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 fly 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- 
cations 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. 
