Fungicides 101: Basics and Use in Minnesota

1. Fungicides 101:Basics and Use in Minnesota Private Pesticide Applicator Training Lizabeth Stahl, Extension Educator – Crops and Dean Malvick, Extension Plant Pathologist

2. 51 Do you plan to apply a fungicide POST to any of your CORN acres in 2012? (select answer that best fits) • Yes • Maybe – based on scouting for disease • No 0 of 120

3. 52 Do you plan to apply a fungicide POST to any of your SOYBEAN acres in 2012? • Yes • Maybe – based on scouting for disease • No 0 of 120

4. 53 Are you more likely to use a fungicide in corn because Goss’s Wilt has been confirmed in MN? • Yes • No 0 of 120

5. What is a Fungicide? • A Fungicide is “a chemical agent that kills or inhibits the growth of fungi or fungal-like organisms” • Fungicides can be classified a number of ways including: • Mobility in the plant • Role in protection • Preventative/Protectant, Curative • Eradicant & Anti-sporulant • Breadth of activity (single or multi-site) • Mode of action • Chemical group or class • Fungicide Resistant Action Committee (FRAC) group Soybeans infected with the fungal pathogen Sclerotiniasclerotiorum, or “white mold”

6. Contact Fungicides • Remain on the surface – don’t go deeper, not translocated or absorbed • Coverage is critical • Have no after-infection activity • Also referred to as protectant • Must be present BEFORE the pathogen infects • New plant growth is not protected • Typically inhibit spore germination and stop infection • Often effective against different kinds of pathogens • Often target multiple sites of action in fungi • Threat of pathogen resistance is LOW Contact-Protectant For example: Manzate, Dithane, Pennozeb, Captan (seed treatments)

7. Systemic Fungicides • Fungicide is absorbed into the plant tissue • There are no fully systemic fungicides for field crops • Protection from the inside, but is eroded via: • Dilution • Deactivation • May offer some after-infection activity • Most new tissue not protected • Reapplication: ~12-20 days • Can affect few to many pathogens • Often target a single site of action within a pathogen • Resistance risk: MEDIUM to HIGH Source: Syngenta

8. Systemic Fungicide Types • Locally Systemic: • Absorbed into the immediate area of application, not translocated far from site of uptake (a.k.a. local penetrant) • Examples: Headline, Trilex • Upwardly Systemic • Move only outward and upward (through the xylem) • Examples: Allegiance, Apron XL, Bumper, Dynasty, Folicur, Protege, Quadris, Tilt, Topsin-M Locally Systemic Upwardly Systemic Contrast to glyphosate - a systemic herbicide that can move down to plant roots

9. Classification: Mode of Action • MOA: How a fungicide kills or suppresses a target fungus i.e. Strobilurin Family: Fungicides in this family bind to a particular biochemical site in the fungus, stopping energy production by the fungus and leading to fungal death.

10. Mode of Action • Single-site: • Active against only one critical point, enzyme, or protein in the metabolic pathways of a fungus • Tend to be systemic • One mutation at the target site can result in a fungicide-resistant strain – at HIGH risk for fungicide resistance • Example:Strobilurinsare site-specific fungicides. • Multi-site: • Affect several different metabolic sites within the fungus

11. Classification by Chemical Group /Class • Examples: strobilurins, triazoles, dithiocarbamates • The chemicals in a group or class may or may not have a similar chemical structure Classification by Fungicide Resistance Action Committee (FRAC) Code: • Developed to reduce problems with fungicide resistance • Fungicide resistance means that a fungicide may no longer be effective for disease management • Separates fungicides into groups (codes) by MOA • Avoid using products with the same FRAC code more than once/season to reduce development of resistance Various publications and this web site list FRAC codes : www.frac.info

12. Considerations for Fungicide UseThings to know before applying a fungicide • Accurate Diagnosis of Disease – Critical to be certain that the right product is used for the right problem • Can be simple or difficult • Can take time • Help from a Plant Disease Clinic like the U of MN’s may be needed • Important to know: • Plant part infected (roots/stems/leaves?) • Modes of infection and spread • What weather conditions are conducive for disease • Latent periods of disease • How a fungicide would affect the pathogen NCLB or Goss’s Wilt? Proper disease identification is a critical first step in disease management

13. Before Using a Fungicide - Also Consider: • Disease incidence Number of plants or plant parts affected • Disease severity Amount of tissue affected • Host plant genetics • S, MR, or R for the disease? • Weather conditions - recent & future • Host growth stage & PHI • Fungicide timing, application, & efficacy • Yield potential • Treatment cost (product & application) • Treatment cost vs. potential benefit

14. Factors Important For Effective Control • Residual of Product • Rate and Coverage – (more critical for fungicides than insecticides - insects are mobile) • Durability • Adhesion in rain & irrigation, breakdown in sunlight? • Fungicide activity often declines within 12 hrs after mixing • Plant Part Target (density and structure of canopy?) • Timing • Vulnerable point in life cycle of the pathogen • Early applications when infection starts are usually more effective than later applications Simply applying a fungicide does not assure successful disease management Target Fine to Med droplet size (above) vs .Coarse (below)

15. Potential Negatives of Fungicide Use • Cost (fungicide and application) • Lack of disease management • Drift and phytotoxicity • Potential toxicity to humans or animals if not used properly • Corn: Arrested ear development from pre-tassel applications (~V12-V14) • Side effects on beneficial fungi • Examples: soybean aphid and spider mites in corn • Risk of resistant fungal populations developing Soybean Aphid attacked by fungi Spider mites in corn Photo from B. Potter

16. Fungicide Resistance • Reduced sensitivity is thought to result from genetic mutations or naturally occurring sub-populations of resistant individuals • Experience with the strobilurinsworldwide indicates there is a high risk of development of resistant pathogens. • Resistant strains have developed in fungi that cause diseases of cereals, turf, and cucurbits. • In 2010 in TN, confirmed resistance in frogeye leaf spot pathogen in soybean to strobilurin fungicides

17. Resistance Management Strategies • Minimize Exposure to Fungicides • Limit unnecessary use - is control necessary? • Apply based on monitoring and/or forecasting • Integrate Management Strategies • Use R varieties/hybrids when possible • Use appropriate cultural practices • Scout – note disease incidence & severity • If use warranted • Diversify • Use combinations of single-site & multi-site fungicides • Alternate MOA (FRAC codes) • Avoid using same a.i. or FRAC group > once/season • Don’t use reduced rates • Apply fungicide preventively or early in disease cycle when warranted • Always read & follow pesticide labels FRAC Code on front page of product label

18. Fungicide Use in MN • Using a fungicide when the risk of disease is high enough can make sense • In small grain - can be very effective & pay economically • In corn and soybean - disease levels rarely reach levels where a foliar fungicide application would be economical • Fungicide applications for “plant health” (application in the absence of disease): • Inconsistent results in University trials for corn and soybean • Potential negatives: • Kill “good fungi”, increased input costs, increased risk of developing resistance, corn yield loss if applied pre-tassel, etc.

19. Frequency (%) of at least breaking even with fungicide application (From the 2008 Regional Trials (13 states including MN & ONT) Based on 65 trials with Headline applied at 6 fl oz/A at VT-R1.

20. Conclusions from 2008 Regional Trials • Disease pressure was light in most trials • Yield response to fungicide in all trials, but • Yield response was non significant and low. • When foliar disease was a factor, yield response was greater. • Results indicate that fungicide application are most effective and most likely to pay-off in situations where significant leaf disease is present. • Results typical for Upper Midwest & MN

21. Fungicide Seed Treatments Can protect seed & seedlings from seed- and soil-borne diseases Challenges: • Fungicide with appropriate activity may not be available • Product may have little or no systemic activity – so may not move with expanding root system • Typically @ an effective concentration for 10-20 days • May be beneficial in some fields but don’t expect a consistent advantage • Does product have efficacy against all important pathogens present? NOTE: Contact fungicide seed trmts • No movement into seed, no control of internal pathogens, and protect only until seed coat breaks Systemic fungicide seed trmts • Movement into seed, root, and shoot tissues, and offer control of internal and emergence pests

22. Soybean Seed Treatment Examples North Dakota State 2011 Fungicide Guide, NDSU.

23. 225Which is a good option to dispose of leftover treated seed? (select only one) • Feed it to your livestock • Dump it in a pile & let it compost • Mix it in with a load from your bin and take it to the elevator • Burn it in a wood or corn-burning stove • ALL of the above • NONE of the above 0 of 120

24. What to Do With Leftover Treated Seed • Be careful to not inadvertently contaminate a load of grain • ENTIRELY CLEAN out any wagons used, etc. • Follow instructions on bag for disposal • Best option is to plant leftover seed • Could spread it on idle land and disc it in • Check seed bag as some treated seed may be hazardous to wildlife • Don’t just leave it on surface where birds, other animals or children could get to it and possibly ingest it • Do not feed to livestock & keep out of human food chain

25. What about PPE?Check the bag! Soybean Example: Courtesy of Pioneer Hi-Bred International

26. Resources http://pdc.umn.edu/ www.extension.umn.edu/cropdiseases/

27. References/Resources • Field Crop Fungicides for the North Central United States, Mueller & Bradley, 2008. North Central IPM Center : http://www.ncipmc.org/fieldcrops/fungicide_manual.pdf • Characteristics of Fungicides Used in Field Crops, Report on Plant Disease, No. 1002, September 2005, U of IL Extension: http://web.aces.uiuc.edu/vista/pdf_pubs/1002.pdf • North Dakota State 2011 Fungicide Guide, NDSU, available online. • South Dakota Wheat Fungicide Recommendations, SDSU, FS952, http://www.sdwheat2.org/files/Fungicide09S952.pdf