The effectiveness of seed treatments for controlling plant diseases

1. The effectiveness of seed treatments for controlling plant diseases Dr. Mary Burrows Montana State University Bozeman, MT

2. Reasons for seed treatment From: McMullen and Lamey. 2000. Seed treatment for disease control. NDSU extension publication PP-447

3. General Agronomic Recommendations • Use certified or high quality seed: no old seed • prevent introduction of new diseases into your fields • prevent making an old problem worse • Select best yielding cultivar for your area • adaptation and disease resistance • Use appropriate chemistry • Seeding date - know your diseases! • Delayed seeding in fall may reduce amount of Fusarium and crown root rot • Delayed seeding in spring may reduce Pythium infection • Delayed seeding reduces incidence of TCK, dwarf bunt (Telletia controversia Kuhn), but increases common bunt

4. Why do we need to treat seed?? • Give crop the best possible chance to emerge and establish • Improve the general health of the grain crop. In 1972, 30% of the Montana wheat crop carried smut spores Release of Carboxin followed by other systemic fungicides In 1997, < 2% of the Montana wheat crop carried smut spores

5. Survey of Canada, 2005 32% of wheat fields had smut 57% of barley fields had smut Smut spores are readily available We cannot predict when this disease will become an urgent issue Varieties, cultural practices, and the weather change from year to year

6. Think of seed treatments as an insurance policy You may not see a positive effect every year. However, when the proper conditions occur for disease development, seed treatment will help your crop with improved emergence and stand establishment resulting in an increase in yield and quality.

7. Cost of seed treatments • It costs roughly $1 to $1.50 to treat a bushel of seed • It takes roughly a bushel to plant an acre • If you can gain even ½ bu in yield through applying a seed treatment you will at least break even

8. Seed treatment application • Many formulations • Application and mixing depends on formulation

9. Seed treatment modes-of-action • Nonspecific, disrupt a number of enzymes required for metabolism • Captan, Maneb, Mancozeb, Thiram • Mitochondria function: cell energy • Carboxin (Vitavax) • Nuclear division: organism replication • Thiabendazole (LSP, Mertect) • RNA synthesis: no RNA, no protein production • Metalaxyl (Apron, Allegiance) • Sterol biosynthesis: membrane function • Imazalil, Difenoconazole, Triadimenol (Double R, Dividend, Baytan) • Glucan synthesis: cell wall and membrane function • Fludioxonil (Maxim)

10. Safety when handling pesticides • An approved chemical respirator and gloves are recommended even if not required by the label • Do not use treated seed for food or feed • Do not use an auger exposed to treatment with feed grain • Be careful to wash out the seed truck before using it to haul feed grain • Rinse and properly dispose of chemicals • Add rinse water to treated seed

11. Seed treatments • Add recommended rate • Overtreatment may lead to decreased emergence • Undertreatment may not provide good control • Undertreatment may lead to fungicide/insecticide resistance • Check labels for compatibility before mixing insecticides and fungicides • Some combinations are toxic to the seed

12. There are a wide array of seed treatment options available • We will be updating the seed treatment MontGuide this fall • http://www.montana.edu/wwwpb/pubs/mt9608.html • http://www.ag.ndsu.edu/pubs/plantsci/ pests/pp622w.htm

13. Least samples Most Samples Disease Picture in Montana: Clinic samples 2006 Seed treatment will have an effect on these diseases

14. Diseases controlled by seed treatments in cereals • Dryland seed rot • Damping off • Fusarium crown rot • Smut • Bunt • Take-all (some control can be provided by Baytan)

15. Dryland seed rot • Inadequate moisture for germination • After 3-4 weeks, Penicillium and other opportunistic fungi will attack the seed • Reduced stand • Use Dividend, Raxil, DBGreen, or Double R

16. Damping off • Excess moisture at planting • Several fungi that are always present in the soil attack the seed or seedling • Can be prevented by any broad-spectrum seed treatment

17. Fusarium crown rot(foot rot) • Caused by Fusarium spp. • Same fungus that causes scab • Hosts include wheat, barley, oats, corn, grasses

18. Fusarium crown rot history • Ubiquitous; probably present in the original prairie soil infecting native grasses • Early 1900s H.L. Bolley “wheat-sick soil” • Campaign across ND to use good seed and practice rotation • Posters in store windows

20. Yield loss from Fusarium crown rot • Long-term annual estimates of yield loss in Saskatchewan and Manitoba • 5-6% spring wheat • 11% barley • North Dakota estimates were similar, 9.5% yield loss for durham wheat

21. Fusarium crown rot trialsHuntley, 2005, spring wheat **An outlier was removed. If included, % yield reduction would be 11.7%

22. Fusarium crown rot trialsHuntley, 2005, durham wheat **An outlier was removed. If included, % yield reduction would be 11.7%

23. Future: Fusarium crown rot control • Seed treatment • Late seeding (not practical) • Don’t over-fertilize • Crop rotation to non-host: DON’T PLANT INTO CORN STUBBLE • Plant tolerant varieties • plantsciences.montana.edu/crops

24. Smuts and bunts Bunt • Favored by a cool, wet spring • Soilborne and in contaminated seed • Seed treatments are effective Loose smut

25. Seed treatment effects on covered smut of spring barley, 2005, Bozeman Similar story for loose smut of barley, common bunt of wheat

26. Dwarf bunt

27. Dwarf bunt • Tilletia controversa Koch (TCK) • Winter wheat • Occurs when plants are exposed to prolonged snow cover • Soilborne spores germinate under the snow and infect young plants • Control with seed treatment (Dividend)

28. Seed treatments for smuts and bunts

29. Seed treatments for “alternative” crops • Chickpea • Treat for Pythium – essential for good emergence (Metalaxyl: Apron, Allegiance) • Treat for seedborne Ascochyta (LSP) • Lentil and dry peas have the same products registered as Chickpea; some additional products; check the labels • May or may not have to treat for damping off and seedborne ascochyta depending on environmental conditions, varieties • Kodiak is registered for peas (Bacillus subtilus GB03)

30. Ascochyta blight: get your seed samples in now! Montana State University Seed Laboratory http://plantsciences.montana.edu/seedlab/index.htm PHONE: (406) 994-2141 2 lb chickpea 1 lb pea and lentil Add 1 lb for purity and germ $36 Ascochyta + $22 purity and germ

31. Legumes (pea, lentil, chickpea) • Ascochyta – don’t plant if >1% in lentils; chickpea use 0% cutoff • No great fungicide controls (Bravo, Headline, Quadris) • http://www.agr.gov.sk.ca/docs/crops/integrated_Pest_management/disease/ascochytafungicides.asp • Fusarium or Rhizoctonia: yellowing of plant at flowering, fails to set seed • If the weather is humid, could have anthracnose problems

32. Seed treatments for “alternative” crops • Safflower • Seedborne rust • Vitavax, Dithane, Manzate, Penncozeb, Thiram

33. Alternaria on safflower • In 3 years of field trials, Quadris, Headline, and Endura increased yields by 24->100%, oil content by 5-11%, and seed weights by 8-11% • A single application at first flower was nearly as effective as 2 or 3 applications

34. Economics of fungicide applicationnet returns over unsprayed-3 yrs. Variety Safflower $0.275/kg, aerial application=$16.80/ha, Quadris =$35.65/ha

35. Downy mildew on camelina Seedborne No seed treatments registered