We’re living central Haiti at 1500m. One of the predominant crops in our area are sweet potatoes but it’s our assessment that there is a lot of room to improve yields here. Sweet potatoes are so suited for our climate that they actually grow as weeds here. Once a field has been planted in sweet potatoes it will always have sweet potatoes.
One problem that we’re having is that a certain percentage of the roots are infested with a mystery disease. I have seen any insects. When you cut into one of the sweet potatoes it’ll have black streaks throughout it. If you happen to cook one by accident it VERY bitter and tastes incredibly toxic. Our neighbours’ sweet potatoes have the same issue. The picture below is of a particularly bad sample.
Thanks for sharing photos. I have an initial thought based just on the pattern on the damage but photos of any lateral roots and the outside of the tuber would help confirm or deny my thought. Do you have any photos of the roots and of the outside of the tuber?
I don’t still have this particular sweet potato. I actually took this picture a few months ago when I found this particularly bad specimen. I will keep my eye out for another one that I can take a picture of. I can say though that I have not been able to identify good sweet potatoes from the bad without cutting into them. With some batches that we’ve bought from neighbours we’ve had to cut into them all rather than boiling them whole just simply to avoid getting a mouthful of bad sweet potato.
I have noticed recently that some of the leaves that are growing on various plants around our place seem to be infected with something. I don’t know yet if there is a correlation with the bitter root problem but I’ll put a picture here. It might be a red herring though. Also some sweet potatoes seem to develop a waxy, black coating that I usually peel off but again I haven’t correlated that with the bitter taste. I can also try to add a picture of that here when I find it.
To be honest, the first photo you sent reminded me strongly of what root-know nematode damage looks like on the inside of banana corms when you cut them open, but if you don’t see scabby lesions on the surface of the sweet potato tubers, I don’t think it could be caused by RK nematodes. They need an entrance into the tuber and would leave a mark on the outside. From what you are describing, I do think that it’s a soil pest/pathogen and that the leaves you photographed are a separate issue (not a bad one by the looks of it as it is affecting <30% of the leaf surface).
I’ve recently connected with some of the sweet potato experts at CIGAR trying to ID a variety in Central Africa. I’ll ask them to look at your photos to assit with a possible diagnosis!
