50 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1053 
to coincide with emergence <>f the adult. Aldrin, chlordane, DDT, 
dieldrin, heptachlor, and toxaphene were applied at the rate of 1 
pound, and lindane at ] ■_. pound of toxicant in 25 gallons of water per 
acre. The average yields of seed per acre for the two best treatments 
were 697 and 627 pounds for dieldrin and heptachlor. as compared 
to 44*2 pounds for the checks. It was esl i ma ted that, after deducting 
tlie cost of the insect icides and their application, there were net profits 
of Sis 1 and $133 per acre, respectively, for the dieldrin and heptachlor 
treatments. 
When onion bulbs were soaked for 15 hours in a 0.1-percent emulsion 
prior to planting, the average yields of seed per acre for chlordane, 
heptachlor. and Systox treatments were si'.*, 715, and 70S pounds, 
respectively, as compared to 564 pounds for the check. 
New Insecticides Evaluated for Pea Aphid and Pea Weevil Control 
Various new insecticides were evaluated for control of the pea aphid 
in experiments continued in Washington, Idaho, and Oregon. Meta- 
cide in a spray was superior to parathion ai the same dosage for 
control of the pea aphid, and was less dangerous to apply. Malathion 
as a spray at 2y 2 times the strength of parathion, and a commercially 
prepared safened parathion at the same strength were approximately 
equal in effectiveness to parathion spray. 
A series of tests for pea weevil control showed that none of the 
insecticides with a low potential in residue hazard exceeded DDT in 
effectiveness. 
Green Peach Aphids Show Signs of Insecticide Resistance 
Green peach aphids on potatoes in Washington may lie developing 
some resistance to insecticides. Field experiments there to develop 
methods of controlling these aphids, and indirectly to retard the spread 
of leaf roll and other virus diseases carried by them, have since L948 
shown the decreasing effectiveness of DDT as a means of control. 
In experiments on early crop potatoes excellent control was ob- 
tained in 1!>.VJ with DDT-paratnion-sulfur dusts, DDT-parathion 
(•in ul-ion sprays, and malathion imi i u Isi on sprays, Neii 1 km- I >DT dusts 
nor DDT-oil sprays gave satisfactory control. On late crop potatoes 
none of these insecticides or TEPP dust gave satisfactory control, 
although the dosages were increased to two or three times the usual 
amount. 
Further Studies Needed on Systox as Potato Aphid Control 
Systox will control four species of aphids affecting potatoes in 
Maine, field experiments there have disclosed. Systox was applied 
weekly in .-pray mixtures to foliage of the growing plants as well as 
in t he furrow jusi before planting the potato seed pieces. Very small 
quantities of the insecticide were sufficient, the minimum total-season 
amount - of act i\ e ingredient being 0.78 pound per acre when applied 
to t he plants and <».;;7.', pound in t he furrow. Better Control of aphids, 
particularly the potato aphid, was obtained by stopping weekly appli- 
cations of DDT about Angus! l and using one or two applications of 
parathion, or malathion than by continuing with DDT 
