Guide to diagnosis of chlorotic and poor vigor wheat in fall
NOTE: For treatment options and a description of the appearance of both winter grain mite and brown wheat mite, see Wheat Insect Management 2011 at your local Extension office, or at: http://www.ksre.ksu.edu/library/ENTML2/MF745.PDF
* Hessian fly. Seedlings infested by Hessian fly in the fall are typically not yellow, but are often stunted. Affected plants usually have an unusually large, broad greenish leaf for about a month in the fall. Stem elongation is typically much shorter than normal.
* Flea beetles. These tiny insects cause whitish streaks on the upper surfaces of leaves. If streaking is severe, plants may die.
* Poor quality seed. Seed with unusually low test weights may emerge, but have poor seedling vigor. Certified seed in Kansas has a minimum test weight of 56 pounds per bushel. If test weights are less than that, seedling vigor may be less than desired. Seed size does not in itself have an impact on seedling vigor. Some varieties tend to have small seed, but this does not have any impact on seedling vigor. If the seed is smaller than normal for a particular variety and has low test weight (in the low 50s or less), this can result in poor seedling vigor, however.
* Seedling blight. This is one of the most common causes of post-emergence seedling death or sickliness. If the plants may emerge just fine, then seem to “go backwards” in the fall, the root system or coleoptile region may be diseased or dead. Several fungi cause seedling blight, and these diseases are often worse on early-planted wheat. Seedling blight may not kill the seedlings outright, but can lead to later problems with common root rot, crown rot, sharp eyespot, and dryland root rot (also known as dryland foot rot). Suspected plants can be sent to the K-State Plant Diagnostic Lab in the Department of Plant Pathology for diagnosis. Contact your county Extension agent for more information on submitting samples.
* Atrazine carryover. Wheat planted into soils with atrazine residue emerges then dies back from the tips of the oldest leaves first. Atrazine carryover is most likely to occur where there were high application rates, high soil pH, coarse-textured soils, and under dry conditions.
* Low soil P levels. Phosphorus deficiency symptoms are not common on seedling wheat, but can occur under extreme conditions. Symptoms will include stunting and purpling of the leaves.