Scientific research into the spread of plant pests and diseases
There have been scientific studies looking into how tree and plant pests and diseases are spread, and how we can help limit this spread.
In 2007, a Forest Research study analysed how frequently Phytophthoras could be found in mud and leaf material on the boots of walkers who had visited sites infected with Phytophthoras. Those in the survey sample had been known to have walked in sites infected with Phytophthoras. The results of the study found that 30% of the samples from walker’s boots were contaminated with Phytophthoras. The source of the contamination was fragments of infected leaves, which had broken down and incorporated into the litter layer of the soil. This is of greater concern when considered with the fact that Phytophthora kernoviae (the Phytophthora pathogen that affects larch trees found in the SW of the UK) can survive in both air-exposed and litter-embedded infected leaves for more than a year.
In 2012, an Australian study looked into the effectiveness of vehicle washing and roadside sanitation treatment in limiting the spread of pests and diseases. The results strongly suggest that the possibility of Phytophthora lateralis spread in soil or mud on footwear should not be disregarded. Boot cleaning, at the very least with water and a stiff-bristle brush, should be undertaken to help limit the spread of pests and diseases.
In 2005, a small study in New Zealand demonstrated the importance of cleaning boots after visiting a site known to have a Phytophthora infection. The study found that the Phytophthora remained infectious even after one year after being found in the soils. The authors recommended that contaminated soil should be removed from boots following a visit, and that the cleaning should be done in a secure location, so as not to infect any water courses. Such actions would, the authors noted, potentially prevent the spread of the Phytophthora to new locations. Given the longevity of Phytophthoras it is important that any contaminated material is not moved into a new site or area.