386 REPORT OP STATE BOARD OF HORTICULTURE. 



through the wash and thus get some of the poison, according to the theory, 

 but it seeks a minute crack or crevice and works its way in below the surface 

 bark, on which the wash is applied, before it begins to eat. We believe this 

 last fact, regarding the entrance of the newly-hatched borer into the tree, 

 will explain much of the ineffectiveness of washes. It is very difficult to so 

 thoroughly cover the bark of even a young peach tree that many minute 

 cracks will not be left or soon be made through the wash by climatic condi- 

 tions or by the growth of the tree. 



Crude carbolic acid is another favorite ingredient in washes. Hale says 

 it is the "meat" of his wash, on the theory that its odor is offensive to the 

 moths. In our experience in combating the peach-tree borer or any other 

 insect, we have seen little or no evidence that substances having offensive 

 odors had any repellant effect in keeping the insect away from the food-plant 

 of its progeny. Asafoetida did not in our experience, and we do not believe 

 that any of the effectiveness of tarred paper protectors was due to their 

 odor, for others get just as good results from newspapers; they form a me- 

 chanical and not an odorous barrier to the insect. Hence, we do not believe 

 that carbolic acid is a useful ingredient of washes. 



Most, perhaps all, of the washes, act simply as a preventive, mechanical 

 coating over the bark to keep the newly-hatched borers out. Such sub- 

 stances as i-aupenleim, dendrolene. and gas tar seem to be ideal washes, but 

 the first two usually kill young trees, and the last also has a similar reputa- 

 tion in some localities, although we saw no evidence to indicate that tar was 

 injurious to well-established young peach trees. Perhaps someone can so 

 modify these ideal washes as to retain their eff'ectiveness as a preventive 

 and yet eliminate their plant-injuring qualities. Future compounders of 

 washes should work along this line. 



We think that most of the above generalizations regarding washes may 

 also apply to washes designed to prevent the work of the apple-tree borer. 



When to ax>ply washes or other ijreventive measures — In New York the appli- 

 cations vshould be made between June 15 and July 1, and they should remain 

 in perfect working order until October 1. In Canada, July 15 will usually 

 be soon enough to make applications, and they should last until November. 

 In the south the ai^plications should be made in April, and they will appar- 

 ently have to last for three or more months. 



Final conclusions — In our four years of warfare against the peach-tree 

 borer we have been thoroughly convinced that it is a very difficult insect 

 enemy to control. No method of fighting it has yet been devised by which 

 the peach grower can hope to get a single year's respite ; the trees must be 

 treated anew each year and thus the warfare is a perpetual one. 



The following substances injured oi- killed our trees, and are therefore 

 classed as dangerous : Paris green and glue, raupenleim, dendrolene, white 

 paint, white paint and paris green, printer's ink. 



The following is a list of things we found to be practically ineffectual or 

 useless : Wire cages, carbon bisulphide, asafoetida and aloes, lime, salt and 

 sulphur ; resin wash, hard soap, tallow, tansy, whale-oil soap, whitewash, 

 lime and linseed oil, hydraulic cement wash, pine tar, Hale's -wash (one 

 application. ) 



