Infestation of Heterodera schachtii on sugarbeet storage roots
AbstractStudies on the parasitism of the sugarbeet cyst nematode, Heterodera schachtii Schmidt, indicate that this parasite attacks the feeder roots of the sugarbeet (Beta vulgaris L. var. saccharifera Alefeld). Franklin (1951) observed that sometimes a few females may also occur on the tap roots and Steele (1971) found larvae of the nematode inside sugarbeet seedling tap roots, but not in large or fully grown tap roots. He used slices of storage roots as a substratum to culture H. schachtii and noticed that the nematode did not develop on tissues close to periderm (Steele, 1972). Therefore he assumed that the periderm might act as a barrier to the nematode and that infestations observed in large tap roots could have been facilitated by the parasitic action of fungi and bacteria which overcome the periderm defence. Other attacks of the sugarbeet cyst nematode on storage roots were observed in Northern Italy (Tacconi, 1977, personal communciation) and in the Fucino area in November 1976. Heavy infestations were again noticed in October 1977 on mature tap roots harvested in the same area. Several large storage roots were completely covered by a layer of white females and cysts, while in others the infestation was confined to a restricted area (Fig. 1). When the roots were pulled from the soil few nematodes remained attached which might explain why the infestation of the storage roots is often overlooked. Because of the heavy infestation detected on the storage roots further investigations have been conducted on the damage caused by this nematode on the host tissues.