58 ANNUAL REPORTS OF DEPARTMENT OF 
and the practice of certain crop rotations that are detrimental to wireworm 
development 
in the course of several Held experiments in the Northwest it was found that 
the Incorporation Into the soil of 800 pounds of crude oaphthalene per acre 
while the land was being plowed, and during the prevalence of Boil tempera- 
tures reaching 7" I', or higher, killed from approximately '.'."» to '.•'.' percent of 
the wireworms. Better results wen* obtained with oaphthalene fumigation In 
Loam or sandy loam Boils than in silt loam soils. 
As an example of the effectiveness of Boil flooding as a method of wireworm 
control under favorable conditions of soil temperature it nia.\ be stated that as 
a result of flooding one part of a potato field in the State of Washington for a 
period of 7 days after harvest Km percent of the wireworms were killed. The 
flooded part of the held contained an average of approximately 20 wireworms 
per square foot before treatment. During the period of flooding in this field 
the soil temperatures at depths of <;. 12, and is Inches, respectively, averaged 
approximately 7'A° F. The part of the held not Hooded contained an average of 
8 living wireworms per square foot. 
That the drying out of soil through the withholding of irrigation water con- 
stitutes a practical method of reducing injury by wireworms in Irrigated lands 
was demonstrated in the State of Washington in a typical field tot wherein 
potatoes were planted in 1985 in a held following alfalfa that had been dried out 
during 1034. The drying-out process had reduced the wireworm population to 
an average of less than one per Cubic foot At the lime of marketing the potato 
crop produced in this held, only 4 percent of the potatoes were classified a- culls 
due to wireworm injury whereas, in an adjoining held which was not subject to 
a drying-out process prior to planting, the potato crop was damaged so Beverely 
by wireworms that it was not worth harvesting. 
Both sweetclover and red clover were found unsatisfactory crops to use in 
rotations in infested fields where wireworms were numerous, since these crops 
provide very favorable Conditions for the increase of the wireworm infestation, 
as contrasted with alfalfa, which provides unfavorable condition- I'm- wireworm 
increase. 
Subterranean applications of dilute solutions of dichlorethyl ether applied t" 
trap rows of beans planted to attract the wireworms has given Indications "t* 
exerting a marked control of these pests. 
'idie Gulf wireworm increased in Importance, particularly as a pot of pota- 
toes, in Alabama and South Carolina. Field experiments indicated that damage 
by this pest may he reduced greatly by adopting crop rotations that will include 
sod and that will avoid the planting of potatoes in the same land during succes- 
sive years. Promising results were obtained by trapping the adults under potato 
vines raked into windrows after harvest and then burning the vine- underneath 
which the adults had congregated. 
BEAN AND PEA INSECTS 
The Mexican bean hectic continued to he the most important pest of beans in 
the United states and in widely separated parts of the Infested area caused 
severe damage to beans nol treated with Insecticides. Field experiments with 
Insecticides in <>hi<> and Virginia on beans grown for the green-bean market or 
for canning have demonstrated thai this pest can he controlled at a minimum 
cost by appi\ ing sprays or dusts containing rotenone derived from derris or cube 
without danger of Incurring harmful residues on the market product. Cry. .lite 
sprays also were effective, hat the use of this materia] must be discontinued 
after the pods Iimvo formed in order to avoid the p«.s<il»iliiy of harmful residues 
on the harvested beans, it has been found necessary i" discontinue recommend- 
ing magnesium arsenate as a control for the Mexican bean hectic. During LOSS 
this Insecticide caused -even- burning of bean plant- ami was not so effective as 
Insecticides containing rotenone <>r cryolite. Laboratory studies disclosed that 
the a< tive Ingredients of derris were adsorbed and translocated in treated plants 
in aucb ;i manner as to prevent extensive feeding of bean beetle larvae on foliage 
that developed on the plant- after the Insecticide had been applied. This 
residual effect of rotenone-containing Insecticides had been observed previously 
field conditions. Results in Colorado of tests on Irrigated beans grown 
tor ti,,. dry-bean market demonstrated that, based on Increased yields ami 
caiciiiat.<i financial returns, sprays containing cryolite provided the best control. 
Intensification of the pea-canning Industry in the Pacific Northwest par- 
ticularly in Washington and Oregon, emphasizes the need for determining 
