Many Plant Disease Problems - Knowledgebase Question

E.Aurora, NY
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Question by fleetwood7
August 8, 1998
I have a problem with my plants getting some kind of insect or something on their leaves. It seems to affect
alot of my plants with the same thing. The roses will look white and powdery, the hollyhocks got spotted, dried up
and died, the lupine did the same as the hollyhocks. The same thing happens every year with the plants. They are all grown in the same area and get the morning sun. When I look under the leaves it looks like real tiny speckles. I'm at my wits end with this happening every year even though I cut down the diseased parts and toss them away, a few weeks later it comes back again. Could you please help me on this I've tried powders and sprays on them also.

Answer from NGA
August 8, 1998
The plants you mentioned are all very susceptible to leaf problems. Your roses may have powdery mildew; hollyhocks are technically perennials but many people treat them as biennials because they are prone to pest problems; lupines too have pests--mine are often heavily damaged by aphids. These plants also need full sun, so if they are just getting morning sun they could be somewhat stressed by lack of light.

To treat these problems, first you need to identify the culprits. If possible, bring some samples to your local Extension agent (ph# 716-652-3370) for ID, or get a good book with photos of plant pests--a good one is Rodale
s Pest and Disease Problem Solver, by Linda Gilkeson et al., published by Rodale Press.

Some leaf diseases respond to regular sprayings of compost "tea", or a seaweed foliar fertilizer. This has the added benefit of providing nutrients. Never spray plants in flower with an insecticide--you can harm the honeybees visiting the flowers--and these creatures are suffering reduced populations as it is. Some people have good luck with insecticides containing neem oil. This is a natural product made from the neem tree.

Sorry I can't be more specific with recommendations. You might try planting some hardier, less disease-prone plants--just so you know it's not just you! Some plants that will do well with morning sunshine include astilbe, azaleas, monkshood, coral bells, hosta, and creeping phlox.

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