78 PROTECTION OF PLANTS — 1924-25 



of diseased plants ran as high as 50%. The fact that it attacks isolated plants 

 or frequently two plants united by runners induced us at first to believe it was 

 bacterial in origin. The exact cause of the disease still remains im perfectly 

 known. 



Last Summer we sent to our field horticultural inspectors a questionnaire 

 which they were asked to fill out. We have also personally inspected a large 

 number of fields and in comparing our notes with the data received from the 

 field men a certain number of facts was noticed which may be reported here. 



1) The disease attacks the strawberry plants specially after the second 

 wintering; 



2) it is particularly serious on dry sandy soils well exposed to sunshine in 

 Summer and not covered by snow in Winter; 



3) a dressing of nitrate of soda and even of manure appears to have a preven- 

 tive effect; 



4) the disease does not develop to any extent in weed infected stands nor in 

 plantations, sheltered during Winter. 



These observations though not absolute have been repeated in a sufficient 

 number of cases to make us believe that they are of some significance. Until 

 we have had an opportunity to complete our observations we are of the opinion 

 of those who claim that this disease is a physiological one. It would therefore 

 be a consequence of an uprooting due to the frost. It is supposed that on 

 account of the action of the frost the roots are broken. When the next Summer 

 drought sets in, the plant lives for a while on its own supphes but when no more 

 water is available it dies out. In such a case, as the soil itself is deprived of 

 water, the formation of new rootlets is made impossible. We have not quite 

 given up the bacterial theory but many more observations would have to be 

 made before we are in a position to prove it. 



Vegetables. 



Last Summer we saw at Joliette a field of cauliflowers infected by a disease 

 which forms blackish blisters on the under side of the leaves. This caused 

 the affected plants to rot and the damage were already considerable when we 

 happened to visit this field towards the middle of August. With such serious 

 infection, there was no time to be lost and we at once urged the use of a 4-4-40 

 Bordeaux mixture with the addition of about half a pint of molasses per three 

 gallons of mixture and one half ounce of soap for the same quantity. According 

 to the report received later on from the producer the result wasvery satisfactory. 



Some leaves of the diseased cauliflowers placed in a moist chamber grew in a 

 few days an organism bearing macrospores belonging to a species of Alternaria, 

 probably Alternaria (Macrosporium) brassicoe Berk. 



