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at tne rate of 35 to 40 pounds per acre. The speed of the machine should 
not exceed 3 miles per hour or 300 feet per minute. Dusting is much less 
effective when the wind velocity exceeds 8 to 10 miles per hour. Spraying 
is an effective method of control "but its economic usefulness is con- 
ditioned by the nearness of an adequate waler supply. 
On the basis of ground derris or cube root containing 4 percent of 
rotenono, 3 pounds should be used per 100 gallons of water. Corresponding 
dilutions should be used with derris or cube containing more or less than 
4 percent of rotoncne. A spreading and wetting agent, in either liquid 
or dry form, is necessary. The application per acre should be from 125 tc 
200 gallons. Pressure should be 225 to 300 pounds, and depends on size of 
disc aporturos, type of nozzle, and pump crpacity. 
It is believed that an infestation that is reflected oy 35 aphids 
per sweep for an average of 5 sweeps in different parts of the field, with 
a standard collecting net, is usually an indication that treatment should be 
"begun. 
The U. S. Department of Agriculture, Bureau of Entomology and Plant 
^ua.rant ine , in Fobraary 1938 distributed a summary of the remarks made at 
the Pea Aphid Conference (315), Indianapolis, I n d. , Lee. 27-28, 1937. 
Shropshire of Illinois reported on the efficiency of the numorous wetting 
agents offered for use with derris and cube. Over 50 of these combinations 
and dilutions very tested in replicated plots. It was found from these tha,t 
some of the best wetting agents were the poorest for use with derris or 
cube for aphid control on peas. More detailed laboratory tests will probably 
be necessary to find out why this difference occurred in field tests. 
Results of experimental work in 1937 tend to verify results obtained 
in 1936 with both nicotine and derris or cube for v>oe aphid control. They 
further show that cube is as effective as derris, assuming that the rotenone 
and total extractives are approximately the same in both samples. Derris 
or cube with a rotenone content of 4 percent was effective for pea aphid 
control when used at the rate of 2 or 3 pounds per 100 gallons of spray, 
assuming that the spray was applied at the rate of 125 to 150 gallons per 
acre. Aresket (liquid) used at the rate of 1 to 600 was used as a standard 
for comparison with other spreaders. 
A rather ^xt ensive set of dust trials was planned for 1937 following 
a limited amount of work on them daring 1936. Most of the dusts were made 
up to contain 1 percent of rotenone, other ingredients being varied as 
desired. Variables included diluents, wotting a-gents, some suggested by 
Dudley and Bronson, and irritants such as nicotine and certain thiocyanates. 
Results with rotenone-bcaring dusts were variable in 1937 as was the case 
in 1935. In many cases the results wore excellent; however, in certain 
instances they were far from satisfactory. These cases were not easy to 
understand, but apparently the poor performance was due to some weather 
condition, such as absence of free moisture (dew or rain) on the plants. In 
spite of some very noov results obtained with rotenone -bearing dusts it is 
felt that they have sufficient merit to warrant recommendation with reser- 
vation. 
