Utah Pests News Winter 2008-09

click here for pdf version

A New Virus Possible on Utah Tomatoes

  Look for these tomato symptoms and report suspects to the UPPDL
 
  Mottled yellowing on a leaf infected with pepino mosaic virus.
 
  Infected fruit shows irregular ripening and a mottled pattern.

Pepino mosaic virus, also known as PepMV, is a relatively new disease of tomatoes in the U.S.  The virus was first identified on pepino (Solanum muricatum) in Peru in 1974, and on tomatoes (Lycopersicon esculentum) in the Netherlands in 1999.  Since then, PepMV has steadily spread throughout tomato producing regions, especially in greenhouse production facilities.  It was found in the U.S. in 2001 in California, Colorado, Texas, and Arizona, and has been identified in many other states since.

PepMV can cause a wide assortment of symptoms depending upon the tomato variety, the plant growth stage at the time of infection, and climatic and growth conditions.  Symptoms usually appear 2 to 3 weeks following infection. In general, the virus causes stunted growth and distorted, needle-like leaves on plant terminals.  Leaves can also have yellow spots and bubbly areas associated with mild interveinal chlorosis (yellowing).  Stems and flowering clusters will display brown streaks while fruit can show mosaic yellowing and irregular or uneven ripening.

The virus is easily transmitted by mechanical means either on hands or tools. Infected seed can transmit the virus as well, although at a lower frequency.

To avoid this disease, plant only seed of certified origin, varietal purity, and guaranteed to be virus free.  There is some research that suggests the virus can be inactivated in the seed-coat by soaking seed in the highly alkaline tri-sodium phosphate (TSP).

In greenhouse culture, maintain a sanitary working environment, and immediately quarantine and dispose of suspected virus-infected plants.  To prevent or minimize mechanical transmission of PepMV and other viruses, always work on the healthiest plants first, and then on the less vigorous plants.

Once a plant is infected, the only recourse is disposal and thorough clean-up of hands and tools before returning to the garden.

We suspect that PepMV probably occurs in Utah.  Some tomato samples submitted to the Utah Plant Pest Diagnostic Laboratory this summer did not appear to fit any viral symptomology I had encountered before.  Upon learning about PepMV, I believe this virus is what I was seeing. At that time, we did not have a suitable diagnostic test to identify the disease. Now, we have access to several options to readily and accurately diagnose PepMV.


-Kent Evans, Extension Plant Pathologist