THE WESTERN" CABBAGE FLEA-BEETLE. 17 



In this experiment radishes were sprayed and only the upper side 

 was treated. A good quantity of the poison remained, no injury 

 resulting from the spray, but no dead beetles could be found. Nine 

 days later a rain fell, leaving many leaves unprotected, the beetles 

 becoming abundant. 



Experiment No. 11 — April 29, 1912. 



A badly infested planting of mustard was dusted with undiluted 

 arsenite of zinc. As in the foregoing experiment a moderate wind 

 was blowing at the time and carried much of the poison away. The 

 result, however, was practically the same, some of the poison remain- 

 ing on the leaves, and although no dead beetles were found the plants 

 were comparatively free from flea-beetle attack a week later. 



It should be remarked that the plants at this time needed water 

 but the irrigating ditch was dry. 



RECOMMENDATIONS. 



It appears to be practically impossible to kill an appreciable 

 number of the western cabbage flea-beetles by spraying with arseni- 

 cals. Repeated experiments have shown that whatever application 

 may be made does not kill the insects but drives them away. In 

 other words, this insect can not be controlled by poisons, but by 

 repellents and deterrents. The beetles are dainty in their feeding 

 habits, carefully avoid foliage which has been sprayed, and attack 

 either unsprayed portions or fry to other plants. Repellents such as 

 tobacco dust are the most efficient of those which have been tested, 

 and of the arsenicals, heavy applications of arsenate of lead have 

 given the most satisfactory results. 



LEAD ARSENATE. 



In large plantings, and especially where cabbage is infested, 

 spraying heavily with arsenate of lead is advised (PI. I, fig. 1). The 

 following formula has given excellent results: 



Arsenate of lead, paste pound. . 1 



Fish-oil soap (as a sticker) '. do 1 



Water gallons. . 10 



This is at the rate of 5 pounds of lead arsenate to 50 gallons of water, 

 or a trifle stronger than the standard formula of 4 to 50. One-half 

 this weight of powdered lead arsenate, or 2 pounds in 50 gallons of 

 water, is equally effective, with a corresponding quantity of soap to 

 act as an adhesive or '.' sticker." It should be applied with a sprayer 

 fitted with elbow extension, and a special effort should be made to 

 coat thoroughly the under surface of the leaves. Two or three appli- 

 cation^ at 5 to 8 day intervals are sufficient even in case of severe 

 infestation, provided the first application is made promptly on the 

 first appearance of the insects. 



