Fig. 8. — Scar in the trunk of a honey locust tree 3 

 months after treatment withSD-3562. A hole had been drilled, 

 SD-3562 injected, and the hole plugged with a dowel. 



Fig. 10. — Bark of honey locust trees in May, 1962, 

 approximately a year after being treated with technical 

 ;SD-3562. A. Small tree in nursery: bark in upper part of 

 picture was not treated; bark in lower part shows chemical 

 linjury. B. Tree of medium size along street: treated bark 

 ,in lower part of picture shows injury; untreated bark above 

 !does not. 



Fig. 9. — Trunk of a honey locust tree 3 months after 

 the bark had been striated with a razor blade and SD-3562 

 had been applied to the wounded surface. 



required to establish the significance of this injury 

 and to develop methods for avoiding it. 



When observed in May, 1962, none of the honey 

 locust or oak trees treated with SD-3562 in 1961 showed 

 foliar damage. 



DISCUSSION 



Systemic insecticides, such as SD-3562, open up 

 interesting possibilities for the control of tree and 

 shrub pests for which there is now no practical control. 

 In addition, they offer possibilities for the develop- 

 ment of improved and more effective means of con- 

 trolling pests for which controls are now known. 



SD-3562 is toxic to the smaller European elm bark 

 beetle, a vector of Dutch elm disease, and may have 

 possibilities for reducing the incidence of this disease. 

 It is effective against the mimosa webworm on honey 

 locust trees when a small quantity of the chemical is 



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