Distribution: Branched broomrape (Phelipanche ramosa) is native to Europe and is reported in more than 70 countries across northeastern and southern Africa, northern Europe, Australia, New Zealand, and North and South America. It was first introduced into the United States from Europe in 1890 on hemp crops in Kentucky, where it was probably brought in on packing material made of hay. So far, this species has been reported in seven states in the US, including Alabama, California, Illinois, Kentucky, New Jersey, Texas, and Virginia, and has naturalized in 35 counties. In California, branched broomrape was first seen in Butte County (1903) and later in Alameda County (1929). Eventually, it spread to other counties in California, including Colusa, Sacramento, San Benito, Santa Clara, San Joaquin, Ventura, and Yolo.
At that time, methyl bromide was readily available and affordable, and the California Department of Food and Agriculture conducted a robust surveillance and fumigation program alongside the grower community, effectively eradicating this pest from production fields. In the more recent resurgence of broomrape, with the restricted availability following the phase out, prohibitively high costs and extensive required regulatory buffer zones have made field application impossible in many locations. As a result, most growers rotate broomrape-infested fields to non-susceptible permanent crops. While other, more affordable soil fumigants exist, their efficacy against branched broomrape has not been examined under California regulatory and crop production conditions. That said, decades of work on methyl bromide alternatives on other crops have not provided efficacious alternatives. In addition, restrictions from both the California Department of Pesticide Regulation and the Air Resources Board make even these alternatives of limited use.