Q. I need some help. About a month ago I was advised by a gardener that two ornamental fir trees needed to be sprayed. He suggested I use Ortho Volck and I did this at the prescribed dilution rate. Now both trees seem to be in trouble as shown in the attached photographs. Did I spray too heavily? What can I do to try to save these firs? “Fir” damage from oil A. Dormant or summer oils are not supposed to be applied to Douglas Fir, Spruces such as birds nest, many juniper and cedars. I assume Volck oil says this on the label. It may cause defoliation or needle drop. In some cases you might have some branch dieback, perhaps enough to ruin its looks. It is safe on pines if you follow the rate of application. You mention that you have fir trees which is unusual in the Las Vegas valley but if these are in any of these categories you could have spray damage. If the damage is not too severe I think they will drop damaged needles and show some new growth from terminal buds and buds inside the canopy (branches). Hopefully they will recover.