Plant Protection 3 : Selected Ornamentals, Fruit and Vegetables

ANNUALS AND HERBACEOUS PERENNIALS
which sooty mould grows and which attracts ants.
Aphids spread many virus diseases into and
within crops during feeding. Green peach aphid
spreads > 100 virus diseases. See Roses J 4.
Bugs (Hemiptera)
Coon bug (Oxycarenus arctatus)
Green vegetable bug (Nezara viridula)
Harlequin bug (Dindymus versicolor)
Metallic shield bug (Scutiphora pedicellata)
Leptocoris bug (Leptocoris mitellatus)
Many species suck sap, usually from new shoots
which wilt and brown. See Vegetables M 12.
Caterpillars (Lepidoptera): Most species
have a wide host range. Caterpillars and their
chewing damage are easily identified (Fig. 13).
Droppings are found on plants or underneath.
Budworms, cutworms (Noctuidae): Corn
earworm (Helicoverpa armigera) and native
budworm (H. punctigera) feed on and inside buds
and flowers causing them to brown and not open. A
small hole in the calyx marks where the caterpillar
entered the bud. Petals must be parted to find the
young caterpillars in flowers, damage continues after
harvest. They are difficult to control, it may be
necessary to spray regularly, starting at first sign of
damage. See Sweetcorn M 89. Cutworms
(Noctuidae) are smooth-bodied, dark-grey to pinkish
caterpillars up to 40 mm long. They hide in the soil
by day and feed on the base of stems of young
plants at night causing them to topple over. See
Seedlings N 68. Looper caterpillars (Chrysodeixis
spp.) chew leaves and can cause severe damage in
shady situations. See Vegetables M 13.
Leafroller moths (Tortricidae): Lightbrown apple
moth (Epiphyas postvittana) caterpillars eat buds and
flower segments. See Pome fruits F 112. Lucerne
leafroller (Merophyas divulsana).
Loopers (Geometridae) chew leaves. See Avocado F 19.
Others: Cluster caterpillar (Spodoptera litura),
painted apple moth (Teia anartoides).
Pest cycle: Complete metamorphosis (egg,
larva, pupa, adult) with one or several generations
each year.
Overwintering: Usually as cocoons or pupae on
host plants, crop debris or in the soil.
Spread: By butterflies and moths flying assisted
by wind, caterpillars crawl. Seedlings and cuttings
may carry eggs, tiny caterpillars or pupae.
Conditions favouring: Usually warm and
moist, above average rainfall will favour some
caterpillars, eg cluster caterpillar, but some like it
cool. Common during summer and autumn.
Control:
Cultural methods: Minimise host weed growth.
Sanitation: Caterpillars (not irritant hairy ones)
may be hand picked or squashed in small
plantings, some may be well camouflaged and
hard to locate. Infested crops and debris should
be destroyed as soon as possible after harvest.
Biological control: Caterpillars are subject to
many natural enemies including parasitic
wasps, predatory bugs, birds and diseases which
do not usually prevent economic damage
(exceptions).
Pesticides/Resistant varieties: The bacterial
insecticide, Bacillus thuringiensis (Bt), may be
applied to young leafeating caterpillars (not
usually internal-feeding caterpillars in flower or
leaf buds, in fruit or in stems, branches or
trunks), and provides economic selective control
if applied regularly during the main infestation
period. It is slow-acting as it has to be eaten to
be effective. Plants resistant to caterpillars, eg
cotton, tomato, are being bred with the Bt gene in
them, eliminating the need for sprays. Chemical
insecticides may be applied if caterpillars are
large and numerous. Caterpillar numbers and
damage should be monitored before chemical
pesticides are applied. See Brassicas M 39.
European earwig (Forficula auricularia)
feeds on seedlings, dahlia, zinnia, other plants, also
foodstuffs and dead and living insects. Adults are
brown and about 12 mm long with pincers at the
end of the abdomen. They seldom fly, and hide
during the day in rubbish, flower and fruit clusters.
Leaves, flowers and petals may be damaged by
their chewing, and develop a ragged appearance.
They also spoil plants with their excrement. See
Vegetables M 14.
Greenhouse whitefly (Trialeurodes
vaporariorum) is a sporadic pest of annuals during
warm humid weather. Whiteflies are tiny, white
insects which fly out in a cloud when plants are
disturbed (Fig 14). Adults and nymphs may be
found on leaf undersurfaces where they feed by
sucking plant sap causing speckled patterns on
leaves. Whiteflies secrete honeydew on which
sooty mould fungi grow. Infestation may occur but
there may be little damage. See Greenhouses N 24.
Leafhoppers (Cicadellidae, Hemiptera)
Apple leafhopper (Edwardsiana australis)
Common brown leafhopper (Orosius argentatus)
Vegetable leafhopper (Austroasca viridigrisea)
Yellow jassid (Erythoneura ix)
Leafhoppers may be abundant and feed on many
plants, eg dahlia, marigold, grasses and weeds, and
range from very small to medium-sized insects.
They pass their whole life cycle on the plant and
feed by sucking plant sap. When disturbed they
hop away. Their feeding causes speckled patterns
on leaves, each speckle representing a feeding site
(Fig. 15). During spring, summer and autumn they
migrate from drying weeds, etc. to crops. Control
is difficult as damage is not usually noticed until
they have flown away. See Vegetables M 15.
Leafminers are the larvae of flies (Diptera),
eg cineraria leafminer (Chromatomyia syngenesiae)
or moths (Lepidoptera), which tunnel inside leaves
spoiling the appearance of foliage (Fig. 16).
Generally each leafmining species attacks only one
plant family or one species. See Cineraria A 28.
Mealybugs (Pseudococcidae, Hemiptera)
may infest stems, leaves and roots. Female
mealybugs are powdery white 3-4 mm long, oval,
slow moving, wingless, flattened. They suck plant
sap causing soft-foliaged plants to wilt and
eventually die. Economic damage may also be
caused by the excreted honeydew which attracts
ants and on which sooty mould grows rendering
plants unsightly. See Greenhouses N 25.
A 8
ANNUALS AND HERBACEOUS PERENNIALS