Garden Pests in New Zealand / A Popular Manual for Practical Gardeners, Farmers and Schools

Natural enemies in New Zealand are two species of hymenopterous parasites, Aphelinus fuscipennis and A. mytilaspidis, the latter also attacking the apple mussel scale. Ladybird beetles also feed upon the insect.

Control requires close attention, and can be effected by the application of lime-sulphur in the dormant season, when it is essential to apply a strong wash to kill off as many scales as possible before reproduction commences in the spring. At bud movement further applications are necessary to destroy the young insects.

Red Orange Scale (Chrysomphalus aurantii).—​The red orange scale is distributed throughout the world, and is especially abundant in tropical and sub-tropical regions, the most southern limit being New Zealand. As a major pest it is peculiar to citrus, but infests to a minor extent other plants—​e.g., plum, apple, pear, quince, grape, fig, euonymus and rose. So far it has been found only on citrus in New Zealand, it being well established in the Auckland province, and also in the South Island on Banks Peninsula. It is very often found on imported oranges and lemons.

This scale is a circular one, with a central pimple-like prominence, as in the case of the San José, but is flatter, about half as large again, and is of a characteristic reddish colour. The damage done to citrus trees by this insect is of a serious nature, as the entire tree or part of it may be killed in severe infestations. A characteristic feature of this species is that no honey-dew is secreted, and hence there is a total absence of sooty mould on infested trees.

Like the San José scale, the red scale is viviparous, and over-winters as partially mature adults, completing development in early spring, when the young insects make their appearance. An average of about 55 young is produced by each female, and development to maturity takes from two or two and a-half months; about one month later young are produced, and their production continues over a period of one or two months; climatic conditions, however, have a direct influence on development.

An important natural enemy is the steel blue ladybird (Orcus chalybæus), imported from Australia; but the most efficient control is cyanide fumigation, or spraying with red oil or lime-sulphur.

The Black Scale (Chrysomphalus rossi).—​Foliage of palms, oleander and citrus is often infested by this reddish-black to black circular scale (Fig. 7, 3); it is almost flat, with a central whitish spot, and measures up to one-tenth of an inch in diameter; when many individuals are crowded together, their outline becomes irregular. This species is not especially injurious, though common.

Oleander Scale (Aspidiotus hederæ).—​This cosmopolitan insect occurs on orchids, oleander, ivy, camellia, palms, citrus, coprosma, and karaka, infesting stems, leaves and fruit. In the case of citrus, this insect delays colouring of the fruit, which becomes blotched with yellow or green. The insect may be so numerous, that it completely covers the whole plant, giving to the latter a white appearance; this is due to the preponderance of white male scales, the female being slightly yellow, with a purplish tint.

The female scale is almost circular (Fig. 7, 7), having a diameter of from one-twenty-fifth of an inch to two-twenty-fifths of an inch, and is rather flat; the male is more oval and of the same size, and in both cases there is a central orange-yellow spot. The eggs are comparatively large, and hatch soon after being deposited. The insect reaches maturity in from four to six weeks.

Greedy Scale (Aspidiotus rapax).—​This European insect is now widespread, and in New Zealand is common on apple, pear, quince, and wattle; it has a wide range of hosts. The adult female scale is convex and of a general grey colour, though sometimes yellowish. The winter is passed in all stages of development.

Rose Scale (Aulacaspis rosæ).—​This is a very common insect, forming white incrustations on the bark of roses, briar, raspberry, loganberry, blackberry, and sometimes pear. The adult female (Fig. 7, 8), which is from one-twelfth of an inch to one-eighth of an inch in diameter, is rather thin and flat, circular or oval in outline, but irregular when crowded; the general colour is white or slightly yellowish. The male (Fig. 7, 9) differs, in being elongated and narrow. This insect can withstand severe winters, and is to be controlled by the use of red oil.

CHAPTER VI.

Sucking Insects—(Concluded).

Plant Lice, or Aphides.

The small, soft-bodied plant-lice, or aphides, usually found forming dense colonies on all sorts of plants, are pests well known to every gardener; they attack plants by inserting into the tissues their delicate piercing mouth-parts, and drain the nutrient sap (Fig. 8, 1g). All parts of a plant may be infested, and the insects, owing to their ability to reproduce abundantly and rapidly, may destroy the plant, or at least injure it by stunting its growth, curling the leaves, or deforming the flowers and fruit. In many cases aphides copiously secrete honey-dew, upon which sooty mould grows, rendering the plant unsightly; on this honey-dew ants feed, and are frequently seen associated with aphides. Apart from their direct injurious effects, aphides are of outstanding importance, in that they transmit some of the most serious plant diseases. Of all the species occurring in New Zealand, only one species is supposed to be a native.

Most aphides live exposed upon the host plant (e.g., Rose Aphis), but some (e.g., Woolly Aphis) secrete a protective covering, while others cause a malformation of the plant tissues which form a partial protection as a semi-gall (e.g., Elm-leaf Aphis), or a complete protection as a true gall (e.g., Leaf-petiole Gall-aphis of Poplar).

Aphides present certain variations in structure, and, generally speaking, the one species presents four or five types (Fig. 8, 1): the asexual (parthenogenetic) wingless and winged females that give birth to living young (viviparous) in the absence of males, and the sexual forms, both males and females, the latter producing eggs (oviparous).

The best character by which the New Zealand aphides are to be recognised is to be found in the pair of longer or shorter horn-like processes, or “cornicles,” projecting from the upper surface of the abdomen; in some species, however, the “cornicles” are reduced and inconspicuous (e.g., Woolly Aphis), or altogether absent (e.g., Grape Phylloxera). The “cornicles” are frequently called “honey-tubes,” since for many years it was thought that they secreted the honey-dew; it has been shown, however, that the honey-dew is secreted from the rectum, and that the function of the “cornicles” is to secrete a waxy protective substance, which may take the form of a powder or woolly threads. The wings, when present, are membranous, the front pair being much larger than the hind ones, and when not in use usually close roof-like over the body.

In their life-histories and habits aphides present many variations, sometimes of considerable complexity, but fundamentally the processes are as follows:—​Eggs are laid on the host plant during the autumn, and give rise to wingless females in the spring; these females (being asexual or parthenogenetic, since they reproduce without being fertilised) are viviparous, producing living forms similar to themselves. Some of these forms remain wingless, while others may develop wings, upon which a wider dispersal of the species depends, but in both cases such females are asexual and viviparous. Several such generations may develop until the autumn, when males and females appear, the latter being oviparous, producing the over-wintering eggs when fertilised by the males. Very often, however, the life-cycle is considerably complicated by the winged forms flying to other host plants and establishing there colonies differing in many respects from the parent stock; from these secondary hosts there is a return migration to the original species of plant. Again, the migrations may be restricted to different parts of the same plant, from the leaves or branches to the roots, for example. Most aphides are readily controlled by means of insecticides, such as nicotine-sulphate, or kerosene-emulsion. They are also very often held in check by natural enemies, such as aphis-lions, hover-flies, ladybirds, and numerous forms of hymenoptera. The following species are some of the commoner aphides met with in New Zealand:—

Black Peach—aphis (Aphis persicæ-niger).—​From early spring, even before the foliage develops, this aphis may be found heavily infesting the young, succulent shoots of peach; it also occurs on cherry, plum and nectarine. The adult insects are black and the immature stages pale reddish-brown, dull brown, or lemon-yellow. During the winter the insect lies underground about the roots of the host plant, and thence migrates to the young growth in spring. At first only wingless forms are seen, but as the season advances the winged migratory aphides develop; at that time the foliage is so severely attacked that it becomes crumpled and functionless (Fig. 9, 1), while the developing fruit is distorted and rendered useless. The heat of the late summer destroys the aphides still on the foliage, but sufficient numbers descend underground for protection, where they live over winter.

Green Peach—aphis (Rhophalosiphum persicæ).—​This aphid occurs on a wide range of plants, including the peach, and, as a rule, is most abundant during summer and autumn; as the name implies, the general colour is green, though some individuals are reddish or brownish-yellow; the wingless forms have black-tipped “cornicles,” and on the abdomen of the winged insects are dark markings.

Black Cherry—aphis or fly (Myzus cerasi).—​This aphid has now a world-wide distribution. In New Zealand it has been found on cherry and plum, though in other countries its hosts include peaches, red and black currants, and cruciferous plants, such as common mustard, shepherd’s purse, etc. This species exudes copious honey-dew, upon which sooty mould develops, thus rendering fruit unfit for use. The principal injury, however, is due to the destruction of shoots and leaves, the latter frequently curling up when the insect clusters in dense colonies upon the infested plant. The complete life-cycle has not been followed under New Zealand conditions, but the shiny black eggs occur on the bark and buds of cherry trees during the winter. In spring the eggs hatch, and the insects, rapidly reproducing, attack the young shoots and leaves. Observers in other countries have noted that there is a summer migration of winged females to cruciferous plants, where colonies are established, and whence there is a return migration during the autumn to the original host. The wingless females are black, with part of the legs yellow, while the young individuals are pale in colour; the winged females have a green abdomen, from which arise the black “honey-tubes.” Since all the over-wintering eggs have hatched by the time the buds open, the insect can be then controlled by applications of nicotine-sulphate.

Cabbage Aphis (Brevicoryne brassicæ).—​The cabbage aphis, or cabbage green fly, is widely distributed throughout the world, and has become a serious pest in New Zealand, causing considerable damage to cruciferous crops; it infests rape, turnip, cabbage, Brussels sprouts, cauliflower, as well as related weeds, such as wild mustard, shepherd’s 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.

Pine Tree Chermes (Chermes pini).—​This is a widely-distributed species, occurring upon both Austrian and insignis pine in New 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 form of the aphis 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 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 close to the soil; if such scion roots form, they should be cut away and the soil removed from the union.

Rose Aphis (Macrosiphum rosæ).—​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, antennæ, 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 lanigerum).—​Although frequently called “American Blight,” the apple woolly aphis is probably a native of Europe. It occurs throughout New 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 woolly 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. However, 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 predominating; 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 New 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 greatly minimised. The most important check to the aphis is the Aphelinus parasite (Aphelinus mali), the influence of which has been spectacular under New Zealand conditions.

Plum Aphis (Rhophalosiphum nymphææ).—​This insect is sometimes very common during spring upon the shoots and leaves of plum in New Zealand; in other countries it has been found to migrate to and infest the flowers and leaves of water lilies. The insects assume various shades of green, the winged females having the head, thorax, and legs blackish; the “honey-tubes” vary in colour, and may be reddish, blackish or yellowish.

Poplar Gall Aphis (Pemphigus pupuli-transversus).—​Upon the leaf stems of poplar trees in many parts of New Zealand sac-like growths (Fig. 9, 7), measuring anything from half an inch to one inch in length, may be found. These are the galls formed by the North American poplar gall aphis. In each gall are colonies of the aphis surrounded by a mass of flocculent secretion. The walls of the gall are thick and tough, with the outer surface wrinkled, while at the end, toward one side, is a slit-like, or sometimes circular, opening surrounded by a thickened rim, presenting much the same appearance as the mouth of a sack gathered together and tied. For the most part, these insects are wingless females only, but during the summer, and particularly toward the end of autumn, winged females develop and migrate to cruciferous plants, such as cabbage, rape, mustard and turnips, or weeds allied to these cultivated forms, upon the roots of which they establish colonies surrounded by a woolly secretion. In spring a return migration to the poplar takes place, and galls are again established.

Leaf-hoppers.

Leaf-hoppers form a group of small, narrow-bodied, sap-sucking insects; as the name implies, they infest the foliage of a variety of plants, and when disturbed have the habit of suddenly leaping or hopping to safety; the species present in New Zealand are usually of a greenish or yellowish colour. The adult insect is winged (Fig. 8, K, L), and the female lays her eggs in the plant tissues (H); from these eggs the young wingless hoppers (I) hatch and attack the plant; as they grow, wings develop (J), but until then the insect depends for locomotion upon its hopping powers.

The most outstanding species in New Zealand is the apple leaf-hopper (Typhlocyba australis). This insect causes considerable damage to apple trees unless controlled, which can be effected by spraying with nicotine-sulphate against the young insects in the spring.

White-flies.

White-flies, or mealy-wings, are minute sap-sucking insects, having the body and wings covered with mealy wax. The female (Fig. 8, P) lays her eggs, frequently in circular batches, upon foliage, and the young insects (N) are active, but settle down and commence feeding soon after hatching. Later the insects change to another form (O), without legs and antennæ, and so resemble scale insects to a certain extent; from the latter, however, they may be distinguished by the waxy covering, bearing spine-like processes, and by being surrounded by a distinct marginal area. An important species in New Zealand is the greenhouse white-fly (Trialeurodes vaporariorum), against which fumigation with calcium cyanide is the best as a check.

Thrips.

The foliage of many plants is sometimes infested by very minute black insects, known as thrips. A species commonly met with is that found upon ripe peaches. Thrips are readily identified by the structure of the wings (Fig. 8, 4), which are but narrow strips fringed with long, rigid hairs. These insects, by puncturing the plant tissues and sucking up the nutrient sap, very often are responsible for infecting healthy plants with disease, such as mosaic.

According to the species of thrips, the female lays her eggs either in the plant tissues or upon the surface. The young insects are wingless, but attack the plant in the same manner as does the adult; as development proceeds, the insect transforms to a pupa, from which the adult ultimately emerges. A characteristic symptom of thrips infestation is a silvering of the foliage, while the leaves are further rendered unsightly by the minute specks of hardened excreta ejected by the insects. Many thrips pass their whole development upon the host plants, while others pass part of their lives underground. One of the commonest species met with under glass and out of doors is the greenhouse thrips (Heliothrips hæmorrhoidalis). Thrips are readily controlled by means of nicotine-sulphate.

CHAPTER VII.

Leaf-Feeding Insects.

Leaf-feeding insects have their mouth-parts developed for the biting off and mastication of their food; such insects are, in general, earwigs, crickets and grasshoppers, the caterpillars of moths and butterflies, beetles and their grubs, and the grubs of saw-flies. Such insects vary, not only in their period of activity, some feeding at night, others during the day, but also in the manner under which they set about it. Many feed exposed upon the surface of the plant, while others require protection, such as is afforded by the webbing together of leaves. Some feed upon the leaf epidermis only; some eat holes in the leaf-surface, or gnaw irregular notches from the leaf-edge; while the grosser feeders completely devour the whole.

Earwigs.

In many parts of New Zealand the European earwig (Forficula auricularia) causes considerable damage in gardens, while in Central Otago it sometimes ruins the stone fruits. During the winter this insect lies underground, where the female will be found with her cluster of eggs. In the spring these eggs hatch, and the small whitish young earwigs (Fig. 4, 2) emerge from the ground to feed largely upon the pollen and pistils of flowers. At that time the insects and the injury they do are not very noticeable, but as the earwigs grow in size they become conspicuous and extend their depredations to the foliage of plants and to fruit. Earwigs are nocturnal in their habits, and during the day take shelter among fallen leaves, under stones, sacking, or boards, etc., lying on the ground, and may even burrow into the soil itself.

In the control of the earwig, a great deal can be done by what may be called clean gardening—​that is, the removal of all places likely to shelter the insect above ground during the day. Another important means is systematic trapping, one of the simplest methods being to place crumpled newspapers on the ground at nightfall, in which many of the insects will seek shelter, the papers being collected and burned next day. But the best method is the use of the following poison bait:—​With 12lb. of bran mix 6 quarts of water, to which has been added 5oz. of glycerine and 6oz. of sodium fluoride; to this mash add 4lb. of treacle, taking care to thoroughly mix the whole.

This bait is spread at nightfall in places frequented by earwigs, and should be repeated regularly, especially after wet weather. It is obvious, if satisfactory results are to be secured, that there should be a co-operative campaign organised among the residents of an earwig-infected district.

Crickets and Grasshoppers.

Fortunately, neither crickets nor grasshoppers (Fig. 10, 1 and 2) are a serious menace to the New Zealand horticulturist, though at times, especially in the warmer parts of the country, crickets may do some extensive damage. The control of these pests is a difficult matter, since they are mobile insects, and breed in places outside the boundaries of the horticulturist’s activities. Some benefits can be secured, however, by thorough cultivation, which breaks up the egg-masses which are placed in the ground. In the case of serious outbreaks, the use of a poisoned bait would have to be resorted to, and the following is recommended from the several recipes in use:—​With 25lb. of bran mix 3 or 4 gallons of water in order to make a thin mash; to this, add 2 quarts of molasses and 1lb. of Paris green, thoroughly mixing the whole. If crickets alone are to be dealt with, then use a little more of the Paris green. This mash is spread on the ground invaded by the insects.

Caterpillars.

Of the leaf-feeding insects, the caterpillars of moths are the most commonly met with, there being a considerable number of destructive species. Caterpillars (Fig. 10, 3) can be readily distinguished by their structure from the grubs of other insects. They resemble short earthworms in shape, and in having the body divided into several segments, of which there are usually thirteen; but here the resemblance to worms stops. There is a distinct head—​the first segment—​provided with jaws, and on the under side of each of the next three segments, or thorax, is a pair of short feet. The remaining segments comprise the abdomen, and possess sucker-like feet, varying in number according to the kind of caterpillar; in some forms there may be as many as five pairs of such feet, in some three pairs, and in others two, but in all the pair on the terminal segment persists. Many caterpillars are more or less hairy, and others comparatively nude. The following are amongst the most injurious kinds:—

Leaf Rollers.—​It is a common sight to see small greenish caterpillars sheltering between two or more leaves of plants that have been tied together by the silken threads spun by the caterpillars; protected thus, the insects feed more or less in security. These caterpillars belong to several species of the tortricid moths, which are themselves comparatively small and drab in colour. Of these species, the most abundant one, comprising over 84 per cent. of the leaf-roller population, is the Australian apple-leaf roller (Tortrix postvittana); the caterpillars of this insect by no means confine their attacks to the apple, but feed equally well upon pear, orange, grape, rose, insignis pine, oak, pelargoniums, etc. Apart from attacking the foliage, the caterpillars frequently tie a leaf to the surface of apple and stone fruits, and feed upon the skin of the latter, causing a blemish.

The apple-leaf roller passes the winter in the caterpillar stage between two leaves. In the spring these caterpillars transform to pupæ, which give rise to moths from the end of August to about the end of October; there are at least two broods of caterpillars during the year, but the limits of these broods are not clearly defined. The caterpillars are attacked by several species of parasites.

Leaf-rollers are easily controlled by the arsenical sprays used against codlin moth, but these sprays must be continued into the late summer after their need against codlin moth is past.

Diamond-backed Moth (Plutella maculipennis).—​The caterpillars of this moth (Fig. 10, 4) are commonly found attacking the leaves of cabbages, rape and other cruciferous crops and weeds. These caterpillars are small and greenish, and, if disturbed, suddenly drop suspended by a silken thread attached to the plant. The damage they do is very often extensive, considerable areas of the foliage being devoured. When fully developed, each caterpillar spins a silken cocoon on the under side of the leaf, and there transforms to the pupæ, from which a moth eventually emerges. The insect is small, narrow, and has a light-coloured, diamond-shaped marking along the back. The moth is nocturnal, and shelters amongst the denser foliage during the day; it emerges at night, and lays its eggs upon the leaves. The life-cycle from eggs to adult occupies some 36 days, more or less, according to the season, and there may be six or seven generations during the year.

In control, an important point to note is that the diamond-backed moth breeds upon cruciferous weeds—​watercress, shepherd’s purse, and hedge-mustard—​as well as on the old plants of a crop left in the ground; it is from such places that infestation of future crops arises, and the clearing up of such breeding places should be given close attention. Under garden conditions, control can be secured by spraying the plants with arsenate of lead (to which a spreader must be added in the case of cabbage), which should be done especially when the plants are young.

Kowhai Moth (Mecyna maorialis).—​The caterpillar of this native moth sometimes becomes epidemic, when it does considerable damage to kowhai, broom, lupins, and sometimes clover. The caterpillar, which measures about an inch when mature, is of a greenish colour, having rows of black tubercles with white centres along the sides, and a double row of white spots along the back; from the black tubercles black bristle-like hairs arise. The caterpillar spins a silken cocoon, in which it pupates. The moth is comparatively small, the fore wings being yellowish-brown with darker markings, and the hind wings orange-yellow with a blackish border. There are at least two broods of caterpillars annually: the first in the spring, and the second during autumn. Arsenate of lead will give effective control on garden legumes.

Cut-worms.—​This term is applied to the caterpillars of a number of night-flying noctuid moths; these caterpillars are smooth-bodied and rather worm-like, in some cases measuring from one and a-half to two inches in length when full grown. They feed at night, and their method of attack is characteristic in that they nip off young plants close to the ground (Fig. 10, 5), so that the latter fall over, when they are devoured by the caterpillars; this habit has given rise to the name “cut-worms.” During the day the cut-worms are to be found curled up in the ground close to the plants they have been attacking. The moths of these caterpillars are rather stout-bodied, and measure about three-quarters of an inch long. One of the commonest species is the cosmopolitan greasy-cut-worm (Agrotis ypsilon).

Though cut-worms are active throughout the growing period of plants, most damage is done to young and tender plants at the time of establishment, and this is particularly noticeable in the spring. When plants are grown isolated in rows, and the area is not too large, complete protection from cut-worms can be secured by enclosing each plant in a tin collar pushed into the ground and projecting a few inches from the surface; these collars are removed when the plant is well established. In localities where cut-worms are very troublesome it is advisable to reduce their numbers by means of a poison bait made as follows:—​50lb. of bran and 1lb. of Paris green are thoroughly mixed in a dry state; when this is done, and just before being used, the bran is moistened with water, sweetened with molasses, until the bait reaches a crumbly, but not saturated, condition. This bait may be broadcast over the infected area or laid around each plant as a barrier. This bait must be applied every few days until the plants have reached a stage when they are able to withstand cut-worm attack.

A great deal can be done to check cut-worms by removing dense growths of weeds and rough herbage growing in unused parts of the garden; in such places the insects breed, and are a source of infestation. Another point to consider is that thorough cultivation will destroy many pupæ that are lying underground, and which would otherwise give rise to another generation of moths.

“Army-worms.”—​These caterpillars are similar in their appearance and general habits to the cut-worms, but differ in their method of attack. When present in numbers, they move through a crop—​especially cereals—​eating as they go, and leaving nothing but devastation in their wake, much as does an invading army on the march. They are not of so much interest to the horticulturist as to the farmer.

Tomato-worm (Heliothis armigera).—​This caterpillar (Fig. 10, 6) is one of the most conspicuous caterpillars met with in the garden. Its habit of boring into and eating the contents of tomatoes gives it the name of “tomato-worm.” It is a cosmopolitan insect, and is especially destructive to flower buds and fruit, a wide range of plants being attacked. The caterpillars vary in colour, some being greenish and others brownish, with reddish, yellowish or white markings. The moth, which belongs to the noctuid group, is on the wing both day and night, mostly during the earlier part of the year; it is a stoutly-built insect, measuring somewhat over half-an-inch long; its colour is a brownish-orange, with oblique darker bands on the wings. As the insect passes the winter and spring as a pupa in the ground, thorough cultivation will help to destroy a considerable number. The use of arsenate of lead sprays, however, is the most effective control for the caterpillars.

Hawk or Sphinx Moth (Sphinx convolvuli).—​This conspicuous insect and its caterpillars are most abundant in the Auckland province, though found as far south as Christchurch. The caterpillars feed on convolvulus, but do considerable damage to the foliage of the kumara and sometimes tobacco. The caterpillar is the largest met with in the garden; it is stout in form, and measures up to 3 ½ inches when fully grown. It is to be recognised at once on account of the dark red, horn-like process arising from the end of the body. The caterpillar may be of two colours—​the one green, with diagonal yellow bars on the sides; the other, brownish-yellow, with dark lines on the back and sides. From about February to November the insect lies in the ground as a pupa. The latter can be recognised by a curved process arising from the head and lying along the body. The moth flies rapidly during the last and earlier months of the year; it is a large, conspicuous insect, about 1 ½ inches long, with greyish-brown mottled wings, while the abdomen is conspicuously barred with white, red and brown. Arsenate of lead against the young caterpillars during November to February would act as an efficient control.

Cabbage White Butterfly (Pieris rapæ).—​This butterfly (Fig. 10, 7) is a recent importation, having been first noted at Napier in 1930. Since then it has spread with marvellous rapidity throughout the North Island, and has appeared in the South Island, in the vicinity of Timaru.

The caterpillars of this insect are particularly severe in their attacks upon the foliage of cabbages and cauliflowers, though they also feed upon many other related plants, such as lettuce and radish, besides cruciferous weeds. The caterpillars of the white butterfly are not to be confused with those of the diamond-backed moth, already described. The full-grown white butterfly caterpillar is a conspicuous insect, and measures up to an inch and a-quarter in length; it is easily distinguished by its leaf-green colour and velvet-like appearance, while down the centre of the back is a narrow orange stripe, and on each side a brownish line formed of little spots. The chrysalis measures about three-quarters of an inch long, having a pointed process from the head, and a keel-like ridge on its back, while the colour varies according to the surroundings with which the chrysalis blends; it is not protected by a cocoon of silk, and may be found upon the food plant or any other support near by.

The butterfly itself is a very conspicuous insect, measuring about two inches across the expanded wings. The female is of a yellowish-white colour, with darker to blackish markings at the fore-angles of the front wings, while there are two similar spots on the surface of the same wings, and one on the hind pair. The male is whitish, with a dull greyish-green or bluish hue, marked much as the female, except that there is only a single spot on the surface of each wing.

The eggs (Fig. 10, 7b) are bottle-shaped, and stand erect upon the leaf surface, where they are laid singly, and not in batches; they are visible to the naked eye. The eggs hatch within a week after being laid. There are several generations each year.

The cabbage butterfly can be controlled by the use of lead arsenate. It has been found effective when planting out to first dip the seedlings in lead arsenate at the rate of 1lb. in 50 gallons of water, to which 1lb. of laundry soap is added as a spreader. During the growth of the crop the same strength of arsenate and soap can be applied as a spray.

Magpie Moth (Nyctemera annulata).—​One of the commonest and most conspicuous day-flying insects of the garden and field is the magpie moth. It is black in colour, relieved by an orange-banded abdomen and whitish spots on the wings, two on each of the front wings and one on each hind one. Its black, hairy caterpillars, commonly called “woolly bears,” have narrow brick-red lines along the body, and very often do some considerable damage to cinerarias; they also attack weeds, such as ragwort and groundsel.

The small globular eggs are laid in clusters on the leaves of the food plant. At first they are pale green, later becoming dark yellow, and just before the young caterpillars emerge from them they change to a leaden colour. When fully fed, the caterpillar seeks a sheltered place (beneath stones, under, bark, etc.), and there spins a loose cocoon, in which it transforms to the chrysalis; the latter becomes blackish or brownish in colour, with yellow markings. There are several generations during the year.

Cinerarias can be protected by spraying with lead arsenate, or, better, by removing the caterpillars by hand and destroying them.

Cabbage Tree Moth (Venusia verriculata).—​The foliage of the cabbage tree is frequently holed on the surface and notched along the edges—​this is the work of the cabbage tree moth caterpillars. The history of the insect is as follows:—​The nocturnal moth measures about an inch and a-half across the expanded wings, which are characteristically coloured by alternating chocolate-brown and yellowish-white lines running from wing-tip to wing-tip across the body, so that the insect merges into the general pattern and colour of a dead leaf, upon which it usually rests. The eggs are green, and at first blend with the green leaf, on which they are often laid in batches; when on dead leaves they become conspicuous. Later the eggs change colour to brown, and finally red. The caterpillars congregate in the unopened foliage, and their injury becomes apparent as the leaves open. The larvæ transform to chrysalids in silken cocoons, loosely spun in any suitable crevice upon the trees. If it was necessary and practicable to protect ornamental cabbage trees from the attacks of this insect, it could be done by removing dead leaves from the crown and spraying with arsenate of lead to which laundry soap had been added.

Bag Moth (Œceticus omnivorus).—​This is an insect that never fails to attract attention on account of its cigar-shaped bags (Fig. 10, 8), constructed by the larvæ, and are to be found attached to a variety of plants, upon the foliage of which the larvæ feed, though they are not serious pests. Each caterpillar spins its own tough silken bag, which it never leaves, and to the outside of which it frequently attaches fragments of leaves and twigs. Though the male is a normal moth, and flies about (it is practically black, and densely haired, with translucent smoky-black wings having an expanse of about an inch and a-quarter), the female develops in an abnormal manner, and assumes a grub-like form, never leaving the bag woven by its caterpillar.

If it should be found necessary, as sometimes happens, the only satisfactory way of controlling the bag-moth is to remove by hand and destroy.

Beetles.

Unlike the caterpillars of moths, there are very few beetles in New Zealand that are important leaf-feeders. Though few in numbers, however, the outstanding ones are very destructive. The beetles themselves, as well as their larvæ, according to the species, may attack foliage, but in other cases it is only the beetles that feed on foliage while their larvæ live underground on roots. The following species are outstanding:—

Cockchafers.—​These are the adults of the grass grubs, and there are several species, all native to New Zealand. The commonest and most destructive one (Fig. 11, 1a) is the so-called brown beetle (Odontria zealandica), misnamed the “turnip fly,” which is on the wing for about six weeks each year, during November and early December as a rule. It swarms at dusk, creating a loud, droning sound, and is responsible for widespread damage by defoliating garden plants and field crops, as well as trees.