Epidemiology study of phytoplasmas in pome fruit ('apple proliferation' and 'pear decline')
Themes
Crop production
Crop protection
Kind
project
Type
fundamental
practical rersearch
Runtime
–
Body
Several important diseases can occur in fruit growing. Two of these, apple proliferation and pear decline, are both caused by a phytoplasma (a bacterium without a cell wall). The culprits causing these two diseases are Candidatus Phytoplasma mali and pyri, respectively. Recent years have seen increasing incidence of symptoms attributable to an infection with phytoplasma in our neighbouring countries. Especially for organic fruit growing these diseases are a real threat, as no chemical crop protection agents can be sprayed as control measure (directed against insects that transmit the phytoplasmas).
Are apple proliferation and pear decline present in Belgium?
Phytoplasmas infect the phloem of their host plants, leading to growth disturbances. There are many symptoms which are not always visible on any part of the plant. Most typical symptoms are the witch broom and early red colouring of leaves for apple proliferation and pear decline, respectively. A large-scale monitoring was executed in which samples of “suspected” orchards (low-stem (IPM, organic), high-stem) were collected and analysed for the presence of phytoplasmas using PCR. The results revealed that not only in trees with symptoms, but also in apparently healthy trees, Candidatus Phytoplasma mali was present (up to 50% infection in one of the sampled orchards). Also Candidatus Phytoplasma pyri was previously detected. In the ongoing monitoring this phytoplasma has already been found in 4 of the 45 surveyed communities.
How do the phytoplasmas disperse in the Belgian fruit growing regions?
In future project research, we will investigate which insects are acting as vectors of phytoplasmas in Belgian apple and pear growing regions. The major focus will be on apple and pear suckers (psyllids), but also other piercing/sucking insects such as stink bugs might play a role. The first results pointed out that several psyllids (Cacopsylla mali, C. melanoneura, C. picta and C. perigrina) which were collected in a diseased orchard were also infected with Candidatus Phytoplasma mali. However, despite several laboratory tests, it could not be shown that these insects are also able to transmit the pathogen to other trees. For stink bugs, effective transmission of phytoplasma could not be demonstrated either. Further research is required to find out which insects are effective vectors, and what their migration characteristics are.
Prevention of further spread by effective control measures
Based on profound insights into the current presence of both phytoplasmas in Belgium and the insects responsible for their distribution, we aim to work out a range of control actions. This will stop the further spread of the phytoplasmas.
Research institute
Financier
Federal Public Service of Health, Food Chain Safety and Environment (Project REPEDAP) (2013 - 2014)
References
Onderzoek naar epidemiologie van fytoplasma’s in pitfruit (‘apple proliferation’ en ‘pear decline’). In: De biologische landbouw in Vlaanderen: Onderzoek 2013-2014. L. De Cock (ed.), NOBL, Merelbeke, p 84-85.
Cooperation
pcfruit vzw TWO Zoölogie, CRA-W Gembloux, ILVO, PCS