124 REPORT OP THS ^JOMMISSIONER OP AGRICULTURE. 



season, i. e., wlietlier the rainy weatlier is early or late. However, 

 otlier things being equal, quick-growing varieties are probably safest. 



It is thought that something may be done to check the rot by the 

 careful use of fungicides. As soon as brown or black specks begin 

 to appear upon the vines they may be dusted with Podechard powder,* 

 which treatment should be repeated as often as necessary. 



David's powder, f a remedy which proved very useful in the vine- 

 yards of France in 1880, for the destruction of a fungus similar to the 

 Fhytophthora, may also prove useful in combating this fungus. It 

 is recommended for trial. 



As these remedies are only tentative, parallel strips through the 

 field should be left untreated, that the treated and untreated strips 

 may be comi^ared at the close of the season. Only in this way can 

 any definite results be reached. 



PEAR BLIGHT. 



A glance at the back volumes of the Annual Report of this Depart- 

 ment will show that this subject of "Pear Blight" has frequently 

 been discussed. Theories without number have been advanced as to 

 the cause of this malady and numerous remedies have been recom- 

 mended for trial or stated to effect a positive cure. In the report for 

 1854 blight is attributed to high culture, causing the tree to grow late 

 in the fall, thereby preventing the wood from being well matured. 

 In the report for 1851 the opinion of one writer is to the effect that 

 "too much trimming, too much moisture, and too rich soils are some 

 of the causes of blights in pear and apple trees." In the report for 

 1862 we find it stated that one form of "blight" in pear trees is in- 

 duced by evaporation from the leaves at a time when the roots are 

 unable to absorb moisture. The blight is attributed to insects in the 

 report of 1803. In the rejjort for 1868 we have the statement that " it 

 is now fully established that the active agent in this disease is fungoid 

 growth." In the report for 1872 it is affirmed that "Pear Blight is 

 a local fungus fermentation of the genus Torula." 



Remedies. — In the report for 1849 "Amputation of the diseased 

 limbs far below the least appearance of disease, having care to keep 

 the knife clean, so as not to inoculate healthy trees with the poison- 

 ous juices of diseased ones, and apply crude iron filings to and around 

 the roots," is the recommended treatment. 



In the report for 1851 it is stated that "the best and only remedy 

 for blight of pear and apple trees is a full and unsparing use of the 

 knife. Cut below the blight some distance; if you lose the limb you 

 save the tree." In the report for 1870 mulching the trees is recom- 

 mended to prevent blight. 



Through the recent investigations of Professors Burrill and Arthur 

 the true cause of Pear Blight has been demonstrated to be due to a 

 bacterium. To Professor Burrill is due the honor of first having dis- 

 covered the real nature of this disease, and the experiments made by 

 Professor Arthur have not only verified those of Professor Burrill, 

 but have been extended so as to settle the c[uestion beyond dispute. 

 These gentlemen are now recognized authorities on this subject, and 

 Professor Arthur was engaged to prepare a re]3ort upon it, as a part 

 of the work of this section, which is here submitted. 



*See page 100. f Soe page 102. 



