42 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1951 
and shrubs, and a single application protected ripening peaches 
for l- days. Three applications of 30 pounds of a 5 percent dust an 
acre at l-dav intervals destroyed an infestation on young bearing 
and prevented establishment <>l" an infestation on sweet 
corn. Two applications 5 days apart of an emulsion spray at the rate 
of L.5 pounds of toxicant an acre protected hybrid corn against beetle 
dam 
More effective than DDT against the plum curculio, methoxychlor 
is especially promising for protecting apples against this pest Lnclu- 
of 3 pounds of a 50-percent metnoxychlor wettable powder to 
LOO gallons in the calyx and first two cover sprays held curculio injury 
to a very low level under condition- of light infestation in Indiana. 
Elsewhere methoxychlor was equally promising for the purpose, espe- 
cially when ased in combination with lead arsenate. The perform- 
of methoxychlor in controlling the plum curculio on peaches 
has been errat ic. 
E rlier promising results in controlling light infestations of the 
codling moth and the cherry fruit fly with methoxychlor were con- 
firmed in the Pacific Northwest. In small-plot field tests in Wash- 
ington met how <•! dor controlled the codling moth as well a- did DDT. 
1 1 also gave a high degree of control of the cherry fruit fly in Ori 
Against this fruit fly a wettable-powder spray was slightly superior 
to a dust, but an emulsion was ineffective. 
Additional studies pointed to the possible value of methoxychlor 
for control of the apple maggot and grape berry moth. In New York 
five applications gave excellent control of the apple maggot. In L949 
about 95 percent of the apple- in the experimental orchard were in- 
fested; in 1950, follow i ag the treatment, the infestation was reduced 
to less than 6 percent. In Ohio methoxychlor alone (2 pound- of 
ettable) has consistently given control of the grape 1 
moth nearly equivalent to that of the standard schedule of DDT alone 
I L5 pounds of 50-percent wettable). Neither material used alone is 
quite as effective as when it is in combination with parathion. 
Nov Ensecl Vectors of Vims Diseases of Stone Fruit Found 
periments at Logan, Utah, indicate that the black cherry aphid 
can transmit the virus, or viruses, responsible for wilt, or decline dis- 
and sour cherry trees growing on mahaleb rootstocks. 
Field observations indicate that Colladonuz geminatua (Van Duzee) 
11 the most important vector in Washington orchards. However, 
three additional species of leafhoppers capable of serving as carriers 
of wes tern K. disease v f us I Say I . /■" 
(Stal), and Keonolla confhcens (Uhler) have been discovered by 
erating Washington State entomologists of the Tree Fruits 
B I i riment Station at Wenatchee. Leafhopper transmission 
of western X Prom infected cherry trees to healthy peach trees 
demonstrated by the Washington State entomologists and con- 
firmed by Bureau v in Utah. Leafhopper transmission of 
ern X disea e from infected chokecherry to healthy peach trees 
i demonst rated in I Ftah, 
The important results of the vector studies may be attributed largely 
■ ■ close co< perntion of the Washington, < Oregon, and Ftah Agri- 
