No. 7. DEPARTMENT OF AGRICULTURE. 481 



thinks, that a series of basic sulphates are formed by the precipita- 

 tion of the copper by the lime in making Bordeaux mixture, that 

 when upon the trees or plants these become soluble by the action 

 of carbon dioxide and moisture and therefore are present in the plant 

 substance and available when needed to check the development of 

 parasitic fungi. In other words the plant is put into a condition to 

 resist parasitic infestations and insect depredations. As already 

 stated whatever the conditions produced in the plant to resist fungus 

 infection the substances that check this infection have a deleterious 

 effect on the plant organs. 



In a trial of tree spraying mixtures for fungus diseases, standard 

 Bordeaux mixture made of four pounds copper sulphate and four 

 pounds stone lime and fifty gallons water, Bordeaux mixture and 

 iron sticker made of two pounds copper sulphate and four pounds 

 iron sulphate and six pounds of stone lime with fifty gallons water, 

 and self-boiled lime and sulphur made of ten pounds stone lime and 

 ten pounds sulphur and fifty gallons water, the following results were 

 obtained : 



On the apple trees of the same variety in the same orchard on the 

 same kind of soil those sprayed with the self boiled lime and sulphur 

 the fungus diseases were not entirely kept down, but there were no 

 obvious injurious effects on the trees. Those sprayed with the iron 

 sticker and Bordeaux mixture the fungus diseases were kept down 

 and there was little injury to the trees. But the trees sprayed with 

 straight Bordeaux mixture were nearly entirely defoliated. These 

 occurrences are not uncommon, but are by no means conclusive. The 

 iron sticker, which by the precipitation of the iron in the sulphate 

 by the lime water becomes the gelatinous ferrous and ferric hydrox- 

 ides, is added to hold the insecticides and fungicides for a longer 

 time and in this way prolong tree disinfection and insect destruc- 

 tion. It is obvious from this that in order that spraying in the future 

 may be more eflScient that the greatest care and keenest observatioon 

 is demanded so that we do not inflict greater injury than the bac- 

 terium we are trying to destroy would have inflicted, especially is 

 this so as long as we are obliged to use disinfectants that are in- 

 jurious to the trees, the foliage and the fruit. I said disinfection of 

 trees. I like the term because it brings us face to face with the con- 

 ditions that confront the physician. He disinfects the room in which 

 patients have been ill with so-called bacterial diseases in order to pre- 

 vent the disease from being conveyed to others. Here another avenue 

 for investigation opens up into which we have now not time to enter. 



An illustration of the effectiveness of insect poisoning and fungus 

 disinfection came under our observation in York county in 1909 and 

 1910. In one section of this county there was considerable com- 

 plaint that Paris green did not kill the potato bugs and in some in- 

 stances even Bordeaux mixture when applied sufficiently early did 

 not in any way check potato blight. 



In 1909 there was a scarcity of Paris green in the potato growing 

 section of York county .and dealers were obliged to scour the country 

 to secure enough to supply the demand. Over 7,000 pounds were 

 used in one section during this year. 



In the vicinity of Brogueville and Cross Roads, York county, a 

 number of farmers whom we visited told us how potato spraying had 

 well nigh completely failed, in fact seemed to have done more harm 



31—7—1910 



