20 



FOUR COMMON FUNGOUS DISEASES OF THE GARDEN. 

 W. Lochhead, Macdonald College. 



1. Gooseberry. Mildew. 



(Sphaerotheca mors-uvae, B. & C.) 



This disease is so destructive to English varieties of gooseberries in 

 some localities that it is difficult to harvest a crop. The leaves and 

 shoots as well as the fruit are attacked and become covered with a fine 

 whitish cobweb-like growth of mycelium and a delicate white powder. 

 This powder is composed of myriads of summer spores called conidia, 

 which are produced in chains on erect threads of the mycelium. These 

 conidia are readily carried from one bush to another, so the disease 

 spreads rapidly. Later in the season minute roundish brownish black bod- 

 ies, the perithecia, are formed on the mycelium, each with a roundish sac 

 within containing eight colourless spores. These ascospores, or winter 

 spores, remain within the perithecia all winter, and are liberated in the 

 spring. "When they are blown by the wind to the new leaves of the goose- 

 berry, under favorable conditions they will germinate and infect the plant. 

 The disease is in this way enabled to develop from one season to the next. 



At first the mycelium covering the affected parts is very dense and 

 white, but the threads soon become brown and thick-walled. 



The fungus derives its nourishment from its host by means of minute 

 sucker-like branches, haustoria, of the mycelium, which penetrate the skin 

 or epidermis and feed upon the contents of the cells. The disease attacks 

 the gooseberry early in the season, and is usually observed first in the 

 shaded parts of the plant. Young shoots are often so sapped of their 

 vitality that growth is prevented and fruit buds do not develop. 



Treatment. — As a rule the powdeiy mildews, to which the Gooseberry 

 Mildew belongs, are readily controlled by Bordeaux and other fungicides, 

 since they live on the surface of their hosts, but this disease is an exception. 

 Much difficulty has been found in controlling the spread in spite of 

 repeated applications. Experiments conducted by many growers show 

 that good results are secured by the repeated application of potassium 

 sulphide at the rate of 1 ounce to 2 gallons of water. The first spraying 

 should be made when the buds open and subsequent applications every 



