Orange spots and yellowing of Rose leaves - Ask Extension
Hi! After the recent rains we noticed small, orange / rust colored spots on our rose leaves last week (we believe it is a mountain rose, although we h...
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Orange spots and yellowing of Rose leaves #872636
Asked June 11, 2024, 2:04 PM EDT
Hi! After the recent rains we noticed small, orange / rust colored spots on our rose leaves last week (we believe it is a mountain rose, although we have lost the nursery tag). Due to lack of knowledge about fungal issues, we have been watering our roses from the top, getting the leaves an foliage wet and that seemed to exacerbate the issue. The spots have been growing bigger by the day. Now most leaves on our three bushes are yellow. Photos of the plants are attached. The condition is worsening quickly, especially in the last 4 days. Since yesterday even the flowers seem wilted and in very poor condition. We would appreciate your diagnosis of this condition/disease, and the recommendations to treat the same. Thanks so much!
Washtenaw County Michigan
Expert Response
Good Morning,
Typical rust symptoms are small orange blisters on the underside of leaves. Low levels of rust will not cause significant damage.4 Like black spot it survives the winter in infected leaves or stems in and around the rose bush. In the spring, rust spores are blown to new leaves or plants. Spring and early summer conditions are favorable to rust.1
Recommended steps to prevent/control rose rust include:
Rust on rose leaves – Toronto Master Gardeners
I hope this helps. Thanks for using our service.
Typical rust symptoms are small orange blisters on the underside of leaves. Low levels of rust will not cause significant damage.4 Like black spot it survives the winter in infected leaves or stems in and around the rose bush. In the spring, rust spores are blown to new leaves or plants. Spring and early summer conditions are favorable to rust.1
Recommended steps to prevent/control rose rust include:
- Fungi and bacteria require high humidity to produce more inoculum. Therefore, good air circulation within and around rose bushes is critical for preventing rose rust and other diseases. Make sure your roses are correctly spaced apart and well pruned so the leaves will dry out quickly after a rain.
- Water your rose bushes at the soil level (not on the leaves), a drip irrigation system would be ideal. Water in the morning so any water on the leaves has time to dry out during the daytime.
- Ensure your rose bushes are planted in a sunny location, ideally getting 6 hours of sun daily.
- If/when your rose bushes display symptoms of rose rust, apply a foliar fungicide as needed to control the rust, following the manufacturers application instructions carefully. You can purchase a suitable fungicide at most reputable garden centres.
- Dispose of any infected leaves to prevent spread of the fungus to other rose bushes.
- Sanitize any garden tools you use to prevent spread of the disease – a bleach & water solution works well (proportions for a solution can be found online).
- The spores of rose rust fungus will overwinter in leaves and repeatedly re-infect the rose bushes the following spring. Make sure you rake and dispose of all old rose leaves as well as other garden debris from around your plants.
Rust on rose leaves – Toronto Master Gardeners
I hope this helps. Thanks for using our service.
