20 MAINE AGRICULTURAL EXPERIMENT STATION. I912. 



Other observers, the writer sent a circular letter to Station 

 botanists, horticulturists or pathologists of the several apple 

 growing states that had been subjected to the heat wave of July. 



Practically every reply confirmed the Maine experience in 

 regard to the injury, its relation to the side of tree and fruit 

 exposure, and all were unanimous in crediting the injury to sun 

 and heat. Some also included drought as a factor. 



In regard, however, to the relation of spraying to sunscald 

 of fruit, these observers are of divided opinion. Of 12 replies 

 8 state that spraying during the heated term increased the de- 

 gree of damage. The others consider the injury due to sunburn 

 pure and simple. 



The writer inclines to the belief of the majority of his cor- 

 respondents, to the extent that spraying during the hot weather 

 appeared to increase the severity where injured areas were 

 present before this last spray was applied. Whether or not the 

 chemical nature of the spray has any influence in raising the 

 degree of injury produced is still an open question. As tlie 

 data for 191 1 shows, the amount of scald varied directly with 

 the strength of lime-sulphur spray used. On the other hand 

 the injury on the lead arsenate plots, although considerably less 

 in amount, was qualitatively equally serious, as Figs. 8 and 9 

 indicate. Unsprayed trees suffered no greater injury than 

 shown in Figs. 5 and 6. 



The distinguishing characteristics of spray injury as separate 

 from sunscald, given by one of the aforementioned correspond- 

 ents who attributes the injury of the past season entirely to 

 sunscald, tends to confirm our opinion as just stated. His 

 statement is as follows : 



"The sunscald with us (fruit of apple), appeared as discol- 

 ored sunken spots or maculations with a sharply defined mar- 

 gin. In the case of spray injury the tissues are never sunken, 

 nor is the margin well defined, and the epidermis is scurfy, not 

 smooth as in the case of sunscald. The epidermal tissues are 

 brown and the discoloration more marked immediately beneath 

 the epidermis in the case of sunscald, but in the case of spray 

 injury they present no abnormal appearance." 



An examination of Figs. 5 and 6 and Figs. 10 and 11 will lead 

 one to conclude that if such distinctions hold, we have in the il- 

 lustrations just referred to, sunscald as evidenced by the discol- 

 ored, more or less sunken spots with rather well defined mar- 



