18 



and this is also true of fumigation. Many of our oil sprays 

 have been known to injure apple and even shade trees when 

 in the dormant condition, and judgment must be used in 

 applying them. Even kerosene can sometimes be sprayed on 

 certain plants without injury, although at other times it may 

 kill the plant. Kerosene used directly or diluted with water 

 is dangerous to many trees, as are various other oils. 



Bordeaux mixture, even when properly prepared, causes 

 burning to fruit trees under certain conditions (Fig. 10). 

 In the south such injuries are more common than with us, but 

 even here russeting of the fruit sometimes occurs from Bor- 

 deaux, as well as burning of the foliage. Meteorological con- 

 ditions are responsible for some of the injury from spraying; 

 for instance, spraying during cloudy periods, when the 

 foliage and wood are not properly matured ; and spraying 

 mixtures left on the foliage in solution for a long or short 

 period cause injury. Therefore, trees sprayed in the sun- 

 shine, when the solution quickly dries on the foliage, are less 

 likely to burn. There are also many other factors which 

 enter into burning of the foliage and russeting of the fruit, 

 such as soil moisture. 



Sunlight as a Factor tn Apple Orchards. 



No factor has a more important bearing on vegetation than 

 sunlight. Through its action on foliage, plants obtain most 

 of their food from the air, and tissue is rendered less sus- 

 ceptible to disease, since the physiological effect is to inhibit 

 growth and render tissue more resistant. Aside from the 

 necessity of pruning apple trees to make them low headed 

 to facilitate picking the fruit, pruning is very important 

 from the disease standpoint. Proper pruning and thinning- 

 give light a chance to reach all the branches, fruit and 

 foliage, and thus modify the tissue and make it more resist- 

 ant. Light is also important in preventing sun scald, winter- 

 killing and other troubles. 



A few years ago sun scald was quite common on neglected 

 apple trees in our State. The most notable feature connected 

 with the injury was the fact that it was confined to the shaded 



