Answer: I think what you are describing are spider mites. Spider mites are tiny warm season arthropods that insert their tiny, scissor-like mouthparts into leaves and petals and cause tiny yellow spots to form as they suck out the contents of the plant cells. Hot, dry weather accelerates the life cycle of the spider mites. Because spider mites flair up in dry weather, their control is somewhat difficult. Plants that have wilted slightly are much more susceptible to pesticide injury than turgid plants. Also, plants are much more likely to be burned if pesticides are applied during midday. Plants should be watered thoroughly before spraying them with pesticide and should be sprayed in early morning or late afternoon so that the pesticide residue is dry before the bright, noon sun hits it. Horticultural oils and soaps are moderately toxic to spider mites and they are relatively safe for humans. Soaps and oils have virtually no residual activity so both pesticides must be applied two or three times for complete control (about 5 days between sprays). Be sure to carefully read the product label and apply as recommended. Aside from the above, you can try simply hosing your corkscrew hazel off with a strong stream of water from the hose. Wash both the upper and lower surfaces of the leaves and repeat this treatment every few days for a couple of weeks. Since spider mites like dry, dusty environments, this simple act may drive them away. Best wishes with your landscape.
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