Viruses devastate Salinas Valley lettuce

Richard Smith/UC

Salinas Valley lettuce exhibiting symptoms of INSV infection. The summer lettuce crop in California was significantly impacted by plant diseases caused by insect feeding and soil-borne pathogens. This led to a short supply of lettuce for U.S. markets and record-high prices.

Growers tallying their losses as consumer prices rise.

Todd Fitchette | Nov 09, 2022

Salinas Valley lettuce growers are tallying their losses from a set of plant viruses that continue to increase in frequency and intensity across the region.

“It was a disaster as we wrapped up the year,” said Salinas Valley lettuce grower Mark Pisoni. “I’ve seen 20-acre fields without a single head of lettuce harvested.”

https://6fdfb5948ae3bfb3b86d56ae1c97a8db.safeframe.googlesyndication.com/safeframe/1-0-39/html/container.html

As knowledge of the widespread outbreak spread, lettuce growers in the low desert of southern California and southwest Arizona planted lettuce earlier than normal. Some of those lettuce crops are being harvested this week as growers try to capture record-high lettuce prices. The U.S. Department of Agriculture reports iceberg prices above $90 per box, with romaine prices trailing that by a few dollars per box.

What caused this?

Laboratory tests of lettuce plants point to Impatiens necrotic spot virus (INSV) and Pythium wilt, according to Steven Koike, director, TriCal Diagnostics in Hollister, Calif. Koike admits that disease diagnosis can be confusing in that the symptoms resemble each other. This can make it difficult to determine the primary cause of death for the lettuce plant.

The two pathogens largely responsible for the lettuce deaths happen independently, but one may encourage the other. Mary Zischke, facilitator for the INSV and Pythium task force with the Grower Shipper Association in Salinas, said INSV seems to be the trigger Pythium wilt as plant stress increases.