Severe leaf distortion in some South Island trial sites appears to be a direct reaction to aphid leaf feeding since no aphid-borne viruses were detected in affected leaves. Aphid control on young plants is, therefore, advisable. Harvest Plants are harvested in autumn. Tops are cut to about 5 cm above ground level before plants are lifted using a digger that can work to a depth of 30 cm. Shoot residue must be removed before roots are cut into 5-10 cm long pieces and thoroughly washed.
Clean roots are essential to meet quality standards.
Choosing a friable soil with relatively low clay content can make a substantial difference to the ease of root washing. In a preliminary experiment under irrigation at Redbank Research Station, the effect of crop density on production was studied. The high density plots produced greater fresh and dry root yields than the lower density plots, and double the German production. In Germany, the production of foliage is an additional crop and harvesting is undertaken by mowing the plants at 10 cm above the ground. There are no New Zealand data to provide a comparison.