cypress leyland turning yellow
I found that all my cypress leyland are turning yellow. It strated 4-5 months ago, and now has affected all 90 trees. Year was warm and very very humid with lots of rains.
(I preayed them 2 weeks ago with mixed insecticide for spyder and something extra (grizli+other).
Is this a problem and what should I do?
From your photo it looks like just the interior foliage is turning brown - this is a normal process - the older foliage has come to an age where it dies - this happens on all conifers in the spring/summer.
If the foliage on the tips of branches die, then that is very bad but that does not appear to be your problem.
Unfortunately, the yellow was spreading from the inner to outside, including tips of new branches. I put iron and spray it for spider, and two more stuff (dont know how to say in English).
After that, not sure what was the effective treatment, but in few days all of the yellow become dry and dark brown. New branches with green started to emerge. I belive all was settled, but yesterday noted one more small branch turning yellow, so should repated the teatment most likely...
Your symptoms may be one of several problems: fungal disease, perphaps mites, or perhaps cultural aspects. I suggest you have your local County Extension Specialist take a look at your plants. Without inspecting the plants, i cannot offer a reliable diagnosis.