Tracking tomato disease poses challenges

Tomatoes and potatoes across the northeast have been devastated this year by a disease known as late blight.  A major national grower, Bonnie Plants, has come under scrutiny for its alleged role in the outbreak.   

Infected Bonnie tomato plants were found at Lowes in Ithaca and retail outlets on Long Island in early June.  Since then, the disease has spread widely throughout the county.  Quantifying the loss is difficult, according to CCE-TC, because so many farms are affected.

A company press release asserts that “Bonnie Plants cannot justifiably be targeted as the source for the recent Northeastern occurrence of Late Blight” and voluntarily responded to the discovery of the disease by destroying more than $1 million dollars worth of plants. Bonnie, which was founded in 1918, plants more than $400 million worth of vegetables each year.

“It will take an investigation to determine where the pathogen came from,” says Dr. William Fry, Cornell University professor, Dean of Faculty, and expert on the late blight pathogen.  Recently, he spoke to more than 30 concerned home gardeners at a CCE-TC information session.   

According to Bonnie Plants, state inspectors had not found any sign on the disease in their facilities until July 7, when five tomato plants tested positive for it in the New Berlin, NY greenhouse (the source of most Bonnie plants available for sale in Tompkins County).  The company notes that the disease had earlier been discovered on commercial potato plants in NYS.   

Several strains of the late blight pathogen exist, Fry explained to me in a phone conversation.  His lab has examined about 40 to 50 samples from tomato plants in gardens, farms, and garden stores across New York State, and they seem to be the same strain genetically, which appears to be different from the strain present on NYS potatoes this year.   

Due to our harsh winters and the pathogen’s biology, late blight cannot survive on tomato plants, in tomato seeds, or in soil from one year to the next year, according to Fry.  Potato blight strains, however, can remain in tubers and resurface in subsequent years.   

In an email to me, Bonnie Plants General Manager Dennis Thomas wrote, “In addition to state inspections, Bonnie’s greenhouse employees are well acquainted with signs of plant disease and they continually monitor and conduct inspections on all plants for signs of any plant disease on a daily basis."  Additionally, he wrote, "It is believed that the reason Bonnie has been targeted as the source of the disease is because Bonnie supplies literally millions of tomato plants to retailers nationwide, and tomato plants host Late Blight disease. The number of other tomato brands at retailers, nationwide, is quite small in comparison. However, even though Bonnie was (unjustly) targeted as the 'source' of the disease, Bonnie acted swiftly, voluntarily and responsibly and removed all tomato plants from NY retail without ever having clear, scientific proof that the plants, in fact, had Late Blight disease.  Bonnie did so, at a cost of over a million dollars and extreme logistics, because the removal of host plants would certainly curtail any further spread of the disease- and this is where Bonnie’s interest rested—curtailing the spread of the disease."

Looking ahead, next year is a new year and the disease outlook could be quite different.

(9/4 note: this post was edited slightly from its original version)