Ailing mugo pine
Have a 20-year old 9-foot tall pine that has some parts/sections with needles turning brown and dropping off. I see some whitish substance along some of the larger stems as well as on the tips of the ends. I sprayed it with 3-gallons of soapy water and went inside and trimmed out the affected (infected?) branches.
Should I use a magnifying glass and look for insects/? I do not believe it has been overwatered but it might have been. Once, a few years back, the pine nearly died with an infestation of some type of worms--hundreds if not thousands of them. I sprayed them and they all fell off. Plant survived. Would you like a photo?
A diagnosis cannot be made based on the photographs. I suggest sending a plant specimen to the ISU Plant and Insect Diagnostic Clinic. Information on submitting plant specimens to the clinic can be found at https://hortnews.extension.iastate.edu/pidc/plant