Help identifying pests on Tangerine tree

nathanpb(8)January 29, 2013


I have a tangerine tree in my backyard that had some issues this past season and I am hoping someone can help me identify the cause and best treatment. We live in New Orleans. I took some of the leaves into a couple nurseries but got conflicting advice.

The leaves have a reddish brown rust color throughout. There are also grey spots all over the trunk and branches.

The tree produced very little fruit this year. The few it did produce also had a rust color and some dropped early.

I also have a satsuma tree next to this one that produced just fine but also has some grey spotting on the trunk.

I have been looking at a lot of pictures and am thinking scale or spider mites, judging from the coloration on the leaves? Not sure about the grey spots?

For treatment, we would much prefer oils or biological (for mites), rather than strong pesticides or systemics. We have a one year old who loves fruit :)

Thanks in advance for the advice!


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ken_adrian Adrian MI cold Z5

google lichens for the trunk things.. cant tell from the distance of your pic ...

do you 'see' anything on the back of the leaves???

can we have a pic of the whole tree ...

even evergreen trees lose leaves.. does this seem to be the older leaves.. being shed in winter????

how much shade is this tree in???


    Bookmark   January 29, 2013 at 9:38AM
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Thanks Ken,

I did google lichens and that looks to be the case. Good to know that they are considered harmless.

I will have another look at both sides of the leaves today and include photos. Also of the whole tree.

The tree hasn't really dropped its leaves yet. The discoloration of leaves seemed to be spread throughout but I will have a closer look.

The tree is in partial shade because it is close to the side of our house.

Thanks again. I'll get back with photos.


    Bookmark   January 29, 2013 at 11:01AM
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rhizo_1 (North AL) zone 7

Ken, do you think that the stuff on the leaves looks like black sooty mold?

    Bookmark   January 29, 2013 at 3:52PM
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ken_adrian Adrian MI cold Z5

hard to tell.. looks like aphid poop also .. or is that BSM.. lol ...

is this under the canopy of another tree above???


    Bookmark   January 29, 2013 at 4:09PM
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OK, I had a much closer look at the tree this afternoon and am including some photos in subsequent posts.

Following are photos of the overall tree, close up of the grey spots (lichens?). Also a close up of the discoloration on the leaves and one leaf I found that clearly has larvae of some kind. On close examination, I could see little bugs crawling on the leaves. From a google image search, my best guess is spider mites? I couldn't get a good photo of them.

To answer your questions, this tree is not in the canopy of another. The infected leaves are pretty evenly distributed all over the tree. The tops of the leaves are worse than the undersides.

Any recommendations for treatment?



    Bookmark   January 29, 2013 at 9:38PM
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Photo of underside of one of the leaves. Larvae?

    Bookmark   January 29, 2013 at 9:39PM
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    Bookmark   January 29, 2013 at 9:41PM
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jean001a(Portland OR 7b)

Whoa! Thanks for the close-ups.

The underside of the leaf has a humongous population of scale insects! Poor tree is being sucked dry.

    Bookmark   January 30, 2013 at 12:18AM
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rhizo_1 (North AL) zone 7

Ouch! Amazing what some good pictures can reveal.

    Bookmark   January 30, 2013 at 4:52AM
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ken_adrian Adrian MI cold Z5

boy oh boy ... i guess we ruled out everything else.. though that wasnt much necessary looking underneath ...

on an infestation that bad.. on non-eating tree.. i personally would go systemic ... but that is basically useless on a food tree ...

so horticultural oil it is.. and i would figure out how to NOT spray the building ... maybe clip a tarp to the gutter to insure such.. who cares about the neighbors house.. lol ...

low pressure and large drops .... is usually the easiest way to control drift ...

i would not be surprised.. if it loses a lot of leaves ... the future is in the buds ... so just maintain it properly ... and let it recover.. once you make the kill ... i do NOT favor fertilizing an overstressed tree ... on the thought that it will make it recover faster ... most likely.. a LITTLE of this or that wont matter ... just dont go crazy with fert ... and if its anywhere near a fert'd lawn.. just skip it.. its roots will get what it needs ...

timing of application to suffocate the crawlers is usually the important part of the process ...

often.. the way you discover scale.. is the high number of ants.. milking the scale ... yeah.. disgusting... scale go away.. ant go away ... ignore them ... if any [i hope this isnt a new fog.. lol]


ps: aphid poop??.. today the fog lifts.. aka 'honeydew' ... does scale leave honeydew.. as an aside ..????

    Bookmark   January 30, 2013 at 7:48AM
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Thanks for all the responses. That is really helpful. I will look into the best time to spray oil and get that started.

Ken, I didn't see any 'honeydew' or ants. However, I could actually see the scale insects and larvae.

    Bookmark   January 30, 2013 at 9:09AM
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