Monday, May 7, 2012

Citrus With Some Mussel

I already know what you are thinking, this guy really goofed up this time.....that is not how it is spelled. Just hang with me for a minute, all will be explained.
I am tickled to death that my name has gotten around the internet as much as it has. Now mind you, I live in North Charleston, South Carolina. I got an e-mail from a very nice guy out in San Diego, California. He came across my name and blog trying to diagnose what he thought was a very serious problem. He was afraid that he had Citrus Scab.
Just so you know, Citrus scab, which is caused by the fungus Elsinoe fawcetti, affects the fruit, leaves, and twigs of susceptible varieties of citrus. It can be particularly severe on lemons, Temples, and Murcotts and on Minneola tangelos. It is often a problem on grapefruit, but rarely occurs on round oranges. Sweet orange is generally only infected if trees are located very close to infected trees of other varieties. His problem was on a Valencia Sweet orange. Never underestimate the information that somebody is trying to get when diagnosing a problem, it being a Valencia was VERY important here.
Anyway, this is the picture that he sent me:

I want to be honest here. I knew it was not Citrus Scab, but I did contact a couple of my Citrus buddies to make sure we had a positive ID.
It turned out to be Lepidosaphes beckii, Citrus Mussel Scale. This type of scale also goes by the names, Purple Scale, Orange Scale, Comma Scale and Mussel Purple Scale. This scale is highly specific to Citrus, rarely to never being found on any other plant.
This is one of the most destructive insect pests of Citrus throughout the world. The small insects attach themselves to leaves, fruit, and small branches causing injury by sucking the tree's sap. It is of Oriental origin, which makes sense because Citrus is of Oriental origin. It poses major problems for Citrus in Central and South America, South Africa, Australia, Hawaii, Florida, Texas and California.
If you put a magnifying glass to this pest, it would look like this:

Photo courtesy of University of Georgia

The 1/8 inch adult female lays eggs under its mussel-shaped scale and up to four generations may occur annually. Damage to fruit occurs in heavy infestations, where spotting and often deformity of fruits affects market value. Areas surrounding scales remain green long after the rest of the fruit ripens. Another good way to tell if you have a problem is, if there are ants having a big old parade up and down your tree, start watching for scale. Ants feed on the sugar secretion that scale puts out. They also often defend scale insects from predators and parasites.
Control is difficult. That coat of armor that they wear protects them from most insecticides. Scale insects are most vulnerable at juvenile or ‘crawler’ stage; however they are also very difficult to see. The use of a horticultural oil is your best bet. Ideally, good spray coverage during plant dormancy or when crawlers are active is the key to successful control of scale. Bark as well as foliage should be treated.
Trees that do not have a dormancy period i.e. citrus are best treated when crawlers are active in Spring and again at the end of Summer. Spot treatments may also be required until infestation is under control. It may take 2 to 3 years before the infestation is properly managed and the affected tree shows signs of recovery.
There are some natural enemies of scale, they include parasitical wasps, lady beetles, spiders, lacewigs and predatory mites. Small birds also feast on scale. Beneficial insects can be bought and released to control scale. You might want to remember that beneficials will die if released onto leaves that have been treated with insecticide.
For my e-mail friend in San Diego he was relieved it was not Scab, However it sounded like he had a pretty bad infestation.......His work has just begun.
Happy Growing!


  1. Thanks so much for posting this! I've been scouring the Internet trying to figure out what these are. I'm in San Diego as well; seems to be pretty common!

    1. I found your post today after inspecting my lemon tree after the frosts of late. Thank you for the photos and all the information. I think we'll need a lot of that oil. Any recommendations on a brand or specific product?

  2. Thank you. I too have been trying to identify the pest on my Meyer lemons. The tree seems healthy and as long as I don't want to grate the lemon peel for anything, all is good. Still, I would like to get rid of them, thus I needed to identify them. You have been very helpful. If anyone is interested, my tree is on the border of L.A./Orange County, CA.

  3. I am so glad I stumbled on to this blog! What a great blog. I too am in Southern CA in a beach area and have noticed these weird "things" that looked like strawberry seeds on the tops of my oranges and some of my grapefruit. We bought our home about 3 years ago and with it came two big citrus trees that I believe may be as old as the house (built in 1929). I really didn't pay too much attention to them the first year; pruned and fertilized the second year and now I'm seeing what must be purple scale. I am so bummed. It looks like it has gotten worse. Right now it is in the low 80's high 70's - is it too hot to treat with oil? How do I get up high enough to reach the top? I would be heartbroken if either of the trees died on my watch.We've been juicing the oranges and grapefruits and now I'm wondering if it is safe to eat them if they have scale? I clean and peel them, but now I'm paranoid! I've never used a pesticide on the tree so all of the fruit is organic. So I would prefer to use an organic treatment.

    Here are some photos for reference:

    I've been donating roughly 800-1000 lbs of fruit every to a program that serves the needy. I really hope I have exposed anyone to anything dangerous to their health.

    1. Hello Anonymous, Thank you for those kind words! I am glad you found my blog and enjoy it.
      Yes, it is probably a little too warm to spray oil. If you can do it on a cloudy day, or possibly late in the evening after sunset and it is a cooler (relatively) day, that would work. To get to the top, a ladder or pressure sprayer would work.
      They are perfectly safe to eat. Especially if you clean and peel them, no issues there what so ever.
      That is very awesome that you donate all of that fruit! Again, it is perfectly safe, you have not even come close to hurting anybody. If you use Neem oil, it too is safe and works very well.
      How serious is the scale problem? If it is not too severe, it may not harm the tree. It won't hurt to wait until it cools off.
      As a side note, your trees are ABSOLUTELY BEAUTIFUL!!! I sighed when I saw them.
      Thanks again for the kind words and good luck with the scale.
      Happy Growing!

  4. Thank you so much for answering my questions so quickly!

    The scale seem to be hit & miss - some of the oranges are covered on top and others aren't. I will try to pressure wash them as much as I can (we are in a pretty bad drought) and closer to fall I will spray with neem oil. Hopefully that will help.

    Awesome blog - thanks again!

    1. I'm curious if you ever got rid of the scale. I live in la mesa and have them too! MY orange is about 25 ft tall so I cant get to the top of it to spray, and the scale is patchy, heavy in some parts of the tree and nonexistent in pothers. I also want to donate, we have so much fruit this year!

  5. Yes, thank you so much, been searching for what the heck this is for some months. I'm also in San Diego and have noticed that it spread to an orchid I have in my kitchen where I wash my oranges. Going to stop composting the the rinds too :(

  6. Ahhhh mystery solved! My lime tree has these! So glad to get an answer. I’m torn as it’s next to our chicken coop so I don’t want to spray anything. I’ve been trying to wash the limes and knocking off each bugger! Ugh. I miss many. I’m in Santa Barbara

    1. Jan, Neem oil would be safe to use around the chickens.