Potato Problem
Charlie (plot 22) asked us to have a look at his 'strange' potatoes. He had lifted a plant to see how it was doing and found a sparse crop of potatoes beneath, and these tubers growing from the stem.
Following a lot of research (thank you Google) we discovered that these aerial tubers, as they are known, are definitely not a good sign! The most common cause is a fungal disease called Rhizoctonia Solani - also known as black scurf and sometimes also called stem canker.
The Rhizoctonia disease causes canker to form on stems and underground shoots (stolons) and by late season this damage to the plant causes problems: "Tubers forming on diseased stolons may be deformed. If stolons and underground stems are severely infected with Rhizoctonia canker, they cannot carry the starch produced in the leaves to the developing tubers. In this case, small, green tubers, called aerial tubers, may form on the stem above the soil. Formation of aerial tubers may indicate that the plant has no tubers of marketable quality below ground." - Department of Plant Pathology, Cornell University, New York.
Charlie is not going to be pleased when we tell him! The disease was probably brought in on infected seed potatoes but is transferred through the soil, which can easily become infected. The fungus causes more damage if the seed potatoes have been planted into cold, wet soil.
Currently, there is no completely effective control of this disease. General advice seems to be to practice good crop rotation and not grow potatoes in the infected area of soil for at least 3 years. Particular care also needs to be taken not to transfer the soil to other areas of the allotment and to practice strict hygiene with tools - especially rotavators.
As with any diseased plants, the affected material should be burned as soon as possible. This is also a good reminder that anything out of the ordinary needs to be treated as a danger until a proper identification can be made. Thankfully, Charlie has done the correct thing in showing and discussing this with other people but has kept it on his plot and not gone wandering around the allotments with it.
Following a lot of research (thank you Google) we discovered that these aerial tubers, as they are known, are definitely not a good sign! The most common cause is a fungal disease called Rhizoctonia Solani - also known as black scurf and sometimes also called stem canker.
The Rhizoctonia disease causes canker to form on stems and underground shoots (stolons) and by late season this damage to the plant causes problems: "Tubers forming on diseased stolons may be deformed. If stolons and underground stems are severely infected with Rhizoctonia canker, they cannot carry the starch produced in the leaves to the developing tubers. In this case, small, green tubers, called aerial tubers, may form on the stem above the soil. Formation of aerial tubers may indicate that the plant has no tubers of marketable quality below ground." - Department of Plant Pathology, Cornell University, New York.
Charlie is not going to be pleased when we tell him! The disease was probably brought in on infected seed potatoes but is transferred through the soil, which can easily become infected. The fungus causes more damage if the seed potatoes have been planted into cold, wet soil.
Currently, there is no completely effective control of this disease. General advice seems to be to practice good crop rotation and not grow potatoes in the infected area of soil for at least 3 years. Particular care also needs to be taken not to transfer the soil to other areas of the allotment and to practice strict hygiene with tools - especially rotavators.
As with any diseased plants, the affected material should be burned as soon as possible. This is also a good reminder that anything out of the ordinary needs to be treated as a danger until a proper identification can be made. Thankfully, Charlie has done the correct thing in showing and discussing this with other people but has kept it on his plot and not gone wandering around the allotments with it.
Submitted by Tigger
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