Biotic and abiotic disorders of forage crops Dr. Mary Burrows Montana State University Bozeman, MT.
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Transcript of Biotic and abiotic disorders of forage crops Dr. Mary Burrows Montana State University Bozeman, MT.
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Biotic and abiotic disorders of forage crops
Dr. Mary Burrows
Montana State University Bozeman, MT
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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?
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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
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The most common nutrient deficiencies
• Cereals: Nitrogen, Phosphorous
• Alfalfa: Phosphorous, Potassium, Sulfur
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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
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What does nitrogen deficiency look like?Reduced tillering, stunting, poor kernel fill, and low grain protein
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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
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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
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Phosphorous deficiency
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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.
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Potassium deficiency
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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
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Sulfur deficiency
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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 soilhttp://landresources.montana.edu/soilfertility/
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How do I tell if it’s a nutrient deficiency or a disease?
• Symptoms
• Patterns
• Soil test
• Send in a sample
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Sample Submission• Accurate Diagnosis depends on a
good sample and symptom description
Enter sample information into PDIS (Plant Diagnostic Information System)
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Foliage diseases
Check for injuries, disease on the main stem/trunk
Keep most roots and soil intact if possible
Samples must contain the right material: an entire plant or several plants if practical
Diseases may show up on any part of the plant.
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Dead Plants Tell no Tales
Avoid dead plants Choose plants which show
a range of symptoms: moderate to severe
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19
Packaging & Shipping
Good Intentions
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20Actual Results
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Packaging and Shipping blunders
Soil on foliage during shipping creates “diseases” that were not there when the sample was collected.
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Packaging and shipping blunders
Don’t add water or wrap in wet paper towels
Sample soup
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Good Packaging
Plastic bag to keep soil on roots
Dry paper towels to protect leaves from contact with plastic bag
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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.
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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?
![Page 26: Biotic and abiotic disorders of forage crops Dr. Mary Burrows Montana State University Bozeman, MT.](https://reader036.fdocuments.in/reader036/viewer/2022062304/56649ec95503460f94bd6716/html5/thumbnails/26.jpg)
Crown rot symptoms in alfalfa
Verticillium, Fusarium, Rhizoctonia, Phytophthora, Pythium, Phoma, Mycoleptodiscus, Stagonospora, and Macrophomina
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Brown root rot of alfalfa• Phoma sclerotioides
• Most active in late winter and early spring
• Very broad host range, including grasses
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2006 Survey
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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
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Stem nematode in alfalfa• Ditylenchus dipsaci
White flagging Stunted plants, shortened internodesSwollen nodes Crinkled leaves (between veins)
2009, Yellowstone Co.
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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
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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
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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
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Spot and net blotch of barley• Primarily important under irrigation
• Residue borne
How do you control?
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Smuts and buntsBunt
Smut
• Favored by a cool, wet spring
• Soilborne and in contaminated seed
• Seed treatments are effective
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Seed treatment effects on covered smut of spring barley, 2005, Bozeman
Treatment
Emergence (pl/3m)
Smutted heads/6m
Yield
(kg/ha)No treatment 144 62 57.3
Allegiance 145 49 59.4
Charter+Allegiance 147 0 64.7
BAS 500XBF + Allegiance
145 2 62.9
BAS + Charter + Allegiance
144 0.3 63.1
Raxil MD 146 0 63.4
Dividend XL RTA 140 0 63.3
Similar story for loose smut of barley, common bunt of wheat
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Dwarf bunt
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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)
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Seed treatments for smuts and buntsBarley Wheat
Coveredsmut
Loose Smut
Dwarf bunt(TKC)
Common bunt
Charter + + - +
DBGreen + - - +
Dividend + - +Use high rate
+
Raxil + + - +
Vitavax + + - +
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Reasons for seed treatment
From: McMullen and Lamey. 2000. Seed treatment for disease control. NDSU extension publication PP-447
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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
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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
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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
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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
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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
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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
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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
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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
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Be a First Detector
First Detectors are the front line for early discovery of new invasive pests.
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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
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MODULE 1 – Mission of the NPDN
0
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time (weeks)
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Importance of Early Detectioncritical control point
lowimpact
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pathogendetection
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Montana State UniversitySchutter Diagnostic Lab
Physical address
121 Plant BioScience Bldg. (PBB)
Mailing Address
119 Plant BioScience Bldg.
P.O. Box 173150
Bozeman, MT 59717-3150
(406) 994-5150 or -5690
http://diagnostics.montana.edu/