What's wrong with this dwarf white pine?

Question

This pinus strobus nana is about four years old and has done very poorly this year. Alkaline clay base soil with a full sun, south exposure and a mulch of pine needles.

The soil has a ph of a little over 7. There are no signs of fungal/bacterial disease

The tree was planted four years ago. There was a lot of dieback this spring but this is the first year the needles have been so yellow.

I can add more organic soil and use acid fertilizer but changing the ph of the soil radically is a daunting prospect. Sulfur might do the job.

Symptoms: The mealy bug problems referred to here seem to be gone but the colour is chlorotic and the interior branches are black rather than the usual brown bark colour. USDA zone 4 with lows to -30 Deg C.

Answer 1

The tree is suffering from nutrient deficiency due to an unsuitably high soil pH. To properly absorb nutrients, these trees need a lower pH, like 4.5-6.0. Organic matter will be useful in helping the microbes thrive that feed the tree, but they will not live in a high pH. Try applying sulphur to the area in a circle around the tree about twice the diameter of the dripline. Even after a good pH has been accomplished, it will need to be maintained on a regular basis, as acid topsoil will neutralize when sitting over a pH neutral or an alkaline subsoil.

If this method is not practical, then your choices are limited, and will include using acidic fertilizers, as you've mentioned, or consider removing the tree and planting something more tolerant in that spot.