PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Pest cycle
There is a complete metamorphosis (egg, larva,
pupa and adult). At certain times of the year males and
females of most species make nuptial flights from the
nests. The mated female, or queen, then sheds her
wings and seeks a place in which to found a new
colony. Nests of most species are made in the ground,
under logs or stones under bark of trees or in old
stumps, landscape timbers or in termite mounds. Some
live in cavities in trees, others more rarely in nests
amongst the foliage of trees. Black or brown ants
invade buildings. A colony of ants may have more
than one nest, and workers may be seen passing
restlessly to and fro along regular runways for long
distances through grass, along walls or other surfaces
from one nest to another. These nests may be
connected by tunnels below ground. The queen
excavates a chamber or cell within which she remains,
laying eggs. Eggs hatch into legless larvae which are
fed by the queen, with secretions from her salivary
glands, until they enter the pupal stage. Pupae change
into worker ants that construct tunnels, forage for
food, tend the queen, care for eggs, feed larvae (usually
reared in groups) or move them from place to place in
the nest. Soldiers (sub-castes of workers) defend the colony.
‘Overwintering’
As all stages in nests.
Spread
By ants crawling and mated queens flying.
By transportation of ants, larvae and eggs in soil,
grass sod, mulch, potting mix, on timber,
containers, vehicles, machinery, infested nursery
stock, hay, straw, landscaping materials. Humans.
Conditions favouring
Each species has optimum temperature conditions.
Many are attracted to their food source.
Management (IPM)
Are you a commercial grower or home gardener?
1. Obtain/prepare a plan that fits your situation.
Obtain leaflets on ant control for you local area.
2. Crop, region. Recognize variations. Are the ants in
containers, adjacent to glasshouses, barbecue areas?
3. Identification of ant species can often only be
accomplished by a trained taxonomist (page xiv).
4. Monitor pest and/or damage and record results as
recommended. Examine trees, etc, during the warmer
parts of the year and the warmer parts of the day,
although some ant species are active at night.
5. Threshold. Have any thresholds been established?
If so, what are they, eg economic, aesthetic,
environmental? Do you need to calculate your own
threshold? Will depend on the ant species, eg
For fire ants eradication is being attempted so
there is a nil threshold.
Fruit trees. Thresholds vary but examples include
when ants are present on 50% or more of shoots
examined for scales or other pests. On rare fruit
when noticed or when 5 out of 50 trees are infested.
6. Action. Take appropriate action when any threshold
is reached. Distribution of baits, tree banding, control
honeydew-producing insects, eg scales.
7. Evaluation. Review IPM program to see how well it
worked. Recommend improvements if required.
Control methods
Controlling ants reduces aphid, mealybug and scales.
Cultural methods. Maintain crop vigour.
Sanitation. Clean up plant debris, other litter or
food scraps. Store food in air tight containers. In
orchards, skirt trees regularly, keep weeds under
control so that ants cannot climb up trunks.
Biological control. Many vertebrates prey on
ants; wasps, flies and nematodes parasitize them.
However, there is currently no effective bio-control
agent available for controlling ants in Australia.
Plant quarantine.
AQIS. Many species are not yet in Australia.
State/Regional Quarantine, eg the National
Fire Ants Eradication program. There are legal
requirement to report suspected fire ant outbreaks
in some parts of Australia, areas are quarantined
and eradication procedures implemented.
Physical & mechanical methods.
Drown ants in pots by placing pots in water.
Sticky materials used to bands trees prevent ants
reaching the tops of trees to feed on honeydew,
mate, or deposit eggs; some are chemicalimpregnated
barriers. Labour intensive but some
barriers can provide up to 3 years protection.
Cultivating around nests discourages ants.
Insecticides.
Some insecticides used for commercial ant
control are highly toxic.
If practical locate and treat the nest.
No chemicals are registered for use on crops.
Spread baits that worker ants can take back to
the nest during foraging to feed the queen.
Small colonies in home gardens. Many dusts,
etc are available from garden centers for ant
control. Apply according to label directions.
Soil around the base of tree may be treated
but, depending on the persistence of the
insecticide, ground sprays may only last a short
time as subterranean colonies generally survive
and rapidly return to pre-treatment levels.
Table 17. Ants – Some insecticides and other controls.
What to use?
IN HORTICULTURE SITUATIONS
Group 1A, eg carbaryl; Ficam (bendiocarb); Baygon (propoxur)
Group 1B, eg Lebaycid (fenthion); various (chlorpyrifos)
Group 2C, eg Choice (fipronil)
Group 3A, eg pyrethrins; Baythroid (cyfluthrin);
Cislin (deltamethrin); various (permethrin);
Permaguard (diatmocous earth/pyrethrin);
Temp Residual insecticide (beta-cyfluthrin)
Group 20A, eg Permit required for this bait - Amdro
(hyramethylnon/soybean oil/ground corm); Maxforce
(hydramethylnon)
Spray oils, etc, eg various oil sprays; eucalyptus oil, Beat-a-Bug
(garlic/ chilli/pyrethrin/piperonyl butoxide); Hovex
antkiller (boron decahydrate).
Sticky materials, eg Tac-Gel (polybutene); Trappit Tanglefoot
(natural gum resins/vegetable oil/wax)
When and how to apply?
Permits may be needed in some states.
Some insecticides are taken back to the nest before
ants sense that anything is wrong. Generally slow
acting. Colonies may die within weeks.
Various Nest Kill Ant Baits (boron, fipronil) are
available for use indoors.
Ants may move nest sites when disturbed or with
change in food supply, this can make their
control difficult.
Controlling soft scales and other honeydew
producers will control ants on trees and shrubs.
Used to band trees to trap ants attracted to honeydew
produced by some sap sucking insects, eg aphids.
120 Insects and allied pests - Hymenoptera (ants, bees, sawflies, wasps)