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Wednesday, May 27, 2015

Controlling Spider Mites in Italian Cypress

Q. I have three Italian Cypress trees that are 20 feet tall.  I have a problem with spider mites and want to know the best way to reduce their populations.  I started spraying them with high pressure water and it got rid of all the webs. Since the trees are so tall I cannot effectively apply a pesticide using my Ortho sprayer and garden hose.
Webbing in Italian Cypress does not always mean spider mites. You need to do the paper test explained below to see if mites are the problem or not.
A. How did you confirm that the problem is spider mites? They are easy to misdiagnose and there are problems that can appear like spider mite problems and they are not.

For instance, not all spider mites create webbing and not all webbing in Italian Cypress means it has spider mites. You can find webbing in Italian Cypress from spiders that are actually good guys and helping you out.

Spider mites normally occur during hot weather. We seldom see them during cooler weather.
An Italian Cypress which has spider mites will have the green needles or foliage beginning to die or turn color, usually grey first. If I look at these needles they will have a dusty appearance if spider mites are present.

Spider mites are extremely small. This one is highly magnified.
They are about the size of the dot at the end of this sentence .

This isn't dust but these are dead spider mites that litter the surface of the foliage. If I see Italian Cypress with dusty needles or foliage I begin to think they might have spider mites. The way I usually determine if spider mites are the problem is to take a white piece of paper and slap the branch of Italian Cypress against the paper pretty hard. This dislodges the spider mites from the foliage and onto the paper.

I then hold the white piece of paper in bright sunlight very still for 15 to 30 seconds. If mites are present, I will see tiny little dots the size of a large period crawling around on the paper. If I brush my fingers lightly across this moving dot on the paper, I will see red smears on the paper.

If the Italian Cypress appears damaged, the foliage or needles appear dusty and I get red smears on the white piece of paper I will conclude the damages from spider mites.

Soap and water sprays are somewhat effective if done on a regular basis (couple of times during hot weather or after a dust storm) as a preventive. Otherwise you would have to apply a miticide effective against spider mites for good control. You would apply two applications about ten days apart to control the hatching of young mites from eggs which are not controlled with the first spray.

Unfortunately this would require that you spray the entire tree if mites are a problem. It is really hard for homeowners to spray much above 10 feet. I do not know of any miticides that you can apply to the soil and get good control.

First, make sure the tree has spider mites and that is the problem. Insecticidal soaps are good first choice but they are not extremely effective in controlling this pest. If you do get it confirmed that it spider mites and they are out-of-control, you will have to spray miticide. Watering Italian Cypress too often causing root disease problems can give them a similar appearance as branches begin to die.

Spraying trees above 10 feet is difficult for homeowners. Pest control operators and arborists have equipment to do this.

3 comments:

  1. Would azadirachtin soil drench kill spider mites? I'm not referring to neem oil but to azadirachtin, active ingredient in products such as Azaguard, Azamax, Azatrol and others.

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  2. Thank you for this informative article.
    Would azadirachtin soil drench help fight spider mites when it's impossible to spray?
    I don't mean need oil, which is effective only as spray, but azadirachtin the active ingredient in products such as Azamax, Azatrol and others. I've read azadirachtin is systemic, is taken up by the roots and moves upwards in the tree. Would greatly appreciate your comment on this.

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    1. I have used neem products for years because of the marketing and encouragement of its use on the Internet. I have had mixed results. I will admit I am not a huge fan of neem products but I use them in rotation with other things like soap, oils, Spinosad, Bt and pyrethrin depending on the insect problem.

      I don't know the products that you're mentioning by name.I will tell you as much as I know about neem and its use under the circumstances that you mention. This is a product that has a lot of hype. It is systemic but is considered mildly systemic. It decomposes fairly quickly and sunlight. It is considered a good product repelling insects feeding on plants whether it is used as a foliar spray or applied to the soil as a root absorbed systemic. I could not find any solid recommendations using it against spider mites. It has a reputation for having erratic control of pests. For instance, it can control locusts but not grasshoppers. This is probably because the source of azadirachtim is not regulated in neem products or it could be the insect themselves. It might also be because of the insect and how it feeds. For instance, it has a reputation for controlling some aphids but not others. This makes it very hard to recommend and doesn't give general users much confidence. There is a lot of garbage out there. Some people swear by it and other people like me are on the fence. I can't tell you to use it unless Italian cypress or ornamentals and spider mites are on the label. It is up to you whether you want to try it or not.

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