Dutch elm disease (DED) devastated elms on an incredible scale. Breeding for resistance has resulted in a number of varieties with robust resistance, but for existing trees protection is difficult. Sanitation in combination with the biological control developed by my university group in the 1980s can limit losses of often valuable trees, for infection through beetle transmission to 0.1% annually as has been proven in 25+ years experience.
DED is caused by the fungal pathogen Ophistoma ulmi. Spores of this fungus are transported by elm bark beetles feeding on young twigs. Therefore the first symptoms typically are wilting twigs. When the disease spreads, ultimately the whole tree wilts and dies. A complicating factor can be that dying trees can spread the disease to neighboring elms through root contacts; only mechanical disruption of such root contacts stops this type of disease transmission.
An effective biocontrol for DED infections by elm bark beetles has proven its value, see:
The biocontrol product is marketed as ‘Dutch Trig’, see Dutchtrig.com
