EEPORT OF THE SOCIETY 97 



Relation to Late Blight Rot 



The rot caused by Phytophthora infestans when severe is seen at digging 

 time and the heaviest losses begin to show soon thereafter in storage but Fwsa- 

 rium rots inflict heaviest losses in the later storage period. It is obvious, how- 

 ever, that small lesions caused by P. infestans are eminently suitable as points 

 of entrance for Fusaria and infection by Fusaria commonly occurs. The rot is 

 then not "dry" as in the case of infection bj^ Fusarium alone. 



A feature of importance is the amount of rot in storage which occurs in cer- 

 tain 3^ears even after consistent spraying with Bordeaux is practised. Murphy 

 (Ottawa Bull. 44) has mentioned this and I have had many request for inform- 

 ation from Quebec farmers. During a warm wet autumn the spraj'ed plants 

 remain green and continue to grow well on to harvest. At digging time, the 

 tops are still green and under such conditions some Late Blight is almost sure 

 to be present. Spores fall on moist tubers and infection maj^ occur which does 

 not manifest itself until later in storage. Even if no Late Blight be present, 

 the tubers are immature so far as their skins are concerned and therefore are 

 easily injured. Through these injuries Fusaria enter and in the spring there is 

 the likelihood of heavy loss from dry rot. It would probably be better to cut 

 the tops some seven to ten daj'S before digging to remedy this, and experiments 

 are under way to determine the efficacy and economy of such a procedure. 



Storage Conditions 



Moist warm storage is suitable for the rapid spread of dry rot (and other 

 storage rots) and it is therefore important to be able to ventilate well and to 

 maintain a temperature about 35° F., or slightly lower so long as the freezing 

 point is not reached. 



Fusaria can live over the summer on refuse in the corners and on the walls 

 of bins, and clean bins are essential to safety. 



EflFect on plants 



If infected tubers are used for planting the rot may continue so that no 

 plant develops or the shoots are weak and spindling. It is entirel}^ inadvisable 

 to use even doubtful seed. 



Control 



1. Avoid injury to tubers as much as possible. 



2. Use cleaned and disinfected bins. 



3. Keep the storage places cool (35° F.), well- ventilated, and dry. 



4. Avoid digging tubers for storage with immature skins. 



5. Plant healthy seed tubers. 



7 



