258 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



During 1923 flag smut of wheat was found in one new State, 

 Kansas, and in nine additional counties in the States of Illinois and 

 Missouri, In Illinois the State department of agriculture found the 

 disease in the counties of Macoupin, Greene, Scott, Logan, and 

 Hancock, In Missouri this bureau, cooperating with the Missouri 

 State College of Agriculture, discovered flag smut for the first 

 time in St. Charles, Warren, Platte, and Buchanan Counties, In 

 Kansas infestations were found by men from this bureau and the 

 State Agricultural College in four counties in the northeastern part 

 of the State, namely, Wyandotte, Leavenworth, Atchison, and 

 Miami. 



Rosette. — The rosette of wheat, the cause of which is as yet un- 

 known, recurred in Illinois and Indiana, both in experimental plats 

 and commercial fields. Extensive sowings of wheat strains on soil 

 infected with rosette, in cooperation with the Illinois, Indiana, and 

 Wisconsin stations, have shown that many of them are immune. Se- 

 lection of disease-free plants in a badly infested field resulted in im- 

 munity from the disease in the progeny of these plants. This mass- 

 selected lot is similar iji appearance to the very susceptible variety 

 from which the selections were made. Attempts to establish strains 

 of this and other varieties resistant to both flag smut and rosette are 

 under way. 



8cah. — By studying both healthy and infected wheat and corn 

 seedlings grown in parallel series at different soil temperatures, it 

 has been found that at comparatively low soil temperatures the wheat 

 seedling develops very sturdily, with thick cell walls, which soon 

 become lignified and suberized and as a result are highly resistant to 

 the attacks of the fungous parasite. At higher temperatures it was 

 found that wheat seedlings developed with much less vigor, with 

 cell walls much thinner and largely pectic in nature. As a result 

 they are readily penetrated by the parasite. The reverse was found 

 to be true in the case of com seedlings; that is, weak, susceptible 

 plants developed at the lower temperatures and vigorous resistant 

 plants at the higher soil temperatures. This is in accord with the 

 behavior of these seedling blights under field conditions. 



Special studies also were made on the head-blight development of 

 wheat scab. It was found that high humidity during the blooming 

 stage of the wheat head is most favorable for infection. This was 

 found to correlate perfectly with the greatest losses from wheat scab 

 during 1919 and 1920 ; that is, in the areas where summer rains came 

 at such times as to produce high relative humidity during the flower- 

 ing stage, there the greatest losses from wheat scab occurred. 



Take-all. — The true Australian take-all of wheat, caused by the 

 fungus Ophioholus graminis Sacc, was found in the States of Ore- 

 gon, Washington, California, Arkansas, Kansas, Tennessee, North 

 Carolina, and New York. During the past year the disease was not 

 reported from Virginia, although it had been found at one point in 

 that State previously. In Tennessee it was found to a limited extent 

 at one point. In North Carolina it was found only sparingly in four 

 counties. 



Barberry eradication to control blach stem rust. — The campaign 

 for the eradication of the common barberry to prevent or materially 

 reduce epidemics of black stem rust is conducted in cooperation with 

 the State agricultural college in each of the 13 States in the eradica- 



