REPORT OF STATE BOARD OF HORTICULTURE. 153 



important that tlie siDvaying sliould be frequent enough to 

 keep well protected the parts liable to attack. Sometimes it 

 is necessary to spray every day or every two or three days, 

 wliile at other times ten days may elapse between sprayings. 

 tSpraying, like cultivation, pi'uning, and other field opera 

 tions, is largely a matter of judgment, and the more thor- 

 oughly the subject is understood the more effective the work 

 will be. 



WHY IS IT NECESSARY TO SPRAY EVERY YEAR? 



Il is impossible to exterminate fungi. We may hold them 

 in check, or we may even prevent entirely their growth upon 

 certain plants ; but they are often so small, their habits of 

 life so variable, and their spores so resistant that extermina- 

 tion is out of the question. It is impossible to know at the 

 beginning of the season whether the conditions will be favor- 

 able or unfavorable for the development of fungi, hence, in 

 order to be on the safe side, it is necessary to begin each sea- 

 son with spraying. It is essential, therefore, that spraying 

 should be as regularly a part of the field work for successful 

 crop raising as plowing, fertilizing, and the other operations 

 necessary for crop production. Furthermore, the effects of 

 spraying are cumulative, that is, the effects of spraying and 

 keeping fruit trees free from disease this year will give a bet- 

 ter crop next year. Even with trucking crops that die down 

 in tlie fall the danger from disease next year in a particular 

 field will be greatly reduced if the field is kept free from dis- 

 eases this season. 



DOES SPRAYING SOMETIMES IN.JURE FOLIAGE AND FRUIT? 



If fungicides are not properl}" made they will burn the 

 foliage and discolor the fruit. It is a Avell-known fact that 

 the foliage on some plants is much more tender than it is on 

 others, and for this reason it is necessary to suit the strength 

 of the fungicide to the host-plant. Certain fungicides, like 

 bordeaux mixture, cannot be used in spraying fruit that is 

 nearly ripe, since the fruit would be stained by the mixture, 

 and thereby rendered unsalable. 



WHY' DOES SPRAY'ING SOMETIMES FAIL TO PREVENT DISEASE? 



There are several reasons why spraying sometimes fails to 

 accomplish the results expected. It may be that the fungi- 



