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Tuesday, October 10, 2017

Brown Branches in Italian Cypress. Spider Mites?

Q. I think my Italian cypress has mites. Some of them are dying rapidly with pale leaves that hang out and crumble if you grab them. They are about 10 to 12 feet tall. 
Italian cypress is notorious for having brown branches at some point in the life. Spider mites can be the cause during the hot summer months but the usual culprit is watering too often. They are from a Mediterranean climate which is typically cool to cold and wet in the winter and hot and dry in the summer. They historically don't grow in climates with frequent rains or frequent irrigations. Water them with alot of water and then hold off on the next irrigation.

A. Make sure this problem is from spider mites and not watering too often. Italian cypress are Mediterranean plants that should be watered after the soil begins drying. Otherwise frequent irrigations rot the roots and causes problems similar to what you are describing.
Spider mites in Italian cypress happen during the hot summer months, not the cooler times of year. Often upon close inspection the branches have a "dusty" appearance.
            It would be a shame to apply pesticides when they aren’t needed. Pesticides are sometimes needed but applying pesticides, whether they are needed or not, always creates other problems. Sometimes the problems they create can be worse than the problem they solve.
Spider mites in Italian cypress usually have webbing that can be seen in the brown area. This is not true of all mite damage to plants.
            Spider mites are always present on plants during the heat of the summer. They are controlled naturally and kept in check by many different predatory insects including “good” or predatory mites.
            If you apply a pesticide to control mites, it kills the “good mites” as well as the bad ones. Once that happens, the bad my population can “blossom” back into a big problem and then it’s a vicious cycle between control and pesticide applications.
Webbing can be seen with spider mite damage on Italian cypress
            Most bad spider mites are “web spinners”; in other words, you should see webbing amongst the branches as well as a “dusty appearance” on the foliage if bad guys are active. This webbing is not true of all damage by mites. Some mites are not “web spinners”. “This dusty appearance can be from wind-blown dust but it can also be from large numbers of dead mites.
             The presence of wind-blown dust on the foliage can encourage spider mite problems. The dust interferes with “hunting” by predatory insects. Hose off Italian cypress after dusty winds and once a month during the heat of the summer. Let them hunt.
            Use a hand magnifying glass and look for eggs in the dust. Eggs are extremely small but round and translucent under a lens. Once mites are a problem, you will see lots of their eggs amongst the dust.
            Use a white paper test. Take a plain piece of white paper and “slap” a living but dusty branch against it 2 or 3 times. Hold the paper still in the sunlight and look for tiny specks the size of this period (.) to crawl around. These are mites.
            Browning of the leaves, webbing, a dusty appearance, round translucent eggs and little dots crawling around on a white piece of paper are clear indicators you have spider mite problems that need to be controlled.


  1. I will be writing with a question and photos about my problem with borers cutting the bark and killing branches like the problem in the photo.
    I've had spider mites before as Mr. Morris describes and his solution is the best way to go i.e. hosing the dust off once a month. My best investment to aid cleaning the dust off was a power pressure washer, especially with 40 soaring cypress trees in my yard.
    Once a month I save time and a lot of water with the power pressure washer which penetrates and cleans the entire plant beautifully!
    From my experience and the fact that the dead branch in the photo is surrounded by healthy looking branches looks like it was singled out by borers. I was actually intending to submit photos and questions about systemic insecticides to treat for borers to Mr. Morris this week anyway!
    Bob Cardillo, Master Gardener

  2. I have had spider mite problems on my Italian cypress and although the new growth is green, the old growth remains brown. Will this ever clear up?

    1. It depends. If the browning is extensive because of heavy feeding then probably not. If the browning is from light to moderate feeding then it has a good chance of coming back. Growth will be from the tips of all the tiny shoots that are brown. It may take awhile for visual improvement since it grows fairly slowly. Fertilizer and deep infrequent watering will help push new growth. If the brown "needles" crush and fall of when you squeeze it, then it will probably not grow back. Remove stems by pruning deep inside the tree, covering the cuts with outside growth.... hiding the cuts so to speak.

    2. Italian cypress does get borers so look for them in the trunk.