- The Type and Severity of Disease
- Stage of the Crop
- The Resistance Rating of the Cultivar
- The Environmental Conditions
- The Agronomic Practices Used
- Quality of Application
- Scouting and Accurate Identification of the Problem
- Cost of Control vs. Potential Loss
- Availability and Cost of Fungicide
- Alternate Fungicide Chemistry
- Further Information
- are you trying to control a monocyclic or polycyclic disease?
- what is the disease cycle of the pathogen?
- if it is a seed or root disease that is likely to cause a problem, the decision to apply a fungicide must be made before planting, i.e. seed or soil treatment
- remember, you aren’t going to ‘see’ the pathogen, your first indication that it is there is when symptoms develop, so you need to be ready to go!
- timing is everything! Apply when you’ll get your ‘biggest bang for your fungicide buck’. This means regular scouting of the field and knowing what disease you are dealing with. It pays to anticipate problems well in advance
- typically, the earlier the disease hits, the more likelihood that damage will occur. Hence, applying a fungicide early will reduce additional build-up of inoculum
- pay attention to prohibitive statements and withholding periods, (WHP) whether they apply to harvesting, cutting or grazing of the treated crop. The WHP could mean as many as 3-4 weeks prior to harvest, or in some cases there could be a total prohibition on grazing the treated crop.
- refer to state guides for disease resistance ratings of cultivars
- some crops are more susceptible at the seedling stage and become more tolerant as they age, e.g. against root diseases. Conversely, some crops become more susceptible once they reach the flowering stage, e.g. ascochyta blight in chickpea.
- how much rain has been received in the past week? Is more rain forecast?
- are there any relevant prohibitive statements on the product label?
- fungicides are most effective if they can be applied before a rain event. If nearing the end of the period of effectiveness, i.e. 10 - 14 days for a some fungicides, you may want to consider application earlier if rain is forecast
- disease risk can change in a matter of hours, depending on rainfall. The longer the period of time that favourable weather conditions are present, the more loss to disease can be expected. That is why it is essential to know the optimal temperature and moisture requirements for each disease.
- check the field records and monitor the crop. What practices were used that may have increased or decreased disease risk?
- are the plants weakened from any other stresses, environmental or agronomic, that could favour disease? For example, residual herbicides favour diseases such as ascochyta blight in chickpea because plants are weakened and maturity delayed.
- uniform coverage is essential for both seed and foliar treatments. For seed treatments, calibrate application equipment before each new seed lot to ensure proper mixing of product and application rate. Adding water may help coverage of seed, or putting through an auger again for mixing. Always follow label recommendations!
- for foliar fungicides the best way to ensure good coverage is by using high water volumes.
- application onto a wet plant (following a dew or light rain) will help distribute the product. Check the product label to see if spreader or sticker ingredients have been added or if it is recommended to add them.
- there is limited information available on sprayer technology and fungicide application. Sprayer modification such as using split-application nozzles that have an angled spray pattern have been used for some diseases. The angled spray pattern improves coverage of vertically oriented heads such as for fungicide application against fusarium head blight. Follow label instructions!
To gain a full appreciation of the disease severity within a paddock it is important to view several locations. A fence line is not necessarily representative of the whole paddock. Accurate identification is also critical as many crop ailments are not caused by fungal pathogens and therefore will not benefit from a fungicide application.
- what is the yield potential of the crop? The higher the yield and/or current market price, the greater the likelihood of a positive economic outcome from a fungicide application
- use the two equations below to crunch some numbers to determine the ‘break-even point’ for a fungicide application. Try putting in different values for expected yield, expected yield increase and selling price:
A common question from farmers is ‘which fungicide is better?’ If you are applying a product at the right time and disease risk is present … the difference between individual products is splitting hairs.
As discussed, it is important to avoid fungicide resistance from developing in a fungal population. Alternate fungicides with different chemistries whenever possible, (Table 12.1). In some cases, this is difficult to do since many fungicides are within the same chemical family, e.g. there is only one product for cereal leaf diseases that includes a product that is not a triazole. There is more choice for pulse fungicides.
NOTE: Not all active ingredients are registered for use on both cereals and pulses. Always check the product label before applying any agricultural chemical.
For more information about current trade names of these fungicides, refer to CropLife Australia’s current Fungicide Activity Group Table. Information presented in this table is drawn from the Fungicide Resistance Action Committee, (FRAC) and CropLife Australia.
CropLife Australia is involved in FRAC and promotes the responsible use of pest management methods to ensure sustainable agriculture.
Table 12.1 Fungicide chemical groups for resistance management and related information Adapted from CropLife http://www.croplife.org.au/
|Activity Group Code (FRAC Code||Chemical Group||Mode of Action||Active Ingredient||Type of Activity||1Risk for Resistance|
||Inhibition of mitosis and cell division||Carbendazim Thiabendazole Thiophanate-methyl||Systemic with apoplastic mobility (protectant, curative)||High|
|2||Dicarboximides||Inhibition of lipids and membrane synthesis||Iprodione Procymidone||Systemic with apoplastic mobility (protective, curative)||Medium to High|
||Inhibition of sterol biosynthesis in membranes||Cyproconazole Difenoconazole Epoxiconazole Fluquinconazole Flutriafol Propiconazole Tebuconazole Triadimefon Triadimenol Triticonazole||Systemic with apoplastic mobility (protectant, curative, eradicant)||Medium|
|4||Phenyl Amides (PA)
||Affect RNA synthesis||Metalaxyl Metalaxyl-M||Systemic (protectant, curative)||High|
|7||Carboximides / Oxathiin||Inhibits mitochondrial respiration (SDHIs)||Carboxin Oxycarboxin||Systemic (apoplastic mobility)||Medium|
||Inhibition of mitochondrial respiration||Azoxystrobin Azoxystrobin Famoxadone||Systemic activity with apoplastic + acrepetal mobility (protectant, curative)||High|
|12||Phenylpyrroles(PP)||Affect proteins involved in membrane permeability||Fludioxonil||Low to Medium|
||Act as general toxifiers with several sites of action (sites may differ between group members)||Captan* Chlorothalonil Copper Metiram Mancozeb Sulphur Thiram Zineb||Contact (protectant)||Low|
|17||Hydroxyanilide||Inhibition of tubulin formation during mitosis||Fenhexamid^||High|
* Permitted use only (PER81406) ^ Permitted use only (PER14211)
This chapter was prepared by Penny Pearse1, Provincial Plant Pathologist, Saskatchewan Agriculture and Food, Regina, Canada firstname.lastname@example.org
More detailed information can be obtained from: DEDJTR AgNotes Series www.vic.gov.au/graindiseases
DEDJTR chemical use information http://agriculture.vic.gov.au/agriculture/farm-management/chemical-use
Cereal Seed Treatment Guide (SARDI) www.pir.sa.gov.au
Victorian Cereal Diseases Guide (AG1160) www.vic.gov.au/cerealdiseaseguide
Victorian Pulse Diseases Guide www.vic.gov.au/pulsediseaseguide
Victorian Winter Crop Summary www.vic.gov.au/victorianwintercropsummary
CropLife Fungicide Activity Group Table 2015 www.croplife.org.au
CropLife Fungicide Resistance Management Strategies 2015 www.croplife.org.au
Wallwork H (2015) Cereal Seed Treatments (SARDI) www.pir.sa.gov.au, http://www.pir.sa.gov.au/ data/ assets/pdf_file/0005/237920/cerealseedtreat2015_web.pdf
Wallwork H (2000) Cereal Root and Crown Diseases www.grdc.com.au/bookshop
Wallwork H (2000) Cereal Leaf and Stem Diseases www.grdc.com.au/bookshop
Australian Pesticides & Veterinary Medicine Authority www.apvma.gov.au
APVMA Public Chemical Registration Information System https://portal.apvma.gov.au/pubcris
BACK TO THE BASICS