Potato

Project managers: Jannie Hagman¹  and Björn Andersson, Department of Crop Production Ecology, SLU.

Potato is easily attacked by leaf blight, particularly in organic growing where the potential to control the disease is limited. When potato is attacked by leaf blight, the haulm must be killed to prevent the disease spreading to the tubers, soil and the surroundings. Once the potato haulm has been killed, the plant can no longer continue to store carbohydrates and tuber growth ceases. The time of the attack is thus very significant. If it occurs early in the season, the yield losses can be very great.

The aim of this project is to determine growth curves for different potato varieties, in both fresh crops and in crops affected by leaf blight. The intention is to use these curves to calculate the effects of various degrees of leaf blight attack and to calculate the size of the tuber yield at different times during the growing season. This can be done by taking continuous harvests during the season. The trial is a type of harvest investigation. The first harvest is taken when the largest tuber is approx. 30 mm and harvesting continues at least once a week for a total of 12 harvesting occasions.

The experiment includes three different potato varieties with different susceptibility to leaf blight - Fresco, Matilda and Escort. These different varieties have different rates of development and yield capacity. Fresco is an early variety that is very sensitive to leaf blight. The disease develops rapidly, but since Fresco is an early variety the tubers have time to develop a relatively long way before growth is interrupted. The variety Matilda is somewhat more resistant to leaf blight than Fresco. Escort is a variety with good resistance to leaf blight and can often escape attack right up to harvest. To allow tuber development to be assessed in a healthy crop to full maturity, the trial includes a treatment with chemical control of leaf blight.