ICERYA PURCHASI.

Northern Advocate, 9 April 1887, Page 3

ICERYA PURCHASI.

Mb 11. A. Wight's letter to the "Bee and Poultry Journal " reads as follows : — ; I have to thank Mr Eeader Wood for a very interesting letter upon the state of his well-known lemon orchard at Parnell, and for the specimens of the Icerya Purchasi accompanying it, and beg to sympathise with that gentleman upon his severe loss, as Mr Wood states that of his 250 fine trees not "half-a-dozen" remainjthat are of any use. Mr Wood expresses his opinion that the syringe is of little. use in removing the insect, owing to the difficulty of reaching it on the undersides of the leaves, and" complains of the great difficulty in getting rid of it, as, as soon as its ravages have been checked, it seems to reappear as abundantly as ever. With regard to this insect and its congeners the reader could not do better than procure the back numbers of this journal, and peruse them.. In the February and March (1886) numbers the Editor has given long and minute descriptions of the Scale insect, with illustrations, including the Icerya Purchasi or White Cottony cushioned Scale. The lemon being an evergreen is a great disadvantage in dealing with this destructive insect, as the leaves present an obstacle to the action of the spray. It is however as yet considered to bo the only remedy [The best authorities in America, as we have often said before, recommend as a remedy for scale on evorgreens, not caustic potash, but a strong decoction of tobacco juice, applied with a spray nozzle at a temperature of 130 degrees* Eah. It must be hot and strong to do its work effectually, and the application should be repeated at intervals, until no scalo is left alive upon the trees.— Ed.l In using the syringe there, are certain conditions to bo observed. The one is the strength of the liquid to be used, and the other is the prouer time to use it. Caustic potash is, I believe, now admitted to be the best remedy for all lands of scale insects, but unfortunately there is often little dependence to bo placed, on the strength of the drug. Used in moderation it \yill do the tree good, but it is quite possible |to make the solution strong enough to injure, if not even to kill the tree outright, and when one is directed to dissolve one pound of caustic potash in three gallons of water it is first necessary to ascertain the exact strength of the potash, as it varies so much as three or four times, and it is probable that when Mr Wood used the syringe ho might not have made the decoction strong enough, even though he may have followed explicit directions, or he may have used it in too dry weather. The action of the caustic, potash is to bum the scale. The liquid will kill fill the young scales that are moving about in a very short time, but the mother scale, ensconced in her horny covering, is not so easily destroyed. The' liquid requires time to burn round the edges of her shell and enter within. As soon as the liquid falls upon the bark or leaves it begins to evaporate, and when that process is completed its caustic properties are at an end. You should therefore choose dull, moist (not rainny or sunny days) to use the syringe, and never in the morning of a fine day. Let it be towards late afternoon or evening. In order that my readers may more fully understand the reason of this precaution I might as well give a brief description of part of the insect's habits, oven although it lias already been furnished as far as requisite by our Editor in the numbers alluded to. , « The scale in its first days is a very minute insect, hardly perceptible to the naked oye.' For a few days it is tolerably active until it fixes itself down upon the bark, into which it inserts his sucker, and remains stationary — the male, until it undergoes its final changes, and. emerges into the peafect winged insect, when it moves about again to seek its mate to propagate its species, and to die ; but the female remains stationary till death. During this period of inaction there is secreted on the back of the insect a substance which hardens and becomes a shell or covering, under which the animal lives, and where the young are brought forth. Under the body of the mother is secreted a cottony cushion, on which the eggs are laid and into which the young retreat, and as their number und size increase, so does the body of the parent shrink upwards, die and

dry up, until nothing' is left but the hornj covering, ivhich now forms a roof oyer thi brood. These soon emerge and run the sani( course, and as a female will produce as manj as 500 at a time, and there are three broods ir a year, it is quite easy to imagine the enormous rate of increase that must tako place in a few yenrs whore the evil has been neglected oi imperfectly fought. Tobacco water is a very good remedy, and both th?i :i-:<1 Hi a potash arc best used pretty hot;, but tli-j i::*lcr is the surest. As for kerosene oil in any shape, as far as my own experience goes, I would not use it for any purpose on trees, and " ideod I don't much like the use of any kind of oil to any great extent. [In wh.at we have written in previous numbers of this journal on the remedies for scale blight wo especially warned readers against the use of kerosene oil upon fruit-trees, giving the results of careful experiment made with this insecticide in California. — Ed.] The Icerya is like many other insects in one respect. It has been known to exist ■for a very long time, but it is only lately it has committed such fearful havoc. An old entomologist, about 60 years ago, writing on the subject of the scale insects of the genus " coccus " (the Progallinsectes of Reaumur) says : — " These curious insects are certainly hurtful to vegetation by causing a too abundant transudationof their juices ; and they consequently excite the jealously of those who cultivate- the finer trees, such as the peach, the orange, the olive, and the fig. Certain species attack also tho roots of plants. But upon the whole the advantages" which we derive from these insects amply counterbalance whatever injuries dey may occasionally inflict upon us." The above writer of course alludes to the coccus cacti, in respect of the benefits to trade, but it is evident that m his time the scale that has driven the orange 150 miles from the Cape and is now threatening orange and lemon trees with extinction, was not then so well known as at present. Some circumstances either of tho introduction of more favourable food (for the insect is a native of New Zealand), or the absence of its natural enemies from one cause or another is no doubt with this insect, as with others which from time to time press forward as pests the reason why, for a longer or shorter period, they become so conspicuously destructive. The vine pyralis (first cousin to the eodlin moth) ravaged the vines of France, eating the leaves aud seeds, for a period of ten years ? costing tbe country millions, and creating great distress, but it has ceased to be a prominent evil. Then there was the dacus fly on the olive, the apple blight, the terrible phylloxera, the peach disease, : the codlurmoth, and now the icerya on the lemon. These evils seem to run their allotted course and die out, but at the same time they appear to be getting moro and more frequent and serious, which no doubt is owing to tho greatly increased facilityjof transmission, for whilst owing to that cause the different countries of the earth are enabled to enjoy the luxuries of each other's growth, so do they suffer from their several pests, and it unfortunately happens that whereas these pests, being for tho most part devourers of the said imported luxuries, are transmitted with them, their natural enemies, the carnivorous insects, are not so easily brought with them, and having thus escaped from their persecution, they go on and increase without check. Tho enemy of the scale, the Coccinella septempunctata (or Ladybird), is here, and, I observe, is 'much 'on the increase, but tho -"Lace fly" (Ephemera), whose larvro are perhaps its greatest enemies, as far as I know, is not to bo found in Now Zealand. Tliis scale seems much more fatal to the lemon than to the orange in this country, but it attacks all the Citrusjtribe, and is found not only on tho Acacias, but occasionally on, the .Elm, the Oak, the Lime, the Alder, the Holly, and more particularly the Oleander. As to the rapidity of their increase there seems to be a difference of opinion. Whilst some authorities seem to limit the family to a few hundreds at one brood, Figuiere (who is very correct) alludes to its "laying fts thousands of eggs," and another author (Rearaur) has made a calculation to show that "in the course of five generations a single mother may be the means of producing 5,904,900,100 ! " This we must understand to be the result of a kind of compound multiplication sum, with three or four generations to thp year, for the males are in a very small proportion indeed to the females. I rather suspect the idea that the insect gives the preference to the lemon over the orange in this 'colony is, owing to that f ruit-^boing mqro gfljiprally — ami - Aiiccoaef nlly - grown here. Again, it is supposed to bo more fatal, or I should perhaps say more rapidly fatal, to trees grown in clayey soils than where the land is dry, warm volcanic. In Mr Wood's case, at Parnell, the soil is stiff clay, but it is trenched 20 inches deep and well drained to four feet deep, and nothing could ■ exceed the health of the trees, which wero unusually rich both in foliage and fruit. The lemon, indeed, will flourish well on clay soils if properly drained, as I know by experience, having had trees in such soil which yielded crops that were simply enormous, but it was worked and manured three feet deep, and drained four feet, and heavily mulched with rich manure. In such cases it is not the poverty of the tree that induces the insect nor the richness that will save it. It will be greatly to be deplored if this scale brings about the destruction of lemon culture in this colony. The Northern districts, that is Auckland, and to the north of it, are preeminently suited for this industry, and there is no doubt that, uninterrupted by such a calamity it would one day become a most valuable trade. It all goes to show tho necessity of proper legislation upon orchaid matters. As our worthy editor remarks, iii the .'number of March, the salary of a competent colonial entomologist " would be as nothing compared with the public benefits to be derived from his work." When the eodlin moth had got fairly established here for several years tho Government, after great pressure, were so foolish as to made an enactment that it remained two years a dead letter. Then, awakening suddenly to the case, they sought on all sides for practical advise to make a better, but not having the patience to wait till such advise had time to arrive, they forged ahead and amended their Act by making it ten times ,worse, and then broke down and gave the task up as beyond their ability for the time being. Now comes the Icerya, and other pests are behind it. Some are here now and there are more and more to come, aud are we to treat them all the same way ? are we to have seperate "acts for each pest ? with the same delay in each case, with soperate officials to carry them out, and separate special taxes to pay their saleries ? Will the Government of New Zealacd never learn tho necessity of passing a moro compreheneive Act, an " Orchard Pest Act," to deal not only with all present, but witli all future pests; with district officers to work under tho directions of a proper entomologist, whose duty it would bo not only to look in to the orchard, but to keep his eye upon importations, to guard against tho advent of obnoxious insects from other countries, where they are rife, and to be ready to meet them on their first landing, as we would meet an enemy on tho beach. Such regulations would be worth the while of the Now Zealand fruit growers to pay a reasonable special tax for, but to wait till everyone is half ruined, and then to force an obnoxious tax upon orchardists, and leaving the the carrying out of details |to ignorant or tyrannical officers, whose object is to obtain a salary, and perpetuate the cause of its receipt is a queer way to help the struggling settler out of his difficulties. A reasonable tax for a natural benefit no one would object to, and a protective duty on.fruit would cover it. For instance if the duty on imported apple 3 were doubled during those months when our own are in season, and halved (or dene away with) when we have none in the market, it would bo a great help to us, arid do littlo harm to either the importer or consumer. Mr Reader Wood who would naturally bo at some pains to ascertain, informs me that birds do not eat the cottony scale. The birds aro generally supposed to prey upon them in some countries, and, where they aro plentiful even vnice aro fond of feeding upon them, but I suspect it must bo some species of bird we have not here, and probably their scale would be tho Coccus Hicis, which is as large as a pea, or some of those other species which form sugary secretions ; Chermis mannifer, which is described as an Indian insect about the size of a bed bug, the feathery or cottony substance extending from which is formed of a saccharine secretion, which aosumes the form of a bunch of feathers with a consistence like that of snow. This insect would become an intolerable pest were it not speedily devoured by numerous enemies. Before leaving this subject I should like to mention a few experiments of my own which I have been trying with a certain species of the' scale insect for some time, in hopes of finding some effectual remedy for that class of hemeuoptera. A few years ago I had a very fine cactus plant in a pot, which I kept in a garret, where there was also some ferns, but no other kinds of plants. For a very long time it was perfectly free from any land of parasite, that I could see, and certainly from the scale that is notf on it ; but one day I perceived a specimin of a scale that lat once took to be the Coccus cactus or cochineal

insect of commerco'. I have never been in the countries where this insect is cultivated^ nor seen it alive, but it it is not the same it so closely resembles "ohe plates and descriptions of it, that the difference would be hard to tell. (I send a sketch to the Editor.) How this iusect could come to this particular plant situated as it was is to me a mystery. The earth had not be in changed or added to for two years! The garden was not near the house, and in it there was no cacti, which plants will not live through the winter because of the frost. Two fresh ferns had been brought into the room, and there was no such insects on those that were there. Well I destroyed the scale, again it appeared, and dressed the plant with tobacco water, but to no purpose. I then immersed the whole plant, pot, earth, and all, but still after a time they reappeared. In quite a different part of the nouse, down stairs, I had some cacti which were entirely free from this insect, and I removed ttie inflicted plant to the same room, standing it upon a small round table; on another stand, about three feet distance, I placed another cactus plaut of a different variety (the upright spinous) which was, and always had been, free from this insect. TJuder both pots I placed a large plate of water, supporting the pots on small stones so as to prevent the insect from creeping from one to the other. Though I watched very closely, I never could see any male insect (which are winged) among them. They may have been there; no doubt there must have been a few among them, but I never could find them. Nevertheless, in about six months I perceived the ins»ct on the other plant, and since then it has spread to the other in the same room. The original cactus is what is known as the chain cactus, from what I can see, the insect after it appears after destruction, comes out of the joints and not from the earth. From what I have .tried I don't believe any possible kind of spraying will ever kill off this insect so effectually that it will not reappear. lam now engaged trying the effects of fumigation, but the experiments are not; suffici^tiy advanced for me to give any decided results, The fumigation with various kinds of smoke will kill them is plain enough, but there are stages in their complicated existdence, in which I fear, they can resist even that process. At one time I thought that small sized pet orange plants, might be cured by making a waterproof cloth cylinder to place over the tree, tied tight round the tree, and filled with tobacco which can be drawn off and used again, but experiments have failed to endorse the hope. From as far as I have gone lam inclined to think that orange trees, in a glass house can be easily and perminently cured by fumigation, that the same could be pratised successfully even with large citrus in the open air, by placing a movable cover of cloth over them and using brimstone (with the care it requires), but that the cure would be less permanent. KOMAT.A