I’m not going to lie — other creatures as well as humans adore roses. But here’s the good news: Many modern roses have been bred for resistance to common rose pests and diseases. More improvements show up every year, so roses are definitely a case of where newer is often better.
Just as with humans, if the rose plant is in good health, it’s far less vulnerable. So review and apply the care advice I give in the previous sections. That said, forewarned is forearmed, so here’s some straight talk about the most common potential foes. Take a look at the list of least-wanted insects:
• Aphids:
These critters are tiny, pear-shaped sucking insects that especially relish new growth. They excrete honeydew, a sticky, sweet substance that can turn black as sooty mold grows on it. (Ants may appear to eat this but don’t harm your rosebush otherwise.) Knock aphids off with a stiff blast from the hose, or spray with insecticidal soap. Never spray when the temperature is above 80 degrees.
• Japanese beetles:
These metallic-looking copper and green bugs are really creepy, especially when they appear in great numbers. In small infestations, you can bravely pick them off and drown them in soapy water (don’t squish them — you’ll just releases attractant pheromones!). Japanese beetles are late risers, so if you go out early in the morning, you can shake the sleepy critters into a plastic baggie. If the infestation’s bad, you may have to spray with Sevin (check with your local garden center, and always follow label directions exactly).
• Thrips:
Thrips are tiny yellow or brown bugs that lead to misshapen leaves, deformed buds, and discolored flowers (with brown spots). They especially love light-colored roses and are most common in early summer. You can spray with insecticidal soap or neem oil. Roses are also vulnerable to some pretty unpleasant fungi. Check it out:
• Black spot:
Rose leaves develop small black spots with fringed edges. The fungus that causes black spot is worse in hot, humid weather. To treat, remove and destroy affected leaves (don’t add them to the compost pile). Prune the plant to improve air circulation, and water in the morning. Some sprays that fight this disease include summer oil (a light horticultural oil), neem oil, a baking soda solution, sulfur-based sprays, and strong chemicals — ask at your local garden center.
• Powdery mildew:
This fungus appears in dry weather, creating a white powdery residue, especially on the leaves. You can spray with summer oil, a baking-soda solution, an antidesiccant (which prevents drying out), or a sulfur-based fungicide.
• Rust:
This fungal disease is most common in dry weather. Get rid of affected leaves, and water carefully only at ground level. Spray options include dormant oil, lime-sulfur fungicide, or rusticide (again, check with your garden center and follow label directions exactly).
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