397 



phur " solution, is not readily washed off by rain. Some experi- 

 ments which have recently been carried out show that this lime- 

 sulphur wash is efficacious against "powdery mildew," and the 

 experience lately obtained in other countries indicates that in 

 certain cases the wash may be useful in combating attacks of apple 

 "scab" or "black spot." 



Experimental work. The experiments carried out in connection 

 with "powdery mildew" were briefly as follows. In one set of 

 experiments young hop-plants affected with the well-known hop 

 "mould" or mildew (Sphaerotheca Humuli] were treated in the 

 following manner. A considerable number of leaves were chosen 

 which bore patches of the mildew in a powdery and actively grow- 

 ing condition ; each leaf was then divided by a line down its midrib 

 into two halves. Each half of these selected leaves bore from one 

 to four patches of mildew. One half of each leaf was painted 

 over with the lime-sulphur wash, while the other leaf which 

 served as a " control " or check was either left untreated or 

 was painted over with pure water. In every case the patches of 

 mildew on the treated half of the leaf were killed the spawn 

 (mycelium) of the mildew drying up, but not changing colour ; on 

 the other half of the leaf the mildew continued to increase rapidly. 

 Further, no fresh infection took place on the treated half of any 

 of the leaves, although spores (conidia) must have constantly been 

 blown there from the powdery patches on the untreated part of 

 the leaf. In one series of experiments investigations were made 

 with regard to this point. Healthy young hop-plants were chosen, 

 and one half of some of the leaves was treated with the lime- 

 sulphur wash. Spores (conidia) of the hop-mildew were then sown 

 on both the treated and untreated halves of each leaf. In no case 

 did any infection take place on the treated part of the leaves, 

 while (under the condition of the experiment) the untreated half 

 of the leaves became virulently infected, and after fourteen days 

 bore numerous powdery patches of " mould." 



In another series of experiments a number of young hop-plants 

 which were all beginning to be infested with hop "mould," were 

 divided into two sets of equal numbers, each set being so far as 

 the eye could judge, equally affected with the mildew. In each 

 experiment one set of plants was well sprayed with the lime-sul- 

 phur wash using a Vermorel nozzle on an " Eclair dtame"' knap- 

 sack. A fine misty spray was obtained and the leaves of the 

 treated plants appeared, when the spray had dried on them, as 



