I was working out amongst the citrus trees earlier this month, and noticed that my Delta Sweet Orange on C-35 rootstock has what appears to be foot rot (Phytophthora). You might be able to see a vertical lesion in the trunk, which is about 2 inches long and runs to the soil line. It isnt real moist or gummy, and the canopy of this five year old tree is very healthy.
As much as I have seen this disease on other's trees, I have never attempted to treat it. Since making this discovery, I have double diked the water basin so no water will ever touch the trunk when I irrigate. I have read where I should remove the loose bark and paint the wound with Bordeaux solution. Is it likely that this disease will go away on its own? When should treatment begin?

Usually, foot rot frequently, has some quantities of gum being exuded. However, the vertical crack is but only a couple inches. Many times if it is foot rot you should see a dark sooty looking color when you scrape the bark away to remove the surface layer. - Millet

Perhaps it isnt foot rot, but just a natural split occuring. There was no gum or black discoloration. I have always seen this disease at its peak, and never have really taken notice of early symptoms. Ill just keep checking it out and hope it isnt foot rot.

Looks like a lot more damage than just the split. I think you might have a significant problem there.

I guess I should say why I think there is a serious problem. I see more than the split. A large area around the split seems to be sunken in. This indicates to me that the underlying wood is dead. I am not sure about the technical term, but I would call this foot rot. Foot rot or not, it may threaten the life of the tree if not addressed. You can check this out with a good stiff knife, by probing the area, working back from the split. Once you know the extent of the damage, you can plan how to deal with it.

Ned

Hello,

well, the picture isn't clear enough, in my opinion. The dirt around the stem is clear, but the trunk isn't in focus, so here some inches count.

So if the bark around the 'lession' is sunken or not, I cannot see this....


So I would advice to carefully cut the rind around the lession, and 'open' this wound... See if the cambial layer below the rind is dark.
Because often foot rot will not cause gummi sap appearing, because the lession is to fresh and he deal with a high tolerant rootstock.
So here the growth of the cambial layers will insulate the fungal growth and block it from to servere spread, but lesions may occur (compare: Compendium of Citrus Diseases, APS Press, 1. and 2. Edition)

So to determine, the crack should carefully observed and the rind should be cut with a sharp knife, and if there is a lession found, a bordeaux mixture may help, but Fosetyl-Al is more promising against phytophthora fungal infections, so I personaly recommend the later.

I agree with Steve about the picture. Cleaning the area a taking a clearer picture would be helpful, but personal observation is the best way to evaluate the problem I have had to deal with what I believe to be foot rot with one of my trees, and, it my case, I saw no sap.

Even though the picture is not clear, it still appears to me that the area around the wound is sunken, or at least does not appear to be the bark of a healthy tree.

Ned