The effects of this damage typically manifest in the new growth first. The pathogen then multiplies in the apoplast (the spaces between plant cells). It is most commonly spread from affected tissues by the wind and rain, but can also be spread via insect vectors and pruning tools.ĭisease occurs when the pathogen enters the plant through wounds or natural openings like the stomata (air pores) in the leaves, and releases toxins which by-pass the plant's immune system and damage plant cells. It can lay dormant until the right conditions for development occur. The pathogen can overwinter in cankers and other diseased plant material like twigs and leaves. The bacterium favours wet, cool conditions with infection likely to occur in winter or spring. There are no fungicide sprays available to home gardeners for the control of lilac blight. There is some evidence that white flowered varieties are more susceptible and dwarf varieties less so. Young trees are more susceptible to the disease than mature ones. In general lilacs do not require much fertiliser. Do not over fertilise (especially young plants) late in the season, and ensure you are using a balanced fertiliser the use of high nitrogen fertilisers can result in a large amount of soft new growth that is more susceptible to infection.Try to maintain overall good health of lilacs by pruning them in the spring, once they have finished flowering, to increase air circulation. Weakened plants can be more susceptible to lilac blight and the impact of this disease on such plants can be more severe.Ensure fallen leaves are raked up and disposed of (by burning, burial or consigning to the council green waste) as the pathogen can overwinter on plant debris.Spread can be further mitigated by disinfecting your tools between cuts. Do not prune when leaves are wet as this could further spread the infection. Make your pruning cut at least 6-8 inches below the infected area into healthy wood. It is best to prune out affected twigs and branches as soon as you notice them.Avoid overhead watering of young plants to help prevent spread of the bacteria. Because the disease is favoured by cool, wet conditions it can be naturally restricted during periods of hot, dry weather. Lilac blight is difficult to control as the bacteria are readily dispersed by wind and rain.If chemical controls are used, they should be used only in a minimal and highly targeted manner. The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. Malvern Autumn Show - 22–24 September 2023.RHS Garden Wisley Flower Show - 5–10 September 2023.RHS Garden Rosemoor Flower Show - 18–20 August 2023.RHS Garden Hyde Hall Flower Show - 2–6 August 2023.RHS Flower Show Tatton Park - 19–23 July 2023.RHS Hampton Court Palace Garden Festival - 4–9 July 2023.
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