G A R D E N P E S T S I N N E W ZEAL A N D 



flabby nodules to develop on the roots (Fig. 9, 4). These nodules, or 

 galls, later decay. The root-feeding aphides are wingless, and reproduce 

 by means of eggs' for several generations. Although they may go on 

 developing thus for many years, it usually happens that, toward autumn, 

 some of the insects transform to winged females, which fly to other 

 vines or are carried thence by the wind. There each female feeds on 

 the lower leaf surface, and deposits two kinds of eggs, some larger and 

 some smaller ; from the larger develop wingless females, and from the 

 smaller wingless males, which are unable to feed. After fertilisation, 

 each of these females deposits a single egg upon the older bark of the 

 vine ; such eggs do not hatch until the spring, when they give rise to the 

 wingless females that start the galls on the leaves. Control depends on 

 the use of phylloxera-resistant stocks, since it is from the root colonies 

 of the aphis that the foliage is re-infested in the spring. An important 

 feature is to prevent the scion from sending down roots where the union 

 of the scion and root stock is clo'Se to the soil ; if such scion roots form, 

 they should be cut away and the soil removed from the union. 



ROSE AIM i is ( Nacroxi])lnun rvxfv). The rose aphis is perhaps one 

 of the best-known insects of the garden, mainly owing to its prevalence 

 upon the young growth of all kinds of roses ; it sometimes occurs on 

 apple, tomato and rhododendrons. In a colony some of the insects are 

 pink, and others bright green, though in the winged forms the head., 

 antenna 1 , thorax, a row of spots on each side of the abdomen, and the 

 "honey-tubes" are black ; in both winged and wingless forms the eyes are 

 red. In the case of severe infestations, plant growth is retarded and 

 the leaves and flowers become distorted. Control can be effected by 

 applications of nicotine-sulphate, kerosene, or soap solution. 



APPLE WOOLLY APHIS (Eriosoma lanigemm). - - Although fre- 

 quently called "American Blight," the apple woolly aphis is probably a 

 native of Europe. It occurs throughout Xew Zealand, and was' a very 

 serious pest until controlled by the Aphelinus parasite. The presence 

 of this insect is made apparent by the characteristic white woolly patches 

 (Fig. 9, 6) which appear upon the apple trees, due to the woollv material 

 secreted by the aphid. Another feature is that the part of the tree 

 attacked, even after the insects have disappeared, is disfigured by gnarled 

 swellings, due to abnormal thickening of the inner bark. This species 

 also infests apple tree roots, which become similarly malformed. How- 

 ever, root infestation has been overcome by using root stocks, such as 

 Northern Spy, that are immune. The individuals comprising a colony 

 of woolly aphis are variously coloured, yellow, green and red pre- 

 dominating; a considerable amount of honey-dew is secreted. This 

 species has been found to migrate to the foliage of the elm and mountain 

 ash, but in Xew Zealand the elm-infesting form has not been found to 

 occur. The insect becomes active in spring, and rapidly increases 

 until the autumn. Under favourable climatic conditions, winged 

 females develop and produce males and females, the latter laying eggs. 

 The woolly aphis is preyed upon by the nine-spotted ladybird, but, as 

 this beetle -is itself the victim of another insect, its utility is t>Teatly 

 minimised. The most important check to the aphis is the Aphelinus 

 parasite (Aphelinus mall), the influence of which has been spectacular 

 under Xew Zealand conditions. 



47 



