PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
RESISTANCE.
WHAT IS
RESISTANCE?
RESISTANCE
MANAGEMENT
STRATEGIES
Classification by
Croplife Australia is
according to how
the pesticides kill
the insect, fungi
and weeds and is
used for resistance
management
It does not indicate
toxicity,
that some groups are
more toxic than
others as indicated by
the signal headings
on their labels (see
page 237).
Resistance is the ability of disease organisms to survive doses of fungicide that
would normally provide control. Resistance is so extensive it is difficult to find
effective fungicides. Fungi which produce large numbers of spores with many
infection cycles per season, eg powdery mildews, grey mould, brown rot, develop
resistance more quickly. Continuous use of systemic fungicides with only one mode
of action can lead to resistance problems after less than 20 applications due to the
continual selection of resistant spores.
Reduced yields. Prolonged use of some systemic fungicides has led to reduced
yields due to increased disease in some fruit crops.
In Australia, fungal diseases of ornamentals, turf, fruit and vegetables which
have developed resistance to a range of chemicals include:
– Downy and powdery mildews
– Grey mould (Botrytis) and other postharvest diseases of fruit
– Brown rot of stone fruit, apple and pear scab
– Late and early blights of potato and tomato
The application of fungicides must be part of an IDM program which include nonchemical
control methods to preserve beneficial fungi and other micro-organisms and
delay resistance development. IDM strategies should be in place before resistance
becomes a problem.
Fungicide Resistance Management Strategies.
– CropLife Australia has classified fungicides into Fungicide Activity Groups
which indicate how the fungicide kills or suppresses the fungus (page 338,
Table 58). Some disinfectants and biological fungicides are not classified by
CropLife Australia (page 343, Table 59, page 344, Table 60). Contact Croplife
Australia for updates on classification and click on Resistance
Management:
www.croplifeaustralia.org.au/
– To minimize the development of resistance and prolong the life of existing
fungicides, observe 1 2 3…. groups on commercial fungicide labels.
Follow resistance warnings. Rotate fungicides between different groups as
recommended. Remember, persons using commercial fungicides must undergo
training. Home garden products available from garden centres are not
required to have fungicide activity groups on their labels.
– CropLife Australia has prepared management strategies for some diseases on
some crops, to minimize the development of resistance.
Crop-Disease Resistance Management Strategies have been developed, eg
grey mould (Botrytis) on grapevine, lettuce, ornamentals, pulse crops,
strawberry; powdery mildew of cucurbits, grapevine, strawberry; downy
mildew on cucurbits, grapevine, lettuce, onion, poppies.
Follow label instructions and warnings. which include resistance
strategies. Application of some fungicides for control of some diseases is
restricted in order to prevent or delay the likelihood of resistance developing.
Do not exceed recommended rates of application if a specific fungicide is no
longer giving control of a disease. “Example” and “Company” are used in the
following general instructions to avoid using specific insecticide or company
names.
Applications may
fail for reasons
other than
resistance, eg
Incorrect identification
of the disease.
Wrong fungicide may
have been used. Many
fungicides control only
1 or 2 types of fungal
diseases.
Equipment not
calibrated properly.
Applied at wrong time
Weather unsuitable for
application.
FUNGICIDE RESISTANCE WARNING
GROUP 3 FUNGICIDE
Example is a member of the DMI froup of fungicides. For fungicide
resistance management, Example is a Group 3 fungicide. Some naturally
occurring individual fungi resistant to Example and other Group 3
fungicides may exist through normal genetic variability in any fungal
population. The resistant individuals can eventually dominate the fungal
population if these fungicides are used repeatedly. Example and other
Group 3 fungicides will not control these resistant fungi, thus resulting in a
reduction in efficacy and possible yield loss. Since occurrence of resistant
individuals is difficult to detect prior to use. Company accepts no liability
for any losses that may result from the failure of Example to control
resistant fungi.
Some labels may include: Refer to specific Croplife Resistance
Management Strategies on the label
Fungal diseases - Integrated disease management 337