Q.What could cause needle defoliation on a 12′ Norway spruce in NW IL IN A VERY ISOLATED approx. 3′ chest high South facing area
and N.W. area on same species, 10′ apart, while the third s is perfect, spaced the same? All 3 get full sun. The 3 all looked perfect going into fall, yet the following spring two out of the 3 looked sparse, and the approx. 40″ diameter heavily defoliated. Sent samples to U. of IL. plant clinic and results stated it was abiotic. Any insight? I will be checking my Sinclair/Lyon “Diseases of Trees and Shrubs”. Soil samples of our Drummer sandy loam were good, and am now sending tissue samples for nutrition deficiencies, but the isolated location is confusing. Treatment with Growth Products, mycorrhizae L, essential amino acids, humus,etc., and trunk cambial injection of enamectin benzoate substantially improved the density of this issue, and was performed the 1st time last early summer. Thank you,
I would look first to your water management. Is the tree irrigated and how often? Is it possible that the tree has been under watered or over watered? Is there any possibility of a water leak in the proximity?
And what about disturbance to the soil and root system? Trenching, compaction, sewer repairs, gas line leak. These are abiotic issues, as is herbicide damage from over spray or drift.
If the U IL plant clinic stated probable abiotic disorder from foliage samples, that only means they did not detect any pest or pathogen in the foliage or twigs. It does not rule out root rot or stem cankers or borers in the trunk. Only with a site inspection can all factors be considered.
You mention stem injection with emamectin benzoate. Was that done by a professional with Arborjet technology, or did you do it yourself. Because you say cambial injection, but a systemic insecticide like that needs to go into the xylem tissue for uptake; the cambium would be too shallow. But maybe you are using a general term for the living tissue layers. And if it was a professional, what was the target pest determination? Or did you just use it as part of a shotgun approach to cover all bases? Emamectin does not have any fungicidal properties, only for arthropod pest control, insects and mites. This insecticide is slow to take up and translocate. It is recommended to inject in fall for next season pest control. It should not have affected the foliage density unless there was a pest feeding on the tree that the chemical brought under control. This chemical when used according to directions has a two year residual effectiveness. So if the injection timing was last summer, and the foliage condition improved right away, but declined this year, then I don't think the pesticide had anything to do with it, unless there was a target pest identified.