Pea Enation Mosaic Virus

Cause


Pea Enation Mosaic Virus (PEMV) mainly infects legumes in the temperate regions of the world. The virus is spread in nature most efficiently by the pea aphid (Acyrthosiphon pisum) and to a lesser extent by the green peach aphid (Myzus persicae). There are 8 total species known to transmit PEMV.

Host/site


Plant hosts include chickpea, lentil, faba bean, broadbean, sweet pea, certain species of lupine; Hungarian, common, and hairy vetch; and several species of clover including Alsike, white, crimson, and subterranean. Weedy subterranean clover is the principal overwintering host but it probably overwinters in many common perennial legumes. This virus can be detected in seed but is not transmitted by seed.

Identification


Plant Symptoms and Indicators
  • Infected pea plants develop mosaic and chlorotic vein flecking (appears as translucent windows) and veinal enations (blisterlike outgrowths), which are very characteristic for PEMV.
  • Plants are stunted, and proliferation of basal branches is common.
  • Pods are distorted, split open, and may show prominent enations.
Life cycle
  • At least 8 species of aphid can transmit the virus but the principal vector is the pea aphid, Acyrthosiphon pisum. After the aphid acquires the virus, it is 8 or more hours before it can transmit it to a pea plant, but the aphid retains the ability to transmit the virus for at least 24 hours, during which time it can fly or be blown long distances (Ocamb).
  • Four to six days post initial infection pea plants develop a slight downward rolling of the leaves, followed by an often bright, distinct yellow mosaic on the leaves. The yellow mosaic spots become translucent and clearly delineated.
  • As the disease progresses, plants develop growth malformation, stunting, and sometimes a top and/or tip necrosis resulting in the loss of strong growth from the main stems and branches.
  • Later in infection, diagnostic blisters or enations (blister-like outgrowths perpendicular to the leaf plane and associated with the veins) may develop on the underside of the leaves. Pods are often malformed and warty looking, and contain few if any seeds.

Natural Enemies


  • Because PEMV transmission is tied to pea and green peach aphid infestation, the presence of aphid predators and parasites would combat infection.
  • See Biological Controls for more information.

Monitoring


  • Visually inspect plants each week for aphids and symptoms of disease.

Action Thresholds


Preventative action should be taken at the first sign of the virus.

Cultural and Physical Controls


  • Using cultivar resistant strains when possible is considered the only "satisfactory control"
  • If using susceptible varieties, planting before March 31 helps avoid aphid infestation. Especially important for late plantings intended for fall crops or for over-wintering.
  • Spray water to knock aphids off plants.
  • Squish aphids with your hand

Biological Controls


Green peach aphid or pea aphid predators and parasites can be used to prevent an outbreak of PEMV.

The most common enemies of these aphids are:

  • Lady beetles(Coleoptera: Coccinellidae)
  • Flower flies (Diptera: Syrphidae)
  • Lacewings (Neuroptera: mainly Chrysopidae)
  • Parasitic wasps (Hymenoptera: Braconidae).

Chemical Controls


Not recommended.

References


Cockbain, A. J. "Plant Viruses Online - Pea Enation Mosaic Enamovirus." Plant Viruses Online. University of Idaho. Web. 23 May 2010. <http://pvo.bio-mirror.cn/descr572.htm>.

Ocamb, Cynthia M. "Information on Pea." An Online Guide to Plant Disease. Oregon State University, 01 Jan. 2009. Web. 22 May 2010. <http://http://ipmnet.org/plant-disease/disease.cfm?RecordID=781>.

Zitter, T. A. "Virus Diseases of Peas Fact Sheet." Vegetable MD Online. Cornell University. Web. 23 May 2010. <http://vegetablemdonline.ppath.cornell.edu/factsheets/Viruses_Peas.htm>.

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