Very large spruce with needle cast ?

Asked August 22, 2018, 6:12 AM EDT

I have a large spruce (75 plus feet) that is approximately 50 yrs old. This year I noticed the tree has lost needles on the north side of the tree making for many bare branches. The needle lost starts on the low branches and extends upwards 30 feet or more. The north side of the tree is shaded. The south side of the tree has some bare lower branches but minimal. I had a company come out yesterday and start treatment on the tree for what they diagnosed as needle cast?? . Yesterday's treatment consisted of injections into the roots???. From what I have read about needle cast is this the time of year for treatment?? I mentioned spraying to the person treating the tree in which he replied the tree is too large. Before I get too far along with this tree service and the treatment plan they are taking, how and when should I treat this disease affecting my tree?. Is this the right time of year, late summer vs. spring?? Can I treat it myself?? From what I have read online, how does a deep root application help my problem???. This application yesterday was $250.00. How should I proceed??? Thank you.

Oakland County Michigan

1 Response

You did not specify if your spruce is a Colorado Blue Spruce (which is out of its preferred climate and arid, high altitudes and cooler weather) or other kind.To get the upper hand on spruce needle cast, plant species of spruce other than Colorado blue spruce which is the most susceptible spruce to Rhizosphaera needle cast. Shifting slowly to these disease resistant or tolerant species will reduce pesticide use in the Great Lakes.

The typical needle cast problem on a blue spruce is rhizophora, which is typically treated by spray in May. You are correct that spraying a 75' tall tree would be next to impossible. Please read information in the links provided below. Needle cast diseases are the main reason for the casting of last year’s needles. I don't have pictures, so you will need to check your tree to determine if you are losing last year's needles and this year's are still attached. It's very possible your tree is suffering from more than one disease.

Recommended treatment for needle cast disease of spruce trees (rhizosphaera) typically is a spray treatment in May with one or two follow -up sprays. Having said that, prevention of infection is key—fungicide treatments may have little or no curative effect. Prevention methods include selecting appropriate varieties for Michigan (Norway and red spruce are most resistant to needle cast), allowing adequate space around the tree for good air movement, and full sun with little to no competing plants.

I'm hoping you contacted a tree service with a certified arborist on staff and that is the person who evaluated your tree and made the recommendation for root treatments. If not, you need to contact a certified arborist to examine your tree and recommend appropriate treatment.

I would ask for efficacy data from the arborist (or tree specialist) who treated your tree. He should be able to provide evidence that the treatment works and is more effective than fungal sprays. The sprays do work and take about 4 applications over 2-3 years. If the arborist cannot provide convincing evidence that his product is superior and cost effective I would talk to another arborist.The injected product maybe relatively new and has not been reviewed by ag specialists.