I have 2 pine-like trees with small needles, conical shape, that are prone to...

Asked April 28, 2014, 6:14 PM EDT

I have 2 pine-like trees with small needles, conical shape, that are prone to get spider mites. They look beautiful, but I went out today to see if the ends off the branches had any brown areas (spider damage) and found the inside of most branches were dead. Is this the way these trees grow, or is it mites??? Also, can they be trimmed back???

Anne Arundel County Maryland trees and shrubs alberta spruce

2 Responses

Your trees are most likely Alberta Spruce trees, and yes they are prone to spider mites, and yes, browning of the interior foliage could be the result of spider mite activity. If so, that damage probably occurred last year. It is not uncommon for needled evergreens in general to display a lack of green foliage on the interior, so if your trees generally look green and are producing new tip growth, your best strategy would be to monitor for mite activity periodically, especially as the temperatures increase.
To monitor for mites, take a sheet of white paper to the tree and hold it under a selected branch. Rap the branch sharply and examine the paper carefully. If you seed tiny little creatures moving about, they are predator mites and are 'good guys'. They eat the 'bad guys'. Having looked for movement and if there are stationary specks on the paper, wipe you hand across the paper and look for red smears. Those would be the spider mites. If there are more moving specks than smears, don't bother spraying. Should the numbers reverse, you could spray the tree with a summer diluted horticultural oil. This will kill the spider mites and spare the predators.
Another important part of your strategy would be to water the plants and give them a good shower when we suffer hot, dry summer periods..
Don't trim them back to brown wood. Only trim lightly in order to shape the tree, retaining green foliage on the outer tips.
LS

Thank you for your advice. It was most informative.