The virus which causes Brassica Stunting Disorder (BSD) has been identified as Turnip Yellows Virus (TuYV). This destructive virus causes stunting of cabbages and can reduce the cut rate of a crop by up to 60%. It has spread throughout most of South Africa and is causing considerable losses. Typical symptoms of this virus include stunting; purpling/yellowing of the leaves; flattening of the leaves; side shoots with no head formation and poor root formation. The identification of the pathogen is relatively easy if one cuts across the stem – one observes the blackening of the vascular tissue (phloem) forming a black ring in infected plants. Infection typically occurs in clusters, 4-6 weeks after transplanting.
Research has identified the Green Peach Aphid as the vector responsible for the transmission of the virus and no resistant varieties have been identified at this stage.
Growers are advised to take the following precautions:
- CONTROL BROADLEAF WEEDS NEAR FIELDS- THEY SERVE AS VIRUS RESERVOIRS
- AVOID TRANSPLANTING DURING TIMES OF HIGH APHID PRESSURE
- SPRAY PREVENTATIVELY FOR APHIDS – SPEAK TO YOUR CHEMICAL ADVISOR FOR A PROGRAM. SOME GROWERS HAVE SUCCESSFULLY USED A SYSTEMIC INSECTICIDE TREATMENT TO REDUCE INFECTION DURING THE EARLY STAGES OF THE CROP CYCLE.
- REMOVE AND DESTROY INFECTED PLANTS
For a more information, refer to the documents below: