532 



appeared iii early summer, but as yet, the secondary host plant has 

 not been found. The injury is practically confined to the older needles,^ 

 which become discoloured and fall off about the time the new ones are 

 fully developed. This Aphid is readily controlled by spraying with 

 contact insecticides. 



From 1911 to 1913, caterpillars of Therina spp. caused vast damage 

 to hemlocks, Tsiiga heterophjlla, but a great diminution of them was 

 noticed in 1914, due to natural causes, chiefly parasitism by a 

 Tachinid fly. A similar condition of affairs obtained in 1915 and in the 

 summer of 1916. Isolated hemlocks have been infested by a species of 

 Chermes, the foliage being covered in spring with a white woolly 

 secretion from the stem- mothers. Death due to defoliation was caused 

 in some cases. Further investigations are necessary into the life- 

 history and habits of this species. Predaceous larvae of Syrphid flies 

 were observed feeding on these insects in 1915 and have probably kept 

 it under control. Many large Western cedars {Thuja plicata) have been 

 found dead at the top, but this is probably due to fungus heart rot and 

 no insect has been found doing serious damage to the foliage or bark. 

 The Douglas fir, except that it acts as a secondary host of Chermes 

 cooleyi, has been found to be practically immune from insect pests. 



It was at first proposed to spray the trees with a high power spray 

 which would reach to a height of 100 to 130 feet, using a contact spray 

 (nicotine sulphate and soap) against Chermes and a poison spray (lead 

 arsenate) against Therina caterpillars. Owing to the disappearance 

 of the latter in 1914 and the fact that so many of the smaller spruces 

 were too seriously injured to be worth saving, this idea w^as abandoned 

 and methods of reafforestation were considered as being more practical.. 

 Trees attacked by bark-beetles and dead trees have been removed, and 

 a general clearing aw^ay of debris will probably be undertaken while 

 some system of replanting is being inaugurated. The introduction of 

 exotic species of Conifers has been suggested as the basis for the future 

 development of an arboretum which would be of considerable 

 educational value. 



Fryer (J. C. F.), Plum Aphides.— J/. Bd. Agric. London, vol. xviii, 

 no. 7, October 1916, pp. 661-664, 2 plates. 



The presence of Aphis pruni is easily recognised by the characteristic 

 curling of the leaves, which are often covered with sticky honey-dew. 

 It attacks all varieties of plum, damson and blackthorn, and to a slight 

 extent peach, apricot and apple. The eggs, Avhich are laid in autumn, 

 hatch in early spring, giving rise to the purplish or brownish stem- 

 mothers. These produce several generations of wingless females, 

 until the end of June or July when winged forms appear. These desert 

 the plums and migrate to host plants which have not been identified,, 

 but are believed to be weeds, such as thistles and ragworts. They 

 return to the plums in autumn, giving rise to the sexual forms. The 

 control measures recommended include spraying with lime-washes 

 in February, or preferably March. Contact insecticides, such as 

 emulsions of nicotine, quassia or paraffin may be effective, but it is- 

 essential that the spraying should be done either before the blossom 

 has opened or after the petals have fallen, and in any case before the 

 leaves have curled. 



