Phytophthora nicotianae

(black shank)

 Although never reported in France, it is important to thoroughly understand the symptoms caused by this fungi-like soil micro-organism, Phytophthora nicotianae (formerly Phytophthora parasitica var. Nicotianae). Indeed, it is a dreadful disease causing considerable damage in many countries. It has been observed in many neighboring European countries, like Germany, Spain and Italy.
 
This parasite causes discoloration and death of roots, and lesions on the stem base (figure 1-4). These lesions  are black, hence the name of the disease "black shank". The symptoms are accompanied by various degrees of total wilting of plants leading to their death. The most characteristic symptoms are observed in the stem, the pith is dark brown, retracted in places, separated into plate-like disks. Remember that Rhizoctonia solani causes very similar symptoms and thus misdiagnosis is possible. If you have any doubts, contact a specialised laboratory.

Figure 1	Figure 2	Figure 3	Figure 4

 
For furher information on this root parasite, see the fact sheet of Phytophthora nicotianae.