CODLIN MOTH (Cydia pomonella).—?The codlin moth caterpillar burrows in developing apples and pears, and such “wormy” fruit is known to everybody.

The moth itself is seldom seen, since it lies concealed until after nightfall, when it becomes active and lays its eggs. The insect (Fig.12a) measures about three-quarters of an inch long, and is inconspicuously, though beautifully, coloured; the fore wings, which cover the body when closed, are light grey, crossed by fine bands of a darker hue, giving the appearance of watered-silk, while at the extremity of each wing is a large bronze spot; the hind wings, seen only when expanded, are of a light brown colour. The minute flat eggs are laid on the foliage of leaves, on the fruit, or even on young bark; they appear at first as glistening white specks, but, as development advances, a red ring develops, and finally a black spot just prior to the caterpillars hatching.

In some places the first larvÆ developing in the spring enter the fruit by way of the calyx, but under New Zealand conditions it is more usual for entry to be made by boring through the skin of the apple. Having completed their development in the fruit, the caterpillars bore their way out and spin their cocoons beneath the loose bark of the tree trunks; in these cocoons pupation takes place, and from them the next generation of moths develops.

Although in New Zealand there is usually only one generation produced each year, three or even four develop in other countries. The winter is passed by the larvÆ in their cocoons, and pupation takes place just prior to the period when the moths emerge in the spring. As the moths continue to emerge and lay their eggs for a period extending from November to February, it is essential that regular applications of arsenate of lead be made during that time in order to protect the fruit from the larvÆ hatching from the eggs laid by the moths. In localities where the spring larvÆ enter the calyx of the fruit, it is essential to apply the first spray just after the petals fall, so that the poison may lodge in the calyx before it closes. The removal of rough bark from the trunks of both apple and pear trees is a help in controlling the insect. Another method sometimes used is to band the tree trunks with strips of scrim; under these bands the larvÆ collect, and the former can be later removed and destroyed with their tenants.

Currant Clear-wing Borer (Sesia tipuliformis).—?This destructive moth has been carried to and established in New Zealand, as well as many other parts of the world. In currant gardens its larvÆ cause the death of canes by eating out the pith. The moth (Fig.12b) is a very conspicuous and beautiful insect; the wings, which expand to about three-quarters of an inch, are transparent and bordered with golden-purple, a bar of the same colour crossing the surface of the fore wings; the body (about half an inch long) is metallic-purple, the thorax having a yellow stripe on each side, while the abdomen, barred with golden bands, terminates in a fan-shaped tuft of purplish hairs.

The moths are active each year in the spring, when they lay their brownish, globular eggs singly on the bark of the currant canes. The resultant larvÆ bore into the stem and destroy the pith, passing the winter in the damaged canes. In the following spring the larvÆ become active once more and approach the surface, where pupation takes place shortly before the moths emerge.

There is only one generation each year, and control lies in the removal and burning of infested canes in late winter.

Tomato Stem Borer (Gnorimoschema plÆsiosema).—?Tomato growers are frequently faced with the problem of the destruction of tomato plants caused by the attacks of the larvÆ of the tomato stem borer moth. This insect caused considerable damage for the first time in Auckland some fourteen years ago, though it was known in other parts of the country as well.

The moth itself (Fig.12c) is a small one, measuring about a quarter of an inch with the wings closed. In this position the insect is wedge-shaped and conspicuous. Against the general greyish-brown colour is a dark brownish area on each side. The eggs are laid on the tomato leaves, in which the young caterpillars tunnel as they work toward the leaf petioles, down which they burrow into the main stems. In the damaged stems, pupation takes place. Under favourable conditions, this insect may pass through at least three generations during the season.

Control depends upon sanitation and the use of arsenate of lead sprays. All infested stems, together with plants after the crop has been removed, should be burned; as the insect is known to attack potato plants and tubers, care should be taken to destroy all potato tops after harvesting. Frequent applications of arsenate of lead are essential to protect the tomato plants, especially during the earlier part of the season.

When on this subject, mention should be made of the potato-tuber moth (PhthorimÆa operculella), which is somewhat similar to the tomato-stem borer, both in appearance and habits. The larva of this insect is best known from its habit of boring through potato-tubers; these burrows become filled by a fungus after the larvÆ have vacated them. The adult potato-tuber moth is a night-flyer, and lays its eggs upon the leaves of the plants; the larvÆ burrow down the stems, and may even reach the tuber below ground. When seed is not properly buried, the moth will also lay its eggs in the “eyes,” and so directly infest the tuber; this danger applies also to potatoes in store or in bags.

In the control of the potato-tuber moth, the following points should be noted:—?Select only sound seed and cover well when planted. On harvesting the crop, do not leave the bagged potatoes standing in the field overnight, as they are exposed to infestation; neither cover the open bags with the potato-tops, as is commonly done, since this will attract the moths. Destroy all tops immediately after harvesting. Dusting potatoes in store with slaked lime will tend to act as a protection against the moth.

Round-headed Borers.—?Apple, almond, and citrus trees, together with gooseberry and such ornamental and shelter trees as poplars, tree-lucerne, and goat-willow, are sometimes damaged by round-headed borers, which tunnel in the stems and branches. These borers (Fig.12d) are white in colour, narrow-bodied, and cylindrical, the segments being usually well defined, and belong to a group of beetles known as long-horned beetles, a group of insects to which the common hu-hu beetle belongs. These beetles are narrow-bodied, and their antennÆ are comparatively long and conspicuous.

To control these pests, the only thing to do is to cut out and burn the badly-infested parts. Where a borer is located (and this can be frequently done by the presence of the powdered wood ejected from the burrows), the culprit may be killed by injecting into the tunnel some carbon bisulphide and plugging up the openings with some clay or other similar substance.

Leaf-mining Flies.—?Very often the leaves of cineraria and chrysanthemum are disfigured by the tortuous tunnellings of the maggots of minute flies (Fig.12e). The adult insects are two-winged, and in structure resemble in many respects miniature houseflies. The eggs are laid in the leaf tissues, in which the whole development of the maggots and pupÆ takes place. The white maggots are small, legless and headless. Spraying with black-leaf 40 would act as a deterrent to the flies, while infested leaves should be removed and destroyed before infestation becomes general.

Grass Grub (Odontria zealandica).—?As explained in the preceding chapter, the grass grub is the larva of a native cockchafer beetle (Fig.11, 1). This grub, by feeding upon roots, causes extensive damage to pastures and lawns, as well as to many garden plants, including strawberries. In the case of pasture and lawns, the presence of even a considerable number of grass grubs is not detrimental unless they occur concentrated in definite areas, when the damage is pronounced. With garden plants, however, which are isolated when compared with the dense root masses of grasses, the attacks of one or two grubs upon the roots of a single plant may cause serious injury.

Grass grub damage to grasses is not merely due to attack upon the roots. While feeding, the grubs swallow soil with the roots, rendering the former spongy, and so disturb the normal circulation of moisture about the grass roots. In the case of infested lawns, it is advantageous to roll infested areas in order to pack the soil pulverised by the grubs, and re-establish normal circulation of soil moisture. Another important feature in grub control is to stimulate root development by means of fertilisers. A recently-developed method of “grub-proofing” lawns is to broadcast over every thousand square feet of turf to be treated one bushel of screened sand or clean soil, in which 5lb. of lead arsenate powder have been intimately mixed. This is said to remain effective for a period of three years; but such fertilisers as nitrate of soda, superphosphate, sulphate of potash, and potassium chloride should not be used on “grub-proofed” turf, as they react with the lead arsenate, and reduce its effectiveness, though rotted manure or ammonia sulphate may be used.

The control of grass grubs damaging the roots of strawberry and other plants is a difficult matter, though some benefit is to be derived by making holes about four inches deep with a stick in the soil near to the infested plants and pouring in a little carbon bisulphide; the holes should be closed immediately. To protect strawberry beds, if they are not too extensive, the most satisfactory method is to cover the plants with scrim, stretched on frames, at dusk during November and early December, when the beetles are flying; this will prevent the insects from infesting the ground with their eggs. The use of sulphur smudges, already referred to, is of great importance in this respect.

Subterranean Grass Caterpillars.—?These caterpillars are the larvÆ of native moths (Fig.12, f1) belonging to the genus Porina, and when they become epidemic they cause much more extensive damage to pasture and lawns than do the grass grubs. When full grown, the greyish-black caterpillars (Fig.12, f2) reach a length of about three inches; they are soft-bodied and rather flaccid, and live in underground burrows of varying depth. After dark, these caterpillars come to the surface and devour the grass, eating it close to the ground, much soil being swallowed by the larvÆ during the feeding. This soil is evacuated, and resembles earthworm castings, but is mixed with silk spun by the caterpillars; the emergence holes of the caterpillars, about the diameter of a lead pencil, are conspicuous on the surface denuded of its covering of grass. Pupation takes place underground, and when the moths emerge the pupÆ first move to and project beyond the surface of the ground; these pupÆ are large and easily recognised by the wing-cases, which are very short compared with the length of the body. The moths are on the wing during spring and summer, the rest of the year being spent in the larval stage. The moths are night-flyers, and are amongst the largest species in New Zealand, their wings having an expanse of from one to over two inches; they are heavy-bodied insects, and vary considerably in colour. One of the commonest, species is brownish-yellow, or sometimes a smoky-grey, with a white streak bordered with black on the fore wings; the hind wings may be pinkish.

The most satisfactory method of controlling the insect is to roll infested lawns after dark, in order to crush the caterpillars whilst feeding on the surface. Flooding an infested lawn with water will bring most of the caterpillars to the surface, when they can be collected and destroyed. Spraying grass in spring and early summer with arsenate of lead will tend to poison the immature caterpillars. There are at least three species of insect parasites that attack these larvÆ, and there is also a fungus which invades and destroys the whole body, taking the shape of the insect; such fungus-infested caterpillars are commonly called “vegetable caterpillars.”

Wireworms.—?The roots of garden plants and germinating seeds are often damaged by hard, wiry beetle grubs, reddish-brown or whitish in colour, called “wireworms,” so named from their resemblance to short pieces of wire; they have three pairs of legs behind the head and a sucker-like appendage on the last body-segment (Fig.12, g2). These grubs transform to narrow-bodied, brownish or blackish beetles, known as “click-beetles” (Fig.12, g1) from their habit, when overturned, of righting themselves by a springing action, during which a distinct and sharp clicking sound is made; the spring apparatus consists of a spine, the tip of which fits into a notch on the under side of the thorax.

Practically nothing is known as yet in regard to the biology of the New Zealand click-beetles. They are extremely difficult to control, and the larval stage covers a period of two or more years.

Narcissus Flies.—?There are two species of narcissus flies—?the larger (Merodon equestris) and the smaller (Eumerus strigatus) both occur in New Zealand. The larvÆ of these flies attack bulbs of various kinds, the hosts of the larger fly being narcissus, hyacinth, tulip, amaryllis, habranthus, vallota, galtonia, scylla, and leucojum; and of the smaller fly, narcissus, hyacinth, onion and shallot. These flies are two-winged insects, the hind wings being wanting as such, and belong to a group called the syrphid, or hover flies.

The larger narcissus fly (Fig.12, h1) resembles somewhat a humble-bee (which, however, has four wings); its stout and very hairy body measures about half an inch long. There is considerable variation in colour, though black or brown predominates, with greyish or yellowish hairs, and bands of the same colour; the bands, however, are absent in some individuals.

During spring the insects fly about in the sun, and lay their eggs at the leaf bases of the host plants, or on the exposed neck of bulbs, or in the soil close by. The larvÆ, which are legless, yellowish grubs, enter the bulb, and may completely destroy it. Infested bulbs may be detected by an unnatural softness near the neck when pressed between the fingers.

The smaller narcissus fly (Fig.12, h2) is about half the length of the larger, of a shiny black colour, with metallic reflections, and is not clothed with hair. The eggs are laid in the ground, or at times upon the plant itself. Several larvÆ of this fly may be found in the one bulb; the larvÆ resemble those of the larger fly, but are smaller, and have three small processes at the end of the body. The smaller narcissus fly usually attacks the bulbs already damaged by some other agent, though it has been known to infect sound bulbs.

Control of both these flies depends upon the destruction of infested bulbs. Recent researches have shown that the flies themselves can be poisoned in large numbers by a spray made of 4oz. of sodium arsenate, 1lb. of crude glycerine, 2lb. of white sugar, and four gallons of water; this spray is applied during bright and warm weather.

Springtails.—?These are very minute, soft-bodied insects, which are very active, and have a habit of springing with the agility of fleas. There are several species, but two are of interest to the horticulturist.

One of these (Fig.12, k1) is white in colour, narrow-bodied, and lives underground, especially in damp places, where it damages germinating seeds, or the roots of seedlings; even older herbaceous garden plants are attacked. As a control, it is important to drain the soil in damp locations and to dig in calcium cyanide about two weeks before planting or sowing.

The second species is blackish and more or less spherical (Fig.12, k2); at times it does considerable damage in the spring to the seed-leaves of young plants as soon as they appear above ground. Spraying small areas—?e.g., of cucumbers, turnips, etc.—?with black-leaf 40 would help to protect the plants; as the eggs are laid in the ground, and as these develop best under moist conditions, thorough cultivation prior to sowing the crop is an important controlling factor.