some plants in new garden turning black

Question

I moved into my house 6 months ago and there were only a few established plants. We have added plants over the summer, including an olive tree. Over the last few weeks on the left-hand side of the garden, we noticed some of the foliage of the plants turning almost black (i.e. a hydrangea had blooms that were completely black and this soon spread to the geraniums, although by cutting the buds off the geraniums seems to have recovered). We have lost a camellia and now we are concerned about a young olive tree which is planted on the right side of the garden and until a few days ago was thriving.

The leaves seem to have a silvery powder on the top and the tiny fruits which were actively growing have now turned black and dried out. We have also noticed that one of the new leaves looks like it is curling up. We have spent so much money on this garden, and we can’t really afford to lose so many plants. Help. I have looked up diseases on olive trees but can’t seem to find the pest/disease that makes the fruit do this. Please advise what treatment I can apply. Also, a lonicera is starting to die back, but I am not sure if at this time of year that would happen anyway.

Answer 1

Check whether your plants’ symptoms match those described in these articles about sooty mold:

https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
https://www.gardeningknowhow.com/garden-how-to/info/what-is-honeydew.htm

This problem can affect a wide variety of plants, including olive trees as well as your flowers.

The black, dried up olive fruits could be caused by olive berry rot (Pseudocercospora), peacock spots (Cycloconium), or anthracnose. Olive berry rot would also cause a silvery or gray appearance on the leaves. Anthracnose can also affect other plant species and would cause spots on leaves:

http://ipm.ucanr.edu/PMG/PESTNOTES/pn7420.html