PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Biological control.
Natural controls are present but appear to have
little or no economic effect. Most common
biocontrols are parasitic wasps and ladybeetles.
– Diseases, eg red-headed fungi (Fusarium spp.).
– Predators, eg native ladybird (Rhizobius lindi),
lacewing larvae, moth caterpillar (Batrachedra sp.),
predatory green and brown lacewings, predatory
beetles and mites, scale-eating caterpillars.
– Parasitic wasps (on scales). Avoid long-lasting
sprays which might have residual effects.
Wasp depositing an egg in a scale insect
Commercially available. Green lacewing
(Mallada sp.) larvae feed on crawlers. A wasp
(Aphytis melinus) can be purchased for red scale
control. List of suppliers www.goodbugs.org.au
Plant quarantine.
AQIS. Presence of San Jose scale on fruit will
result in its rejection as export grade fruit to
European countries.
Lucid keys - www.lucidcentral.com/ Scale
insects: Identification Tools for Species in
Quarantine.
State/Regional quarantine. San Jose scale does
not occur in SA.
Local quarantine. Avoid introducing infested
plant material (stock, buds, grafts or cuttings)
into a property.
Pest-tested planting material.
Maintain scale-free stock plants.
Do not propagate from infested plants. Careful
inspection of propagation wood is essential, if in
doubt, discard it! It can be difficult to disinfest
propagation wood from this pest.
Carefully examine young trees when received
from the nursery and, if infested, dipped in a
suitable oil emulsion (excluding the roots) and
then drain, tops downwards in the shade before
planting out in the orchard. This can delay
appearance of scale in an orchard for years.
Insecticides. Because scales can be found
under rough bark, behind buds and within cracks
of the bark, it is essential to spray thoroughly right
to the base of the trunk.
If any scales are found, spray thoroughly with
a registered chemical at bud movement.
Winter oil is the preferred treatment. Oil sprays
smother scale insects but eggs are not killed.
Spray oils can also be applied at the susceptible
crawler stage. To determine when crawlers are
hatching set traps of double-sided sticky tape.
Tightly encircle infested twigs or branches with
the tape, examine it with a hand lens to identify
crawlers. Crawlers will appear as yellow or
orange specks. Check tapes weekly.
Do not apply spray oils during fog or rain or
during hot weather (above 34 o C). Some plants
are prone to damage from spray oils.
Avoid indiscriminate use of broad spectrum
sprays that kill natural enemies and have long
lasting residual effects.
Treat isolated infestations by spot spraying,
pruning or hand-picking to remove scales.
Resistance. Reliance on just one chemical will
hasten the development of insecticide resistance
in scale populations. Follow Croplife Australia
Resistance Management Strategies.
Try to control the crawlers which have not yet
produced their protective waxy covering. Control
of scale is difficult because of the ‘timing
window’ that allows the grower only limited
periods in which to apply control measures.
Armoured scales resist their actions well.
Eradication, pruning and discarding seem to be
the best methods of controlling armoured scale.
Contact sprays are only effective on scale crawlers
and mealybugs that are actively moving over the
plant. Adult scales and mealybugs that have
developed their waxy covering are difficult to kill with
contact pesticides. Systemics give good control of
adult scales and mealybugs that are feeding. Once
the pest has stopped feeding it is too late to control it.
Table 32. Armoured scales – Some insecticides.
What to use?
DECIDUOUS TREES
Light infestation
Group M2 (fungicide), eg Lime Sulphur (polysulphides)
Spray oils, eg Winter Oils, Dormant Oils (petroleum oils);
White oil, Pest Oil (petroleum oil);
Bioclear , EcoPest Oil (paraffinic oil)
Well established infestations and especially on mature
and rough-barked trees, one example:
1st spray Winter oil (petroleum oil) during dormancy.
2nd spray The insecticide selected will depend on the need to
control other pests, eg mites, caterpillars.
3rd spray Only if winter sprays have been missed; the
insecticide selected will also depend on the need to
control other pests, eg mites, caterpillars.
EVERGREEN TREES
Group 1B, eg various products
Group 7B, eg Insegar (fenoxycarb) - suppression only.
Group 4A, eg Confidor Guard soil insecticide (imidacloprid)
is registered for red scale on citrus
When & how to apply?
Apply 1 spray in mid-winter. If infestation is light on
deciduous ornamentals usually one application of the
winter spray is usually sufficient.
Apply spray oil before budbreak.
High volume sprays have traditionally been used to
thoroughly wet the trunk and branches (the whole tree
above ground level).
Do not use 2 full strength oil sprays in 1 season.
Only apply after monitoring has indicated that the
infestation is well established.
Apply 1 spray in mid-winter.
During the growing season, on fruiting varieties,
sprays are best applied after harvest is complete.
Seek advice on what and when to apply as some are
more toxic to mite predators than others, also some
may cause fruit damage.
If infested trees have cracked bark it is very difficult to
locate the scales or contact them with sprays.
170 Insects and allied pests - Hemiptera (bugs, aphids, etc)