beneficial | Pest/Disease/Weed | Crop/Product | Country | Quarant.
|
|---|---|---|---|---|
| Fusarium crown and root rot | ||||
| Fusarium oxysporum |
