Monday, June 18, 2007

Powdery Mildew on My Campsis grandiflora

My mature Campsis grandiflora is showing signs of a whitish/grayish film on some of its leaves. This has happened in the past, but never much before late September or October. Is this powdery mildew, or perhaps something else, and what might you suggest to eradicate it?

Your situation does sound like a case of powdery mildew. Since it has been rather warm already this summer and with the few extremely heavy rainstorms we have gotten, it does not seem all that peculiar that the issue is affecting your Campsis earlier than usual. Campsis grandiflora is prone to powdery mildew but luckily these days there are cultivars being bred and sold that are considered to be more resistant. As you probably know from past years experience this fungal issue is not going to kill your Campsis, but the white film on the leaves is unsightly and does not help the plant as it tries to photosynthesize. The best solution that I have learned over the years is a homemade concoction that you use as a foliar spray. Add to a gallon of water two tablespoons baking soda and a drop of dish soap (Palmolive, Dawn, etc.) to give the mix a little viscosity. Once this is mixed, use it as a foliar spray and cover as much of your vine as possible. Continue to apply until the mildew seems to diminish. It may take a few applications over two or three weeks’ time. This usually does the trick.

Otherwise, think about the amount of airflow in the area where the vine is. Powdery mildew often occurs because of a lack of decent airflow, therefore pruning either the vine or other trees and shrubs in the area might prevent this from becoming such an issue in the future. My last thought is that Campsis grandiflora can be rather drought tolerant once established. Since you describe the vine as being mature then I would think you can cut back on supplemental watering at this time of year and hopefully the plant will still grow and flower well for you without the added powdery mildew.

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