This is a variegated pink lemon tree. The tree seemed healthy through the summer - if a bit twiggy. It bloomed, and held several lemons. There were a few brown spots on the leaves, but it didn't appear serious.

When brought in for the winter, the leaves began showing lots lots of spots, and a significant amount of leaf and fruit drop occurred.

It should be noted that the soil temperature had probably dropped to low. The pot is now insulated to prevent this. The tree has just started a growth flush - probably to replace all the dropped leaves.



Here's a photo of some of the diseased leaves. This is the only tree showing this problem - I have 10 trees that don't show it. The remaining fruit seem unafected.

This tree did come from Florida, so I guess canker is a possibility, but I (not having ever actually seen canker except in photos) don't think it matches the description. The lesions are large, thin, not raised or corky, and the margins are brown, not yellow. Canker looks to be lots of small corky spots.

Any ideas what this problem is and if it is treatable and how or with what?

Thanks for the help,

Pelham

I would first guess sunburn or some sort of chemical (insecticide) damage.

Ned

As a guess, it looks like a condition called Mesophyll Collapse which is a nonpathogenic disorder. The actual cause is unknown for certain. However, it is believed that it can be brought on by drought, or when the leaf loses moisture through transpiration, faster than the water can be replaced by the roots. Mite infestations are thought to increase the risks of mesophyll collapse, also nutritional disorders. The symptoms appear as chlorotic areas on the leaf blade between the midrib and leaf margins, that later turn to a light brown. You can look on the Internet for further information - Millet

Sometime you may want to check out what the behavior of
a molybdenum deficiency in an acid soil is like on Citrus. This
may be applicable to the symptoms shown in the photo.

Snickles