The project examines factors influencing black dot development to help identifying crops at risk to reduce symptoms development through early harvesting.
One option for the management of black dot is early harvesting, which reduces symptom development. In order to select crops for early harvesting it is essential to know which crops are likely to be at risk by examining the factors influencing BD development. The research has shown that the ability to predict the risk of black dot occurring varies with potato variety. The methods of haulm destruction and the different storage conditions studied during the project did not effectively reduce the development of black dot.
Observations were made over 3-year study to try predicting black dot (BD) development on harvested tubers by assessing stems and stolons for the presence of the disease in 124 potato crops and related to the disease on the tubers at harvest. In some years significant associations were observed in some cultivars. In 2000 and 2002 in the cv. Estima if stems or stolons showed black dot symptoms as the crops were starting to senesce then the disease was likely to be present on tubers at harvest. In cv. Maris Piper a significant association between black dot on stems in September 1999 with disease at harvest was observed. No relationship between black dot on stems and stolons in the growing crop and disease on tubers at harvest were observed in the cvs. Saxon and King Edward. To explain these results a glasshouse and field experiment were performed to identify when symptoms of black dot develop on underground parts of a potato plant. These showed that infection by C. coccodes could occur soon after these plant parts had formed. Visual symptoms did not appear till just prior to senescence on stems and stolons and during senescence on tubers. Methods of haulm destruction and different storage conditions did not effectively reduce development of black dot on tubers. Reasons for this and its commercial implications are discussed.
