Citrus Growers Forum

dauben · Posted: Tue 29 Jul, 2008 11:20 pm

Well, I noticed a branch with some leaf discoloration and I guess I'm kind of like the person who has a headache that swears it must be a tumor. Since Citrus greening isn't technically here in Southen California yet, I thought I'd run these pictures by the experts here in the rare event that I happen to be the first case and they need to cut my tree down. Diagnosis anyone? The tree is a non-varigated Rio Red Grapefruit.

Phillip

Millet · Posted: Wed 30 Jul, 2008 12:30 am

I don't see anything wrong with your tree. Perhaps just a little mesophyll collapse brought about by soil moisture stress accompanied by hot dry winds. Nice looking tree. - Millet

dauben · Posted: Wed 30 Jul, 2008 12:56 am

Millet wrote:

I don't see anything wrong with your tree. Perhaps just a little mesophyll collapse brought about by soil moisture stress accompanied by hot dry winds. Nice looking tree. - Millet

Ahh, the dreded mesophyll collapse. I should have known. I'll have to quarantine all my trees . . . innoculate the seedlings . . . run for cover . . . only to be eaten alive by a 5.6 earthquake. We're doomed!!

Okay, okay, I had to look it up. For those of you like me who don't know what mesophyll collapse is, here's a synopsis:

Quote:

Mesophyll Collapse

Mesophyll collapse is a non-pathogenic disorder of citrus of unknown cause. Leaves of both oranges and grapefruit are affected. The disorder begins as translucent, irregular areas of different sizes scattered throughout the leaf blade. One or more light green spots may appear, later turning brown as cells within the tissue die. Only the soft tissue inside the leaf between the veins (mesophyll) collapses at first, giving these areas the translucent appearance. Palisade and epidermal tissues are unaffected initially but may die later.

Symptoms appear readily following periods of low soil moisture and hot dry winds. For this reason, water deficiency is often thought to cause mesophyll collapse, but mite feeding, damaged root systems and excessive transpiration also are associated with mesophyll collapse. Nutritional imbalances also are implicated in mesophyll collapse of citrus.

Thanks Millet!! I'm glad to hear that I'm safe. For now . . .

Phillip