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UNITED STATES DEPARTMENT OF AGRICULTURE |. eg: ©! 
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Number 228 Activities for March April, 1933 
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(Not for Publication) Og ta eee 
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TRUCK CROP AND GARDEN INSECTS 
Weather in relation to beet leafhopper populations.—-Reporting 
on the meteorological factors useful in forecasting outbreaks of Eu- 
tettix tenellus Bak., J. C. Chamberlin and F. H. Harries, Twin Falls, 
Idaho, state that "the maximum temperatures of the preceding year, 
February to November inclusive, are by far the most influential fac-— 
tors in determining leafhopper populations the following year. This 
temperature factor is followed in importance by the winter precipita— 
tion in well-marked storm periods from November to February, inclusive, 
while the third most important factor is the precipitation during the 
‘Critical’ (as far as the uncultivated hosts of E. tenellus are con-— 
cerned) period of September and October of the preceding fall. Properly 
weighted, these factors can be shown to account for all but about 8 
percent of the variations in sugar-beet tonnages in the Twin Falls— 
Jerome area since the establishment of the industry (1916)." 
ae ee ee, 
Sanford, Fla., reports that "In cooperation with the Food and Drug Ad— 
ministration a field experiment was conducted to determine the effect 
of weathering and stripping at harvest time on fluorine residues on 
celery, using a natural cryolite compound, a barium fluosilicate com- 
pound, and a 30 percent sodium fluosilicate dust. Although 3.77 inches 
of rain fell after the first application, it is evident that none of 
these treatments could be permitted on the basis of the tolerance al- 
lowed for arsenical residues. Even the heavy rain after the single ap- 
plication, which weathered for 21 days, failed to reduce the residue 
sufficiently." 
tes spp.) from larvae to adults there occurs a tremendous loss in weight. 
In a preliminary study of this phase of development it was found that 
about 25 percent of the prepupal weight is lost by the time of full col- 
oration of the beetle. Only about one-fifth of this takes place in 
change from prepupa to pupa, regardless of the fact that a rather heavy 
prepupal skin is cast. About 20 percent is lost in the change from 
pupa to adult, even though the skin cast is extremely thin. The loss in 
the transformation from prepupa to pupa ranges from 4.4 percent to 6.5 
percent. In the change from pupa to adult the loss ranges from 19 per-— 
cent to 25 percent. The larger individuals tend to experience the 
larger percentage of loss." 
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