Considering Aluminum Toxicity When Diagnosing Bare
Patches and Stunted Plants in the Field Carol McFarland1, Joey Blackburn1, Dave Huggins2, Kurt Schroeder3 and Tim Paulitz2
1Dept. Crop and Soil Sciences, WSU; 2USDA-ARS, Pullman, WA; 3Dept. of Plant, Soil and Ent. Sci., Univ. of Idaho
Yes –
Symptoms are most likely being caused by a “root-rot”/fungal pathogen. Take-all, Rhizoctonia root rot and Pythium root rot, are all diseases that can be accurately identified by the WSU diagnostics lab.
No –
The roots do not look rotted, they look distorted. Are there knots, or “witches brooming” along the length of the roots rather than at the end which creates more of a short, stubby “club-root” effect?
Yes –
If cysts, knots or lesions are present along the length of the roots this is likely being caused by “cyst,” “knot,” or “lesion” forming nematodes
No – The distortions are only found at root tips and form “club-root” along with browning and thickening of the roots. These are symptoms of Aluminum Toxicity and soil tests should assess pH, available Al and lime needs
Scout the affected area, carefully observing and
considering field history, seasonal weather, current
crop, patterns of symptoms and known regional issues
Gently pull up an affected plant; if it resists, gently dig
it up, trying to preserve as much of the roots as
possible. Carefully wash off any excess soil.
Are the roots formed in a “normal,”
smooth, branching way and having a
whitish color?
No –
If the roots are off-white, brown, dark brown or
black –
Do they look like they have “rotted”? The
rotting from the roots can often be seen on the
crown and on the lower portion of the stem.
Yes –
Think about:
Patterns and history, did this happen last
year?
Environmental conditions – was this part of
the field more susceptible to winterkill,
drying or too much water?
Herbicide carryover, especially if there is leaf
distortion on the upper part of the plant.
Carryover can be exacerbated by
environmental conditions.
Nutrient deficiency – what nutrients did you
test for this year? Many nutrient deficiencies
can cause yellowing and stunting of the crop.
Wireworm or other insect feeding, can you
dig in the soil and find the insect?
Bare Patches and Stunting in the Field
Acknowledgement
http://ipm.missouri.edu/ipcm/2012/5/
Early-Corn-RootDevelopment/fig4.jg
http://www.ces.ncsu.edu/wp
content/uploads/2013/09/RK
Nsmall.jpg
http://www.fao.org/docrep/0
06/y4011e/y4011e1w.jpg
http://bulletin.ipm.illinois.ed
u/photos/pythium_root_rot
http://www.agric.wa.gov.
au/objtwr/imported_ima
ges/takeall_webpic.jpg
Take-all Pythium
Cereal-Cyst
Nematode Cereal Root-Knot
Nematode
http://fieldcropnews.com/wp-content/uploads/2011/06/IMG_4553-1024x682.jpg
Herbicide Carryover with
too Much Moisture
Nematodes
Wireworm
Photo Credit: Timothy Paulitz
Root Lesion Nematodes
Rhizoctonia Al Toxicity
Photo Credit: Timothy Paulitz Photo Credit: Timothy Paulitz
Aaron Esser
Take-all
http://www.plantmanagementnetwork.org/pub/php/diagnosticguide/take-all/images/mathre4big.jpg
http://grains.agric.wa.gov.au/sites/grains/files/ba
rley%2520water%2520stress%2520taylor.jpg
Drought Stress
http://1.bp.blogspot.com/-
nkz9laWHHzc/TgufpGTMF0I/AAAAAAAAAac/s1CnvrLNu7I/s1600/CornUgly22090.JPG
Photos: Timothy Paulitz
Drought Stress
Photo: Timothy Paulitz
Root Lesion
Nematode
• Biotic (living) e.g. fungal pathogens, wireworm,
nematodes
• Abiotic (non-living) e.g. too wet, too dry, herbicide
carryover, nutrient deficiency, nutrient toxicity
http://extension.udel.edu/kentagextension/wpcontent/blogs.dir/11/files/blog
ger/_8xC9bwq6AVU/R8vS_WJP8MI/AAAAAAAADQM/7GU_jsGvUb8/s160
0/mnwheat2.png
Mg deficiency Al toxicity
Photo Credit: Timothy Paulitz
• Soil pH is the “negative log” of Hydrogen ion (H+)
concentration in the soil
• This means that each pH “step” up or down is a
ten-fold difference in acidity
• H+ is toxic when the pH becomes very
low
• pH governs all soil chemistry
• Neutral pH is 7
• Bacteria(e.g. Rhizobia spp.) do not tolerate low pH
• Fungi, including many fungal pathogens like
Pythium, prefer low pH soil
• Crop yields are
impacted at low
soil pH
pH: “The Master Variable”
http://pmel.noaa.gov/c
o2/files/phfig1-
revised.jpg
Soil Acidification and the Palouse
• Soil acidification can occur naturally over time
• Native soils of the Palouse had near-neutral pH
• Since the 1950’s, as ammonium-based fertilizer
use increased, pH has rapidly decreased
• Different soil types will acidify faster or slower
depending on their properties
• Remediation with CaCO3 will correct acid soils
Healthy roots
https://encryptedtbn3.gstatic.com
Where does the Al Come From? • Soil is made from sand, silt and clay
particles
• Clay particles are comprised of O, Si,
Al and Fe in varying configurations
• As pH decreases, Al is released from
the clay and moves into the soil
solution where it can be plant-
available Gibbsite
Funded by The Washington Grain Commission
Diagnostic Key- Use as a guide to take informed next-steps
• Diagnosing bare, sparse, stunted or yellow patches in your field is challenging
• Commonly, factors can combine in a complex of symptoms
https://encryptedtbn1.gstatic.com/images?q=tbn:ANd9GcTqffFtZ3UQfwQocSvpjNvAoNq6lwQ
es4ztICXqXnu0zm4UKcD
Aluminum Toxicity in Crops
http://farm5.staticflickr.com/4083/5083645621_70b94d1e50_z.jpg
• Soil pH influences nutrient
availability
• If the pH is too high or too
low, essential nutrients can
become “unavailable”
• Some elements, such as Al,
can become too available
• Al affects the cells at the
growing tip of the root
• Results in darkening and
thickening of the root and
characteristic “club root” tips
• Impaired roots cannot take up
important nutrients or water
• Field symptoms of Al toxicity
are stunted, slow-growing,
often yellowing plants
• High soil concentrations of Al
can inhibit seed germination
and seedling growth
• Tolerant crops and varieties
can excrete organic acids
that “bind” Al and reduce its
availability to plants
• Al tolerant crops and wheat
varieties can help mitigate the
effects of Al toxicity, but soil
remediation should be
strongly considered
Stunting in the field from Al toxicity
The roots of the plant on the right
show “club root” from Al toxicity
A scanning electron micrograph
of a healthy root and “club root”
References:
Bennett, William F. Nutrient Deficiencies & Toxicities in Crop Plants. 1 edition. Amer Phytopathological Society, 1993.
Brady, Nyle C, Ray R Weil, and Nyle C Brady. Elements of the Nature and Properties of Soils. Upper Saddle River, N.J.: Prentice Hall, 2004.
“Cereal Cyst Nematode | Fact Sheets | Soilquality.org.au.” Accessed November 14, 2013. http://soilquality.org.au/factsheets/cereal-cyst-nematode.
“Guide to Wheat Diseases and Pests.” Accessed September 19, 2013. http://wheat.pw.usda.gov/ggpages/wheatpests.html#aluminum.
Mahler, R. L., and R. E. McDole. “The Influence of Lime and Phosphorus on Crop Production in Northern Idaho 1.” Communications in Soil Science & Plant Analysis 16, no. 5
(1985): 485–499.
Mahler, R. L., A. R. Halvorson, and F. E. Koehler. “Long-term Acidification of Farmland in Northern Idaho and Eastern Washington 1.” Communications in Soil Science & Plant
Analysis 16, no. 1 (1985): 83–95.
Marschner, Petra. Marschner’s Mineral Nutrition of Higher Plants, Third Edition. 3 edition. Academic Press, 2011.
“Montana Wheat Diseases - Fungal, Lower Stems & Roots.” Accessed November 14, 2013.
http://scarab.msu.montana.edu/Disease/DiseaseGuidehtml/webFunglower.htm#PYTHIUM ROOT ROT.
“Post Root Diseases of Wheat and Barley: What Do They Look Like and What Do They Do to the Crop? « Plant Health International.” Accessed November 14, 2013.
http://planthealthinternational.com/new-root-diseases/.
“Wireworm Research Page, Aaron Esser, WSU Extension.” Accessed November 18, 2013. http://lincoln-adams.wsu.edu/agriculture/Wireworm.html.
Rhizoctonia