266 



THE TROPICAL AGRICULTURIST. 



[September i, 188I2. 



INSECTS INJUIUOUS TO FOREST AND 

 SHADE TREES. 



By A. S. Packard, Jan., M. D. Bulletin No. 7 of the 

 Uuitetl States Entomological Ooinraission. (Washington: 

 Government Printing Office, 18S1.) Pp. 275. 8vo. 



"We think it might have been better had the author 

 somewhat uioiUfied tlio title. Every insect known to feed 

 upon a particular tree is treated upon. In his introductory 

 remarks the author states that Kaltenbach enumerates 537 

 species of insects as injurous to the "Oak" in Europe; 

 a very large number are given as injurious to the same 

 tree (using the term in a broad sense) in_ America. It is 

 obvious, when we come to analyse this list, that only a 

 very small proportion of these are strictly noxious insects, 

 and then only when they occur in extraordiuary numbers, 

 which is only occasionally. It is natural for certain cater- 

 pillars tp feed upon certain plants, and the damage they 

 occasion is in proportion to their number. We have to 

 deal here only with tree', and beyond the unsightliness 

 caused by occasional destruction of foliage on a large scale, 

 we doubt if the trees suffer permanent injury from leaf- 

 fee(hng larvaj. Naturally a certain amount of functional 

 disturbance must result; but surely an equal or greater 

 disturbance arises from judicious pruning or loppmg, even 

 although this is usually carried out at the season of least 

 functional activity. Our author, however, regards these 

 insects as -'para-sites," not specially injurious, adding that 

 the deadly forms are comparatively few. Probably under 

 this latter limited class he includes some of the wood or 

 bark feeders. He is possibly right in some instances, but 

 we feel sure that the morbid conditions commonly attributed 

 to the presence of lignivorous insects are more frequently 

 due, in the first instance, to " something wrong ac the root," 

 inducing an unhealthy state which the iusects seize upon 

 just as flies attack carrion, or visit an ulcer on a beast's 



At this moment a lady (Miss E. Ormerod), eminently 

 qualified for the position, has received the distmction of 

 being appointed honorary entomological referee to the 

 Royal Agricultural Society— the first time that economic 

 entomology has received any official recognition in this 

 country. She can, and doubtless will, do umch good (as 

 she has already done) in enlighteaiug our agricultural classes 

 as to the nature of the insect pests that trouble them, 

 and by iustillUig into their minds the axiom that "prevention 

 is better than cure." Keep up a vigorous state of health, 

 and the damage caused by insects will occasion little anxiety 

 as a rule, and to this end the advice of an economic 

 entomologist should mainly be directed. But there are 

 exceptions, and when these assert themselves in an extra- 

 ordinary degree (as will sometimes happen) we fear the 

 only thing is "to grin and bear them." — Gardeners' Chronicle. 



INSECTS. 

 When Shakspeare penned those trite and true words, 

 "The worst of creatures fastest propagate," he must, 

 one would think, have known something of gardeners' 

 troubles, and of the insects with wliich they have to contend, 

 for truly the rate of increase of some of these is marvellous, 

 and where they spring from, or how many of them origmate, 

 is a mystery. Take red-spiders, for instance, the most 

 minute of the lot, and the puzzle is how such pests get 

 into a quite new house freshly planted with Vnies or 

 Peaches, and yet, it the conditions are favom-able, hosts 

 of them soon come into existence au.l spread with the 

 greatest rapidity. Bad as red spiders are, however, they 

 are quite outdone by green-fly,which breed so fast as to almost 

 outrun all calculation, and if one or two only appear on 

 a plant, their progeny, and those issuing from them, are 

 soon all oviir the leaves, sucking out the juices and curling 

 them up. What tliey have a special liking for just now 

 are Koses and Peaches, which both show unmistakable signs 

 that the enemy is at ,vork, for, look where one will, crippled 

 shoots are to'be seen, and if these are not liberate I and 

 set going at once, they will be a long time in getting 

 over the check. Tobacco-dust, though highly dangerous to 

 leave on for any lengthened period, is an excellent remedy 

 against aphis, as with a distributor, which may be carried 

 in- 'the pocket while disbudding is going on, a puff may 

 i)e given to any .'■hoot affected, and the progress and bree^. 



ing of the insects at once stopped. The best time, how- 

 ever, to apply the tobacco-powder is early in the morning, 

 while the trees or bushes are moist with dew, as then it 

 adheres readily, and as it at once acts on the fly, and 

 causes them to leave their hold, they may easily be 

 washed oft by means of water from a garden engine or 

 .syringe. By looking over Peaches and Nectarines occasionally 

 and treating them in the way referred to, they may be 

 kept clean without having recourse to Gishurst or other 

 insecticides of a similar nature, none of which can be 

 used while the fruit is in such a small tender state without 

 much risk of injury to the delicate skin. To make short work 

 of greenfly on Koses and cleanse the plants of their presence, 

 there is nothing I am acquainted with equal to nicotine soap, 

 which has the active properties of Tobacco in it, and by 

 diluting it to the proper strength it may be syringed on, 

 or the long shoots bent down and dipped in without 

 causing much waste. Quassia chips boiled with some soft-soap 

 in the water forms a good and cheap insecticide, and if 

 a little tobacco-juice or nicotine is added, fly quickly vanish 

 under its influence. The only way of dealing etfectually 

 with the Rose-maggot, so snugly ensconced in the leaves 

 it so de.xterously curls, is to give each a loviug squeeze 

 between the finger and thumb, wliich may be done without 

 bruising or harming the young tender foliage, as the grub 

 is soft and collajjses under the gentlest of pressure. The 

 Gooseberry caterpillar, so prevalent in some gardens, may 

 be got rid of by the use of lime, which shoulii be sown 

 thickly on the ground under the bushes, as there the larvie 

 lie and hatch and issue forth as soon as the weather gets 

 warm. Currants, so subject to greenfly, which affect the 

 tips of the young branches, are best managed by iiijijuug 

 the points out, as the aphis cannot exist on the old 

 hardened leaves, the tissues of -which are too tough for 

 them to get the sap through. The worst of all the aphis 

 family are the black, which usually affect Cherries, and 

 the only way of destroying them without harming the 

 shoots is to use a strong solution of nicotine soap and 

 immerse them all in. The liquid at once penetrates their 

 oily coating, and by its quick action seems to dissolve 

 them. The aphis peculiar to Plums are almost as difficult 

 to kill, and the best way of battling with these and the 

 black on dessert Cherries is to remove the young shoots 

 early by timely stopping, as by doing this they may in 

 many cases be kejot away altogether. As to red-spider, the 

 best remedy where they affect trees on open walls is cold 

 water, dreuchiugs of which from a garden engine they 

 cannot endm:e. Dryness at the root is a frequent cuuse of 

 these parasites affecting Peaches, to prevent which it is a good 

 plan to mulch all trees with balf-rotteu manure, and this 

 should be done early, so as to keep the moisture in and 

 maintain the soil in an equable condition of warmth. By- 

 and-bye, when the fruit is swelling fast, au occasional soaking 

 of sew.oge will do much towards keeping the trees in vigorous 

 health, and will also assist them greatly in carrying their 

 load. — F. Shepp^lrd. — Gardeners' Chronicle. 



THE ROYAL AGRICULTURAL SOCIETY'S JOURNAL. 



The first part of vol. xviii., second series, lately issued, 

 contains matter of great interest, and fully sustains the 

 high character which has been earned for the journal in 

 recent years. The first article is from Rothamsted, and 

 deals with the amount and composition of rain and drainage 

 waters. A great amount of evidence is produced, proving 

 the process of nitrification in the soil, and showing the 

 comparative activity of the action at different seasons. 

 The practical conclusions may be noted. Most of the 

 nitrogen of farm crops is derived from the nitric acid of 

 nitrates within the soil, and this may come from the 

 nitrogenous compounds in the soil itself, from animal and 

 vegetable manures, from the ammonia of artificial manures, 

 and from the ammonia supplied by rain and condens.ation 

 from the atmosphere. This latter source, however, is very 

 limited. There is a difference in the r.apidity with which 

 ammonium salts arc converted into nitrates. Thus, the 

 nitrogen of rape cake and farmyard manure is more slowly 

 changed into nitric acid than that from aramoniura salts. 

 The nitrogenous compounds of the soil itself are very slowly 

 changed into nitric acid. Where there is no vegetation 

 and drainage in operation, there is a loss of nitric acid 

 by solution from the soil. This loss is greatest duiiug 



