416 REPORT OF STATE BOARD 0¥ HORTICULTURE. 



PEAR SCAB. 



{Fusicladium pirinum (Lib.) Fckl.) 



By Prof. B. M. Dl ggar. 

 GENERAL ACCOUNT. 



During the past two years a number of inquiries have been i^eceived con- 

 cerning pear scab, and among- the smaller orchardists or others with a small 

 number of trees, equally as many inquiries have related to the well-known 

 pear blight. Consequently, it has seemed well to incorporate in this bulle- 

 tin such brief accounts of these two diseases as will give the information 

 desired. 



The injurious effects of pear scab are well understood by many orchard- 

 ists ; and by some the disease is combated faithfully and successfully, but to 

 others it is an inevitable attendant of pear culture. During the past sum- 

 mer I was surjjrised to find how often jjear scab is confused with certain 

 insect punctures and other minor injuries. I presume, however, that no one 

 who ever grew so susceptible a variety of pear as the Flemish Beauty could 

 long remain ignorant of the scab. Although much is lost when colors are 

 not reproduced, one sees there the essential characteristics of the scab in 

 pronounced form upon the fruit. 



With many varieties of pear, this cracking may accompany the scab as 

 as well as the leaf blight, or, apparently even certain irritating external 

 agencies may produce the cracking, provided the respective agencies affect 

 the pear during the growing period. 



On the fruit the pear scab produces at first merely brownish or olivaceous 

 markings. These discolorations are due, in part, to a short surface growth 

 of the fungus, and to the deadening- of the epidermis of the pear. During the 

 past year Prof. L. H. Bailey received from Michigan some leaves so badly 

 affected that the fungous growth covered the greater portion of both sur- 

 faces, and the leaf was considerably curled therefrom. 



Pear scab has been known botanically since 1832, when it was found in 

 Belgium ; but it is only within the past twenty years that it has had a place 

 in economic literature. Hereafter, at least until unsusceptible and other- 

 wise satisfactory varieties are introduced, to the successful orchardist a 

 knowledge of scab is as essential as a knowledge of pruning. 



SPECIAL CHARACTERS OF THE FUNGUS. 



(a) Microscopic ajjjiearancc — The olivaceous growth on the fruit, leave.-. 

 and twigs is largely made uj) of short erect threads, somewhat uneven at the 

 tips. These threads produce the spores or reproductive bodies. 



(6) How the fungus jjctsses the winter — It has been seen that pear scab often 

 attacts the twigs of the first year. The fungous threads are extremely 



