REPORT OF THE BOTANIST 259 



SESSIONAL PAPER No. T6 



DISEASES OF ORNAMENTAL TREES AND PLANTS. 



leaf spot of elm (Dothidella Ulmea, [Cchw.] Ell. & Ev.). 



This is a very common trouble, confined to our elms, both native and cultivated, 

 -a- d. in severe cases, causing extensive premature defoliation. The disease generally 

 attacks the leaves ami shows itself as a grayish area of dead tissue in the centre of 

 v Inch from one to several black spots are to be found. These latter are the young 

 fruit bodies and during the winter, as the leaves lie on the ground, the spore-sacs or 

 fisci develop within them. The spores mature in the spring and give rise to the first 

 infection of the elm leaves. 



As a means of controlling the disease, it is recommended to collect and burn the 

 fallen leaves in the autumn so as to prevent the formation of a crop of spores from 

 tbem in the spring. 



A row of young elms imported from France, growing in a nursery not far from 

 the Experimental Farm, was found to be infected by this common disease. It was 

 here plainly observed, however, that the fungus is not exclusively confined to the leaves, 

 but does also occur on the petioles of the leaves from which it spreads to the tips of 

 young shoots, which twist downwards and are finally killed. The elms were carefully 

 kept under examination, but in no case did an attacked twig make a recovery, 

 "Removing and burning these twigs where they occur would protect the trees from 

 becoming crippled. 



BLACK SPOT. TAR^POT OP, LEAF BLOTCH OF THE MAPLE (Rliytisma AcPrnitim, [Pers.] Fr). 



The leaves of various species of maple are often affected with large black spots, 

 which may injure the leaf so much as to cause it to fall. The behaviour of this fun- 

 gus is much the same as the Leaf Blotch of Elm. and the same treatment is advised 

 should it become serious enough to merit attention. 



hose rust (Phragmidium svbeorticum, [Schrank] Wint). 



In the earlier part of the season, the rust shows as bright orange-red spots on the 

 ^aves, petioles and stems. Later in the year, these give place to spots of a dark-brown 

 or black tint and are composed of the resting spores. This disease is rarely serious 

 and no control measure can be recommended as likely to give satisfaction. 



Other parasitic fungi whose occurrence may be here recorded, are Entomosporium 

 mespili, (D.C.) Sacc, on English Hawthorn from Nova Scotia; Dasyscypha 117//- 

 Icommii, Hart, from Nova Scotia; and Lophodermium nervisequum, (D.C.) Rehm. 

 •n Abies sp. from New Brunswick. 



hollyhock rust (Puccinia malvacearum, Mont.) 



This is a very common and destructive disease of the Hollyhock, which also 

 attacks other plants of the same family, being particularly abundant on the common 

 round-leaved Mallow (Malva rotundifolia, L.). It is sometimes difficult to find an 

 individual of this last species with leaves entirely free from the pustules of the disease. 

 While most of the best-known rust fungi pass through two or three well-marked stages 

 in their life-history, in this case only one is present, this being the teleutospore 

 stage, or, as it would be termed in most forms, the resting spore stage. Unlike most 

 spores of this type, however, those of the Hollyhock Rust do not require to rest or to be 



16— m 



