698 PARKS 



Control: Use same method as for black spot. leaves. Spray plants with Bordeaux (4-4-40) in the 



Boxwood. Leaf blight (Macrophoma candollei). Dis- fall and before growth begins in the spring. A weaker 



tribution wherever boxwood is grown. Leaves turn solution (2-2-50) may be used during the growing 



yellow and are covered with small black pustules. season. 

 Defoliation results. Control: Rake up and burn fallen 



GENERAL ADVICE 



Every park is to a large extent an individual problem and general 

 advice on the care of trees can be given to cover only relatively small sections 

 of the country. It is suggested that park managers facing any new problem 

 of disease control write to the United States Department of Agriculture for 

 specific and expert advice. This will always be given by correspondence, 

 and sometimes personal inspection by experts is provided. 



SECTION IV 



WILLIAM MIDDLETON 



Associate Entomologist, Bureau of Entomology, United States Department of Agriculture 



Trees growing under all conditions are subject to insect attack, but 

 the more artificial the conditions of growth the greater the number of 

 insect enemies with serious possibilities. Several conditions closely asso- 

 ciated with park buildings are often directly responsible for insect injury to 

 trees. These are: thinning out dense stands, changing grades or earth 

 levels, introducing new and vigorous competitors for the available water 

 and food materials, and finally, planting trees in unsuitable situations or 

 under unfavorable conditions. 



Thinning out dense stands has a very decided influence on the avail- 

 able water supply through the elimination of shade and is frequently fol- 

 lowed by dying tops and ends of branches and borer attack. The changing 

 of grade levels, filling in hollows, or cutting down hills, also affects the 

 moisture and air conditions of the earth surrounding the roots of the trees 

 present and is followed by much the same tree difficulties as the foregoing. 

 Competition is the usual forest struggle and plays an important and an 

 often valuable role, but it is possible, through injudicious planting, to injure 

 considerably very desirable trees. 



With regard to planting, we believe that the tree and site should both 

 be selected. Never choose too many of one kind of tree and always select 

 locations for trees that meet the needs of the trees. Too many of one kind 

 of tree intensifies the park problem of the enemies of that species and gives 

 these insect enemies optimum conditions for multiplication (abundant food 

 material). Different trees vary somewhat in their requirements for soil, 

 depth of soil and moisture, and an oversight of these essentials is very apt 



