DUTCH ELM DISEASE IN ILLINOIS 15 



Spraying 



Spraying with special formulations of methoxychlor or DDT will 

 help to protect healthy elms from fungus infection by preventing 

 bark beetle feeding. 



The heavy applications of these insecticides required/or hark beetle 

 control are hazardous to birds and other umrm-blooded animals. Meth- 

 oxychlor, although more expensive, is less hazardous than DDT. 

 To minimize the hazard it is recommended that methoxychlor be 

 applied as the spring dormant spray and that DDT be applied as 

 the fall dormant spray. Methoxychlor, as a fall dormant spray is not 

 effective for a period of time sufficient to control elm bark beetles 

 throughout the following spring and summer. According to avail- 

 able data it was effective for only 100 days in tests conducted by the 

 University of Wisconsin and 150 days in USDA tests in Washington, 

 D.C. Some municipalities in Illinois now use methoxychlor as a 

 spring dormant spray. 



Properly formulated concentrates of these insecticides are avail- 

 able commercially. Although they will not give complete protection 

 of all sprayed trees, when combined with sanitation and the pre- 

 vention of fungus transmission through grafted roots they give the 

 best protection against Dutch elm disease known at present. These 

 insecticide treatments reduce the chance of infection by killing many 

 of the fungus-bearing beetles before they can gnaw through the bark 

 and deposit fungus spores in the sapwood of healthy trees. 



A single dormant spray is recommended for elms sprayed on a 

 communitywide basis. It may be applied in fall or spring, at any 

 suitable time after the leaves have fallen — in late October or Novem- 

 ber, or until new flowers or leaves appear, in April or early May. 

 This spray should contain 12 percent insecticide if it is applied with 

 a mist blower or 2 percent insecticide if applied with a hydraulic 

 sprayer. 



To effectively prevent bark beetle feeding, all bark surfaces 

 must be completely coated with insecticide. Special care is required 

 to thoroughly coat the crotches of young shoots, especially those in 

 the upper parts of trees. The time to spray trees is when the wind 

 velocity is less than 5 miles per hour, when the bark is dry, when 

 rain is not anticipated for 2 hours after spraying, and when the 

 temperature is above freezing. 



Recently, helicopters have been used for spraying in some mu- 

 nicipalities. At present, there is not sufficient data to show that heli- 

 copters are as effective as conventional sprayers in applying insecti- 

 cides for Dutch elm disease control. 



Caution: Like most other insecticides, these materials are poisons 



