What is this? I found it underneath several leaves on a lemon tree.

March 14, 2009 7:40 PM

What is this? I found it underneath several leaves on a lemon tree.

Is this a mold or bacteria? Or are these some kind of insect eggs? Is my lemon tree in trouble? It has blossoms, and new growth, but i've found this underneath several leaves (none of which are new growth.

posted by tdischino to home & garden (9 comments total)

It looks like immature Scale to me.
posted by The Light Fantastic at 7:48 PM on March 14, 2009

Looks like some kind of fungus to me.
posted by delmoi at 7:48 PM on March 14, 2009

Possibly wooly whitefly.
posted by Balonious Assault at 7:51 PM on March 14, 2009

I thought it looked like some kind of wooly aphid, but this site says :

Q. I have a Meyer lemon tree indoors and it has cotton-looking or woolly aphid feeding on the leaves. I do not want to spray pesticides inside my house. What do you suggest?

-- C.R., Seattle

M.B.: Mite, aphid and scale are common pests on lemon and orange trees. I suspect you have mealy bugs or even cottony scale instead of woolly aphid. Wash these off with a mild soap like Ivory liquid and rinse well. If the lemon tree is large, get friendly and take it into the shower with you. The cottony or fuzzy pests will come back after the first washing when new eggs hatch. Use a cotton swab dipped in rubbing alcohol to dissolve the white protective covering and dry up all colonies of the scale or mealy bug. Do not paint the entire leaf with the rubbing alcohol, only the pest itself. Citrus plants also need as much sunlight as you can possibly give them in the winter.
posted by HopperFan at 7:53 PM on March 14, 2009

I should have mentioned, this is an outdoor tree (and it's really more of a bush than a tree), in the ground. I don't know what specific breed (species?) it is, it produces fruit that is a perfect Meyer lemon, and also produces a rounder fruit that my wife and I call a lem-orange, and it is a very mild and sweet lemon.

Now that I have some ideas of what it is, i'll google treatments for these. Thanks!
posted by tdischino at 8:06 PM on March 14, 2009

Hard to tell from the blurry pic but it might be cottony cushion scale.

Do you notice it only on the lemon part of the tree? (From your description it sounds like the tree is grafted with multiple citrus)

See: http://www.ipm.ucdavis.edu/PMG/r107301611.html
posted by bengarland at 8:44 PM on March 14, 2009

Err: Cottony Cushion Scale
posted by bengarland at 8:45 PM on March 14, 2009

Sounds like the tree is a graft. Is the growth on leaves of the Meyer Lemon producing side or the lemorange side, or both? My guess is that it was supposed to be a Meyer lemon tree and the lemornges are growing from a "sucker," or branch from the root stock (which was was grafted in for its root properties and not intended to produce fruit.) If you don't particulary care for the lemoranges you could remove those branches and theoretically get more/better Meyer lemons from your tree.
posted by contraption at 10:17 PM on March 14, 2009

The image most certianly looks like cottony scale. Neem oil is highly effective for dealing with scale in citrus, and it's organic. To be successful it needs to be applied where the scale are, including under the leaves and into those curled under leaves.
posted by X4ster at 7:39 AM on March 15, 2009