18 THE CURLY-TOP OF BEETS. 



duced ; October 5, four of the eleven plants now have decidedly curled 

 leaves; October 8, seven plants now affected; October 14, nine plants 

 now affected; October 23, ten affected. The beets grown in the open 

 greenhouse beds remained healthy. The beets were quite young; 

 the hoppers were adults. 



In still another experiment in the Garland field some adult leaf- 

 hoppers were placed in a cage with beets not less than three months 

 old, the outer leaves being first stripped off. In this case the disease 

 was longer in manifesting itself, but when it appeared it took the 

 retracted type (figs. 2 and 3). 



NYMPH OF BEET LEAFHOPPER MORE HARMFUL THAN THE ADULT. 



During the season of 1900 the writer sent other lots of beet leaf- 

 hoppers to the Office of Sugar-Plant Investigations, at Washington, 

 D. C, and duplicated these experiments, with similar results." In 

 addition, in order to determine the relative effects of the work of 

 nymphs and adults, some of the former were sent from Idaho and 

 caged with twelve seedling beets, the largest of which was not 

 more than inches in leaf spread. Two days after placing these 

 nymphs in the cage the inner leaves of two beets had begun to curl ; 

 in three days three and on the eighth daj' four plants exhibited 

 symptoms of the disease. At the end of sjxteen days but four plants 

 showed curl in a cage in which adult hoppers had been imprisoned. 

 On the fifteenth day all of the plants infested by the nymphs had 

 decided curly-top symptoms. Thus it is shown that the nymphs are 

 more virulent than the adults. 



In addition to the varied conditions under which these experiments 

 were made, a further set of conditions was introduced in the field. 

 A portion of two rows of sugar beets was covered with a white muslin 

 awning about 15 inches high. The plants under this awning finally 

 thrust their leaves against it and became badly crowded and the soil 

 remained comparatively wet, yet the disease appeared on these plants 

 in about the same ratio as on those in the open field. 



HISTORY OF AN OUTBREAK OF CURLY-TOP IN THE EXPERIMENTAL 



FIELD AT GARLAND, UTAH. 



In the experimental field at Garland, Utah, beet seed was sown on 

 April 14 and the few days following. This is some two weeks later 

 than the average in this locality. In a small plat, separated from the 

 main portion of the field by an irrigating ditch running east and 

 west, were sown several strains of seed from beets grown for several 



a Grateful acknowledgment is made of the valuable nssistance of Dr. C. O. 

 Townsend and Misses N. A. Brown and <\ O. Jamieson in conducting the cage 

 experiments in the greenhouse at Washington, D. C. 

 181 



