28 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



Methoxychlor. — A chlorinated hydrocarbon that can be sub- 

 stituted for DDT. It is much less hazardous to birds and other 

 warm-blooded animals. Although methoxychlor is two or three 

 times as expensive as DDT, the cost of labor in applying the 

 spray is the same. 



Organic Mercury. — A fungicide sold under such trade names 

 as Puratized Agricultural Spray and Coromerc. Under Illinois 

 conditions, it controls sycamore anthracnose and some other leaf 

 diseases. 



Sulfur. — A fungicide that can be obtained in several forms. 

 Sulfur is sold under various trade names. 



Thiram. — A fungicide sold under the trade name Thylate 

 Thirara Fungicide. It is recommended for the control of rusts 

 on crab apple and hawthorn. 



Zineb. — A fungicide sold under such trade names as Parzate 

 and Dithane Z-78. It controls leaf blotch of buckeye and horse- 

 chestnut. 



Feeding 



To maintain the health and to promote the vigorous growth 

 of shade and ornamental trees, it often becomes necessary to 

 provide food materials that are lacking from the soil, or are 

 present in insufficient amounts. In the forest, where humus ac- 

 cumulates year after year, trees are liberally supplied with 

 organic material derived from decaying leaves and plants. This 

 material serves as food and helps to retain soil water. Since, 

 along city streets, in lawns, or in parks, natural sources of food 

 and water often are insufficient, artificial feeding and watering 

 are frequently necessary. Well-fed trees appear to be more re- 

 sistant to drought than those that lack proper nourishment. 



Three chemical elements, nitrogen (N), phosphorus (P), 

 and potassium (K), must be available in the soil to insure the 

 best development of a tree. The levels at which these elements 

 are available, which vary greatly from place to place in Illinois, 

 can be determined by soil tests. An efficient and economical tree 

 food for a particular situation contains the essential elements 

 only in the amounts needed to correct soil deficiencies. 



A complete tree food, which should ordinarily be used if soil 

 tests are not made, should contain all three essential elements. 

 Nitrogen can be supplied by inorganic compounds — nitrate of 

 soda, ammonium sulfate, calcium nitrate — or by organic ma- 

 terials — urea, soybean flour, cottonseed meal, tankage, dried 



