e-GRO Alert by W. Garrett Owen, Jan Byrne and Fred Warner
Tobacco Rattle Virus in peony
by W. Garrett Owen (Michigan State University), Jan Byrne (Plant Pathologist, Michigan State University) and Fred Warner (Nematode Diagnostician, Michigan State University)
Peonies (Paeonia sp.) are herbaceous perennials that display large showy flowers with hues of lavender, pink, purple, red, or white. Peonies flower during spring months, leaving only green foliage behind in the landscape or cut flower fields during the summer. However, in some instances, peonies are forced in greenhouses for early or fall cut flowers sales.
Figure 1. Cut flower peony plants exhibiting a mosaic or mottled pattern of light and dark green on the leaves. (photo: W. Garrett Owen)
On a recent greenhouse visit, a crop of peonies that were being forced for cut flowers was observed. Multiple plants were exhibiting a mosaic or mottled pattern of light and dark green on the leaves (Fig. 1 to 3) and ringspots (Fig. 4). Flower buds also exhibited ringspots (Fig. 5). Uncertain of the virus, a sample of foliage was submitted to Michigan State University’s Diagnostic Services Lab for testing. Dr. Jan Byrne, MSU Diagnostic Services, in conjunction with another plant pathology lab group, tested the foliage with a molecular based test (qPCR). Foliage tested positive for Tobacco Rattle Virus (TRV), also known as Peony ringspot virus or Peony mosaic virus.
Figure 2. Peony leaf exhibiting mosaic or mottled light and dark green patterns on the leaves. (photo: W. Garrett Owen)
Tobacco Rattle Virus
TRV has a wide host range of over 400 species, including: anemone, bleeding heart, columbine, astilbe, clematis, delphinium, hosta, iris, peony, petunia, phlox, sunflower, tulip, and many agronomic, vegetable, and weed hosts. Many of the hosts listed above can remain symptomless.
Figure 3. Mosaic pattern caused by Tobacco Rattle Virus (TRV) on leaves of peony. (photo: W. Garrett Owen)
TRV often stays localized to the roots of infected hosts, but in the case of peony, the symptoms are expressed in the foliage and flowers. This virus is somewhat common in ornamentals; a 2013 survey done by Wisconsin Department of Agriculture, Trade and Consumer Protection detected TRV in 40% of all ornamentals, and 47% of all peony samples tested.
Vectors
The virus is transmitted by nematodes (genera Paratrichodorus and Trichodorus), also known collectively as stubby root nematodes. The nematodes are highly mobile in the growing substrate and are favored by abundant moisture content. TRV is also transmitted by vegetative propagation of infected plant material, movement of inoculated substrate, plant residue, or by propagation and harvesting tools.
Figure 4. Ringspots caused by Tobacco Rattle Virus (TRV) on leaves of peony. (photo: W. Garrett Owen)
Management
Early detection of virus infection is critical to prevent major crop loss. Once a plant is infected with TRV there are no treatment options or possible cures. The impact of TRV can vary from little impact to loss of plant vigor and reduction of flowers. Symptomatic plants with reduced vigor should be removed and destroyed.
Figure 5. Ringspots caused by Tobacco Rattle Virus (TRV) on flowers of peony. (photo: W. Garrett Owen)
In an established growing area, remove infected plants once plants have been confirmed with a viral infection to prevent spread to nearby healthy plants. To date, no nematicides are currently listed for stubbyroot nematodes, therefore avoid replanting the same area with a susceptible host plant species. In the field, soil fumigation may provide some control of the nematode vector.
Literature cited
Wisconsin Department of Agriculture, Trade and Consumer Protection. 2014. Viruses of ornamentals report 2013. 5 May 2017. http://pestsurvey.wi.gov/plantdisease/pdf/ornamentals/Ornamental-Virus-Powerpoint-2013.pdf
Source: e-GRO