ENTOMOLOGY AND PLANT QUARANTINE 
49 
Charleston, S. C, The wireworm popuhitions were not reduced significantly 
in these tests, nor was there any significant difference in the number and 
weight of tubers showing wireworm injury which were produced in the treated 
plots and of those from the untreated plots. 
BEAN AND PEA INSECTS 
Field experiments with insecticides in Ohio and Virginia on beans grown for 
the green-bean market or for canning have shown definitely that the Mexican 
bean beetle can be controlled best at a minimum cost with sprays or dusts of 
cube or derris. Results with cryolite sprays or dusts have continued to indicate 
that the control value of this material is questionable, although it gave a fair 
degree of control under some conditions. In the East the performance of 
cryolite apparently varies to a certain extent from year to year in accordance 
with variations in weather conditions and possibly in the composition of the 
insecticide. In Colorado the results from tests on irrigated beans grown for 
the dry-bean market demonstrated that, based on increased yields and calculated 
financial returns, cryolite spray gave the most efficient control and was sig- 
nificantly better than zinc arsenite spreay, a material commonly employed in 
that territory. Sprays and dusts containing rotenone were also effective against 
the bean beetle in the West, but they cost more than the cryolite spray. Since 
wide publicity had been given to an article which indicated that magnesium 
sulphate (Epsom salt) used as a spray in the proper concentration constituted 
an effective control of the Mexican bean beetle, experiments with this material 
were resumed in the spring of 1937, even though tests conducted in Ohio during 
1928 had demonstrated rhar this material was not toxic to the Mexican bean 
beetle. Laboratory tests with Mexican bean beetle larvae, using dosages of 
Epsom salt 100 times as great as the lethal dosage of calcium arsenate, showed 
that the test larvae fed on the treated bean foliage, that they consumed as much 
leaf area as the larvae placed on jmtreated foliage, that they molted success- 
fully, and that there was no resulting mortality which could be attributed to 
Epsom salt. Since lal»(»rat(>i y studies during 1936 disclosed that the active 
ingredients of derris were translocated in treated plants in such a manner as to 
prevent extensive feeding of the Mexican bean beetle on foliage that developed 
on the plants after the insecticide had been applied, it was decided to ascertain 
the residual effect of derris on bean foliage in various widely separated localities 
in the United States where wide variations in temperature, humidity, and 
intensity of sunlight occurred. Bean plantings were made for this purpose at 
New Haven, Conn.. Norfolk, Va., Columbus. Ohio. Baton Rouge. La., Madison, 
Wis., Manhattan. Kans.. Grand Junction. Colo., Twin Falls, Idaho, Ventura, 
Calif., Corvallis. Oreg., Puyallup, Wash., and Phoenix, Ariz. These plantings 
were treated with a derris spray, and samples of leaves were taken at given 
intervals and sent to Columbus. Ohio, for analysis. In every case, rotenone 
was recovered in sutficient quantities at the expiration of 2 weeks after treat- 
ment to be indicated by the colorimetric method and goldfish test. At Madison, 
Wis., Grand Junction, Colo., Twin Falls. Idaho. Corvallis, Wash., and Columbus, 
Ohio, derris .showed a slower loss of toxicity than at the other laboratories. 
Neither the intensity of sunlight nor high humidity alone appeared to affect 
significantly the decomposition rate. At Phoenix, Ariz., where daily tempera- 
tures averaged 100° F. during the period of the test, rotenone was recovered 
after 10 days. At Ventura, Calif., where no rain fell during the test, all of 
the toxicity had disappeared at the end of 4 weeks. In general, these tests 
demonstrated that the residual properties of derris were such that in any part 
of the United States where cultivat(Ml plants are commonly grown this insecti- 
cide could be used effectively against the species of insects which it is known 
to affect. 
Dust mixtures containing rotenone gave excellent control of the pea weevil 
in large-scale field tests performed in Idaho, Washington, and Oregon. In 
Oregon 60 fields, involving approximately 300 acres of peas grown for canning, 
were included in the tests. The greater part of this acreage was treated with 
a dust mixture containing 0.75 percent of rotenone with talc as the diluent. 
This combination appeared to be more effective than dust mixtures containing 
0.2.'>. 0.50. and 0.75 percent of rotenone, resi)ectiv(>ly. with diatomaceous earth 
as the diluent. Two applications of these dust mixtures were made to all of 
the fields with .specially constructed power dusters. Based upon an examination 
of the peas at the viner. the control achieved in the treated fields averaged 
approximately 97.7 percent. In the Washington canning-i)ea section many tons 
of rotenone dust mixtures were applied to the weevil-infested .sections of pea 
24605—37 4 
