CEREAL PESTS PARASITIC FUNGI 



535 



576. Ergot (Claviceps purpurea, Tul.). -- This fungus 

 is rather frequent on rye and barley. It occasionally at- 

 tacks wheat also, and 

 rarely oats. It affects 

 the spike or panicle 



only (Figs. 167, 168). 



The season's growth of 

 the fungus ends in the 

 formation of hard, purplish 

 sclerotia, taking the places 

 of kernels, and which re- 

 sume active growth in the 

 spring. After a few days 

 of warm, moist weather, 

 stromata become visible, 

 and subsequent growth is 

 rapid. These stromata 

 bear the perithecia which 

 inclose the numerous asci 

 or spore sacs. Infection 

 takes place at flowering 

 time, when the young ova- 

 ries of the host are most 

 susceptible. The fungus 

 then develops rapidly, pro- 

 ducing what is known as 

 the honey-dew or conidial 

 stage. These conidia are 

 probably largely distrib- 

 uted by flies, gnats, and 

 other insects, which have 

 a fondness for sugar. 

 Later the young sclero- 

 tium forms rapidly, and is completed when the grain is mature. 



Ergot causes no extensive damage to the crop, but in 

 the sclerotia are produced poisonous compounds causing, 



FIG. 168. Ergot: a, 6, on six-row barley ; 

 c, d, on hooded barley. 



