Jammry 8, 1874. ] 



JOUBNAL OP HORTIOULTORE AKl) dOi'f AGB GAitDEiJEfi. 



U 



invested with a thick ilowny substance, so lonp as at times to 

 bo seusibly ayitatea by the air. Upon examining this sub- 

 stiuioe it will be found that it conceals a multitude of small 

 winfiless creatures, which exude it from their bodies, while at 

 the same time they are busily employed in preying upon the 

 limbs of the tree. This they are well enabled to do by means 

 of a long beak, or proboscis, terminating in a fine tubular 

 bristle, which, being insinuated through the bark and the 

 sappy part of the wood, enables the creature to extract, as 

 with a syringe, the sweet vital liquor that circulates in the 

 plant. The sapwood being thus wounded, rises up in excres- 

 cences all over the branch, aud deforms it ; the limb, deprived 

 of its nutriment, grows sickly, the leaves turn yellow, aud the 

 tree perishes. The insect which is productive of so much 

 mischief is a species of Coecidaj named Aphis lanigera, or 

 woolly plant louse, popularly called the American blight. It 

 was first observed in England in 1787, but it is uncertnin if it 

 was, as has been supposed, accidentally imported tliere from 

 America. Some entomologists say it came from France. At 

 all events, there is little doubt its original habitat was a 

 warmer climate than that of Britain. It has, however, found 

 its way hence from the latter country. The wonderfully rapid 

 development of the aphis has thus been described by a popular 

 writer :^ 



" It produces in the course of a season eleven broods of 

 young. The first ten are viviparous, or brought forth alive, 

 and consist entirely of females. These never attain their full 

 development as perfect insects, but being only in the larval 

 state (the larvra are active, and resemble the perfect insect, 

 but are wingless) bring forth young, and the virgin aphides 

 thns produced are endowed with singular fecundity. But at 

 the tenth brood this power ceases. The eleventh does not 

 consist of active female larva; alone, but of males and females. 

 These acquire wings, rise into the air, sometimes migrate in 

 countless myriads, and produce eggs, which, glued to twigs and 

 leafstalks, retain their vitality through the winter. When the 

 advance of spring again clothes the plants with verdure the 

 eggs are hatched, and the larva, without having to wait for the 

 acquisition of its mature and winged form, as in other insects, 

 forthwith begins to produce a brood as hungry, as insatiable, 

 and as fertile as itself. Supposing that one aphis produced a 

 hundred at each brood, she would at the tenth brood be the 

 progenitor of one quintillion (1,000,000,000,000,000,000) of 

 descendants." — (Patersou, " Science Gossip," 1865.) 



It will thus be seen what very formidable foes these insig- 

 nificant-looking little pests are to our orchards, and two ques- 

 tions naturally arise — first. What is the cause of their being 

 so? aud second. Where can a thoroughly radical remedy be 

 found against their ravages ? 



There are some particular kinds of Apple trees more attrac- 

 tive to these insects than others. Whether this may be attri- 

 buted to the particular colour of the bark, a deficiency of 

 lime, the presence or absence of certain juices in the sap, or 

 to over-cultivation or climatic influences creating an abnormal 

 condition of the tree, and consequently rendering it more sus- 

 ceptible to parasitical disease, it is hard to say ; but the blight 

 now treated of is evidently more destructive in semi-tropical 

 climates, such as AustraUa and New Zealand, than in Britain, 

 owing in a great measure to the effect which the frequent hot 

 sunny days, succeeded by the cold frosty nights of early 

 spring, have upon the circulation of the juices of the tree, un- 

 duly stimulating their flow in the daytime, and abruptly 

 ehecliing their current at night, by which they burst their 

 vessels and become the food of such insects as have been 

 already described, the insects being often mistaken for the 

 cause of the disease, while they are really the effect of it. 



That the action of the American blight, the scale blight, 

 and the Cicadie on our Apple trees is, to a great extent, the 

 effect of the last-described condition, there cannot be much 

 doubt. 



Assuming, therefore, such an hypothesis to be correct, it is 

 clear that, in place of the various nostrums or specifics — such 

 as the prepai-ations of carbolic acid, corrosive sublimate, 

 kerosine, hme, or sulphur, which are recommended for wash- 

 ing the diseased trees, or the plastering of the infested parts 

 with moistened clay, all of which are very transient in their 

 effects — a non-liable stock to disease should be selected on 

 which to graft any liable variety the grower may desire to culr 

 tivate. That there are such stocks proof against blight there 

 are several authorities for stating, and, moreover, there is a 

 member of this Association, Mr. Lightband, sen., living in 

 our midst, who has Euccessfally treated the disease by grafting 



an anti-blight tree, using a variety of winter Apple, on diseased 



ones. 



In Darwin's book, " Animals and Plants under Domestica- 

 tion," Vol. ii., chapter 21, " On Natural Selection," he says : — 



" From some unknown cause the Winter Majetin Apple en- 

 joys the great advantage of not being infested by the coccus. 



" On the other hnnd, a particular case has been recorded iu 

 which aphides confined themselves to the Winter Nelis Pear, 



and touched no other kind in an extensive orchard 



Liability to the attacks of parasites is also connected with 

 colour." 



Considerable controversy has lately been carried on in the 

 pages of the " Australasian " on remedies for the American 

 bhght, and much has been said in favour of using stocks of 

 the Majetin Apple as a sure prevention of the disease. A 

 Mr. Wade, of Pomona Place, Launceston, Tasmania, in a 

 communication on the subject to the same paper, says : — 



" That on his arrival in Tasmania he devoted especial atten- 

 tion to the check and prevention of Apple blight, aud one of 

 his first ideas was to raise stocks from the seeds of those sorts 

 not affected by blight. He chose the seeds of the Siberian 

 Bittersweet, and the result was success far beyond his most 

 sanguine expectations, for barely 1 per cent, of stocks raised 

 from those seeds were in the least affected by blight, whilo 

 some alongside, raised from promiscuous seeds, were destroyed 

 by it, and that he has continued the system for several years 

 with the same unvarying success." 



Mr. Lightband's operations above referred to have been most 

 successful. The juices of the fresh graft after a while per- 

 meated the whole of the diseased tree, infusing, as it were, a 

 new life and fresh vigour into it. The aphides avoid infesting 

 it, the leprous bark exfoliates, and a clean sound bark takes 

 its place ; the tree continuing to bear two kinds of fruit — that 

 of its original stock, as well as of the anli-bhght graft. These, 

 however, will no doubt in time merge their respective types or 

 qualities, the one with the other. 



From these circumstances it is not too much to say there 

 are good grounds for assuming that, in the first place, as a 

 prevention of the disease, the selection of an anti-blight stock 

 on which to graft the particular kind of Apple desired to be 

 grown will be the best means of insuring a healthy fruit-bear- 

 ing tree ; and in the second, as a cure for trees already 

 aiiected with the blight, the inoculation process of Mr. Light- 

 band is the most rational plan that can be adopted. 



It is not the Apple tree alone, however, that such parasites 

 persecute. The Pear, the Peach, the Apricot, and the Nec- 

 tarine, as well as the smaller fruits, also the Grape Vine and 

 the Hop plant, are all, more or less, infested by a species of 

 one or other of them ; and those who desire to derive both 

 pleasure and profit from their fruit gardens or Hop grounds 

 should not fail to seek for and apply proper remedies iu good 

 time. 



In conclusion, it may not be out of place to advance a few 

 words on the bearing which the theory of natural selection, 

 or the survival of the fittest, has upon the subject now under 

 consideration. It is obvious that without o.n operating cause 

 — one, doubtless, amongst many, such as the parasitical in- 

 fluence of aphides on fruit trees in enforcing, as regards the 

 latter, the necessary process of renewal by stimulating horti- 

 culturists to adopt improved methods of cultivation, as well 

 as instinctively, as it were, to select such stocks as will prove 

 the fittest against the destructiveness of these pests — with 

 little exception many fruit-bearing trees would be left un- 

 tended, and, as a natural consequence, would inevitably de- 

 generate, and eventually dwindle away. In this will be recog- 

 nised one, perhaps, of the many purposes designed for these 

 tiny insects by that Providence Who hath numbered the very 

 hairs of our heads, and without whose knowledge a sparrow 

 doth not even fall to the ground. 



The Vice-President having placed his microscope at the 

 service of the meeting, the author was enabled to illustrate 

 very clearly the peculiar nature of the American blight, as 

 well as the scale bhght. He also exhibited several branches 

 of .\pple trees from Mr. Lightband's garden, showing the 

 curative effect of that gentleman's anti-blight grafting treat- 

 ment. 



A discussion ensued, in which several members took part. 



Mr. Elliot mentioned that when on a visit at the Hon. W. 

 Robinson's, in the Amuri, three years since, while walldng 

 through the orchard one morning he discovered a tree affected 

 with the American blight, much to the disgust of the gar- 

 dener. The trees in this orchard were at the time ten years 



