Euonymous bushes look sick
I have a long row of Euonymous bushes (E. Japonicus, I think), which are mostly sunny. About 3 months ago the leaves started showing white marks on the normally shiny green appearance. I've been spraying with Neam Oil for the last 6 weeks, once every ten days or so. It hasn't made any noticeable positivie change - I'd say that the disease is spreading. We've had the bushes for 30 years and never seen any disease hit them. We haven't done any other pesticide or fertilizer application other than the Neam Oil. I took four leaves off and photographed their front and their back. Also one leaf while still on the bush.
This is powdery mildew and it is a very common problem on euonymus. Take a look at our web page about powdery mildew and what you can do. In addition to applying horticultural oil (following the product label instructions), you can prune the shrubs to thin them out and increase air circulation. Humid conditions are ideal for development of this disease, so improving air circulation can make the environmental less favorable for it. Once a powdery mildew infection is extensive, it is difficult to control. For a plant like this that is known to be susceptible, you might consider applying the horticultural oil earlier in the season next year -- when first symptoms appear. You might also consider replacing these plants with other shrubs that have powdery mildew resistance.