Q: This year, we noticed that one of the hydrangeas was not fully blooming, and then my hubby noticed mites/aphids underneath the leaves. Some of the leaves at the very ends look almost burnt or fried and the hydrangea looks so unhealthy. We have sprayed all hydrangeas with horticulture soap on days when we know that it will not rain. The other 7 are blooming but through-out each one, you can see random leaves that are burnt or fried at the ends also. We hope it will not infect the others as much. Thanking you in advance of your information.
A: I am not certain but I suspect you have a blight called Botrytis Blight which often causes the blooms to die before they open. Botrytis blight is a fungus that can affect leaves, stems, crowns, flowers, flower buds, seeds, seedlings, bulbs, and just about any other part of a plant with the exception of the roots. This disease is especially prevalent during warm, wet seasons (similar to what we have been experiencing). The plants may be too close together; therefore you might consider moving them during their dormant season (late winter or early spring) to allow for better air circulation.
Avoid watering late in the day, morning hours are best. Avoid overhead irrigation on any of your ornamentals; it only increases the chance of spreading disease. Hydrangea prefers a moist, but not wet, organic rich soil. However, it is important to remove leaf debris as soon as it occurs. You may prune a few inches below the dead area, but use sterile methods (clean your pruning shears with a weak bleach solution or alcohol between each cutting). Destroy any of the diseased pruned plant parts immediately. The cultural methods listed previously will help curb the disease, but ethylene bisdithiocarbamate by be applied if you feel it is necessary to spray a chemical. In addition, you can continue to apply insecticidal soap and/or horticulture oil to control the aphids.