30 



THE CURLY-TOP OF BEETS. 



when siloed produced an average of only 13.82 grams of seed; those 

 exhibiting signs of the disease when harvested produced but 13.25 

 grams per plant. The average for the healthy beets was about 375 

 grams, or about twenty-eight times as much as the yield of affected 

 plants. (See fig. 9.) 



During 1905 an important sugar-beet district was afflicted by an 

 invasion of Eutettix tenella which resulted in great loss. The sugar 

 company, however, selected and siloed enough apparently healthy 

 beets to plant 4| acres in the spring of 1900 for seed production. Of 

 these, 1^ acres Avere entirely unproductive; only 1,200 pounds of 



Fig. !). — Average seed yield of healthy and curly-top sugar beets: (A) Average amount 

 from diseased beets, 13. 25 grams; (B) average from healthy seed beets, 375 grams. 



seed were obtained from the other 3 acres, or 400 pounds to the acre, 

 or 36.3 grams per plant. In 1906, when the sugar-beet crop was good 

 in the same district and few leafhoppers appeared, enough beets 

 were selected to plant 8.29 acres. These seed beets yielded 16,800 

 pounds of seed, or 2,038.6 pounds to the acre, or about 177.6 grams 

 per plant. The difference here shown is not so great as in the experi- 

 ment conducted by the writer because not all of the beets siloed by the 

 sugar company could have been as severely attacked during the pre- 

 ceding season ; then, too, the plants used by the writer were set much 

 farther apart than those of the sugar company, thus encouraging a 

 larger yield among the healthy beets. 



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