February, '21] fentox: potato tipburn 77 



extent whatever. Adults confined in cages on potato plants failed to 

 produce any sign of bt:ming if no n^Tnphs were produced or if these 

 were immediately removed after hatching. This indicates that, com- 

 paratively speaking, the adults are not nearly as effective in producing 

 the disease as the n\-mphs are; that they will produce tipburn when 

 introduced in great numbers on potato plants has been shown in field 

 experiments. 



Effect ox Potato Leaves Produced by Other Insects 



To test the injurious eftects of other insects on potato leaves, one 

 series of plants were caged with Buffalo treehopper nymphs (Ceresa 

 biihalus) , tarnished plant bug adults {Lygns pratensis) , aphids (species 

 unknown), and flea beetles {Epitrix cucnmeris) . Each of these insects 

 produced a typical form of injury that in no way resembled the tipburn 

 caused by the leafhopper. Buffalo treehopper nymphs girdled the stems 

 of the plants b\^ causing the tissue at the points of pvincture to collapse 

 and the entire tip to bend over and wilt. Tarnished plant bugs collected 

 at the tips of the plants and caused a Avilting and death of this part. 

 Aphids at first produced no injury, but when the colony increased in 

 nvimbers the plant first yellowed and then died. Flea beetles at first 

 ate the typical round holes in the lea\^es and then when more were added 

 cleaned off the entire leaf epidermis, killing the plant. 



Why Does Bordeaux Mixture Prevent Tipburn? 



It has been known for some time that Bordeaux inixture sprayed on 

 potato plants reduced the amount of tipburn. When it was found that 

 the leafliopper was responsible for the trouble attention was naturally 

 attracted to the effect of this spray on these insects. Fluke ^ carried 

 on some preliminary experiments which indicated that it had a repellent 

 nature, and Parrott- substantiated these conclusions. It was observed, 

 that under certain conditions Bordeaux mixture prevented tipburn to 

 a large extent in our experimental plots, and as a result a series of cage 

 experiments was started to discover the exact effect of this spray on the 

 \-arious stages of the leafhopper. The following results are preliminary 

 but interesting. 



August .30th a number of health)- Rural New Yorker variety potato 

 plants growing in large two gallon crocks were sprayed with lime water 

 and different strengths of Bordeaux mixture, each formula being used 



'Fluke, C. L. Jot:RNAL of Econo.mic Entomology, Vol. 12, 1919, paj 

 ^Parrott, P. J. and Olmstead, R. D. Journal ok Ecomoxic ExtoiMOLc 

 [)20, pages 224-22.5, and Xew York Geneva Tech. Bull. 77, 1920. 



pages 256-257. 



lOLOGY, Vol. .13, 



1920. 



