92 PPOTECTION OF PLANTS — 1922-23 



the spring before the buds are out. This will prevent the beetles going to the 

 other trees nearby. 



Washes for the trunk are unsatisfactory, chiefly because of their staining 

 the bark; and spraying is of no avail. Hymen opterous parasites are undoub- 

 tedly the greatest natural controlling agency. Every year considerable num- 

 bers of the small chalcid fly, Phasgonophora sulcata Westwood, were to be found 

 breeding in the birch sticks. This parasite is of first importance in control of 

 Agrilus anxius. There are also several species of Siricidae, horntails, which 

 attack the larva. No doubt birds play an important part in control. The' 

 downy woodpecker, chipping sparrow, phoebe, king bird and two species of war- 

 blers have been observed at the Arboretum, Central Experimental Farm, among 

 the branches of Betula ulmifolia and B. fruiticosa, both of which were very 

 heavily infested with Agrilus. 



To sum up very briefly: — Agrilus anxius is perhaps the most serious ''nsect 

 enemy of the birch family. Injury is done in the larval stage, by a series of 

 winding tunnels beneath the bark thus girdling and eventually killing the bran- 

 ches and trunk. No effective artificial control is known, but certain natural 

 agencies, such as parasites and birds play a good part. Infested trees should 

 be cut down and burned in the early spring. It is, therefore, very unsatisfac- 

 tory to plant birches of any variety for ornamental or shade purposes and we do 

 not recommend the practice. 



BLUE STEM OF THE BLACK RASPBERRY. 

 By J. F. Hockey Laboratory of Plant Pathology, St. Catherines, Ont. 



This disease has not been previously reported from the Niagara district 

 Probably few are acquainted with it because of the comparatively little atten- 

 tion paid to black raspberries in this section. The blue stem condition as des- 

 cribed by W. H. Lawrence (Wash. Agr. Expt. Sta. Bui. 108, 1912) was found 

 this season in various patches through the district and in isolated seedling plots 

 at the Horticultural Experiment Station, Vineland. 



In most cases the enftire plant was defoliated or nearly so, in the latter case 

 the remaining leaves were yellowish and drooping. Occasionally a plant was 

 found with one or two canes apparently dead whereas the remaining canes shovved 

 the blue colorations developing along the base of the stems with the tips of the 

 canes still normal. The color of the diseased stems is a bluish purple to black 



