REPORT OF THE STATE ENTOMOLOGIST I913 45 



THE USE OF MISCIBLE OILS ON TREES 



There have been during the last three years some exceptionally 

 unfortunate developments following the application of miscible oils 

 to trees, especially sugar maples. Some have questioned the possi- 

 bility of oil being the principal cause of the trouble, and since the 

 matter is of considerable importance and may involve the life of 

 highly valued shade trees, observations of earlier years have been 

 continued and are given in some detail below. The data, in our 

 estimation, abundantly justify a refusal to recommend these mater- 

 ials as applications to dormant sugar maples and warrant the em- 

 ployment of cautions couched in no uncertain terms concerning 

 their employment in a similar way for other trees. It is axiomatic 

 that the remedy should not be worse than the disease. 



LARGER SUGAR MAPLES AND MISCIBLE OILS 

 The behavior of the sugar maple commonly found on roadsides, 

 after applications of certain oily compounds, is so characteristic 

 that there should be little difficulty in recognizing the cause of the 

 trouble. A sugar maple at Port Chester, N. Y., having a trunk 

 diameter of about 8 inches was examined July 16, 1913. Nearly all 

 the lower limbs were dead and a few brown leaves were hanging 

 here and there. This tree, we were informed, was sprayed the last 

 of the preceding November or early the following month, with one 

 of the commercial miscible oils diluted at the rate of 1 to 15. It 

 was the intent of the operator to spray the entire tree thoroughly, 

 but in practice there is little question but that more of the insecticide 

 was thrown on the lower portions of the tree — the parts dead at 

 the time we saw the tree — than higher up. Observation showed at 

 once that it was in a vigorous condition last year, and an examina- 

 tion of the foliage, limbs and trunk failed to disclose any adequate 

 .cause for the trouble, such as insect enemies or fungous diseases. 

 The hanging leaves showed that the foliage started on the dead 

 limbs and if subsequent developments had been closely followed, 

 there are good reasons for believing that the leaves became un- 

 healthy, thin, pale, then brown spots appeared and there was 

 serious drying, which was followed by the assumption of a rather 

 dark brown color and usually by the dropping of many of 

 the leaves. This showed first on the seriously injured parts, 

 that is places to which considerable oil was applied and where the 

 bark was thin enough so as not greatly to hinder penetration to the 



