Is ANNUAL REPORTS OF DEPARTMENT OF AGBICUI/TUBH, Ifl 
cate that a single application will keep wireworms in irrigated lands 
at a low level for 4 or year-. Experiments to determine the effect <>f 
accumulations in the soil on crop production are -till incomplete, hut 
indications are that neither chlordane nor toxaphene will he dissi] 
more quickly than DDT. 
Onion Thrips Controlled With Several New Insecticide! 
Thai DDT. chlordane, and toxaphene will control the onion thrips 
on hull) onions or onion- <_ri(,un for seed, it" applied at fairly h'iL r h 
dosages, ha- been shown by extensive field-plot experiments in Cali- 
fornia and Idaho. Ten-peiv.-nt dusts Were more effective than 5-per- 
cent. and emulsions were betteT than wettable-powder sprays of the 
same strength. All these insecticides appeared to be about equal in 
effectiveness, although there were some indication- that chlordane 
may he slightly better than the other two. On bulb onion- three ap- 
plications are required at 2-week intervals beginning when tin 1 plants 
are 10 inches high. 
Parathion gave promising results when applied as 1- or 2-percent 
dusts, hut it had less residua] action than the other matt-rials. If 
residues do not persist, it may he particularly useful in combating 
thrips on spring onions, which are harvested comparatively soon after 
the treatment. 
New Insecticides Kill Inseets Affeetinp: Siuiar-Beet Seed 
During the past year 5-percent DDT dust has been adopted a- a 
standard insect icide for the conl rol of plant bugs on sugar beets grown 
for seed. In further experiments on insect- affecting sugar-beet seed, 
dusts containing 2 percent of gamma benzene hexachloride or para- 
thion were found to he effect ive against the Say -t ink hiiL r . and a Dl >T 
emulsion was found to reduce the percentage of plants affected by 
curly top disease carried by the beet Leafhopper. However, according 
to informal ion thus far available, the I >I )T emulsions must he applied 
so frequently that the cost of the treatment i< too high to he of practi- 
( al value. 
SweetpOtatOCfl Protected from Weevil Damage 
Suppression of the destructive sweet potato weevil i- vital to the 
success of the important and expanding sweetpotato industry in the 
Southern Stall-. ( her a period of year- <|uarant inc. -ur\ ey. and con- 
trol measures have been applied cooperatively by Federal ami State 
a<_ r ciicie< in commercial production areas in Alabama, Georgia, 
Louisiana, Mississippi, South Carolina, Texas, and northwestern 
Florida. Since L937 a total of 37 counties, including s .'.*oo farm- and 
storage places, have thus been cleared of weevils. En the calendar year 
p.»l^ weevils were eradicated from 916 infested farms, and planting 
re-t rict ions On I hem were w il hdraw n. 
Outside of Louisiana and a limited area in Texas only a very -mall 
proportion of farms in the commercial sweetpotato districts are now 
