Black spots on rose leaves are a common symptom, usually indicating an infection with a fungal disease. In this case, untreated bushes will quickly lose their charm. See what causes black spots on rose leaves and what to do when you notice them. Here are proven ways to combat rose disease that causes leaf stains!
Black spots on rose leaves
Causes of black spots on rose leaves
The appearance of black spots on rose leavesmay be a symptom ofrose black spot . It is one of the most common and dangerous rose diseases caused by the fungus Diplocarpon rosae.
The symptoms of black rose blotchappear from late May to mid-June, and sometimes even in early July, on the oldest, lower leaves. These are round or oval black spots 2-12 mm in diameter. As a result of expansion, the spots blend together, creating large black areas on the leaf blade. The central part of the stains may discolor to a lighter color. Tissue around the black spots begins to turn yellow.
Infectedrose bushes shed their leaves massively in AugustIn more sensitive varieties, the bushes may be completely stripped. Irregular, red and slightly bulging spots are visible on naked shoots. Often at the end of August, new leaves begin to form on the shrubs. This gives the illusion that the condition of the bushes is improving. However,blackspot-infested roses are weakened , have stunted growth, develop fewer flower buds the following year, and freeze frequently in winter.
Flowerson shrubs affected by black spotare of very poor quality. The development of the disease is favored by frequent rainfall, weed infestation and the lack of air exchange around the rose bushes (too densely planted plants).
Anothercause of dark spots on rose leaves may be rose anthracnose(Colletotrichum gloeosporioides), the symptoms of which are often mistaken for black spot.
When rose bushes are infected with anthracnose, round, red, and later brown or dark brown spots appear on the upper side of the leaves
When infested with anthracnose roseson the upper side of the rose leaves circular, initially red, then dark brown or even almost black, spots 5 mm in diameterOn the lower side of the leaves, characteristic flatulence develops in place of the spots. As the disease progresses, the center of the spots dries up and the tissues crumble, creating holes in the leaves. Around the spots, the leaves turn yellow. In the last stage of the disease, the leaves fall off massively.The symptoms of rose anthracnose are visibleat the same time in the shoots and petals of the flowers. Dead spots appear on shoots in places of infestation, where shoots break off.
If in places where black spots were visible, the tissue dries out over time, crumbles and holes are formed, this may indicate an anthracnose infestation
Fighting black spots on rose leaves
Toprevent black spot and anthracnose from occurring on roses , rake thoroughly and remove fallen leaves in autumn. The fungus hibernates in fallen leaves, so leaving them under rose bushes may be a source of infection in the following year. You should also systematically remove and destroy all diseased shoots. When watering, we should try not to wet the bushes. When we observe the first symptoms of diseases, we spray.
Note!
Until recently, it was common practice to burn plant debris infected by diseases or pests. However, according to the current regulations, smoking leaves and branches, even if they come from sick plants, is forbidden.From gardens and plots, we should dispose of them in accordance with the principles of segregation and waste return in force in our commune. Cut branches and removed leaves are called green waste.
Tofight black spot on rose leavesit is necessary to use appropriate fungicides. For use on plots and in home gardens, it is recommended to use agents such as Saprol Hobby Long-Acting, AE Fungicide Stopwatch or Substral Flowers Comprehensive Protection. These are preparations available in a ready-to-use form, in a spray. It is best to use them alternately to avoid the pathogen becoming resistant to a given protection measure. We spray every 3 weeks (until the end of September) at temperatures above 12 ° C.
If you avoid the use of chemical preparations,to combat black spot on rose leavesyou can use the biological preparation Polyversum WP for ornamental plants.
Rose anthracnosis is foughtwhile using Dithane NeoTec 75 WG in a dose of 2g in 1l of water.Spraying with the water solution of Dithane NeoTec 75 WG is performed every 14 days (maximum 4 times a season).
The mentionedpreparations for protecting roses against leaf blotchescan be ordered in our store. We guarantee high quality of service, low prices and fast delivery. To view a range of available protective measures, please press the button below.
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MSc Eng. Agnieszka Lach
