<P> Alternaria diseases are caused by the organisms Alternaria brassicae, Alternaria brassicicola and Alternaria japonica . Their English names are black spot, pod spot, gray leaf spot, dark leaf spot or Alternaria blight . The symptoms can be seen on all aboveground plant parts as dark spots . The infected plants are shrivelled and smaller than normal . Alternaria diseases infect almost all brassica plants, the most important hosts are oilseed brassicas . The fungus is a facultative parasite, what means that it can survive on living hosts as well as on dead plant tissue . Infected plant debris is in most circumstances the primary source of inoculum . The spores can be dispersed by wind to host plants in the field or to neighbouring brassica crops . This is why cross infections often occur in areas where different brassica crops are cultivated in close proximity . The disease spreads especially fast when the weather is wet and the plants have reached maturity . Alternaria brassicae is well adapted to temperate regions while Alternaria brassicicola occurs primarily in warmer parts of the world . Temperature requirement for Alternaria japonica is intermediate . There exist some wild accessions of Brassica rapa subsp . pekinensis with resistance to Alternaria brassicae but not on commercial cultivars . These resistances should be included to breeding programmes . Alternaria epicemics are best avoided by management practices like at least 3 years non-host crops between brassica crops, incorporation of plant debris into the soil to accelerate decomposition and usage of disease - free seeds . </P> <P> Anhracnose is a brassica disease caused by Colletotrichum higginsianum that is especially damaging on napa cabbage, pak choi, turnip, rutabaga and tender green mustard . The symptoms are dry pale gray to straw spots or lesions on the leaves . The recommended management practices are the same as for Alternaria diseases . </P> <P> Black root is a disease that infects mainly radish, but it also occurs on many other brassica vegetables inclusively napa cabbage . It caused by the fungus Aphanomyces raphani . The pathogen can persist for long times in the soil, therefore crop rotations are an essential management tool . </P> <P> White leaf spot is found primarily in temperate climate regions and is important on vegetable brassicas and oilseed rape . The causal organism is Mycosphaerella capsellae . The symptoms are white spots on leaves, stems and pods and can thus easily be confused with those of downy mildew . The disease spreads especially fast with rain or moisture and temperature is between 10 and 15 ° C . </P>

Is savoy cabbage the same as napa cabbage