PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Biological control.
Natural controls. There are many naturally
occurring predators, eg mites and bugs, parasitic
wasps and fungal pathogens. The beetle (Dalotia
(Atheta) coriaria) is one such predator that will
feed on thrips.
Bio-control agents. for thrips generally can be
purchased, eg a soil mite (Hypoaspis sp.)
feeds on thrips pupae near the soil surface, also
predatory mites (Neoseiulus cucumeris,
Typhlodromus montdorensis). Their effectiveness
on gladiolus thrips is untested.
List of suppliers www.goodbugs.org.au
Resistant varieties. Varieties vary in their
susceptibility to injury.
Deep reds and purples are most severely
affected, there are exceptions to this rule.
In general, light coloured varieties are least
liable to show damage.
Plant quarantine. Quarantine new plants and
check for thrips before introducing them into the
property. Examine incoming plants to eliminate
introduction. Inspect corms.
Pest-tested planting material.
Only purchase corms from reputable suppliers who
will guarantee corms are thrips-free. Only save
corms from thrips-free crops.
Physical & mechanical methods.
To prevent infestation of protected crops use fine
thrips-proof mesh screens. Vents must also be
screened.
Insecticides.
Corm, soil and foliage treatments are available
(Table 22 below).
Sprays aim to kill nymphs and adults as they do
not kill eggs inserted in plant tissue and pupae
(mostly in the soil) are protected from sprays.
Systemic foliage insecticides are usually
more effective as there is difficulty in contacting
thrips with non-systemic insecticides. Spray
gladioli for thrips at the 4-leaf stage and again
when the flower pikes appear through the leaves.
Resistance strategy.
– Follow CropLife Australia Resistance
Management Strategies. If spraying is
necessary rotate insecticides with different
resistance groups to delay development of
resistance. See also WFT (page 140).
– Several sprays may be necessary for thorough
control. Time between sprays will depend on
the temperature (time of year). This allows
eggs and pupae that were not exposed to
chemicals at the time of the 1 st spray to
develop into active life stages which can be
killed by a 2 nd spray.
Table 22. Gladiolus thrips – Some insecticides and physical treatments.
What to use?
FOLIAGE TREATMENTS
Group 3A, eg Bifen , Scotts Procide , Surefire Fivestar ,
Talstar , various (bifenthrin)
Many other insecticides are registered for thrips generally.
CORM TREATMENTS
1. Storage at l0 o C
2. Hot water treatments (HWT)
3. Pesticide dusts
Group M2 (fungicide), eg Dusting Sulphur (sulphur)
When and how to apply?
Where gladiolus thrips is a recurring problem, treatment
may need to commence when susceptible varieties are
about 15-20 cm high and may need to continue at regular
intervals until flowering.
The label may indicate need for a wetting agent.
Most insecticides are toxic to bees.
Before storing dust corms with an insecticide dust.
HWT corms before planting. Obtain expert advice on
how to do this so that thrips are controlled but corms not
injured.
Home gardeners can dust corms before storage by placing
them in a bag with a little sulphur dust and shaking.
Insects and allied pests - Thysanoptera (Thrips) 135