Hi. I have 3 large mugo pines planted in a group in the front yard. They’ve had a scale issue for the past few years. Humber Nurseries recommended I spray them with mixture of sulphur and horticultural oil (from a prepackaged kit) in early spring. I did this last year with fairly successful results. There was still some scale this year so I sprayed them again this spring with the same mixture. For some reason this year, unlike last year, there is a lot of “burned” brown needles. I’m not sure if it was the solution that I used or the unexpected cold weather or the one sunny warm day that might have done the needles in. My immediate reaction was to remove the sulphur/oil mixture with a strong spray of water from the hose. It didn’t really remove anything. So then I used up a whole bottle of Safer’s Soap Insecticidal Soap thinking that at least the soap in this might loosen up the oil and then I could remove it with water from the hose. The needles still had tons of the stuff on them. I then spritzed the needles with a diluted mixture of water and dishwashing liquid thinking the grease fighting nature of the soap would loosen the residue on the needles. I let it sit for about an hour and then sprayed hard with water from the hose again. A little came off but not too much. I’ve basically been doing this early morning and early evening for the past week and there is still stuff on the needles (see attached pics). The trees still have the slight odour of sulphur. Some of the branches and new buds are dead but others have the “burned” needles and the buds are green and viable. So I’m assuming that the branches with buds will be fine and the dead needles will just fall off. I still feel I need to get all of the oil/sulphur solution off the pines for their health. My question is what should I do? Is there some kind of wash to remove the oil spray? Was it the sulphur in the mix that did this? Should I have just used horticultural oil? Kind of beside myself with worry. These pines are pushing 30 years old and are the focal point of the yard. I don’t want to lose them. Looking forward to your advice.
Thank you for your question for Toronto Master Gardeners.
The browning needles could be the result of a completely different issue and it is very difficult to give recommendations on what to do without seeing the pines in person. The browning could be caused by many things such as the natural seasonal needle drop, blight, a reaction to drought, fluctuating freezing temperatures in winter, etc.
Our advice is, given these pines are very important to you, you should contact an arborist to come have a look at them. To find one, you can use Landscape Ontario at https://landscapeontario.com/ by selecting arborist/certified tree care from the drop down list and select your area.
We wish you the best of luck in finding the cause of your mugo pine browning and hope that a certified arborist will be able to solve the problem.