The Botrytis Blight of Tulips 319 



In the spring of 1917 the writer observed the disease in an epiphytotic 

 condition. Most of the tulip tops in the ornamental beds in the Cornell 

 University campus were severely attacked. These were late, or Darwin, 

 tulips, and counts made on one variety, Spathulata, showed 100 per cent 

 of the leaves diseased, of which 33 per cent were strongly infected and 

 67 per cent only slightly. Of the stalks, 98 per cent were diseased, 

 23 per cent severely and 75 per cent slightly. The bulbs all showed 

 slight infections, but it is uncertain whether these were infections by 

 Botrytis Tulipae or by Penicillium sp. However, in the variety Spath- 

 ulata 4.6 per cent of unmistakable Botrytis lesions were found, and 

 in the variety Mrs. Grover Cleveland, 5.2 per cent. The presence of 

 sclerotia in these lesions made identification certain. These were prob- 

 ably lesions from the previous year and they show how small an 

 amount of original inoculum is necessary to produce a severe infec- 

 tion on the tulip tops. Accordingly it is impossible to lay too much 

 emphasis on the selection of clean bulbs. The writer believes that this 

 is the most important disease of the tulip in this country. 



SYMPTOMS 



On the bulbs 



On the brown outer skin, or husk, of the affected bulbs, small black 

 sclerotia may frequently be found, about 1 millimeter in diameter. They 

 appear also on the old, dried, flower stalk of the previous season, which 

 sometimes remains attached to the bulb (fig. 22). The removal of this 

 papery, brown skin often reveals lesions on the outer, white, bulb scale 

 which might otherwise have escaped notice. These lesions vary from deep 

 yellow to brown, are usually circular in outline, and have a definite margin 

 which may be somewhat raised. The central part is ordinarily depressed 

 and may have on its surface small black sclerotia (fig. 23). The lesions 

 ate formed sometimes at the apex of the bulb, sometimes at the base, 

 but more often in the region between. Less frequently the sclerotia may 

 appear white, which is due to their immaturity. By removing the outer, 

 fleshy scale and examining its inner side, it will be seen that some of the 

 lesions have penetrated almost to the inner surface. They rarely extend 

 into the scales beneath. 



