Oan.org

The downside of
combination fungicides
Pre-packaged fungicide mixes can elevate the risk of developing
pathogens that are resistant to treatment
gicides based on mode of action. Therefore, combination fungicides have two different modes of action. In theo-ry, this should automatically help with resistance management. Combination fungicides are noth- ing new to the ornamental industry. A few fungicides that have a high risk of resistance development have been pre-mixed with other multi-site materials, which have a lower resistance risk. For example, Spectro (manufac- tured by Cleary Chemical Corporation) This pansy is infested with powdery mildew. In some cases, combination fungicides can encourage the
is a mix of thiophanate-methyl development of pathogens that are resistant to treatment.
(Fungicide Group 1) and chorothalonil By Jay W. Pscheidt development of resistant fungal (Group M5). The thiophanate-methyl Several new fungicides have been pathogens. These new combinations is at high resistance risk since it has or are soon to be registered for the represent a challenge for sustained a single mode of action. It is similar ornamental industry. Some of these fun- plant disease management. to Benlate (also Group 1), which was gicides contain two active ingredients. Fungicide trade names do not make overused when it first came out. A few fungicides for use on turf or for it easy for growers to implement anti- You can still find many Botrytis iso- seed treatments may have three or more. resistance tactics. Combination fungi- lates resistant to this group of chemistry. These are called pre-packaged cides generally have active ingredients The chorothalonil in Spectro has a low mixes or combination fungicides. from two different chemical groups. resistance risk since its mode of action Many of the new ingredients The Fungicide Resistance Action are at high risk of encouraging the Committee (FRAC) has grouped fun- An ongoing series provided by Oregon State University in partnership with OAN APRIL 2012 ▲ DIGGER 41

▲ combInAtIon funGIcIDEs Registered combination
fungicides for the
affects multiple critical fungal systems. blights, leaf spots, anthracnose, rusts, In theory, one should get good disease scab and even some diseases caused by management even if the pathogen is oomycetes, such as foliar Phytophthora Trade name
FRAC group
resistant to the group 1 material.
pathogens or downy mildews. It would number indicating
Newer combination fungicides, seem these are wonderful materials that Mode of Action
however, may have two materials mange many diseases while also man- that have different but single modes aging fungal resistance development.
of action. For example, the fungicide And so when this same material, trade name Pageant (manufactured by called Pristine, first came out in fruit BASF) contains two fungicides: boscalid markets, it garnered a large share of (group 7) and pyraclostrobin (group the market. Other companies noticed 11). As you would expect, use of either and have or are about to follow suit alone for a disease like powdery mil- with similar combination materials. For dew would quickly lead to resistant example, the Luna brand suite of fungi- fungi. Used together, it lowers the over- cides from Bayer may hit market soon all risk for the development of powdery and DuPont is scheduled to launch their mildew fungi resistant to both materials.
versions this spring.
But wait, there's more! There is But there are problems with using a large range of fungal diseases you these combinations. For Pageant, only can manage with both a group 7 and the group 7 (boscalid) material is very 11 material. These include Botrytis effective against diseases caused by GROW YOUR BUSINESS NOT YOUR ENERGY BILLS CASH-BACK INCENTIVES FOR GREENHOUSE AND NURSERY
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Botrytis. So even though there are two materials in the package, it is more like using a single-use material when used against Botrytis. Botrytis isolates resistant to boscalid have emerged throughout the world. There's some concern that indiscrimi-nate use of these newer combination fungicides will encourage the develop-ment of more fungi resistant to these materials at a faster pace. Management guidelines have not been developed for these combination materials. For example, in a crop that needs to be managed for both pow-dery mildew and Botrytis, use of these materials must be re-evaluated. The conditions that favor these fungi are different and occur at different times of the year. A summertime battle against pow- dery mildew might be very effective using a combination fungicide, but result in the non-target Botrytis becom-ing resistant. My recommendation is that if you use products such as Pageant for powdery mildew control, then they should NOT be used for Botrytis man-agement. Likewise, if you use them for Botrytis then use different fungicide groups for powdery mildew. You can use fungicides and still avoid building up resistance from non-targeted threats. The key is knowing what groups of fungicides you are using and what diseases your crop is likely to encounter. When you begin to use the same group of fungicides three or four times during the production of a crop, the risk of resistance increases. You may not realize you are doing this if you go solely by trade names. Many different trade names may be from the same fun-gicide group. One might expect combination fungicides to make disease manage-ment easier, but often, they just make it more complex.
APRIL 2012 ▲ DIGGER 43 ▲ combInAtIon funGIcIDEs Use pesticides safely!
• Wear protective clothing
and safety devices as recom-
mended on the label. Bathe or
shower after each use.
• Read the pesticide label —
even if you've used the pesti-
cide before. Follow closely the
instructions on the label (and
any other directions you have).
• Be cautious when you apply
pesticides. Know your legal
responsibility as a pesticide
applicator. You may be liable for
injury or damage resulting from
pesticide use.
Here is the challenge. Can you use only one fungicide group once through-out the production of your crop? OK, I might let you use one group twice but Manage m re with less… that is the limit. If this sounds like a difficult chal- with Soil Moist™ lenge, then we have to think more Nothing helps stretch budgets
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Integrating many tactics together is maintenance and plant stress, the best way to successfully sustain plant increase growth rates, improve soil porosity and do more with less… disease management from year to year or from crop to crop. Available in the forms, formulas and Judicious use of combination fun- customer blends you need, eco-safe gicides or making your own tank mix Soil Moist granules,disks, tabs and may be more effective in the long run spikes absorb water, then release it for your operation. gradually as soil dries. So each watering lasts up to 50% longer, for 3-5 years.
Jay W. Pscheidt is an extension plant pathol- Whether it's original Soil Moist, Soil Moist Mycorrhizal for strong root development, or Soil Moist Plus nutrient blends, there's never been ogy specialist with Oregon State University a better time to call for technical data and expert advice.
in Corvallis, Ore. He can be reached at [email protected]. Distributed by:
Jeff Viers Nursery Supply Hubbard, OR • Nursery Connection Hubbard, OR Growers Nursery Supply Salem, OR • Steuber Distributors Snohomish, WA Trade-name products and services are mentioned as illustrations only. This JRM Chemical, Inc.
does not mean that the Oregon State 4881 NEO Parkway, Cleveland, OH 44128 University Extension Service either 1-800-926-4010 • 216-475-8488 • fax: 216-475-6517 endorses these products and services or intends to discriminate against products and services not mentioned. 44 APRIL 2012 ▲ DIGGER

Source: http://www.oan.org/associations/4440/files/pdf/Digger201204pp41_44.pdf