When actively sprouting tubers are planted in a cold soil, as is largely the case with early potatoes, there may be non- or late-emergence due to abnormal growth of the sprouts (coiled sprouts), which may even have difficulty getting though the crust of a soil compacted by heavy rainfall. These conditions also favour attacks of black scurf on the sprouts.
Coiled sprouts are also encouraged by an over-incubation of the seed tubers. This phenomenon is often accompanied by swellings in the underground part of the stems revealing hollowed-out pith and sometimes longitudinal cracks (photo 1).
- Seed potatoes should be kept in a cold room until pre-sprouting so as to prevent too rapid an incubation.
- In the pre-sprouting room, growth should be held back by homogeneous lighting of the seed potatoes from the “white dot” stage.
- Planting should not be done too early in a cold soil.
After several months’ storage at a temperature above 6°C, the flesh of some tubers may have internal sprouts (photos 1 and 2). This anomaly is due to the sprouting inhibitor (CIPC) which is inefficient when applied to tubers close to the dormancy break.
This may happen with an under-dosage of the quantity of active ingredient or when the second treatment has been applied too late.
This risk is clearly increased when, simultaneously, the storage temperature is not properly regulated and/or is abnormally high.
Excessive tuber incubation may also cause the same anomaly.
The right doses should be applied with each sprouting-inhibitor treatment. This should be applied by thermofogging, at regular intervals using the recommended quantities and according to the effectiveness of the previous treatment.