October 2007. Cassava plants in a plot in Pohnpei, Federated States of Micronesia, show a blister-like condition on the stem. All the plant in the plot were said to be affected, whereas older plants in an adjacent plot were healthy.
Two suggestions were made:
1. The plant is normal above and below the symptoms suggesting that something damaged the growing point and very young tissues at an earlier stage of growth and it has grown out of it. It could be chemical damage, especially if all the plants have it in the same position on the stem. Did the grower apply any chemical to the plants a month or so ago?
2. The symptom has some similarities (not many, it must be emphasised) to Amblypelta damage seen in Solomon Islands and Papua New Guinea (photo: bottom, left). The similarity is the severity of the damage and its location. However, with Amblypelta, bubbles/granules are not seen. Ambypelta damage causes severe lesions to cassava stems as if a poison had been injected, i.e., a chemical burn. As well as looking for a chemical cause, it might be worthwhile checking, when it is cool (morning or evening), for a hemipteran bug feeding on the stems.