Then I started noticing the leaf spot popping up randomly on other plants. I am feeling cursed by leaf spot and don't want to start the new year with it spreading to everything. My hawthorn bush, the only thing green right now, a huge bush that's been there forever, is also covered in it. There is no way I could possibly pick off all of the leaves on it.

I went to my local garden center with a sample. They told me the Daconil wasn't going to solve such an extensive problem and gave me some horticultural oil. They told me to spray everything and that it would coat the plants with an oil that wouldn't wash off. The oil is supposed to protect the plants from getting the leaf spot and contain what's already there so it can't spread. Of course the man that sold it to me acted like it was some kind of miracle cure. I'm hesitant to believe it is that easy. And the active ingredient is mineral oil.

Anyone know if the man at the garden center was right?

==>>> wow ... is that what the label recommended???

ken

No effect showing leads to several possible conclusions:

1) wrong stuff for the fungus/ disease
2) the Hydrangea were so stressed out it couldn't help anyway

If a disease keeps popping up every year there is something wrong with the plant and / or the site.

You sure your Hydrangea have the right conditions to grow?

IME if there is something wrong with the soil there is zip you can do- and I mean heavy soil if your favourit plant would need sandy soil etc

Bye, Lin

My concern is that now it has spread and I want to contain it. I can't replace all of the soil on my property. I considered removing the hydrangea, but that's not going to help all of the other plants that have been infected and I'd like to try to save it since it has some sentimental value. To linaria, I've come to conclusion 2.

I need to know if the horticultural oil is going to be effective like I was told at the nursery.

It is of primary importance to get an accurate diagnosis of the specific problem for each plant in question and then utilize the appropriate remedy. Hopefully someone on staff at a better garden center can help or check out a Master Gardener clinic or your local extension service.

Often, the incidence of a lot of plant problems is more culturally related than an actual disease issue - fix the growing condition and the problem disappears. Fungal issues like leaf spot are often related to weather, overwatering, watering at the wrong time of day (leaving water on foliage overnight), poor drainage, lack of air circulation or even proper garden clean-up and sanitation. And mulching in winter can help a lot - a good layer of mulch smothers fungal spores that can overwinter on the soil surface and prevent them from splashing up with rains and reinfecting.

Your hydrangea issue is most likely cercospora leaf spot, a very common problem with a number of hydrangea types. If you read the attached info sheet, you'll notice that the condition is primarily due to cultural issues. Correct those and you will correct the problem.