284 DISEASES OF CULTIVATED PLANTS 



The larch is undoubtedly most liable to infection when 

 quite young, and under such conditions, as in nurseries, the 

 fungus spores in the majority of instances gain an entrance 

 through wounds and punctures made by the larch aphis, it is 

 important that the seedlings should be protected against this 

 pest. This can be done by spraying in the spring with the 

 following solution. Dissolve half a pound of soft soap in two 

 gallons of hot water, then add two gallons of paraffin and mix 

 thoroughly until the ingredients do not separate on standing. 

 One gallon of the mixture thus prepared should be diluted 

 with fourteen gallons of water, when it is ready for use. 



In larch woods it is not an unusual thing to meet with 

 numbers of dead trees standing, and also branches lying 

 about, covered with the canker fungus cups. All such should 

 be removed and burned, to prevent further infection. 



Hartig, R., Unters. Forstbot. Inst. Munchen., i, p. 63. 

 Massee, G.,Journ. Bd. Agric., Sept. (1092). 

 Somerville, W., Trans. Engl. Arboric. Soc., 2, p. 363 

 (1893-94). 



Spruce canker. This disease, caused by Dasyscypha 

 resinaria (Rehm.), to the naked eye, or even when examined 

 with a magnifying-glass, is practically indistinguishable from 

 larch canker, caused by D. calycina (Fuckel) ; the structure of 

 the fungus is, however, very different in the two diseases. In 

 this country D. resinaria is most frequent on the spruce 

 (Picea excelsa, Link) ; it also occurs on larch (Larix europaea, 

 D. C.), and has proved very destructive to the Bhotan pine 

 (Pinus excelsa^ Wall.) in Wiltshire. On the continent D. resin- 

 aria has been recorded as a parasite on the spruce fir, 

 and in the United States it does serious injury to Abies 

 balsamea, and is thus described by Anderson : ' On some 

 trees (Abies bahamea} almost every knot and dead branch 

 was surrounded by one of these canker swellings, the canker 

 not infrequently extending all round the tree trunk or branch. 

 When younger stems or branches were affected in this way 

 the portion above the canker, and often the whole stem, had 

 been killed by the girdling. Infection takes place, as a rule, 

 around the base of the imperfectly self-pruned branches of 

 the lower part of the trunk. At these places the spores gain 

 access to the inner living bark and to the cambium, where 

 they germinate and cause the increased growth of the wood 

 and secondary cortex. Wounds caused by insects and by 



