Xanthomonas fragaria is an exotic bacterial pathogen of strawberry. The pest poses a significant production threat to the strawberry market. Angular leaf spot (ALS) disease primarily destroys the leaves of strawberry plants and on occasions, also affects the plant's flowers. It does not affect the fruit grown on infected plants, but has the potential to significantly reduce the performance and yield capacity of an infected strawberry crop.
|Symptoms||Early symptoms of angular leaf spot form on the underside of leaves as small, angular, water-soaked spots that enlarge and become visible on the upper surface of the leaf. Daylight can usually be seen through the angular spots on the leaf. |
As the infection advances, reddish brown spots, 1 – 4 mm across, will develop on the upper leave surface, causing the death of tissue.
Where spots are close together, they may join to form large areas of dead leaf tissue, giving the plant a blotchy appearance. If left unchecked, tissue damage may become so severe as to kill the plant.
|What do you do if you find symptoms||Report any possible infections immediately to Biosecurity Queensland on 13 25 53.|
|Susceptible plans (hosts)||ALS is a host specific disease. The only known susceptible host of angular leaf spot is strawberry plants.|
|Infection and spread||The disease is favoured by prolonged leaf wetness caused by frequent rain, overhead irrigation, or heavy dews. ALS is readily distributed through infected nursery stock or other infected plant material. Local spread of the bacteria is by water splash and wind dispersal.|
|Where angular leaf spot occurs||The infection attacks the leaves of strawberry plants. In some cases, the bacterium has also been known to infect strawberry flowers, but does not directly affect fruit.|
|Significance||ALS presents a significant risk to the Queensland strawberry industry. Although this pathogen does not directly infect the fruit, infection generally causes stress to the plant and the quality of fruit is significantly reduced.|
|Human health||ALS does not affect human health.|
|Management and quarantine||Each time it has been detected in Australia, ALS has been eradicated in order to protect the strawberry industry from the disease. Internationally, copper sprays are used to prevent or reduce infection levels, although this does not guarantee a disease free crop. Cultural practices are also used, including use of disease-free planting material, wide row spacings and planting in free-draining soils. |
Under Queensland legislation the suspected presence of the pest must be reported to a Biosecurity Queensland inspector within 24 hours of the property owner becoming aware of it.