156 EXPERIMENT STATION RECORD. 



distance of 1 ft. In still another 5, the same aniount'of fluid and number 

 of injections were made at the distance of 2 ft. As a result it was 

 found later that where the injections had been made on one side of the 

 tree only, the insects upon the opposite side were not killed. 



The author considers tobacco dust superior to any other insecticide. 

 As a fertilizer it is worth all it costs and as an insecticide against the 

 woolly aphis it is worth much more. In nurseries it may be placed in 

 small trenches dug along next to the rows of grafts, buds, or small trees, 

 and covered over. The application should be repeated each spring. 

 In experiments with this remedy, in the case of large trees, the dirt 

 was removed from around the crown of each tree for a distance of about 

 2 ft. and to a depth of about 4 in. In the excavation thus made the 

 tobacco dust was evenly distributed at the rate of 3 to 5 lbs. per tree 

 and then covered over. This was in June. In August the same trees 

 were given another supply of the dust and in October they were exam- 

 ined. Only 2 out of 15 trees treated were found to be still infested 

 with the aphis. None of the trees died or were in any way injured by 

 the dust. In a single season very badly infested 10-year-old apple trees 

 were completely freed from the pest. In another experiment 15 young- 

 bearing apple trees were selected and the tobacco dust applied in the 

 same way in June and the treatment repeated in August. In October 

 they were examined and not a single woolly aphis could be found. 



In setting out trees, it is advised that the roots be dipped in kerosene 

 emulsion to kill whatever aphides may be present, and that during the 

 first season about a pound of tobacco dust be placed about the tree, 

 increasing this amount each spring until the tree receives about 3 lbs. 

 when G years old. 



Kerosene emulsion is not considered an advisable remedy on account 

 of the expense involved and the difficulty experienced in making it 

 reach the aphides beneath the large roots. 



The cucumber flea beetle as the cause of pimply potatoes, 

 F. 0. Stewart (New York State Sta. Bui. 113, n. .v., 1896, pp. 311-317, 

 pi. 1). — From observations made during 1894-'96, the author concludes 

 that he has definitely determined the cause of the trouble known as 

 pimply potatoes. Minute slender white grubs were found boring into 

 the tubers, roots, and root stalks, which later pupated and appeared as 

 the small black flea beetle (Grepidodera (Epitrix) cucumeris). 



Hitherto the larva*, of this insect has been supposed to be a leaf 

 miner, and the observations recorded here are of importance as adding 

 considerably to the knowledge of its habits and life history. Owing to 

 irregularities in the appearance of the disease, it was at first thought 

 that different varieties of potatoes were differently affected, but it was 

 later found that " slivers" ' without pimples occurred on the same tuber, 

 and it was concluded that in order to produce a pimple the tuber must 

 be attacked at a certain stage of its growth. 



1 The name applied to the wouiid due to the boring of the grub. 



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