44 



of affected shoots and during the succeeding spring grew up 

 into the expanding leaflets and produced disease. Later 

 observation, however, has shown that this is of comparatively 

 rare occurrence. Such facts as are at present available tend 

 to show that fresh infection of the leaves in the spring always 

 takes place by means of spores which have lain dormant 

 during the intervening months, entangled among the scales 

 upon the buds. 



The establishment of a new outbreak of disease by these 

 spores is intimately connected with the weather conditions 

 which prevail at the time. Cold, wet weather, when the 

 leaves are expanding, causes them to become abnormally 

 gorged with water and much more susceptible to an attack by 

 the fungus. It is a widely observed fact that leaf -curl is very 

 much less prevalent in a uniformly warm and dry spring; it 

 has also been noticed that where infection has occurred a 

 return of warm, dry weather, or even the occurrence of a 

 hot, dry wind will check the development of the fungus 

 within the tissues. Peach trees planted near large expanses 

 of water, where the atmosphere is moister and cooler than 

 elsewhere, have been found to be especially liable to the 

 disease. 



Measures of Control. There is only one method of 

 controlling leaf-curl, that is, by spraying. The fact that, if 

 the affected leaves are picked off, a crop of new, clean growth 

 is produced, has led some persons to assume that the removal 

 of the curled foliage will eradicate the disease. This is not 

 the case. The summer growth is always clean and, unless the 

 plants are sprayed in February cr March as described below, 

 leaf-curl will develop again in the following season. 



The secret of success is to spray early, immediately before 

 the buds begin to swell. This time will range between the 

 middle or latter part of February and the beginning of March, 

 according to the locality and the nature of the season. Bur- 

 gundy or Bordeaux mixtures may be used. 



1. Burgundy Mixture. A Burgundy mixture of the fol- 

 lowing composition has been used with excellent results at the 

 Eoyal Horticultural Society Gardens, Wisley* : 



Copper Sulphate 2| Ib. 



Sodium Carbonate 2f Ib. 



Water 12 gallons.! 



* See Home, A. S., Jour. Roy. HorL Soc., Vol. XLI (1915), 

 pp. 110-115. 



f If a smaller quantity of the mixture be required, the proportions 

 would be : 



Copper Sulphate 9 oz. 



Sodium Carbonate 11 oz. 



Water 3 gallons. 



At Wisley, the addition of a small quantity of milk to the above mix- 

 ture was found to be of advantage in facilitating the adherence of the 

 spray to the buds. 



