Cowboy Japanese knotweed control companies are mixing "dangerous chemical concoctions" that are damaging the environment and failing to stop the spread of the invasive weed, Invasive Non Native Specialists Association (INNSA) chairman Mike Clough has said.
Invasive Weed Solutions founder Clough, who recently set up INNSA to raise industry standards, said: "There's a lot of companies coming into the invasive species market from pest control and the damp-proofing industry. Consultants are looking for a decent contractor but a lot of firms are one man and a van. Once you create a website that calls you an expert, everyone says you are.
"People knock up their own chemical mixes and say they are the secret eradication mix. But they can devastate domestic gardens. I'm horrified what the cowboy operators are suggesting to domestic clients, which is why we founded INNSA.
"With knotweed you need to eradicate the rhizome network underground and these people burn off the surface and then leave, but it grows back smaller the next year."
That makes it difficult to inject stems so excavation and removal costing tens of thousands can end up being the only option, he added.
Landfill tax rates for disposing of knotweed are £72 per tonne and Clough said that Environment Agency regulations could mean that a 1sq m excavation could cost as much as £50,000 to dump.
Defra said knotweed costs the country £165m a year, compared with pennywort at £25.5m and rhododendrons at £8.6m. Councils are cutting back, said Clough.
Bolton has gone from three sprays a year to none, meaning the plant is not being checked. Environment Agency figures show UK growth is 3.8ha per season but eradication is 1ha/season.
Santander is now turning down mortgage applications when knotweed is found within 30m of a property.
Research body CABI has been working on establishing a psyllid insect that sucks sap from knotweed, but poor weather has slowed the programme. CABI believes the insects could establish within five-to-10 years.
INNSA is working on raising industry standards and also campaigning to keep active ingredients. Tordon 22K is being withdrawn because it is residual in the soil but ICADE from Dow AgroSciences is one potential replacement.
EC legislation Invasive species threat
The EC has published its proposals on new legislation to prevent and manage the "rapidly growing threat" from invasive species. These are being considered by the European Parliament. See http://ec.europa.eu/environment/nature/invasivealien/index_en.htm.
Trevor Salmon, Defra protected and non-native species policy team head, said: "We are consulting with stakeholders and other interested parties during the course of our considerations, and Simon Mackown in my team is leading on stakeholder engagement."