Tubercle disease
The tubercle disease is caused by the pathogen Pseudomonas syringae subsp. savastanoi pv. oleae (original name Bacillus oleae after PETRI) and is a bacterial disease that can occur in olive trees ( Olea europaea ).
It causes extreme growths known as tree cancers that cause twigs and branches to die off and the quality and quantity of crops to decrease.
Theophrastus (approx. 300 BC) described the disease in olive trees. The growths were first associated with bacteria in 1886. It is transmitted by the olive fly ( Dacus oleae ). The bacterium is found in the fly's intestines and is transmitted during the egg-laying process. The infection occurs in spring, but also in autumn through fine cracks, injuries or frost damage, namely to leaves and all woody parts of the plant, including the roots. The infection is also triggered by improper tree pruning, in extreme cases by removing the cell growths with a chainsaw. All tools should be treated regularly with aggressive disinfectants when pruning trees. The bacteria trigger increased cell growth ( hyperplasia ) and cell enlargement ( hypertrophy ). Cherry- to walnut-sized nodes form, which later burst. After that, the tissue of the cell growth dies. The bacteria persist in the lump and eventually wash out and cause new infections.
The spread of the disease can be suppressed by fighting the olive fly as well as pruning and destroying the infected parts of the plant. The latter measure is hardly possible if the infestation is severe.
The disease also occurs in oleanders with similar damage ( P. syringae subsp. Savastanoi pv. Nerii ).
Web links
http://www.forst.tu-muenchen.de/EXT/LST/BOTAN/LEHRE/PATHO/OLEA/oleabakt.html