636 INSECTS AFFECTING VEGETATION 



Maryland rose growers. There is much danger of the sulfur taking 

 fire in the open kettle and ruining the whole house. 



Mildew, if allowed to get a hold, soon spreads over the entire 

 house, unless conditions are against it. One of the conditions favor- 

 able to the spread of mildew is dry, cool air, such as would come into 

 a greenhouse from ventilation, broken glass or open doors. Under 

 such conditions the plants are to a certain extent wilted. The same 

 air conditions favor the spread of the spores. A close and moist con- 

 dition of the atmosphere is not favorable to the spread of mildew 

 but may make the plants very soft and succulent and the youngest 

 and most succulent portions of the plant are most readily affected by 

 the disease. 



The low-down side method of ventilation, while it retards the 

 appearance of mildew, would not be practicable in a range of houses. 



The mildew should 'be controlled when the attack is compara- 

 tively slight. If mildew show's, no time should be lost in vaporizing 

 sulfur to kill off the spores. As the fungus develops from the spore 

 and matures a new crop of spores in six or eight days it only takes a 

 short time to infect the entire house. During the winter when firing 

 is going on and the pipes are hot, painting them with sulfur will 

 'usually keep down mildew. At other times a sulfur vaporizing ap- 

 pliance will be found very useful. The appliances for burning 

 sulfur are useless to control the trouble and the chance for injury is 

 very great. Outside rose mildew can be controlled by spraying with 

 concentrated lime-sulfur solution, 1 to 50 of water, or any good 

 fungicide, applied frequently. 



A very heavy vapor from boiled sulphur does not injure the 

 foliage but did injure outer petals of half blown roses. 



An overdose of burning sulphur kills the leaves badly but does 

 not seem to injure the petals of half open buds. (Md. E. S. B. 156.) 



ROSE. 



Black Leaf Spot. This is one of the commonest diseases of the 

 rose. It causes the leaves to fall prematurely. Spray with Bor- 

 deaux, 5-5-50, beginning as soon as the first spots appear on the 

 leaves. Two or three applications at intervals of ten days will very 

 largely control the disease. Ammoniacal copper carbonate may be 

 used on roses grown under glass. Apply once a week until disease 

 is under control. 



Anthracnose. An anthracnose fungus (Gloeosponum rosae) 

 attacks the rose, causing defoliation of the canes; indeed the whole 

 plant is attacked. This behaves very similarly to the anthracnose 

 fungus of the raspberry. Young plants are found most susceptible 

 to the disease. The methods of handling are practically the same as 

 for the anthracnose of the raspberry. 



Crown Gall. Crown gall trouble essentially the same in char- 

 acter as that of raspberry, occurs on roses but requires no separate 

 description here. 



Leaf Blotch (Actinonema Rosae) often causes dark spotting of 

 the leaves. The frost-like, branching growth over the leaf-surface 

 is often very pretty in design though injurious in effect. If the rose- 



