WHEAT CULT! !;K. 



3 I 7 



after these spore cases have begun to appear the leaves that were covered by 

 the mildew felt die, and at length the felt drops off. Each spore case con- 

 tains a number of small sacs, each of which holds eighl spores I Fig. L4< I. 

 It is these spores inside the black spore cases that carry the infection forward 

 from year to year. 



The disease is usually mosl prevalent where the growth has been par- 

 ticularly vigorous, and feeding oft' in June and July will, therefore, be 

 effective in reducing leaf growth, and admitting sun and wind., in the 



Fig. 14. — Wheat Mildew (Erysiphe graminis). 



A. Oidiuni st;ii;e, showing the production of conidia. 



B. Peritheeium with appendages. 



C. Perithecium (more magnified) showing asoi nnd ascospores. (After Frank.) 



presence of which the fungus will die. Crops attacked by mildew usually 

 recover on the advent of summer, but uccasionally the disease has proved 

 very malignant, and it distinctly reduces the yield in such cases. The 

 burning of stubble is likely in large measure t<> prevent the continuance of 

 the disease. 



Take-all (Ophiobolus graminis). 



This disease is to be distinguished from Foot Rot disease (Helmintho- 

 sporium), an account of which appears on page 349. 



Take-all is caused by a fungus svhich exists in the soil, and attacks the 

 mots of the wheat plant. The disease makes its appearance in patches 

 which are usually round, but which may be large or small, according to the 

 severity of attack. Not infrequently the yield on large areas is seriously 

 diminished — even by 50 per cent. 



When the wheat is checked before it is out in ear, the disease is usually 

 referred to by farmers as Take-all. .Sometimes affected ['hints give rise to 

 ears which are white and possess no grain ; only in rare cases do the cars 

 contain pinched grain. This condition is referred to as " whiteheads." 



