Plant Research International is conducting experiments on insects from unsprayed apple orchards to investigate whether they transfer the pathogen that causes “witch broom disease” in healthy apple trees.
Foto: Zygina flammigera, one of the insects carrying the phytoplasm. Question remains whether this insect is a vector of the disease
Witch broomstick disease in apple is caused by a phytoplasm, a small bacterium-type of pathogen. Apple trees with this disease show uninhibited side bud sprouting, the so-called witch broom growth. In the Netherlands we see that apple witch broom disease is spreading but the vector is as yet not known.
During the last two years large numbers of insects have been trapped in unsprayed apple orchards. Phytoplasm could be detected in some of these insects by using a PCR tests; this means that they are carriers. But a carrier is not yet a vector. This is why transmission experiments are now being set up to investigate whether these insects can indeed transfer the phytoplasm to healthy apple trees.