ee, 
LIBR ARY 
MONTHLY LETTER OF THE BUREAU OF ENTOMOLOG RECEIVED 
UNITED STATES DEPARTMENT OF AGRICULTURE *& AUG 15 1933 ye 
U8. 2 
“epartment of Asriculture 


, 
__ Number 230 Activities for May 
v4 (Not for publication) 

FRUIT AND SHADE TREE INSECTS 
Methyl thiocyanate shows promise against California red scale on 
Seecitrus.—-H. R. Yust and Lillian Baird, Whittier, Calif., report on fu- 
Migation (in cooperation with H. C. Cupples and J. Hiley, of the Bureau 
of Chemistry and Soils) of Chrysomphalus aurantii Mask. under controlled 
conditions. They state: "The work in May was concerned almost entirely 
with small-scale fumigation tests with methyl thiocyanate compared with 
hydrogen cyanide. Small citrus trees planted outdoors were fumigated 
¢ under a 50-gallon barrel. Four lemons infested with red scale were sus— 
| pended within the barrel during each test. * * * Methyl thiocyanate 
was injected into the barrel in the form of a liquid, sprayed by means of 
) a small nasal atomizer, or as a dust, consisting of liquid methyl thiocya- 
Nate absorbed in diatomaceous earth in proportion of 1 part liquid to 4 
: parts of dust by weight, and injected into the barrel by means of a 
‘ small hand duster. * * * The tests were performed in daylight hours, 
usually with full sunshine, and with temperatures under the barrel at 
| meetime Of fumigation ranging from 79° to 105° F. * * * The results 
| are briefly summarized: (1) The variation in degree of injury was ap- 
parently due largely to difference in the character of growth of the tree, 
the more tender growth being most seriously injured; (2) the tests in- 
dicate definitely that methyl thiocyanate produced less injury to the trees 
| than did equivalent gram-molecular dosages of hydrogen cyanide; (3) the 
tests in which the dosage and exposure were varied indicate that it may be 
possible, by the use of methyl thiocyanate, to obtain a satisfactory kill 
of scale without injury to the tree." 
Reduction of pecan crop demonstrated as caused by black pecan aphid- 
G. F. Moznette, Albany, Ga., reporting on pecan trees sprayed last sea- 
son with nicotine sulphate to prevent premature defoliation by Melano— 
callis caryaefoliae Davis, states that 23 percent of such sprayed trees 
bloomed this spring and that of the check trees, only 1.6 percent bloomed. 
He presents these records as an indication that premature defoliation by 
the black pecan aphid influences the set of nuts the following spring. 
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cause some injury to pecan.—-Howard Baker, Shreveport, La., summarizes 
the effect of applications of oil sprays on dormant pecan trees in 
1932-33 as follows: "(1) Four percent lubricating oil emulsions were 
practically 100 percent safe, bud opening and development being normal 
