Processing tomato growers are struggling to contain a potentially devastating parasitic weed that had not been seen since growers waged a successful eradication campaign four decades ago.
Branched broomrape is so destructive in tomatoes that if it is detected in a grower’s field, quarantine regulations require that the crop be destroyed and the field be disked under, and common sense dictates that a grower rotate out of host crops for many years, said Brad Hanson, UC Cooperative Extension weed specialist, Department of Plant Sciences, UC Davis.
And even that may not be enough to prevent a resurgence of branched broomrape, which causes crop losses in processing tomatoes of up to 70 percent and even 80 percent.
“You could plant non-host crops for 20 years, but then when you plant tomatoes, branched broomrape could emerge again,” Hanson said. “It produces a large number of tiny seeds and many of them are long-lived.”
Hanson is part of a team of UC researchers enlisted by the processing tomato sector to work on a plan to contain the damage caused by branched broomrape, should it become established enough that the California Department of Food and Agriculture zero-tolerance quarantine strategy is replaced by management programs.
This parasitic weed, unable to produce its own chlorophyll, survives only by attaching to the roots of a host plant, often with severe consequences.
Branched broomrape has recently been detected in isolated fields in Yolo, Solano and San Joaquin counties, but the processing tomato business has a history of investing in efforts to eradicate this potentially disastrous weed.