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Monday, October 10, 2011

Junipers Not Ideal Choice for Desert Landscapes and May Have Some Problems

Pictures of carpet juniper with needle drop from reader
Q. Please advise and diagnose how to resolve a problem I have with my juniper bushes. I hope my pictures help.

A. From your pictures the juniper appears to be one of the very low-growing carpet junipers, not sure which one but perhaps green carpet juniper. These carpet junipers can be confusing and can be from several species. Which juniper is important as some junipers are more heat tolerant than others.

            J. horizontalis has among its cultivars probably one of the better heat tolerant rug-type junipers.  Regardless, junipers will do better in this climate if not put into extremely hot environments and surrounded by rock. They usually can handle some of the poorer soils that you can develop in rock landscapes at least for a few years if not more.

            Probably the biggest problems will include not enough water or not watering frequently enough, salt problems and spider mite infestations. Watering too frequently (daily) can cause root rot and death of the plant.

            Make sure there is at least one day between deep waterings during the heat of the summer. One plant will probably require around five to ten gallons per watering. You can determine this by checking your drip emitters for the gallonage per hour and adjusting this amount through the number of emitters per plants multiplied by the fraction of the hour that it remains on during one irrigation.

            Spider mites are a problem on junipers. They are not insects but are more closely related to spiders. They are very small and not seen easily with the naked eye. Their feeding results in speckling or yellow spots on needles. Some needles may turn brown and drop off.
Two-spotted spider mite

            With heavy infestations, fine webbing may be seen on the plant. If not controlled, spider mites can kill junipers. Most spider mites increase in numbers during hot, dry weather.

            Naturally occurring enemies of mites will usually suppress mite populations. Since insecticide use kills these enemies as well as mites, insecticides should be avoided unless absolutely necessary. Miticides, labeled specifically for mite control, are less harmful to these natural enemies. Mites can be removed with a strong spray of soap and water, if applied on a regular basis.

Webbing due to spider mites
            To determine how many mites are present hold a white sheet of paper under a branch and slap it on the paper. The mites knocked off on to the paper will be seen crawling around as tiny spots the size of this period. If dozens of mites are seen crawling on the paper it is time to do something.

            Pesticides labeled for homeowner use against spider mites include insecticidal soaps like Safer Insecticidal Soap or Ortho’s Systemic Insect Killer. As with any pesticide, read and follow all label directions and precautions before using.

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