1G8 TRANSACTIONS OF THE ILLINOIS 



The most generally known of these diseases is the 



BLIGHT. 



(Caused by Micrococcus amylovorus Burrill). 



Prof. Burriirs remarkable discovery of the bacterial nature of 

 this disease, since fully corroborated by the investigations of Prof. 

 J. C. Arthur, of the New York Experiment Station, has set to rest 

 the endless discussions and wild speculations formerly indulged in 

 concerning it; and, from being the most mysterious, it is now per- 

 haps the best understood of plant diseases. Its appearance and ef- 

 fects are too well known to need description here. While no specific 

 has yet been found for it, its ravages need not be greatly dreaded in 

 regions where soil and climate are favorable for pears. Such treat- 

 ment of the orchard as will secure a moderate healthy growth, 

 thoroughly matured before cold weather, together with a prompt 

 and judicious use of the pruning knife on the first appearance of the 

 disease, will usually be sufficient to keep it in check. In some sea- 

 sons, owing to climatic conditions or other causes, the disease seems 

 to be unusually virulent. At such times the orchard may receive 

 some injury even with the best of care, and it is these nnusually try- 

 ing seasons in which the blight sweeps away neglected or over- 

 stimulated orchards. On strong, moist soils the safest treatment is 

 to seed down the orchard at an early age (preferably to clover), and 

 subsequently apply such fertilizers, if any, as may be needed to keep 

 up healthy growth. After the blight makes its appearance in the 

 spring, the trees should be examined regularly, as often as once in 

 two weeks, till after mid-summer, so as to remove any blighted 

 twigs before the disease extends to the trunk or principal branches. 

 Some varieties seem to resist the disease better than others, but per- 

 haps this immunity is due to accidental rather than inherent causes, 

 as experience in regard to this varies greatly in different years, and 

 all varieties seem to be subject to at least occasional attacks. 



ROOT ROT. 



{Folijporus versicolor Fr.) 



This obscure and little known disease has occasioned the loss in 

 Southern Illinois of far more trees than the blight. It was first de- 

 scribed by Dr. Hull in the Transactions of this Society for 1868 

 ( Vol. II, p. 37), and but little has been published concerning it since 

 that time. 



Its presence is usually first indicated by the short, thick growth 

 and peculiar reddish color of the new wood, and the yellowish red 

 or bronzed color of the leaves, together with a decided tendency to 

 over-production of fruit buds. On examining the roots of such 

 trees they will be found enveloped by numerous white-felted fungus 



