Potential for eradication of the exotic plant pathogens Phytophthora kernoviae and Phytophthora ramorum during composting |
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Authors: | J. Blackburn G. Thorp A. Dobrovin‐Pennington S. Pietravalle G. Kerins T. R. Allnutt C. M. Henry |
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Affiliation: | 1. Food and Environment Research Agency, Sand Hutton, York YO41 1LZ, UK;2. University of Warwick, Wellesbourne, Warwick CV35 9EF |
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Abstract: | Temperature and exposure time effects on Phytophthora kernoviae and Phytophthora ramorum viability were examined in flasks of compost and in a large‐scale composting system containing plant waste. Cellophane, rhododendron leaf and peat‐based inoculum of P. kernoviae and P. ramorum isolates were used in flasks; naturally infected leaves were inserted into a large‐scale system. Exposures of 5 and 10 days respectively at a mean temperature of 35°C in flask and large‐scale composts reduced P. kernoviae and P. ramorum inocula to below detection limits using semi‐selective culturing. Although P. ramorum was undetectable after a 1‐day exposure of inoculum to compost at 40°C in flasks, it survived on leaves exposed to a mean temperature of 40·9°C for 5 days in a large‐scale composting system. No survival of P. ramorum was detected after exposure of infected leaves for 5 days to a mean temperature of ≥41·9°C (32·8°C for P. kernoviae) or for 10 days at ≥31·8°C (25·9°C for Phytophthora pseudosyringae on infected bilberry stems) in large‐scale systems. Fitted survival probabilities of P. ramorum on infected leaves exposed in a large‐scale system for 5 days at 45°C or for 10 days at 35°C were <3%, for an average initial infection level of leaves of 59·2%. RNA quantification to measure viability was shown to be unreliable in environments that favour RNA preservation: high levels of ITS1 RNA were recovered from P. kernoviae‐ and P. ramorum‐infected leaves exposed to composting plant wastes at >53°C, when all culture results were negative. |
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Keywords: | Phytophthora pseudosyringae Rhododendron ponticum temperature Vaccinium myrtillus |
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