Assessing The Impact Of Carrot Cyst Nematode On SA Production

The impact of carrot cyst nematodes on local production was studied by North-West University MSc student, Adoration Shubane. Her co-supervisor, Dr Antoinette Swart of the Agricultural Research Council’s Plant Protection Research Institute, reports on the research findings.

- Antoinette Swart

The carrot cyst nematode, Heterodera carotae, has never been studied under African conditions despite having an unquestionable impact on local carrot production.

The carrot (Daucus carota L.) is cultivated worldwide for the fresh market and processing industry. In South Africa, carrots are one of four major root and tuber vegetable varieties consumed.

Cyst-forming nematodes, or parasitic roundworms, are defined by their capacity to retain eggs inside the swollen female body, which is transformed into a resistant, tanned cyst that protects the embryonated eggs after completion of the female’s life cycle. The infective juvenile (J2) emerges from the cyst when it detects root secretions from the growing host. It then enters the root tissue and settles in a permanent site to feed. Feeding is accompanied by swelling of the nematode’s body during the third and fourth stages of juvenile development. In the final moult, the adult female remains swollen and sedentary.

The host range of the carrot cyst nematode is rather limited, and only cultivated and wild carrots are infected. The infective juveniles invade only carrot feeder roots, mainly at the tips. Although the nematode can develop in the early growth stage of the main root, no invasion or development occurs in the tap roots.