176 PEACH LEAF CURLt ITS NATURE AND TREATMENT. 



THE TIME FOR WINTER SPRAYING. 



The proper time for the application of winter sprays for the control 

 of peach leaf curl depends ver}^ largely upon the conditions of climate, 

 season, and situation of the orchard. The object to be attained is to 

 prevent the fungus from infecting the tirst growth of spring. It has 

 become apparent from the many and widely separated experiments 

 which are here described that nearly if not all this infection result, 

 from the spores of the fungus, which are present upon the tree and 

 not, as formerly supposed, from a perennial mj^celium, and it natui 

 all}' follows that these spores are to be destroyed or their germination 

 prevented if the new growth is to be kept exempt from curl. When 

 a spore is about to germinate or has just begun to germinate, its mem- 

 branes are most tender and susceptible to fungicides. That most of 

 the spores of Exoascus deformans enter upon the stage of germina- 

 tion at or about the time of the pushing of the first leaf buds in the 

 spring admits of little doubt. That is the time when the tissues of the 

 peach leaf are most tender, and when their infection by curl is actually 

 known to take place. 



The preceding facts indicate that the time when the fungicide is apt 

 to do the greatest good is just before or at the time of the earliest push- 

 ing of the peach leaf buds. The spray should, be everywhere present 

 upon the trees just prior to the beginning of growth. To obtain this 

 object it should be applied from one to three weeks before growth 

 begins. This time may usually be determined b}' carefully watch- 

 ing the fruit buds, which show signs of swelling some time before 

 they open. When they first begin to swell, the spray may be at once 

 applied (Pis. XXIII, XXIV, and XXV). 



This plan relates to regions of moderate rainfall, where a single 

 thorough spraying, with sprays sufficiently strong and active, will 

 prove sufiicient. In regions of heavy precipitation more spray should 

 be applied to the trees. It should be stronger and have greater adher- 

 ing qualities, or else more than one spraying during the winter will be 

 required to give the best results. If two sprayings are given, it is 

 better to apply both to the dormant tree than to delay the second 

 treatment till the leaf buds have opened The first spraying may be 

 given in the fall or a few weeks before the second. 



THE MANNER OP APPLYING WINTER SPRAYS. 



The source of infection of the spring foliag of the peach by the 

 fungus of leaf curl is local — i. e. , it is to be found upon ever}' portion 

 of the tree. This fact is sufficient to shov that any portions of the 

 tree not reached by the spray will be as subjec to the disease as if no 

 spraying had been done. It thus becomes apparent that very thorough 

 work is essential to the general control of the disease upon the tree. 



