Monterey County UCCE Farm Advisor Steve Koike has reported increased samples of confirmed Impatiens necrotic spot virus in Salinas Valley lettuce fields, and consultants are keeping an eye out for the thrips-transmitted virus, which can render plants unharvestable.

D’Arrigo Bros. PCA Valdez says he has seen INSV in three or four fields, with symptoms ranging from moderate to severe. INSV in romaine resembles bushy stump disease; symptoms start with spotting on tops of plants, which eventually turns necrotic, and various levels of stunting.

“In some fields, we’re just seeing spotting here or there, but in one case it devastated almost half our field,” Valdez says. “We had one field we ended up disking under because 40 percent was infested and we had a bad market.”

Because there is no control in the field for the virus, experts say controlling thrips is of paramount importance to prevent spread of the disease. Eliminating infected carriers of the virus, such as nearby infected crops or weeds, is also important.