S20 



INJURIOUS INSECTS AND FUNGI. 



[Dec. 1895. 



clearly visible to the naked eye, and are slightly flask- 

 shaped. Within these are cylindrically-formed asci (E., Fig. 1), 

 containing eight spores, each having two colourless cells 

 (¥., Fig. 1). They germinate in water quickly, and placed 

 upon trees infect them with canker. Hartig and Goethe have 

 infected forest trees by placing spores of Nectria ditissima upon 

 their living parts. They have also infected trees by placing 

 Nectria spores upon parts injured by hail, or with decayed 

 substances on them, and show that Nectria ditissima is both 

 saprophytic and parasitic. This has also been proved by De 

 Bary. 



In addition to the perithecia emanating from the m5^celium 

 of Nectria ditissima there is, at all events when it is actively 

 parasitic, a formation of conidia evolved from a stroma of 

 cushion shape. This takes place before the development of the 

 perithecia, which contain the spore-bearing asci. These conidia 

 have also been made by Hartig and Goethe to infect forest 

 tree«, and to germinate freely upon decayed and living tissues. 



Methods of Prevention and Remedies. 



One obvious way of preventing the spread of canker is to be 

 careful not to make use of grafts from infected trees, or grafts 

 showing any trace of the fungus. 



Young trees should be examined closely for any signs of canker. 

 Any wounds upon them should be viewed with a strong pocket 

 glass to discover the red perithecia of the fungus. 



Where possible, infected branches should be cut away, and the 

 pieces burnt to prevent the spread of the fungus. 



It would be desirable to note the trees that canker most 

 readily, and to avoid planting these varieties. And if a tree is 

 badly cankered in an orchard, or near other trees, it would 

 probably pay best to cut it down. 



A strong solution made with 20 lbs. of sulphate of copper to 

 100 gallons of water, would undoubtedly check the fungus and 

 destroy it in its conidia and spore stages. This could be applied 

 with a knapsack machine where the trees are small, and upon 

 large trees with the help of a ladder where the disease has affected 

 only a few branches. The spray should be directed for some time 

 on the infected spots, and it would be necessary to spray them 

 two or three times during the winter. 



When trees are badly infected they must be sprayed all over 

 by means of a garden engine with strong pumps and long hose, 

 like the engine used for hop washing. 



Sulphate of iron, dissolved in warm water at the rate of 1 lb. 

 to every gallon of water, would be of value if applied in the autumn 

 and winter. It would at the same time remove lichenous and 

 mossy growths which harbour fungi and insects, and injuriously 

 affect the trees. 



