PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
WHEN. SHOULD INSECTICIDES BE APPLIED?.
Follow label directions for use and insecticide resistance warnings. Companies may restrict
application and/or number of applications of certain chemicals on crops being grown for their use.
GROWTH STAGE
OF HOST
Insecticides must be applied to the appropriate part of the host.
Foliage Flowers Dormant Seeds, cuttings Bulbs, corms Roots, soil
woody plants
SUSCEPTIBLE
STAGE IN PEST
LIFE CYCLE
Cabbage white
butterfly
NUMBER AND
INTERVAL
BETWEEN
APPLICATIONS
SOME PESTS ARE SUSCEPTIBLE TO INSECTICIDES at only at certain stages of
their life cycle, eg
Aphids
Black scale
Cabbage white butterfly
Cineraria leafminer
Codling moth
Pear and cherry slug
Scarab grubs
Steelblue sawfly
- Nymphs and adults on plants
- Nymphs (crawlers) on plants (see below)
- Larvae (caterpillars) on plants
- Larvae (fly maggots) in mines
- Adult moths
- Larvae (slugs) feeding on the plant
- Young larvae (grubs) in soil
- Larvae (spitfires) in the host
MONITOR THE SUSCEPTIBLE STAGE(S)
Know which stage of pest (eggs, larvae, adults), on which part of the plant
(flowers, leaves, stems etc), and what sampling techniques to use.
Better selection and application of pesticide will provide more effective control and
greater safety to workers and the environment.
Correct timing, eg time of year season etc.
BLACK SCALE (an example)
Number of applications. Many insecticides do not kill all stages of an insect.
Black scale on evergreen hosts is controlled by spraying the susceptible ‘crawler’
stage in spring and/or autumn. However, insecticides used to kill the ‘crawler’ stage,
may not kill adults or eggs, therefore a 2 nd application about 10-14 days later after the
1 st spray, is often required to kill the ‘crawlers’ emerging from eggs which were still
unhatched at the time of the 1 st spray (pages 164-166).
Interval between applications depends on the particular insecticide, its
persistence and other factors. If persistence is too short the pest may not be controlled,
if too long, the environment may be adversely affected.
Black scale
(Saissetia oleae)
Insects and allied pests - Integrated pest management 55