Citrus scale

I’ve been spending the day answering gardening questions and thought some of these are worth sharing.

Question from Marblehead, MA: I have rust colored insects attacking my Meyer lemon tree plants. The leaves are sticky and blackening. Can you please recommend a treatment?

Answer: Citrus plants are susceptible to scale, which is the problem with your lemon tree. I have two approaches, both which are effective and non-toxic. The first is to wipe off the scale from leaves and branches with a piece of gauze soaked in rubbing alcohol. Depending on the size of the plant this may or may not be practical. Neem oil does an excellent job in treating scale. A small amount of oil is combined with water and applied from a spray bottle. We offer for sale and recommend Dyna-Gro Pure Neem Oil.

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7 Responses

  1. We have orange and lemon trees which are infested…infested with scale. I am not sure what kind of treatment is required and washing all 6 very mature trees (30 years old at least) would take me a very long time. What would you recommend to treat them and at what time in the growing season…I don’t mind losing a crop if it means these trees will profit and keep our garden the joy that it is. Thank you in advance, Monica

  2. Thirty year old trees are far too valuable to lose and you should treat when the problem appears. My first choice would be a spray of neem oil (azidactrin) properly diluted according to package directions. You can combine this with an insecticidal soap for better coverage. You will probably need to repeat treatment in one week if scale persists. If you cannot locate a neem product use horticultural oil to smother the scale.
    Examine plants for the presence of ants. They set up farming operations to collect the sweet secretions from scale and will spread the scale as well as attack predatory insects. If your trees are planted in ground you may wish to carefully wrap or paint the trunks with some type of sticky barrier. These are remedies that won’t be toxic to you or the environment.

  3. We have a fairly young meyer lemon tree and a key lime tree. They both have been producing fairly well but both have rolled up leaves with some kind of cocoon in it. It hadn’t affected the fruit until this year. Some of the fruit is blighted and some turn black and never get any larger. I read your remedy for scale but this seems to be an insect. Any ideas would be appreciated.

    • It sounds possibly like citrus leaf roller which can damage fruit. If the plants are truly small I would wash each leaf that shows signs of infestation. For a larger tree Bacillus thuringiensis is a suitable remedy. I highly recommend you take a damaged fruit and an infested leaf to the Master Gardener desk at your local extension office. Since you live in Texas they will be able to identify the problem. It’s a good idea to place the samples in a ziplock type plastic bag.

  4. My husband inherited a 30 yr. old lemon tree when his grandfather died. We live in the Chicago area and bring it indoors in the winter. Every winter indoors, it gets scale, which I have treated with pyrethrin based Garden Safe vegetable and fruit spray. It usually cures the plant after several applications. This time, however, I have sprayed it on everyleaf front and back and the branches and checked it every day, and every day new little brown scale are on some of the leaves. I thought the spray was supposed to kills bugs and their eggs on contact. Any advise would be greatly appreciated. Thank you.

    • For scale on a small citrus I clean with a piece of absorbent fabric soaked in rubbing alcohol. Gently wipe every evidence of scale away and repeat in two weeks or as necessary. For a large plant horticultural oil is your best remedy. You can apply with a hand spray bottle. It is quite effective as it smother the insect. Follow directions and repeat if necessary. A thirty year old tree is valuable, aim for excellent control instead of total eradication. Pyrethrin sprays are not particularly effective.

  5. [...] Citrus scale « The Gardener’s PantryMar 15, 2007 … Monica Perin, on October 20, 2007 at 1:41 pm said: We have orange and lemon trees which are infested…infested with scale. I am not sure … [...]

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