Trouble with my Valencia

[lotusblos]

Hi, I just noticed my orange tree has come down with a dark coating on leaves and fruit. This has come on very quickly. Can anyone tell me what it is and how to correct the problem?

[Yorgos]

It's powdery mildew. It's growing on the honey dew that certain sucking insects exude.  You have whitefly, aphids scale or the like. The powdery mildew is a symptom of a bigger issue and is not a problem in itself. You can wash it off the fruit when you harvest.

[Millet]

Yorgos explanation is correct, except the black coating on the leaves and fruit is called Sooty Mold.   You can look up Sooty most on the internet. - Millet

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74108.html

[bsbullie]

The pest which is causing the ultimate sooty mold problem may not be on your Valencia.   It could also be on a surrounding plant such as a palm tree or other nearby tree or shrub.

[Yorgos]

Sooty mold.  Right. Thanks for the correction, Millet. Will sooty mold delay ripening by blocking light on the fruit and adjacent leaves?

[Millet]

Sooty Mold does not directly affect or damage the tree or fruit.  However, if the mold gets to bad, to the point that a majority of the trees leaves become covered with its black covering, it does cut way back on the trees ability to photosynthesize the suns energy.  As mentioned earlier sooty mold grows on the excretions of insects such a scale, white fly and aphids.  Spraying the tree with a good horticultural oil will kill the insects, and at the same time loosen the mold.  Thereafter, a good spray with the hose will wash most of the mold from the tree. - Millet

[lotusblos]

I've had a problem with scale, and I've used horticultural oil on it, but the scale never went away. I found the best treatment was to simply wash off the little critters with a high pressure spray of water. At this time I can't find much scale on the tree. I'll have to take a closer look I guess.

[bsbullie]

I've had a problem with scale, and I've used horticultural oil on it, but the scale never went away. I found the best treatment was to simply wash off the little critters with a high pressure spray of water. At this time I can't find much scale on the tree. I'll have to take a closer look I guess.

do you see any ants on the tree?

[Millet]

Horticultural oil kills scale by suffocation.  It does not remove the dead scale from the leaf but all the scale are dead.  - Millet