62 THE REPOET OF THE No. 36 



had from one to ten or more twigs dead or dying. Diseased twigs were sent to 

 Geneva and examined by J. G, Grossenbacher, who wrote that the trouble was 

 due to an undetermined fungus which entered through openings made by a 

 Cambium Miner, apparently Oposiega nonstrigella.. The disease seemed to enter 

 solely through these wounds. 



Small Cankers on Apples {Leptosphaeria coniothyrium) . Parrott, Gloyer 

 and Fulton in their study of Snowy Tree-crickets have shown how; the cricket, 

 Oecanthus niveiis, is the agent in introducing the fungus that causes the small 

 cankers around cricket egg punctures on apple trees. These cankers are found 

 in Ontario as well as New York. This fungus, Leptosphaeria coniothyrium, is 

 also the fungus that causes Raspberry Blight and is believed by the plant 

 pathologists of Geneva to enter many raspberry canes through the wounds made by 

 the egg punctures of the Tree-cricket, Oecanthus nigricornis. 



Heart Rots of Forest and Shade Trees (Several species of fungi). In 

 almost every city may be seen maple trees with unsightly wounds, due to the 

 burrows of the Maple Borer (Plagionotus speciosus). These wounds commonly 

 allow the entrance of heart rots, which injure the wood and weaken the trees, often 

 shortening its life. It seems reasonable to assume that similar diseases enter 

 various forest trees, through injuries caused by Cerambycids, Buprestids or Ipids. 

 It is true that most of these attack only sickly, dying or dead trees, but some 

 attack healthy trees. Such gaping wounds as those caused in poplars and willows 

 by the Snout Beetle {CryptorhyncJius lapathi) could scarcely fail to admit fungi. 

 The evidence tends to show that this beetle is an important factor in the trans- 

 mission of the European Poplar Canker (Dothichiza populea). 



Referring to a species of Scolytus that attacks White Fir, Hopkins says " AVhen 

 the attack is not sufficient to kill the trees, these wounds heal over, but in the 

 meantime a decay often sets in at these injured places, which extends through 

 the heartwood and for several feet above and below the wound, thus rendering the 

 wood worthless for lumber and often for fuel." In the same bulletin he says 

 " It appears that insects contribute more to the spread of fungus of the bark and 

 wood of the main trunk than do such diseases to the sjiread and ravages of insects." 



Brown Rot op Fruits {Sclerotinia cinerea). The spores of this disease are 

 readily carried by the wind, but they usually fail to infect peaches and sour cherries 

 in Ontario except through wounds or where fruits touch each other. Some varieties 

 of plums and sweet cherries are very susceptible, even though their surfaces be 

 unwounded. The joint investigations of the Bureaus of Entomology and Plant 

 Pathology of the U. S. Department of Agriculture proved definitely the important 

 part played by the Plum Curculio in the spread of this disease on peaches. IlHng- 

 worth, Spencer and the writer in their studies of Cherry Fruit Flies found that sour 

 cherries infested by the maggots of these flies were often conspicuously affected 

 by Brown Rot and that where these insects were completely controlled very few 

 cherries rotted even though they were left on the trees until overripe. Moreover, 

 there is no doubt that placing maggoty cherries in baskets along with sound ones 

 favours the development of rot, especially in warm weather; because even though 

 the infected cherries be not rotten, they exude juice from the breathing holes made 

 by the maggots and this gives ideal conditions for rot development. 



Lack of space prevents our giving more examples of fungus diseases spread 

 by insects, so we shall now pass on to the bacterial diseases. 



