ISSUE 13   July 27, 2006

PLANT DIAGNOSTIC LAB SUMMARY

Below is a summary of samples diagnosed from July 5, 2006 to July 19, 2006 (research samples and seed health testing results are not included):

Host

Diagnosis

Taxonomic name

County

Corn

Drought Stress Damage

Abiotic pathology

Clay

Spruce

Spider Mite Injury

Oligonychus ununguis

Becker

Soybean

Symptoms mimicing growth regulator herbicide injury - likely due to environmental stress

Abiotic pathology

Marshall

Grape

Black Rot

Guignardia bidwellii

Cass

Sunflower

Poor Or Insufficient Sample

 

Grand Forks

Crabapple

Mechanical Damage

Abiotic pathology

Cass

Spruce

Growth Regulator Effect

Abiotic pathology

Becker

Sunflower

Herbicide Injury

Abiotic pathology

Cass

Spruce

Water deficiency

Abiotic pathology

Cass

Symptoms that mimic growth regulator injury on soybean may not be due to herbicide exposure. If you see growth regulator symptoms uniformly throughout a field, consider physiological stress as a possible cause. Researchers in Iowa, Illinois, and southern Minnesota have reported seeing this phenomenon (growth regulator type symptoms, in the absence of possible herbicide exposure), and they speculate heat stress and/or water stress may be the underlying cause(s). See links below for more information:

http://www.ent.iastate.edu/Ipm/Icm/2002/7-22-2002/pgr.html

http://swroc.coafes.umn.edu/SWMNPEST/01News/ipmstuff71201.PDF  

Kasia Kinzer
NDSU Plant Diagnostic Lab
Website: www.ag.ndsu.nodak.edu/diaglab
e-mail: diaglab@ndsuext.nodak.edu
Telephone: 701-231-7854
206 Waldron Hall, PO Box 5012
Fargo, North Dakota 58105


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