The joy of the splendor of a dahlia can quickly be spoiled when mottled leaves suddenly appear. These are usually not a good indication of a he althy plant, but rather an indication of leaf spot disease.
What is leaf spot on dahlias and how do you combat it?
Leaf spot disease on dahlias appears as yellowish spots that later turn gray-brown. It is caused by the fungal pathogen Entyloma dahliae. To combat this, affected plant parts should be removed and disposed of with household waste. A suitable location and the right care help preventatively.
How do I recognize leaf spot on dahlias?
In the early stages,yellowish spotsappear on the leaves of the dahlias. They still appear relatively inconspicuous and are usually only located on the lower leaves at first. As the disease progresses, the spots become larger and turngray-brown to dark brown. The spots can be round to square and are usually between 5 and 10 mm in size. Later the leaves dry out until they finally die. The stems of the dahlia can also be affected.
What is the cause behind leaf spot in dahlias?
There is a specialfungal pathogen behind the leaf spot disease in dahliasThis is called Entyloma dahliae. It only occurs on dahlias and usually on those specimens that are weakened. With the right approach, this fungus, which causes the disease called Entyloma leaf spot, can be effectively combated.
How can this disease be controlled in dahlias?
You should immediately cut off diseased plant partsTo do this, grab a pair of sharp secateurs (€56.00 at Amazon). Remove all diseased leaves and stems. These are then not disposed of in the compost, because the pathogen can survive there for a long time and may later infect dahlias again. It is better to dispose of the diseased plant parts with household waste.
Furthermore, all diseased leaves that have already fallen and are lying in the bed should be collected and destroyed.
If necessary, you can also apply a fungicide.
What role does the location of the dahlia play in prevention?
The location plays abig role in preventing this disease. The dahlias should be planted in a location that is conducive to them. That means: sunny, warm and airy. In addition, the planting distance should be generous so that water can evaporate quickly and the leaves can dry well.
Can dahlia disease be prevented by caring for it?
With proper care, a dahlia remains robust andnot susceptible to leaf spot disease. Pay attention to the following points:
- water regularly
- do not water over the leaves
- use suitable fertilizers and fertilize at regular intervals
- clean out wilted flowers
- check for pest infestation
What can you confuse leaf spot on dahlias with?
It is not uncommon for leaf spot disease to be confused withsunburn,frost damageornutrient deficiency of dahlias. Therefore, take a close look at the spotty leaves and consider whether it could be caused by sunburn (e.g. from watering the leaves in the midday sun), frost damage or a lack of nutrients. Last but not least, an infestation by pests such as aphids can also be the cause of discolored leaves.
Tip
Clean the secateurs afterwards
Once you have cut off and disposed of the diseased parts of the dahlia, it is important to disinfect the secateurs afterwards. If you were to use these on other dahlias without disinfecting them, parts of the fungal pathogen could spread from the secateurs to the he althy plants.
