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_).
[Illustration: FIG. 10.
(1) Cricket. (2) Grasshopper. (3) Caterpillar. (4) Diamond-backed
Moth--a, adult moth; b, egg; c, larva; d, pupa. (5) Cut-worm lying by
damaged plant. (6) Tomato-worm Caterpillar--a, adult; b, larva. (7)
Cabbage White Butterfly--a, adult; b, egg; c, larva; d, pupa. (8) Larva
case of Bag-moth.]
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 3-1/2 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 1-1/2 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.
[Illustration: FIG. 11.
(1) a, Brown-chafer beetle; b, antenna of beetle, showing finger-like
processes; c, larva or grass grub. (2) Bronze beetle. (3) a, Gum-tree
weevil; b, egg capsule; c, larva. (4) Eucalyptus tortoise beetle. (5)
a, Pear saw-fly; b, larva from the side; c, larva from above. (6) Pear
midge.]
This beetle is easily identified. It is rather plump-bodied, brownish,
smooth, and measures about three-eighths of an inch long. Like all
beetles, the front wings are hard, and form a cover over the body when
closed; these hardened wings, or elytra, do not reach quite to the end
of the abdomen, the tip of which remains uncovered. Another definite
character is found in the antennæ, which terminate in finger-like
processes (Fig. 11, 1b). There are several species of cockchafers, to
which all these characteristics, except the colour, might be referred,
but none is so abundant as the species under review. There is one,
however, that is on the wing about the same time as, or a little
earlier than, the brown beetle. This species is somewhat larger, about
half an inch long; it is sparsely clothed with hair, and the elytra are
marked by broad brown stripes, alternated with very narrow darker ones.
The brown beetle lays its spherical eggs in the ground, preferably
amongst the roots of grass, strawberries, etc. The grubs (Fig. 11, 1c)
are well known as grass grubs; they are whitish in colour, the swollen
terminal segment of the abdomen being very often darker. These grubs
are sometimes called “curl-grubs,” from their habit of lying doubled-up
when at rest or feeding in the ground. Towards September each year
the grubs of the brown beetle pupate prior to the beetles emerging
in November. These grubs will be referred to later under the chapter
dealing with subterranean insects.
In gardens and nurseries, the depredations of the beetles may be
lessened by spraying with lead arsenate, or by the use of sulphur
smudges. The use of smudges was developed very effectively as follows
by Mr. D. J. Buchanan, forest ranger at the Tapanui State Forest
nurseries. Sulphur is spread on strips of scrim, which are then rolled
up and placed in containers, such as old paint pots. The latter are set
about the nursery, and fired at evening, when they will burn throughout
the night, the fumes acting as a deterrent to the beetles. When only a
few plants are to be protected, such as bush roses, the beetles can be
warded off by allowing a hose to play over the plants throughout the
night.
Another common cockchafer which is on the wing most of the summer and
autumn is the green manuka beetle (_Pyronota festiva_). This insect is
capable of causing considerable damage as a defoliator. It is active
both day and night. The general colour is bright green, with a dark
stripe down the middle of the back, though some specimens are brown or
coppery; the legs are orange-yellow, and the length of the insect is a
little over a quarter of an inch.
BRONZE BEETLE(_Eucolaspis brunneus_).--This insect (Fig. 11, 2) is very
often confused with the brown beetle, from which, however, it is easily
distinguished. It is active during the day, and attacks the foliage and
fruit of a great variety of plants, eating holes from leaves, so that
the latter appear as if they had been subjected to a charge of shot,
or devouring the epidermis from fruits and berries. This beetle is
active during November to January; it measures about one-sixteenth of
an inch long, is oval in outline, and varies in colour from yellowish,
with darker markings, to greenish or bronzy-black; the antennæ are
comparatively long, and do not terminate in any unusual manner, as do
those of the cockchafers. A characteristic habit of the bronze beetle
is to leap off the plant if disturbed; this habit has been responsible
for the group to which this insect belongs being called “flea beetles.”
The bronze beetle lays its eggs in the ground, where the larvæ feed,
though they are not injurious in that stage. The beetles are to be
controlled by the use of lead arsenate.
GUM TREE WEEVIL(_Gonipterus scutellatus_).--Both the adults and larvæ
of this Australian weevil attack eucalyptus foliage, particularly
bluegum, in most parts of New Zealand, the adult weevils eating from
the leaf margin, as well as devouring tender shoots, while the larvæ
cut elongated holes from the leaf surface.
The weevil (Fig. 11, 3a), which is of a tawny to brownish-black colour,
and clothed with yellowish-white and golden hairs, measures from a
quarter to one-third of an inch in length; it possesses a short snout
on the head. The eggs are yellowish, and are packed in a hard, black
capsule (Fig. 11, 3b), attached mainly to the surface of young leaves.
The larvæ (Fig. 11, 3c) are legless, like those of all weevils, and
yellowish at first, when they are studded with small black dots, and
have a dark stripe along each side. Frequently these young larvæ are
seen with a tail-like thread of blackish excrement projecting from the
posterior end. The plump, fully-developed grub is yellowish-green, with
a wrinkled skin, and is slug-like in general appearance. Pupation takes
place in the ground. This insect over-winters in the adult stage, and
large numbers of the weevils are very often to be found beneath loose
bark on the tree trunks during the winter. Control depends upon the use
of an egg parasite which has been established in certain localities of
the Dominion. In the case of small ornamental trees, spraying with lead
arsenate to which laundry soap has been added should be effective.
EUCALYPTUS TORTOISE BEETLE(_Paropsis dilatata_).--This is another
Australian insect restricted so far to the East Coast districts of the
South Island, where it attacks eucalyptus foliage in company with the
weevil. The beetle (Fig. 11, 4) is tortoise-shaped, varies in colour
from reddish-yellow to reddish-brown, with darker markings on the
back, which is pitted by minute depressions, and has a length of from
one-third to half an inch. Like the weevil, this beetle passes the
winter beneath loose bark.
The eggs are conspicuous and cigar-shaped, being laid in clusters,
lying more or less on their sides, upon the foliage. The larva is
rather plump, and pointed posteriorly; it possesses legs, while at the
tip of the body is a sucker-like false foot. The general colour is
yellowish, varying to a rosy-pink, there being a darker stripe down the
back, while along each side is a similar one above a row of black dots.
PEAR AND CHERRY SLUG, OR SAW-FLY(_Caliroa limacina_).--The slug-like
larvæ of this insect are very abundant upon hawthorn foliage, and if
not controlled do considerable damage to cherry, plum, pear, and peach.
These larvæ (Fig. 11, 5b) are very often called leeches, and devour
the epidermis, exposing the skeleton of the infested leaves; they are
slimy, of a dark green, though orange-coloured immediately after a
moult, and the head end is much enlarged, giving a clubbed shape to the
body, along the under side of which are several false legs. Pupation
takes place in the ground. The adult (Fig. 11, 5a) measures about a
quarter of an inch long, is rather thickly set, black in colour, and
possesses four transparent wings. The female deposits her eggs in the
tissue of the foliage by means of a saw-like ovipositor--hence the
name “saw-fly”--which is thrust through the lower epidermis of the
leaf, when a pocket is formed to receive the egg; each egg pocket
forms a little pimple on the upper surface. This insect is very
easily controlled by spraying foliage infested by the larvæ with lead
arsenate.
Another saw-fly closely related to the foregoing species is the willow
saw-fly (_Pontania proxima_). This species has only recently appeared
in New Zealand, and its larvæ live in galls, or swellings, on the
foliage of willows.
PEAR MIDGE(_Perrisia pyri_).--A serious pest of pear trees, which for
some years retarded the culture of pears, especially in the Auckland
district, is the pear midge. This is a minute, delicate, two-winged
fly (Fig. 11, 6), measuring about one-twenty-fifth of an inch long;
it has a blackish head and thorax, and an orange-red to brownish
abdomen. The female alights upon young leaves just burst from the
bud; and, while they are yet curled, lays her eggs between the folds.
The larvæ, on hatching, live protected in the curled leaves, which
they attack, and which never unfold. The result is that the infested
leaves eventually turn black and brittle, and cease to function. The
fully-developed larvæ drop to the ground, which they enter, and there
pupate. The midges become abundant in early spring, when the first
young pear foliage develops, and they keep on producing generation
after generation until the autumn. The winter is passed in the larval
stage underground beneath the trees.
A parasite has been established against the pest, and is doing good
work. The insect can be reduced to a large extent by thorough winter
cultivation, especially beneath the trees. The insect’s larvæ, being
protected within the curled-up leaves, are not reached by ordinary
sprays, but Dr. R. H. Makgill, of Henderson, secured some excellent
results on young trees by the use of nicotine.
OLEARIA GALL MIDGE(_Cecidomyia oleariæ_).--In many parts of New
Zealand where _Olearia forsteri_ is grown as a hedge, it is very often
disfigured by the formation of malformations, or galls. These are
caused by a native midge known as the olearia gall midge. The midge
itself resembles the pear midge in structure, but is larger, measuring
from one-tenth to one-eighth of an inch long; it is conspicuous on
account of its black thorax and blood-red abdomen. In early spring the
midges appear and lay their conspicuous masses of bright red eggs upon
the buds of the developing shoots. The larvæ, on hatching, set up an
irritation in the rapidly-developing tissues, causing the latter to
swell and become malformed into bunches of rosette-like galls. If the
latter are cut open, a number of the yellowish larvæ will be found,
each in its own compartment within the fleshy gall. There is only one
brood of adults each year. Control can be effected to a great extent by
cutting back and burning the badly-infested parts during winter, and by
pruning the young growth carrying the eggs in the spring. Spraying with
nicotine when the midges are active should also help to protect the
plants.