U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Plant Science Research: St. Paul, MN
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                People

                    Staff Listing
                                    CareersSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Midwest Area St. Paul, Minnesota Plant Science Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications

Title:   Author  item
                                            Samac, Deborah

                                                         - *Debby*
  Submitted to: Compendium on Alfalfa Diseases
                                    Publication Type: Book / Chapter
                                    Publication Acceptance Date: 12/5/2012
                                    Publication  Date: 10/17/2014
                                    Citation: Samac, D.A. 2014. Alfalfa witches'-broom. In: Samac, D. A., Rhodes, L. H., and Lamp, W. O., editors. Compendium of Alfalfa Diseases and Pests. 3rd edition. St. Paul, MN: APS Press. p. 65.Interpretive Summary:
                                Technical Abstract:   Alfalfa witches'-broom was first reported in 1969 in Australia and later in South Africa, Canada, and Saudi Arabia. More recently, specific phytoplasmas associated with alfalfa witches'-broom have been identified from symptomatic plants in the United States (Wisconsin), Italy, Lithuania, Oman, Iran, China, Argentina, and Bolivia. The disease can result in significant losses in forage and seed production. Annual losses of approximately 25% in hay production were reported in Oman due to alfalfa witches'-broom.
  Symptoms: The disease is characterized by a proliferation of shoots leading to a bush- or broom-like appearance. Leaves are small and yellow. Flower abortion is observed in severely infected plants.
  Causal Organism: Alfalfa witches'-broom is caused by phytoplasmas, formerly termed mycoplasma-like organisms (MLOs). Phytoplasmas are small, wall-less prokaryotes that have not been cultured in vitro. The 16S rRNA sequence is the primary tool for identification and classification of phytoplasmas. The majority of phytoplasmas associated with alfalfa witches'-broom were identified in the 16SrI (aster yellows group). Phytoplasmas in the 16SrII (peanut witches'-broom group) and 16SrVII (ash yellows group) were also shown to be associated with alfalfa witches'-broom.
  Disease Cycle and Epidemiology: Symptoms can occur in plants of any age. Incidence of the disease has been reported from 20 to 95% of plants in a field. The pathogen is limited to phloem sieve tubes and is spread by phloem sap-feeding insects such as leafhoppers in a persistent manner. Seed transmission has not been reported.
  Management: No specific management strategies have been reported. As for other diseases caused by phytoplasmas, controlling insect vectors and removing plants serving as reservoirs for the pathogen can reduce disease incidence. Alfalfa cultivars with resistance to the potato leafhopper (Empoasca fabae) have been developed, but their utility for reducing alfalfa witches'-broom has not been tested.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov