Crown Gall is by no means a new disease to the horticultural industry, but a disease that up until now has not perhaps been a major concern for growers.
However, with the impact on the saleable value of crops one of the main adverse effects of Crown Gall, Selchuk Kurtev (Semo), Certis’ IPM manager, explains how growers should manage this potential disease threat.
“Crown Gall is caused by the bacterium, Agrobacterium tumefaciens, which is currently seen mainly on crops in the rosaceous family. The bacterium attacks damaged and susceptible plants by penetrating open wounds, exchanging a proportion of genetic material and causing the plant cell to produce a substance called opine, which can only be utilised by the bacterium. This results in the rapid multiplication of cells to form tumour like growths on roots, stems and branches, known as galls.
“If Crown Gall is present in soils, even mechanical weed removal in soft fruit crops, or root pruning in grape vine crops to improve sugar levels in the fruit, can cause physical plant damage and expose crops to the risk of the disease taking hold,” adds Semo.
The impact of the disease weakens and stunts plant growth, and not least affects the aesthetic appearance of the crop and thus its overall saleable value. “An increasing number of UK growers are encountering problems with Crown Gall infection.
“It is known to remain in soils for up to four years, but with soil sterilants such as Basamid (dazoment) only allowed one year in three on the same soil, and the difficulty in finding ‘clean’ land for crop rotation, managing the threat from this disease is a real challenge for growers.
“An integrated approach to crop management will be vital to ensure this disease does not become an over-powering issue for the sector. Starting clean and staying clean will be key,” says Semo.
Six steps to ‘start clean and stay clean’:
1. Don’t bring the problem in - When purchasing plants, inspect them carefully for signs of galls. Do not purchase plants that show gall-forming symptoms
2. Avoid damaging the plant tissue - Minimise physical damage to crops where possible
3. Disinfect tools and work surfaces - After each cut, disinfect tools with an approved disinfectant, such as Jet-5
4. Destroy infected plants - All infected plant material should be destroyed by burning or secure disposal to reduce the risk of the disease spreading
5. Sterilise soils – Using a soil sterilant and ‘steaming’ are possible options to help reduce populations of bacteria and controlling this pathogen
6. Replant with more tolerant plant species – There are a number of plants showing tolerance to Crown Gall. Consider using these where applicable.
