Impatiens are known for their hardiness in high heat, and because these shade-loving annuals are available in a range of vibrant colors, they’re a go-to for commercial landscapes looking to turn up the volume in plant beds.
But impatiens are not foolproof, as we’re finding out yet again, as we’re spotting more cases of downy mildew cropping up throughout Hawaii.
The key to staying ahead of this disease:
Know the symptoms so you can identify and treat it quickly
Create an environment in the landscape that discourages downy mildew
Consider alternatives to impatiens that deliver their color and vigor — without downy mildew risk
Here’s a closer look at downy mildew treatment for impatiens on Kauai. Arm yourself with knowledge to protect your Kauai commercial landscape!
What Is Downy Mildew?
Basically, downy mildew is water mold. (The photo on the left isn't impatiens downy mildew, but it gives an idea of what the condition looks like.) It presents as a white powdery spots on the undersides of leaves, and you’ll also notice yellowing or stippling on leaves, and stunted growth. Advanced symptoms of downy mildew include a grayish, fuzz on leaves and stems. Leaves and flowers eventually drop.
Downy mildew is caused by a fungus-like pathogen, and the disease develops rapidly on just a few leaves. The pathogen produces airborne spores that can drift several miles, and swimming spores that survive in the soil and plant debris. Infected soil will sabotage healthy impatiens that are planted.
The disease strikes fast because it travels by air and exists in the soil. Splashing from rain and overhead watering, or even a light breeze can spread the spores. Within several weeks, affected impatiens can become completely defoliated. If you think you’ve spotted a diseased plant on your Kauai commercial property, call No Ka Oi to get a professional assessment.
The Best Downy Mildew Treatment Is Prevention
Cool night temperatures and moist conditions are a breeding ground for downy mildew. The disease most commonly spreads when impatiens foliage stays wet for long periods of time. Landscape beds that are densely planted and positioned in deep shade are highly susceptible to the disease. Add overhead watering to that and you’re creating an open invitation for downy mildew.
Discourage the disease with proper watering practices. You can’t stop the rain, and deep, shady landscape beds will naturally retain that moisture. So instead, consider planting alternatives!
If you suspect downy mildew, and the disease is confirmed by a professional landscaper like No Ka Oi, you’ll want those infected plants to be removed from the landscape, along with plant debris like flowers and leaves. Spores can overwinter in the plant debris. Infected beds must take a hiatus from planting for a few seasons. Chemical treatments are not effective for fighting downy mildew.
Beautiful Impatiens Alternatives
Your goal is to keep your commercial property colorful and inviting year-round, so consider these alternatives to impatiens so you can avoid downy mildew all together.
Some good news: You don’t have to ban impatiens from the landscape! Downy mildew does not affect New Guinea impatiens (Impatiens hawker). It mainly wreaks havoc on Impatiens walleriana or hybrids with an I. walleriana parent, along with wild impatiens.
Instead of impatiens, try any of these groundcovers, tropical plants and colorful flowers in your commercial Kauai landscape:
- Golden Duranta
- Red ginger
- Ti plants
And, of course, if you’re looking for a seasoned opinion, look no further than No Ka Oi’s Kauai landscape professionals!
We’re focused on keeping your landscape beds healthy, colorful and beautiful. Contact us to learn more! Give us a call at 808-335-5887, or fill out our simple contact form, and we’ll get in touch with you.