. - 66 - 
Huckett ( 203 ) also reported in I93U that against insects attacking 
vcgeta'oles derris dusts were usuallj'- slightly superior to derris sprays. 
The Mexican "bean "beetle may Tje effectively controlled "by the us-^ of a 
derris-clay, kaolin, or talc dust mi^rture of not less than 0.5-percent- 
rotencne content, applied niuch in the pp-T.e manner as reconmrnded for 
arsenical dusts. Hydrat^d lime rir a nixtur'^ of hydrated line and nono- 
hydrated copper sulfate affect rctenone adversely, hence their use as a 
diluent for derris dust is not recommended. Durini- the sumer ncnths it 
will usually "be necessary to apply sprays or dusts once ev^ry 10 days t'^ 
2 weeks, whereas with the shorter, cooler days of autu'in, once every 2' to 
3 weeks may "be .quite satisfactory. If derris powder is applied in a spray 
mixture" it is advised th^t a strength comparable to 10 pounds of a derris- 
clay dust ^f 1 percent rotenone strength he used in 100 gallons of water, 
or 2 pounds of an undiluted powdered derris root of 5 percent rotenone 
content in 100 gallons of water, plust the addition in either case of a 
spreadf='r, such as dry skim-milk powder, U pounds, or a nisci"ble sulfonated 
oil or neutral coconut-oil soap, 2 quarts. Both derris powder and skin- 
milk powder, should be made into a paste "before Ijeing added to the tank. 
Hydrated line, "bordeaux mixture, o.r ordinary launvdry .soap are considered u:i- 
desirahle in a derris spray, owing to their adverse effect on rotenone. Al- 
though spraying may .he found to "be a, little cheaper than dusting, insofar 
as costs of ingredients are concerned, it vrill. gen^^rally "^oe found n^^cessary 
to spray at slightly shorter intervals to o"btain results similar to those 
o"btained with the dust. 
The South Carolina Agricultural Experiment Stotion ( 3U6 ) in .19,3^ 
reported the results of tests with various nonarsenical insecticides against 
the Mexican "bean "beetle. "Various commercial prepare tirn?. containing pyreth- 
rom, rotenone, ni'cotine, and other materials as, the active ingredients were 
tested. Best results were as follov/s: 
Dilut; 
ion 
Av.^ra.:o kill 
Material 
Old 
New Larvae 
Foliage 
.t^,-lultg 
. Adul t s 
in.iury 
Percent , 
?.-rcrnt Prrcent . 
Frrcrnt 
Black Arrovr 
None 
55 
U7.7 30.6 
None 
Kuhatox 
None 
52.5 
55.7 6U.6 
Slight 
Red Arrow 
1:200 
17.5 
Ib.U 35.3 
None 
Average of two tests using 20' hi'Dornated adult-^ in e-^ch, 10' to lU 
tests using 25 recently raised adults,. and 6 tests using 25 larvae in each. 
Turner and Friend ( 378) in 193U reported tha.t the use of pyrethrum 
and rot'.'none dusts following applications of arsenicals prevented Mexican 
"bean "beetle damage, and a higher percentage of marketa''ole pods resulted. 
These n^npoisonous dusts were also effective when used' throughout the season 
The United States Depa.rtmont of Aericultur ■', Bureau of Siit;'--molo.;y 
and Plant Q;aarantine ( 387 ) in 193H made the following recom-nendation: "The 
"best control for the "bean "beetle is s-nraying vrith magnesium arsenate, the 
spray ^nixturc "being used at the rate of 2 pounds to 50 gallons of T^ratrr or 
2 ounces to 3 gallons. If later treatments prove necessary, a derris or a 
rotenone dust (containing from 0.5 to 0,6 percent rotenone) should he used." 
