I don't know how I missed this but I've just noticed a significant amount of white cottony patches on my hydrangea plant. After a quick online search, it appears my hydrangea has a bad scale infection. It seems like a really bad infection and I feel terrible. I am very attached to my hydrangea plant and I'm hoping it can be saved. Can I prune back the worse of the stems infected and treat the rest with something to save my plant? Would appreciate any help and feedback! Shelbey
I can only give ignorant advice, was hoping someone knowledgeable would reply. When I see white stuff like that, I always think they're mealy bugs and I wipe off what I can with a cloth soaked in alcohol and the spray with alcohol. If you dab them or spray them with alcohol and the white stuff disappears and there is only a little bug skeleton remaining, that approach might work if you do it every three days about three or four times, then whenever you spy a new bug. If you prune off the worst parts, it would be lot more manageable. If they are really scales and the white stuff doesn't disappear from the alcohol spraying, then this would not be appropriate treatment. You would still want to trim off the worst bits, down to what you can keep washing and inspecting; wash off all the scales and keep washing down the stems and leaves. I think scales are hard to fight, since the bugs live under them and escape when you remove them.
BsyB, I think you have Cottony Camelia Scale (Pulvinaria floccifera) on your hydrangea. I have the same problem on a number of different plants, mostly hardy Kiwifruit. I haven't tried controlling them other than pruning off the worst affected branches and rubbing out the remaining ones); but information on the Web states that horticultural oil is effective against them. Use a 2% solution (20 ml per litre of water) and spray thoroughly (until runoff) in the evening when temperatures are between 45 and 90 degrees F and no rain is in the forecast for 24 hours. Apply during the dormant period, as well as late June or early July, with two applications 10 days apart. I plan to try this out myself as soon as I can.
Here is more information about horticultural oil and how to apply it What Exactly Is Horticultural Oil? Personally, I haven't used horticultural oil during the growing season, but I use a Green Earth dormant spray Green Earth dormant spray - Google Search , which is a horticultural oil/lime sulfur mix, on selected shrubs/trees at spring, very shortly before bud break. I use it to control aphids, Peach leaf curl on my Peach tree, on my Pear tree to control thrips, and to control something (not entirely sure what it was) on my Snowball Viburnum. It also controls scales. Since it works perfectly for me I recommend it for you to use at the end of the dormant season. If you are impatient try Summer or All Season horticultural oil (it doesn't contain lime sulfur) now, although it may be already too late to control scale insects. Follow the info on the package how to use it.
