Oct. 1,1920 Fusarium-Blight (Scab) of Wheat and Other Cereals 25 



Winter wheat, disinfected as described above, artificially inoculated 

 with conidia of Gibberella saubinetii, and sown October 20, 191 8, in 

 five 12-inch pots of sterile soil with 10 kernels in each pot, was left in the 

 greenhouse for 15 days and then taken out of doors, where it remained 

 till July, 1 91 9. A similar series of spring wheat similarly treated was 

 sown on April 2 1 in pots of the same size but was left out of doors from 

 the time of planting. Two pots sown with similarly treated but unin- 

 oculated seed were used as controls for each of the two series. In both 

 series the plants recovered rapidly from the primary attack and grew 

 normally, giving plants which were apparently normal, except that their 

 bases and roots were slightly rotted and browned. With the coming of 

 dry weather during the second half of June this rotting and browning of 

 the roots and especially of the bases was intensified somewhat, and the 

 plants began to wilt suddenly. In the field, wilting usually takes place 

 at the time of heading or shortly after. The general symptoms accom- 

 panying wilting of fully developed plants are somewhat similar to those 

 described for the footrot of the cereals in Europe and for "take-all" in 

 Australia. G. saubinetii was isolated from the browned and rotted bases 

 of the wilted plants in the foregoing experiments, as well as from those of 

 some of the similarly wilted plants in the field. 



Head inoculation. — While much work must be done before the nature 

 and exact importance of the parasitism of Gibberella saubinetii on the 

 underground portions of the cereal crops and the factors influencing or 

 controlling it are fully understood, the question of headblighting due to 

 this organism is much easier to follow and is, therefore, better understood. 



The methods used in testing the pathogenicity of Gibberella saubinetii 

 on wheat, rye, barley, oats, spelt, brome grass, quack grass, and timothy 

 are very simple. They consist in producing a heavy suspension of 

 conidia, either from heads already infected or from pure cultures, and 

 spraying it by means of a small atomizer on a number of heads, usually 

 10, of the various hosts mentioned above when they are in the proper 

 condition for infection. This method is successful when the weather is 

 moist and cloudy. In dry weather this method will give either no 

 results or only a very small percentage of infection. Certain results can 

 be obtained only when the infected heads are in some way kept moist for 

 at least three days after inoculation, and even this method will not give 

 good results during extremely dry and hot weather. In the work described 

 above the heads were kept moist by placing some moist absorbent cotton 

 around the stems of a group of heads, then covering both the heads and 

 the bundle of cotton around their stems with a glassine bag. The open 

 end of the bag was tied around the stems just below the bundle of cotton. 

 The heads so treated were heavy and required support. For this reason, 

 garden stakes 5 or 6 feet tall were driven into the ground near the plants, 

 and the bags covering the heads were tied loosely to them. The moist 

 cotton inside of the bag kept the air comparatively moist and created 



