Spud Special: Watch out for black dot at harvest

As always the weather provides us with some real challenges. If it’s not too wet then it’s too dry.


One good thing is that the recent dry spell has helped reduce the spread of bacterial rots, with the main problem now being bruising and how to avoid it. Carrying soil on harvesters is proving difficult at times, if not already doing so can you use a smaller web? Keep the harvester full if you can, even when turning at the row ends.


Despite most soils being drier than normal during tuber initiation there are now reports of black dot development on high-risk packing crops. Periods of stress may have physiologically aged the crop, possibly resulting in early senescence of the canopy.

Although crops have a massive baker content this ageing of the crop may have led to possible early development of black dot in some susceptible varieties, like Estima, Maris Piper, King Edward and also some of the newer packing varieties.


Crops should be assessed at harvest for black dot infection. First signs of infection are usually just the sclerotia (tiny black dots) commonly seen in patches near to stolon attachment to the tuber. If the infection has not progressed further than this at time of harvest, then rapid pull down to below 4C within a month should minimise further development and enable long term storage subject to skin finish.


If the tuber skin in the infection area has already started to discolour then temperature control will not be able to prevent further disease development. Early crop movement will be needed to meet required packing quality standards.


With the recent high temperatures, early sprouting in some varieties in store and even in field prior to harvest may be an issue. The early planting combined with physiological stress possibly accelerating the chronological age of the crop means that there is a strong probability that eyes will open and sprout development will occur earlier than usual in store. This will mean an early commencement to sprout control programs in order to optimise control. Therefore monitor stores closely.

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