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. 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 • Breadth of activity • Mode of Action White mold in soybean Source: Field Crop Fungicides for the North Central United States, NC IPM Center, Mueller & Bradley.

3. Classification: Contact or Systemic • Contact (Protectant): • Remain on the surface – doesn’t go deeper • Have no after-infection activity • New plant growth is not protected • Systemic: • Fungicide that is absorbed into plant tissue • Offer some after-infection activity • Locally Systemic • Absorbed into the immediate area of application • Translaminar fungicides move through leaf surface to the other side • Upwardly Systemic • Moves only upward through the xylem • Contrast to glyphosate - a systemic herbicide that can move down to plant roots Contact-Protectant Locally Systemic Upwardly Systemic

4. Contact/Protectant Fungicides • Typically inhibit spore germination and stop infection • Often target multiple sites within a pathogen • Must be present BEFORE the pathogen • Often effective against different kinds of pathogens • Confined to plant surfaces (not absorbed or translocated) • Threat of pathogen resistance is LOW

5. Local Penetrant Systemic (upward) Systemic Fungicides • Absorbed into the plant, but movement is limited upward or to small area around application site • There are no fully systemic fungicides for field crops • Protection from the inside, but is eroded via: • Dilution and deactivation • Most new tissue not protected • Reapplication: ~12-20 days • Often target a single site within a pathogen • Can affect few to many pathogens • Resistance risk: MEDIUM to HIGH Source: Syngenta

6. Classification: Single or Multi Site of Action • Single-site fungicides: • Active against only one critical point, enzyme, or protein in the metabolic pathways of a fungus • Tend to be systemic • Example: Strobilurins are site-specific fungicides. One mutation at the target site can result in a fungicide-resistant fungal strain. • Multi-site fungicides: • Affect a number of different metabolic sites within the fungus

7. Classification: Mode of Action • MOA: How a fungicide kills or suppresses a target fungus • Examples of Fungicide MOA: • Damages cell membranes • Inactivates critical enzymes or proteins • Interferes with key processes such as energy production or respiration • Example - 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.

8. Biochemical Mode of Action of Fungicides sterol biosynthesis in membranes SBIs: DMIs: Triazoles/ Imidazoles, Amines: Morpholines/Piperidines mitochondrial respiration QoIs („strobilurins“) cell division / tubulin Benzimidazoles (MBCs) RNA biosynthesis Phenylamides (PAs) „Multisites“ e.g. chlorothalonil amino acid biosynthesis Anilinopyrimidines (APs) Source: Syngenta C. P.

9. Classification: Chemical Group or Class • The name given to a group of fungicide chemicals that share a common mode of action (i.e. strobilurins, triazoles, dithiocarbamates) • The chemicals in a group or class may or may not have a similar chemical structure Classification: Fungicide Resistance Action Committee (FRAC) Code: • FRAC 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

10. Considerations for Fungicide UseSome things to know before applying a fungicide • Accurate Diagnosis of Disease – Critical to be certain that the right product is used for the right problem. • Diagnosis can be simple or very difficult and can take time • Plant Disease Clinic at the U of MN and at other Universities may be needed • Type of fungus • Plant part infected • Modes of infection and spread • Weather conditions • Latent periods • How fungicide affects pathogen Proper disease identification is a critical first step in disease management

11. Before Using a Fungicide - Also Consider: • Disease incidence Number of plants or plant parts affected • Disease severity Amount of tissue affected • Host genetics • Recent & future weather conditions • Host growth stage & PHI • Fungicide timing, application, & efficacy • Yield potential • Treatment cost (product & application) • Treatment cost vs. potential benefit

12. Factors Important For Effective Disease Control • Relative efficacy of the fungicide • Availability, toxicity, application, residues • Rate and Coverage - more critical for fungicides than insecticides (as insects are mobile) • Durability - adhesion in rain & irrigation, breakdown in sunlight, movement into tissue • Plant Part Target - density and structure of canopy • Timing - vulnerable point in life cycle of the pathogen; early applications when infection starts 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)

13. Potential Negatives of Fungicide Use • Cost of fungicide and application • Lack of disease management • Drift and phytotoxicity • Potential toxicity to humans or animals if not used properly • Side effects on beneficial fungi (i.e. entomopathogenic fungi and mycorrhizal 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

14. Fungicide Resistance • A fungus, which is normally sensitive to a fungicide, develops less sensitivity to the damaging effects of the fungicideDekker, 1976 • Reduced sensitivity is thought to result from genetic mutations or naturally occurring sub-populations of resistant individuals • Experience with the strobilurins (QoI fungicides) worldwide 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.

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

16. Fungicide Use in MN • Using a fungicide when disease levels are high enough can make sense • In corn and soybean in MN, 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 in corn and soybean • Potential negatives: kill “good fungi”, increased input costs, increased risk of developing resistance, etc. • Seed treatments – • Becoming widespread on soybean - may be beneficial in some fields, but don’t expect a consistent advantage

17. Fungicides as Seed Treatments Can protect seed and seedlings from seed- and soil-borne diseases Seed treatment: challenges • Pesticides with appropriate activity may not be available • May have little or no systemic activity • May not move with the expanding root system • Effective concentration may dwindle too soon Contacts • No movement into seed • No control of internal pathogens • Protection until seed coat breaks Systemics • Movement into seed, root, and shoot tissues • Control of internal and emergence pests

18. How do You Dispose of Treated Seed?

19. China steps up checks on U.S. soybeans after finding pesticide residue • Beijing, December 26, 2008 -- China's quality supervisor said this week that it would step up checks of soybeans from the United States after tons of soybeans were found tainted by pesticides.The General Administration of Quality Supervision, Inspection and Quarantine (GAQSIQ) said the local quality watchdog in eastern Zhejiang Province found some 57,000 tons of U.S. soybeans were mixed with soybean seeds coated with three types of pesticides -- metalaxyl, fludioxonil and thiamethoxam.Such seeds are for planting and usually bear warning colors such as red, blue or green, said the GAQSIQ.In response, the GAQSIQ said it had issued a notice to all local quality bureaus, ordering them to implement an early-warning system within 90 days and step up inspections of U.S. soybeans.The GAQSIQ also informed the United States about the issue and required the U.S. side to intensify quality checks on soybeans destined for China.The GAQSIQ said it had found soybean seeds mixed in many batches of soybeans imported from the United States, which it said indicated there were major problems in the U.S. soybean export system.Source: XINHUA, December 23, 2008 NOT THIS WAY!!!!

20. Resources http://pdc.umn.edu/ Can be ordered via the internet: shop.extension.umn.edu Or Call: 1-800-876-8636 www.extension.umn.edu/cropdiseases/

21. Sources • The information contained in this presentation came from several different sources. Some information is from the authors, several sources are noted in the presentation, and some information is from: • Field Crop Fungicides for the North Central United States, Mueller & Bradley, 2008. North Central IPM Center : http://www.ncipmc.org/fieldcrops/fungicide_manual.pdf • Report on Plant Disease, No. 1002, September 2005, Characteristics of Fungicides Used in Field Crops, U of IL Extension: http://web.aces.uiuc.edu/vista/pdf_pubs/1002.pdf