G6 ENTOMOLOGICAL SOCIETY OF ONTARIO. 



BORDEAUX MIXTURE AS A DETERRENT AGAINST FLEA BEETLES. 

 By L. R. Jones, Burlington, Vt. 



Bordeaux mixture is a remarkable compound. After many comparative tests, ex- 

 perimenters have decided that no other mixture or solution yet discovered is equal to it 

 as a general fungicide. Furthermore, those who have studied its action upon plants are 

 agreed that it exerts upon them some beneficial influence entirely apart from its fungi- 

 cidal effects.* 



So far as I know, however, Bordeaux mixture has never before been experimentally 

 shown to have value as a remedy against insects. Some experiments in this line made at 

 the Vermont Experiment Station during 1893 and 1894 will therefore have so general an 

 interest that I present the results before this Society. 



Potato plants in Vermont suffer from the attacks of the cucumber flea beetle 

 {Crepidodera Cucumeris, Harris). I cannot estimate the amount of the damage to the 

 entire potato crop of the State from these insects, but I am convinced that it is most 

 serious, especially during a dry summer, such as we have just experienced. In con- 

 firmation, I will pass around for your inspection, some leaves taken from our experimen- 

 tal potato plot at Burlington, You will perceive that many of them are com- 

 pletely riddled with the small holes eaten by these flea beetles. These leaves do not 

 exaggerate the condition of the entire plants in many portions of our field. Leaves 

 punctured and even skeletonized, as some of these are, suffer much from the loss of so 

 considerable a portion of their leaf tissue. Moreover, leaves thus mutilated are most 

 disastrously exposed to the effects of drouth during dry weather, and to the inroads of 

 fungi and other parasites during wet weather. Indeed, these secondary injuries follow 

 so closely after the attacks of the flea beetle, and the beetles themselves are so small and 

 shy, that the great majority of potato growers attribute the entire trouble to these 

 secondary agencies. 



Entomologists have tried many remedies against these flea beetles. The one com- 

 monly recommended by them for use on potatoes is the standard insecticide, Paris green, 

 mixed with land plaster and dusted upon the plants. As will be seen from our results 

 below this poison has been of comparatively slight value -with us. Certain fungicidal 

 compounds, however, proved of decided worth in our experiments of 1893. These fungi- 

 cides were originally applied to check the fungous diseases to which potatoes in Vermont 

 are especially liable. Noticing that these sprayed rows were less badly eaten by the flea 

 beetles, a careful count was made of the number of holes in fifty leaflets from each row 

 of one plot under treatment. The results were as follows :t 



In 50 leaflets sprayed with. . . . very weak Bordeaux mixture, 1,794 holes 



ammoniacal copper carbonate, 1,587 



, modified eau celeste, 1,376 



weak Bordeaux mixture, 1,295 



strong Bordeaux mixture, 1,194 



strong Bordeaux mixture and soap, 945 



These plants had been sprayed but once, August 1st. The examination was made 

 August 12th. From our observations during the present summer (1894), we are con- 

 vinced that most of the holes in the leaves rprayed with Bordeaux mixture had been 

 made before the plants were sprayed at all, i.e., before August 1st. The present season 

 observations upon these insects were begun earlier. The beetles w^ere first seen about 

 June 1st. By June 12th some of our early potatoes were badly eaten. This attack 

 lasted but a short time, however, and during the latter part of June and first two weeks 

 of July but few beetles were seen. Suddenly, about July 20th, they again appeared in 

 large numbers, and during the next ten days did great damage to unprotected potato 

 plants. Previous to this time portions of our plants had been sprayed with various 

 fungicides, and all the plants sprayed with the stronger copper compounds, especially 

 with the Bordeaux mixture, have remained practically free from the flea beetle injuries 

 up to date. 



'U. S. Dept. Agric, Div. Veg. Path., Bui. 7, p. 31. 



