BEET AND SPINACH INSECTS 93 



Diseased plants have the veins of the leaves enlarged, and the 

 surface becomes warty, uneven, and the edges curl inward, 

 bringing the under surface into view. The petioles are shorter 

 and bowed outward. The leaves are more brittle than normal, 

 although they have a leathery appearance. Young plants 

 may be killed outright, others are badly stunted ; the sugar- 

 content of the roots is lessened and there is an abnormal de- 

 velopment of rootlets. Cross-sections of the root often show 

 dark concentric circles from the darkening of the fibro vascular 

 bundles. Frequently large fields of beets so affected are not 

 worth harvesting and in many localities the growing of sugar- 

 beets has been abandoned for this reason. When beets are 

 grown the second year for seed, the presence of this disease 

 greatly reduces the crop. 



The disease is transmitted by a small, creamy or greenish 

 white leaf hopper, sometimes tinged with red, about ^ inch in 

 length, both nymphs and adults being capable of infecting 

 the plant on which they feed. This insect is a native of the 

 same region where it feeds on several species of Atriplex and 

 Russian thistle, sea blite and greasewood. Certain species of 

 Atriplex seem to be its favorite wild food plants. The insect 

 hibernates as an adult, appearing in the beet fields in late 

 spring. 



Beet fields do not, as a rule, become infested by leaf hoppers 

 that have hibernated in their immediate vicinity. Apparently 

 the infestation comes from leafhoppers that have developed on 

 their wild food plants in desert regions and that have hiber- 

 nated near their breeding grounds. In late spring these insects 

 migrate in great swarms, passing over high mountain ranges 

 and traveling to distances of several hundred miles. In the 

 course of the migration, the leafhoppers settle in any beet 

 fields in which the plants are in condition to serve as food. If 

 the crop in a field is not up at the time of the flight, it is not 

 likely to become infested from adjoining fields but may be 



