Every spring some 30,000 elms in the Netherlands are vaccinated with the biopesticide Dutch Trig® to protect them from Dutch Elm Disease (Ophiostoma ulmi and Ophiostoma novo-ulmi). Wageningen UR produces spores from the fungus Verticillium albo-atrum to make the bio-agent. Dutch Trig® functions by stimulating the natural defence reactions in healthy elms. This Dutch Trig® vaccination has caused the number of infections in treated trees to decrease significantly in the Netherlands.
Dutch Trig® contains spores of the fungus Verticillium albo-atrum (isolate WCS850). BTL Bomendienst BV is a licensee and distributor for the biopesticide Dutch Trig®. Wageningen UR produces the fungal spores for BTL Bomendienst according to a strict protocol. Small quantities of the vaccine, which has been in use in the Netherlands since 1992, are injected with a special syringe into the wood of the tree.
Annual monitoring of the numbers of diseased elms has demonstrated the effectiveness of this bio-agent. The natural infection rate in trees susceptible to Dutch Elm Disease is between 5% and 15% per year. Only 1% of vaccinated trees develop the disease and half of these infections are due to root contact or old infections; in that case there is no point in injecting with Dutch Trig®. Since 2004, the infection rate has decreased to less than 0.4%. This improvement has been ascribed to perfecting both product and treatment method. Extra attention is being given to the enhanced production and refrigerated transport of Dutch Trig®, and to improving hygiene and ensuring arborists perform the injections accurately. All this means that the infection rate in trees treated with Dutch Trig® continues to fall in the Netherlands.
Dutch Trig® is being used with success in Germany, Sweden, the USA and Canada, as well as in the Netherlands.