Biotic and abiotic disorders of forage crops

1. Biotic and abiotic disorders of forage crops Dr. Mary Burrows Montana State University Bozeman, MT

2. Overview • How do I tell if my forage crop has a nutrient deficiency? • How do I recognize and manage common plant diseases in alfalfa and hay barley?

3. Nutrient deficiency • Macronutrients are nutrients required in relatively large amounts • Nitrogen (N) • Phosphorous (P) • Potassium (K) • Sulfur (S) • Micronutrients are needed in small or trace amounts for plant survival and adequate production • Calcium (Ca) • Magnesium (Mg) • Iron (Fe) • A balance of nutrients is required for optimum growth • Nutrient deficiency can be easily confused with disease: • PATTERNS & testing

4. The most common nutrient deficiencies • Cereals: Nitrogen, Phosphorous • Alfalfa: Phosphorous, Potassium, Sulfur

5. Nitrogen fertilization • Not necessary for alfalfa except small amounts at the time of establishment; adding nitrogen to mature alfalfa can reduce N-fixing bacterial activity • Manage N in cereals for yield and protein

6. What does nitrogen deficiency look like? Reduced tillering, stunting, poor kernel fill, and low grain protein

7. Nitrogen deficiency in cereals • In the spring, often associated with cool wet weather: if there is sufficient soil nitrogen plants will green up when it gets warmer • Foliar symptoms of nitrogen deficiency can be similar to root rots

8. Phosphorous deficiency symptoms • Cereals: lack of vigor and poor tillering; purpling less common • Alfalfa: plants are stunted and unthrifty, purpling of stems and leaves, root development is impeded and they develop a light brown color. Growth is abnormally stiff and upright. Yellowing and death of older leaves occur with severe deficiency

9. Phosphorous deficiency

10. Potassium deficiency symptoms • Cereals: Growth short and uneven and few heads form; leaves bluish green and dying off of older leaves beginning near tips and margins. White blotchy lesions develop when deficiency is very acute. More susceptible to powdery mildew. • Alfalfa: small white spots on the older leaves, often on leaf margins. Leaf tissue between the spots yellows and dies. Often symptoms are more pronounced on regrowth after first or second cutting. Potassium deficient plants are more susceptible to winter injury.

11. Potassium deficiency

12. Sulfur deficiency symptoms • Cereals: overall yellowing and stunting of the plant. It is difficult to distinguish sulfur from nitrogen deficiency • Alfalfa: stunting of plants and yellowing of youngest leaves and veins

13. Sulfur deficiency

14. How do I manage nutrient deficiencies? • Get your soil tested • Alfalfa: every 3 years • Grass: nitrate every year; P & K every 3 yr • Get a tissue test if necessary • Amend soil http://landresources.montana.edu/soilfertility/

15. How do I tell if it’s a nutrient deficiency or a disease? • Symptoms • Patterns • Soil test • Send in a sample

16. Sample Submission • Accurate Diagnosis depends on a good sample and symptom description Enter sample information into PDIS (Plant Diagnostic Information System)

17. Samples must contain the right material: an entire plant or several plants if practical Diseases may show up on any part of the plant. Foliage diseases Keep most roots and soil intact if possible Check for injuries, disease on the main stem/trunk

18. Dead Plants Tell no Tales • Avoid dead plants • Choose plants which show a range of symptoms: moderate to severe

19. Packaging & Shipping Good Intentions

20. Actual Results

21. Packaging and Shipping blunders Soil on foliage during shipping creates “diseases” that were not there when the sample was collected.

22. Packaging and shipping blunders Sample soup Don’t add water or wrap in wet paper towels

23. Good Packaging • Plastic bag to keep soil on roots • Dry paper towels to protect leaves from contact with plastic bag

24. Sample Submission • Try to keep sample as fresh as possible until you can get it to the county agent: refrigerate if possible. • Include photographs illustrating the problem if possible.

25. Overview • How do I tell if my forage crop has a nutrient deficiency? • How do I recognize and manage common plant diseases in alfalfa and hay barley?

26. Crown rot symptoms in alfalfa Verticillium, Fusarium, Rhizoctonia, Phytophthora, Pythium, Phoma, Mycoleptodiscus, Stagonospora, and Macrophomina

27. Brown root rot of alfalfa • Phoma sclerotioides • Most active in late winter and early spring • Very broad host range, including grasses

28. 2006 Survey

29. Crown rot control • Variety selection • Promote vigorous growth with proper fertility and irrigation practices. • Control foliar diseases and insect problems. Crown rot fungi often enter through wounds. • Avoid cutting hay when soils are wet. • Avoid heavy grazing. • Control weeds with herbicides and avoid cultivation practices which damage crowns. • Avoid field sites with heavy or poorly-drained soils. • Rotate out of alfalfa for 2-3 years. • Heavy watering in the fall will delay dormancy • Stop watering end of September

30. Stem nematode in alfalfa • Ditylenchus dipsaci White flagging Stunted plants, shortened internodes Swollen nodes Crinkled leaves (between veins) 2009, Yellowstone Co.

31. Stem nematode on alfalfa • Spread by surface water runoff, irrigation, wind-blown crop debris, infested hay, soil and crop debris clinging to equipment, humans and livestock, and with seed • Prevent introduction of nematodes into a field • Rotate with a non-host (not alfalfa or sainfoin) and control alfalfa volunteers 2-4 years • Some resistant varieties • Cut infected fields slightly higher and when dry to reduce spread

32. Foliar diseases of alfalfaNo fungicides are labeled for forage alfalfa Spring black stem • Phoma medicaginis • Residue-borne • Primarily moves via water; also via equipment, insects, and wind • The first cutting is often the most damaged • Control by early cutting, variety resistance

33. Foliar diseases of alfalfaNo fungicides are labeled for forage alfalfa Stemphylium leaf spot • Stemphylium botryosum • Residue-borne • Primarily moves via water; also via equipment, insects, and wind • Control by early cutting and variety resistance

34. Spot and net blotch of barley • Primarily important under irrigation • Residue borne How do you control?

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

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

37. Dwarf bunt

38. 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)

39. Seed treatments for smuts and bunts

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

41. 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

42. 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

43. Ergot in grasses used for feed/forage • Calviceps purpurea • Sclerotia contaminate seed • Soilborne sclerotia overwinter; viable approximately 3 yr in soil or longer in stored grain • Ascospores dispersed by wind and rain infect florets; conidia formed on ovary surface serve as secondary inoculum • Grain converted into sclerotia • More abundant during moist growing seasons

44. Ergot history (rye) • 400 B.C. Hippocrates prescribed ergoty grain to “further childbirth” • 1039 St. Anthony’s fire • 1692 Salem witch trials • 1935 LSD was synthesized during research on the active ingredients in ergot • Ergot contains Lysergic acid

45. Ergoty grain is toxic to animals4 forms of toxicity • Convulsions • Gangrene • Hyperthermia (increased body temperature) in cattle • Agalactia (no milk) and lack of mammary gland development, prolonged gestations, and early foal deaths in mares fed heavily contaminated feed

46. Ergot toxicity symptomsdepend on: • Type of ergot consumed • Ratio of major toxic alkaloids present in the ergot: ergotamine, ergotoxine, and ergometrine • Frequency and quantity of ingestion • Climactic conditions when ergot was growing • Species of ergot • Other impurities in the grain such as histamine and acetylcholine • Claviceps purpurea is usually associated with gangrenous ergotism

47. Ergot control • Harvest before the heads are mature • Rotate out of grains at least 1 yr • Deep plowing • Plant only ergot-free seed • Control grassy weeds • Seed treatments not effective

48. There are a wide array of seed treatment options available • http://msuextension.org/publications/AgandNaturalResources/MT199608AG.pdf • http://www.ag.ndsu.edu/pubs/plantsci/ pests/pp622w.htm • http://www. greenbook.net • http://www.cdms.net

49. Be a First Detector First Detectors are the front line for early discovery of new invasive pests.

50. Your role as a First Detector • Receive NPDN First Detector training • Take online modules (http://cbc.at.ufl.edu) • Attend classes like this one • Be alert to the unusual or different • Be placed on a national notification registry of First Detectors • Receive pest alerts and other relevant updates