GARDEN PESTS IN NEW ZEALAND 



purse and watercress. Most damage is done during dry seasons, when 

 the plants succumb more readily to attack; if the insects are numerous, 

 they cause the leaves to curl, and give a greyish appearance to infested 

 plants, which may become flaccid and sticky from the copious honey-dew 

 of the insect. The wingless forms are bluish in colour and coated with 

 a greyish powder, but the winged females have the head and thorax black 

 and the abdomen greenish (Fig. 9, 2). In New Zealand all stages may 

 be found throughout the year on winter crucifers or on weeds, though 

 reproduction is retarded during the winter; in the spring the winged 

 females fly to young crops. In very cold climates eggs are laid in the 

 autumn, and these survive the winter. The cabbage aphis is attacked 

 by a number of parasites, and usually the brownish empty shells of a 

 large number that have been destroyed by a small parasite are to be 

 found at any time; other important enemies are the hover-flies, the 

 eleven-spotted ladybird beetle, and the Tasmanian aphis lion. The insect 

 can be controlled by spraying with nicotine-sulphate to which soap has" 

 been added. 



PIXE TREE CHERMES (Chermes pini). This is a widely-distributed 

 species, ocurring upon both Austrian and insignis pine in Xew Zealand. 

 The insect lives in colonies upon the cones, twigs and branches, as well 

 as around the bases of the needles; each aphis exudes a woolly covering, 

 which forms conspicuous white masses when the trees are heavily infested 

 (Fig. 9, 3). Young trees seem to be the more subject to infestation, 

 from which they may recover as they grow, but some damage is caused 

 by the insect by a weakening of the trees, especially where grown in 

 unsuitable localities. It is frequently noticed that individual trees in 

 a plantation are heavily infested, while adjacent trees of the same 

 species are not. The wingless form of the insect, covered by its mat of 

 white threads, is brownish in colour and ornamented with numerous 

 dark spots; there are no '^honey-tubes" on the abdomen. The life-cycle 

 of this insect becomes complicated, when it develops on two types of 

 conifers; in the latter case the primary host is a species of spruce upon 

 which the insect forms galls, and the secondary host may be larch, 

 Douglas fir or pine, upon which gall formation is unusual. So far as is 

 known, only the pine-infesting f orm of the aphis k occurs in New 

 Zealand. 



GRAPE PHYLLOXERA (Phylloxera vastatrix). - This destructive 

 aphis, sometimes called the grape louse, is a native of North America, 

 where it normally infests grape vines. It was accidentally introduced 

 into the grape-growing districts of France, where it became very 

 destructive. It later made its appearance in New Zealand. The insect 

 infests both the leaves and roots of grape vines, the root-feeding stages 

 being the most destructive, in consequence of which vines are now grown 

 on resistant root stocks. The leaf-infesting stages of the insect cause 

 pocket-like galls to form, which open on the upper surface of the leaf 

 by a narrow aperture concealed under a tuft of delicate hairs (Fig. 9, 5). 

 In each gall the aphid matures and deposits several hundreds of eggs, 

 from which wingless females hatch ; these wander to other leaves, and 

 each insect forms a new gall for itself. Several generations develop 

 thus, but later many of the offspring migrate underground and join the 

 root-infesting colonies. The irritation set up by the latter causes yellow 



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