404 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



not immune to hydrocyanic acid, but the dosage required for satisfactory 

 results is so large that effective fimiigation is unsafe for the tree except 

 under the most favorable conditions. 



FACTS CONCERNING MIGRATION OF BEET LEAFHOPPER 



{EUTETTIX TENELLA BAKER) IN SACRAMENTO 



VALLEY OF CALIFORNIA 



Henry H. P. Severin, Ph. D., California Agricultural Experiment Station 

 Almon J. Basinger. M.S., State of California, Department of Agriculture, Bureau 



of Pest Control 



I. Introduction 



According to Ball (1) the beet leafhopper (EutetUx tenella Baker) is 

 not found, except in periods of abundance, in the inland regions north of 

 Sacramento. Ball (1) reports that during the serious outbreaks of curly 

 leaf (curly top or blight) in 1914, considerable damage to the beet crops 

 occurred at Hamilton City. After several years of idleness the sugar 

 factory at Hamilton City resimied operations during 1918. This sugar 

 mill was closed after the 1918 outbreak of curly leaf and since then has 

 not operated. 



n. Curly Leaf 



We (2) have published the results of our investigations conducted in 

 the Sacramento Valley during 1918. In the beet fields near Hamilton 

 City, not a single beet leafhopper was captured on June 6, and no 

 blighted beets were found. Spring brood adults, however, were taken 

 on garden beets at Marysville on June 2, but 5% of these beets were 

 diseased, indicating an earlier invasion of the pest. A trip was taken 

 into the Sacramento Valley on August 19-25, and from 66-86% of the 

 sugar beets showed ctuly leaf symptoms, in the vicinity of Hamilton 

 City. In the southern part of the valley from 36-86% of the beets were 

 blighted. 



f During 1919, at least one or two trips per month were taken 

 to all of the beet centers in the Sacramento Valley during the beet 

 season. The first beet leafhopper was captured on Silverscale or Fog 

 Weed (Atriplex expansa) near Woodland on May 27, but no curly leaf 

 was found in the late planted beet fields. The average percentages 

 of curly leaf in the various beet districts developed as follows during 

 the past season. 



