272 KEruirr of ofi-ick of exi'kuiment stations, 



fiimi<rati()ii was done early in the a ftcniooii, (ho loniato plants 

 Avi'iv somewhat injured hy (lie a|)i)licati()n of 1 ounce of cyaiiid per 

 1,000 cubic feet of space. Tlie same amount of cyanid, however, 

 caused no injury when the fumigation was done in the evening. It is 

 reconunended that no fumi<i:ati()n he done while the sun is shining or 

 while the temperature is above G0° F. In Massachusetts " it was found 

 })ossil)le in some instances to prevent serious injury from this pest by 

 mere cultural measures. Spraying tomato plants in greenhouses is not 

 reconunended. Ilydrocyanic-acid gas was found to be the cheapest 

 and most effective remedy for greenhouse aleurodes. It is recom- 

 mended that this be used at the rate of 0.1 gram of potassium cyanid 

 per cubic foot of space and that the plants be exj^osed after sunset. 

 This will destroy all of the insects except the eggs and a few pupae 

 and Avill not injure tomato plants. In New Hampshire '' the green- 

 house white fly was easily destroyed by spraying with a 5 per cent 

 mechanical mixture . of kerosene. For this purpose a knapsack 

 sprayer was used. In spraying, it is recommended that the operator 

 begin at the top of the plants and work down. The same method 

 was used out of doors with good results. The most successful and 

 satisfactory treatment, however, was fumigation. A greenhouse was 

 fumigated in July at 10 o'clock in the forenoon of a clear day, the 

 period of fumigation being fifteen minutes. At the end of this time 

 all of the flies w^ere dead and the plants of the greenhouse were unin- 

 jured, except the leaves of a lily. Similar treatment applied in the 

 afternoon was also successful and without injury to the plants. 



THE COLORADO POTATO BEETLE. 



Several stations have been concerned in demonstrating the practi- 

 cal efficiency of arsenicals in the control of the potato beetle. In 

 Maine '^ various insecticides have been compared with Paris green. 

 It was found that there is no adequate substitute for arsenical poison 

 in fighting this pest. These poisons may best be applied with water 

 in the form of a fine spray and repeated as often as necessary. There 

 appears to be no reason for using arsenoids or other proprietary 

 arsenical insecticides unless they can be obtained more cheaply than 

 Paris green. In the early experiments of the Maine Experiment 

 Station arsenate of lead was found to be more satisfactory than other 

 arsenicals, though somewhat slower in its action. In later experi- 

 ments, when Paris green, bug death, and arsenate of lead were com- 

 pared, no perceptible differences were observed in the color or size of 

 the vines treated Avith these insecticides. Paris green was somewhat 

 more effective than bug death. The potatoes obtained from plats 



a Massachusetts Sta. Tech. Bui. 1. & New Hampshire Sta. Bui. 100. 



c Maine Sta. Buls. 68, 87, 98, 



