PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Spread
By the adults crawling up to 1,000 metres a day.
Adults do not fly.
By humans, eg various stages (eggs, larvae,
pupae, adults) may be carried on potted plants,
other plant material and in infested soil.
Conditions favouring
Precise timing of life cycle varies from year to
year depending on temperature and humidity.
Warmer temperatures during late summer and
early autumn might allow more adults to survive.
Larvae/adults feed at temperatures as low as 2 o C.
Use of polythene sheeting in strawberries.
Management (IPM)
Are you a commercial grower or home gardener?
1.Obtain/prepare a plan that fits your crop or
situation.
2. Crop, region. Recognize variations.
3.Identification can be difficult so consult a
diagnostic service (page xiv). Adult weevils are seen
between Nov. and Jan. in NSW.
4.Monitor and record your findings of pest/damage.
Monitor indicator plants (very susceptible hosts)
for signs of infestation and keep records.
Check for adults weekly from Nov. to Mar. under
boards or other traps, placed close to susceptible
plants, eg rhododendron. Shake out traps over a
white sheet at midday during summer and count/
record number. Also check under rims of pots for
adults hiding during the day.
Check for larvae during winter near the crown or
root ball when repotting.
Check for larvae on roots of susceptible plants
randomly from March onwards, especially during
hot weather if plants look stressed despite adequate
irrigation. For some plants, 3-5 grubs in a litre pot
(about 120cm diameter) can sever the root system.
Check crop plants regularly during spring and
summer for tell-tale leaf notching.
5. Threshold. May be very low in commercial crops
which can sustain considerable economic damage.
You may have to calculate your own threshold at
which you start control methods.
6. Action. In nurseries, sanitation, purchase of weevilfree
stock, monitoring and bio-control agents can keep
BVW under control. Purchase stock for resale when
adults are not likely to be active.
7.Evaluation. Review IPM program to see how well
it worked. Recommend improvements if required.
Control methods
Control is difficult especially in field grown crops.
Adults tend to live and feed in protected areas of
the plant and larvae live in soil.
Sanitation.
Discard severely infested container plants and
treat remainder. Also destroy infested plant
material and crop debris.
Remove media (and larvae) from potted plants
and repot in clean soil.
Do not re-use potting mix from infested plants
or compost unless it is pasteurized.
Reduce hiding places used by adults during the
day by removing litter on the soil surface.
Biological control.
Natural enemies include predatory wasps,
flies and beetles, various parasitic flies. Chickens
feed on vine weevils in management systems.
Nematodes are commercially available, eg
Heterorhabditis bacteriophaga
Steinernema carpocapsae
Becker Underwood www.beckerunderwood.com/
Ecogrow Environmental www.ecogrow.com.au
They can reduce populations of
BVW larvae by 90-100%.
Nematodes seek out natural
openings on larvae and move
into the blood stream where
they release bacteria causing
septicaemia. BVW larvae die and nematodes
multiply in the dead insects. After 2-3 weeks
thousands emerge to attack other larvae. Follow
instructions carefully for timing and conditions
of application. Nematodes may be more
expensive and usually need to be ordered in
advance but may not need to be registered as a
pesticide, and there may be no re-entry times.
Check.
Resistant varieties.
Some varieties of some species appear to be very
susceptible, eg Pittosporum ‘James Stirling’.
Plant quarantine.
Do not introduce infested media, soil or plants to
non-infested areas.
Pest-tested planting material.
Only purchase stock from BVW-free properties
or from suppliers with a control program.
Check root areas of incoming stock.
Use clean potting mix.
Physical & mechanical methods.
Trap adults in corrugated cardboard around plant
bases, shake out every day over a bucket of
soapy water.
Use Tanglefoot or other adhesive to trap adult
weevils as they climb onto benches. Apply to
table legs to trap adults active at night.
If practiced daily, these may prove effective.
Insecticides.
Destroy badly infested container plants before
treating the rest.
Formulations applied to the soil need to provide
sustained control of larvae.
Soil drenching larvae can be ineffective due to
chemicals leaching out of growing media after
irrigation, the difficulty in contacting larvae deep
among roots and getting uniform coverage of
media where it is protected by foliage.
Spraying adult weevils late in the day or at
night can be ineffective as the weevils tend to
drop to the ground when disturbed. Adults may
develop resistance to insecticides.
Table 13. Black vine weevil – Some insecticides, biocontrol agents.
What to use?
SOIL TREATMENTS TO CONTROL LARVAE
Group 1B, eg SusCon Green (chlorpyrifos)
Biocontrol agents, eg Nematodes (Heterorhabditis
bacteriophaga, Steinernema carpocapsae)
When and how to use?
SusCon Green is incorporated into potting mix used
for container-grown ornamentals. Minimal impact on
non-target organisms.
Insects and allied pests - Coleoptera (beetles, weevils) 107