•2i)-2 Fmtf/icidal Properties of Certain Sjiray -fluids 



Ammonium folysidfhide Solution IV (Table 1). 



This solution diluted ] : 300 has considerable fungicidal power, 

 which varies according to the age of the leaf on which the "powdery" 

 conidial patch resides (see Table 1). At 1 : 100 it is fungicidal for all 

 powdery patches on both old and young leaves, and it checks the 

 development of the young non-powdery stages. At 1 : 75 the check 

 to the young stages is more marked, and at 1 : 50 the mildew in its very 

 earliest stages of development is almost or quite killed. Some details 

 of three experiments in which the solution was used at 1 : 100, 1 : 75 

 and ] : 50 may be noted here, as they s'we clear evidence that the mildew 

 in difierent stages of development has different powers of resistance to 

 the solution. 



In Experiment 55 (1 : 100) one of the leaves sprayed {(■) had 20 

 "humps," showing the early stages of development of the mildew. On 

 the eighth day after spraying three tiny tufts of clustered conidiophores 

 occurred arising from three "humps," while on 17 of the "humps," 

 where the mildew had existed in its earliest mycelial growth, the fungus 

 was killed. On the tenth day, the sprayed leaf bore three .small, more or 

 less powdery patches, while the control leaf bore 20 powdery patches. 

 Where, on the six other sprayed leaves, the mildew had been in the form 

 of vigorous powdery patches, it was killed. 



In Experiment 73(1 : 75) seven leaves were sprayed. On f oui' leaves 

 (a, c, d,f) the mildew was in the powdery conidial stage; on one leaf (b) 

 the only sign of the presence of the mildew was the occurrence of nume- 

 rous "humps," indicating where infection had taken place, although no 

 mycelium was visible (under a lens) on the surface of the " hump " ; 

 on one leaf (e) the patches were at that stage of development when 

 mycelium has been produced but as yet no conidiophores; on one leaf 

 (y) there were a few powdery patches, one very young sterile patch and 

 several "humps" bearing a few sterile mycelial hyphae radiating from 

 their centres. By the fifth day after spraying the patches on the four 

 leaves (a, c, d,f) were all sterile and either dead or dying — some being 

 •semi-obliterated ; while the patches on the control leaves were as powdery 

 as before; on leaf (6) only two of the numerous "humps" bore a few weak 

 conidiophores, while the control leaf bore very numerous powdery 

 patches. It was clear that the solution had dealt summarilj' for the 

 mo.st part with the yomig stages of the mildew. On the .seventh day the 

 sprayed leaf bore four tiny groups of clustered conidiophores arising 

 from four "humps," while the control leaf was almost continuously 



