Aster Yellows of Wheat
Published: 01/24/2022
Aster yellows is caused by a phytoplasma (Candidatus Phytoplasma asteris) spread by leafhoppers during feeding. Leafhopper feeding can cause white flecking or stippling on leaves. When the plant is infected, leaves become yellowish and progressively turn red-brown or purple, usually starting at the tips. Discoloration typically occurs as streaks. Plants may be stunted and excessively branched, and yields may be reduced. Leaves, stems, and heads may become curled and twisted. Symptoms tend to occur along field edges in patches and are often mistaken for other diseases such as barley yellow dwarf or nutrient deficiencies. Symptoms in wheat are often correlated with those in canola or other dicots and weeds in the same season, and can appear at anytime during the growing season.
Conditions that favor the leafhopper vector will favor aster yellows development. Leafhoppers generally migrate from southern states, many of them already carrying the phytoplasma. Leafhoppers take flight when temperatures exceed 59°F and cooler temperatures or rain will stop their migration until weather conditions become more favorable. After feeding and transmission of the pathogen, plant symptoms appear in 2-3 weeks. Wheat plants are most susceptible during early vegetative growth stages and extent of damage depends largely on when infection occurs. Symptoms can be more pronounced under stress conditions such as wet or waterlogged soils.
Resistance has been identified in a few varieties of spring wheat. Applying insecticide to manage leafhoppers is not recommended since leafhoppers may continue to migrate into the field after application. Manage weeds to reduce the number of plants that may serve as sources of inoculum.
This publication was developed by the Crop Protection Network, a multi-state and international collaboration of university/provincial extension specialists and public/ private professionals that provides unbiased, research-based information to farmers and agricultural personnel.
This information in this publication is only a guide, and the authors assume no liability for practices implemented based on this information. Reference to products in this publication is not intended to be an endorsement to the exclusion of others that may be similar. Individuals using such products assume responsibility for their use in accordance with current directions of the manufacturer.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD).
USDA is an equal opportunity provider and employer.
©2022 by the Crop Protection Network. All rights reserved.
