White and gray, furry coatings on phlox are usually a sign of the familiar powdery mildew fungus. Here are tips on how to prevent powdery mildew infestation and how to combat the fungus.
What is powdery mildew?
Powdery mildew (Erysiphe cichoracearum) is a fungus that affects many phlox. The result is white spots on the foliage or even dead leaves. In dry locations with permeable soils, the risk of powdery mildew increases during hot summer months. Phlox are particularly susceptible in late summer, when heat and drought cause the plants to wilt.
Phlox are very popular with many amateur gardeners because of their attractive and very abundant flowering. If you take good care of these perennials, they make for a colorful summer garden. However, varieties of tall phlox (Phlox paniculata) in particular are susceptible to powdery mildew, even though many of them are described as mildew resistant. If you notice a white or gray coating on flowers, leaves and stems, your plant has become infected with this fungal disease.
Powdery mildew is a group of different, closely related tubular fungi that often specialize in a particular genus or plant species. The fungi live on the surface of the plant and penetrate the cells with special sucking organs called haustoria. Here they extract valuable plant substances (assimilates) from the plants and thus ensure that the foliage gradually dies.
This is how you can prevent powdery mildew infection
The best preventative measure against powdery mildew infection is to ensure that phlox remain vigorous and healthy, because vigorous plants are less susceptible to disease and pests. To achieve this, proper care and an optimal location are key. Make sure the soil of your phlox does not dry out too much. Regular watering and mulching will prevent infection with the powdery mildew fungus. Especially in warm weather, phlox needs adequate water to fully develop its blooming. Avoid one-sided nitrogen fertilization, otherwise the resistance of the flame flower suffers enormously. Regular treatments with environmentally safe surface-active sulfur keep the leaves healthy.
The choice of location is also crucial: an airy, sunny spot prevents fungal infestation. Don’t place your plants too close together to ensure good air circulation. This allows the plants to dry out quickly even after a heavy rain shower without accumulating too much liquid – as this favors mildew infestation.
Remove faded plant parts, because moisture collects under the numerous flower and leaf remnants. Remove dead plant parts best directly with sharp secateurs and disinfect them afterwards.
Choose mildew resistant phlox species.
Some varieties of phlox have a certain resistance to powdery mildew. Among these species is Phlox amplifolia. This variety is very hardy and resistant to various infections. The species also tolerates drought well, as well as heat. The meadow phlox (Phlox maculata) is also largely resistant to powdery mildew. Not only does it make a splash in the border, but it is also excellent for cutting into vases. While varieties of tall phlox are commonly considered somewhat sensitive to powdery mildew, there are some among them that are largely resistant. The results of perennial screening are reliable here.
Control powdery mildew on phlox
To fight powdery mildew on your phlox, you should generously remove all affected plant parts as soon as possible. Residual waste is suitable for removal; compost waste is not, because here the fungus can easily continue to spread and attack plants again.
If the infestation is already established on your plants, it is advisable to dispose of the entire plant. Replacement plants should never be given the same location for a new planting, place your new, healthy flowers in another suitable location in your garden.
Home remedies against powdery mildew fungus
A variety of home remedies have also proven effective in the fight against powdery mildew fungus: A well-known remedy is a mixture of milk and water. Mixed in a ratio of 1:9, the liquid goes into a spray bottle suitable for this purpose. Spray your plants with this liquid about three times a week.
A decoction of garlic or onion can also be used for mildew infestation on phlox. To do this, add the peeled, chopped garlic, or onion, to a pot of water and let it all steep for about 24 hours. Then boil the liquid for half an hour, then strain the contents of the pot into a spray bottle after it has cooled. Spray your plants with the homemade decoction about twice a week.
If well-matured compost is available, you can likewise use it as an effective control agent against the powdery mildew fungus on your flame flower. To do this, add the compost to a bucket of water and let the mixture steep for about a week. Stir it daily. Then, roughly filter the contents of the bucket and spread the remaining liquid into the soil and onto the plant. It is recommended to repeat this procedure twice a week.