Answer: It's difficult to provide a control measure without knowing which plants are involved. Yellowing leaves with black spots could indicate a fungal or a bacterial disease, but most of these are host-specific and most control measures are disease -specific. If you submit another question through the Monrovia website with more details, we can help you with the problem. Tell us about the plants displaying these symptoms, including growing conditions, water and fertilizer applications and rates, plus anything else you might think might be helpful in diagnosing the problem.
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