REPORT OF THE SOCIETY 45 



Plums.— Wild plupis were heavily infected by Exoascus pruni causing 

 "bladder plums" but cultivated varieties were not affected. On the other 

 hand the latter suffered from brown rot (S. cinerea) to the extent of about 1%. 



A "wither-tip" the etiology of which at present is not known was sent 

 in from New Brunswick. 



Raspberry. — Mosaic and Leaf curl were still present, the season being 

 such that the former was especially noticeable. In this district the Columbia 

 variety must be added to the susceptible list. 



Grape. — Grape mildew (P. viticola) was common this year on leaves, 

 tendrils, shoots and fruit. 



Ehyi. — On most American elms in Eastern Quebec there was approxim- 

 ately 30% infection with Dothidella ulmi causing leaf spot. 



Butternut.- — Gnomonia veneta, causing leafspot, defoliated practically all 

 the butternut trees at least a month earlier than normal. 



Iris. — Rhizome-rot caused by B. carotovorus was prevalent wherever this 

 ornamental plant was grown. There appeared to be little doubt that injury 

 to the rhizome during spring cultivation opened infection courts in the plants. 



Sweet pea. — Mosaic was noticeable in many plots but was not so common 

 this year as "stigmonose" and leaf curl caused by aphids. 



Streak (B. lathyri) occurred frequently, especially during September, 



Peony. — Leaf and stem spot caused by Septoria pceonice var. herolinensis 

 was very pronounced. 



Botrytis blight was present but not serious. 



During the later summer an Alternaria leafspot a Phyllosticta spot and 

 Cladosporium blight became common. 



In one large nursery the roots of newly planted peonies blackened and 

 died. They were like india-rubber in texture. The trouble appears to be 

 due to a species of Fusarium. 



Contribution No. 15, Dept. of Botany, Macdonald College, Que. 



THE SEED PLOT AS A MEASURE OF PROTECTION. 

 By Omer Caron, Botaniste, Quebec Dept. of Agriculture. 



The technical expert can in many cases control diseases by carrying out 

 certain technical measures, but in the field the efforts of growers to do this 

 are often nullified b}'^ causes beyond his control. 



When one considers the practical aspects of plant protection, it is found 

 that some are difficult to follow because of the cost of labour and the amount 



