In 1895 it appeared in Ohio, and later caused considerable injury in 

 that state both to greenhouse and field crops. In 1899 '^ ^^"^^ noted 

 in England; in Brazil in 1900; in Russia, Austria-Hungary, Java 

 and East Africa in 1902, and in Italy in 1903, showing that the dis- 

 ease has been quite cosmopolitan in its progress. Since its appear- 

 ance in this country it has been generally distributed and quite de- 

 structive to field crops of cucumbers, although from 1892 until 1900, 

 it was not observed in Massachusetts, to our knowledge. Since 1900, 

 however, it has appeared annually on field crops and occasionally in 

 greenhouses, where its appearance has caused little alarm. 



It has been shown that this fungus is perennial in the south and 

 travels north every season, apparently about the time cucurbitaceous 

 crops mature. It usually makes its appearance in Massachusetts 

 about the middle of August, although sometimes a little earlier ; but 

 in 19 1 3 there was a bad infection on greenhouse cucumbers in the 

 Boston district in May, June and July, which caused much loss, es- 

 pecially in unheated houses, where the air often becomes very damp. 

 This is the first time downy mildew has been observed here earlier 

 than August, and this attack may have some connection with the un- 

 usvially warm winter of 1912 — 191 3. 



While the downy mildew is capable of doing considerable injury to 

 greenhouse crops, it is not difficult to hold the disease in check if 

 proper attention is paid to the moisture in the house. In no case 

 should moisture be allowed to remain on the foliage for more than 

 two or three hours, and even in the warm months steam should 

 occasionally be turned on to dry out the house and change the air. 

 All mildews and leaf blights are encouraged by moisture on the foli- 

 age, lack of light during the period of plant development, and stag- 

 nant air. In our experiments, in which we have grown cucumbers 

 and melons under glass every month in the year, we have never had 

 the slightest infection from mildew when the plants were syringed 

 properly ; i. e., only on bright mornings when the leaves will dry 

 quickly. While cucumbers can be grown without syringing, the risk 

 from red spider during the spring and summer months is necessarily 

 great. 



After the middle of September or October first there is little dan- 

 ger of infection, therefore it is better to start the winter crop at this 

 time rather than in August. A slight attack of downy mildew does 

 little or no harm, and if cucumber growers always used the same 

 judgment as lettuce growers, an infection would seldom prove serious. 

 It has been shown that spraying with Bordeaux mixture constitutes 

 an effective preventive in the field, and sulfur and oil painted on the 

 pipes in the greenhouse has proved beneficial. 



This unlooked for attack of downy mildew in the early summer 

 months makes it apparent that in the future all cucumber growers 

 should be on the lookout for early infection. 



