In the Salt Lake Valley there are two things that can keep your evergreens from being healthy and happy, mites and drought. If you have a mite problem, conifer needles are generally stipples and gradually turn an off color yellow. You might find a light webbing with a heavy mite infestation, but all you really need to confirm the diagnosis is a white sheet of paper. Hold it under a branch and shake the branch vigorously. Mites might be small, but they are not microscopic—if you have them, you’ll see little moving spots on the piece of paper. If you’re still in doubt, run a finger over the dots, dead mites will leave a red streak.
To combat these pesky little guys, hose off affected plants with high pressure water (being careful not to damage plant tissue) and spray with dormant oil in early spring before candles open. Spray with Neem Oil (Fertilome Triple Action Spray) probably three times at weekly intervals. Some combination of the above should control the problem.
Conifers are relatively drought resistant, but if they don’t have sufficient moisture during the heat of summer, needle drop will be earlier and more severe than normal. It’s a lot hotter down in the valley than the Utah mountains. Water the tree roots deeply but at greater intervals than your turf. Roots of these plants are at very different depths. Also remember that conifers photosynthesize all year long, a last deep watering before the soil freezes is a good idea, but don’t overwater in the fall as the tree growth slows down.
A lack of nutrients often means a longer period of dormancy than normal, premature needle drop, yellow stunted growth, and increased susceptibility to insect and disease damage. Deep watering with nutrients helps a lot. Also, conifers don’t do well in poorly draining soils, so if you have bad drainage you might want to pick another tree like a Bald Cypress or a White Pine.
Also, herbicides kill plants—so keep them away from your conifers.
If you have any questions, please stop by any Western Garden Center and talk to one of our expert gardeners, they’re always available to answer questions. And remember to follow the label instructions on any pesticide used. Sometimes directions change and the label is always the most up to date.
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