Malformation (Fusarium subglutinans)
Credit: Biovision-Infonet
The fungus produces compounds that have hormonal effect on the plant. The fungus is easily spread by grafting and infected nursery trees. In the orchard the disease spreads slowly despite of masses of spores produced on the panicles.
Symptoms consist of affected flowers taking on, to a greater or lesser extent, the appearance of a cauliflower head. The axes of the panicles are shorter and thicker than normal, branch more often, and a profusion of enlarged flowers is produced. The affected panicles retain their green colour, are sterile and produce no fruits. In the nursery, vegetative malformation can occur. Eriophid mites are believed to be vectors of the disease and their damage symptoms are similar to those caused by F. subglutinans. Symptoms consist of buds producing short shoots and small brittle leaves creating a compact “witches broom” appearance.
What to do:
- Remove affected parts. These could either be burned or placed in plastic garbage bags and exposed to the sun for a day or two to be burned.