u HEAT CULTURE. 357 



Wheat Blight (Septoria sp.) 



During a cold and backward season the young 1« a ves of wheat often turn 

 yellow and die prematurely. With this premature withering, fungi 

 belonging to the genus Septoria are frequently associated. These fungi 

 produce on the leaves very numerous minute brown or black Bpecks scarcely 

 visible to the naked eve. Each speck is a small flask-shaped depression in 

 the leaf blade, containing innumerable fungus spores, the spores themselves 

 are elongated, and are frequently provided with a row of drops or with 

 cross walls. 



Three fungi belonging to the genus Septoria have been recorded upon 

 wheat in Australia. Occasionally the crop may be seriously checked by the 

 presence of species of Septoria, It is not possible, however, to apply a 

 remedy, but burning the stubble would destroy a large number of spores, 

 and thus diminish the spread of the disease. 



"Contortion." 



Several cases came under notice during the season 1913, in which wheat 

 straw had buckled or twisted in its growth, as if constricted or hindered 

 in its normal rate of extension. A kink in the straw resulted, and, as it 

 ripened, the wind caused the affected straw to break at the weak point, the 

 result being that the crop sometimes looked as if people had been trampling 

 recklessly through it. The appearance of the affected straw is shown in the 

 accompanying illustration (Fig. 24). 



Mr. Pridham, Plant Breeder, reported the occurrence of wheat so affected 

 at Nyngan where field plots of Steinwedel showed many of the straws 

 broken down, at Wagga, where two selected bulk sowings, the one of 

 livmer, the other of Bobs, were affected, and at Cowra, in the case of two 

 crossbred wheats which appeared to have strong straws. The particular 

 character of the straw seemed to be of little importance, for the wheats at 

 Nyngan and Cowra had strong straw, while those at Wagga were inclined 

 to be weak. , 



Two explanations have been offered of the cause of this kinking of wheat 

 straw, viz., that it is due to the attack of insects, and that it is due to 

 disproportionate growth in one direction as contrasted with that in another. 



Wheat affected similarly to that above described was reported from 

 Carrathool and Deniliquin in 1900 (Agricultural Gazette, vol. xi, p. 1169). 



Mr. Froggatt visited the former place, and found that instead of the 

 Hessian fly (as had been suspected) the damage was caused by Aphidm. 



These insects attacked the wheat stalk when about 6 inches high, shel- 

 tered in the enveloping flag, sucked up the sap on one side, and caused the 

 young wheat stem to bend over or to twist almost into a knot before shoot- 

 ing again. 



The aphides were subsequently destroyed by parasites: the wheat then 

 shot up, but when about -i^ feet high, and when the heads were filling, the 

 weight caused many of the stalks that had been attacked by aphides to 

 break off where the stems were twisted. 



