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