The majority of exported alfalfa is grown in the western states. Exporters in these states have expressed concern that their overseas customers may not accept the presence of a genetically modified crop. Export consumer preference may also be highly dependent on price. At a minimum, buyers will need to initially differentiate transgenic hay from non-transgenic hay in their export lots. It is likely that the tools and management practices to achieve this will be in place prior to commercialization. For example, sensitive tests to detect the presence of the RR gene in hay and seed are currently being developed. Full approval by government agencies for animal feed and food in the United States and major export markets is currently being sought. The protein responsible for Roundup tolerance has already been approved for feed and food use in other crops in the primary export countries. Roundup Ready alfalfa will not be commercialized until regulatory and safety approval is obtained in the United States and Japan, according to Forage Genetics International and Monsanto. The Japan Feed Trade Association stated in July 2002 that it had no concerns about RR alfalfa, since biotechnology-enhanced canola, soybeans, corn, and cottonseed have been used successfully for feed in that country.Processing tomatoes are an important cash crop to annual agricultural systems in the Central Valley of California. California processing tomatoes have an annual farm gate value of $1.17 billion and are currently the 10th most valuable agricultural commodity produced in the state . In 2020, California produced 11.4 million tons of tomatoes across 230,000 acres, making up over 95% of US tomato production . California is also important on the international market, vertical grow rack system producing about 30% of the world’s processing tomatoes . The San Joaquin and Sacramento Valleys are the two major tomato growing regions in California, with five counties comprising the majority of the production acreage .

The California tomato industry is based on grower-processor contracts in which variety, amount, and often management are agreed upon before planting. Tomatoes typically are transplanted from March until July and harvested from July until October. Tomatoes are mostly planted in single or double plant lines on 60-inch, 66- inch, or 80-inch beds. The industry has widely adopted drip irrigation technology in recent decades, replacing furrow flood irrigation. Tomatoes are mechanically harvested when about 90% of the fruit are red and transported directly to processing facilities. With advances in genetics, management, and equipment, California processing tomato fields produce 50 tons of fruit per acre on average . The California tomato industry is highly specialized and utilizes many aspects of ‘custom farming’ in which a sub-contractor provides a specific service to the grower or processor. Tomatoes are mechanically transplanted, often by a third-party transplanting company or processor that may serve multiple growers and whose equipment may be used in many different fields each season. Tomato harvest follows a similar scheme, with harvesting companies or processors owning and operating harvest equipment, harvesting many fields across the state each year. California tomato growers must manage a variety of pests, including several weed species. Major weeds include black nightshade and hairy night shade , field bindweed , and small seeded broadleaves . Conventionally grown tomatoes utilize a combination of pre-emergence and post emergence herbicides along with cultivation and hand weeding for effective weed control. Before planting, a preplant incorporated herbicide is usually applied to the bed surface and incorporated with tillage equipment during final bed shaping. Common PPI or pre-emergence herbicides used in tomato include trifluralin , rimsulfuron , pendimethalin , S-metolochlor , and metribuzin . Later in the season, common post-emergence herbicides include clethodim , halosulfuron , metribuzin, rimsulfuron, sethoxydim , and carfentrazone . Integrated weed management control practices include crop rotation, use of transplants, drip irrigation, and cultivation . Broomrapes belong to the Orobanche and Phelipanche genera in the Orobanchaeceae family . Broomrapes are obligate parasites, lacking chlorophyll, thus gaining all of their nutrients from parasitized host plants .

Of the numerous broomrape species, seven are economically important to agricultural crops globally . These include crenate broomrape , nodding broomrape , sunflower broomrape , foetid broomrape , small broomrape , Egyptian broomrape , and branched broomrape . These broomrapes parasitize plants from the Apiaceae, Asteraceae, Brassicaceae, Fabaceae, and Solanaceae families including crops such as carrot, sunflower, rapeseed, faba bean, and tomato . Broomrapes cause economic damage to agricultural crops by reducing yield, with reproductive tissue disproportionately affected . In Chile, tomato growers report up to 80% crop loss in fields infested with branched broomrape , while growers in Sudan have reported total crop failure . Yield losses from broomrape infestations are thought to amount to $200 million annually in Turkey . Broomrape population density has increased in many near eastern and north African countries alongside production of broomrape-sensitive crops, threatening food supply in this region . Parasitic plants, including broomrapes, threaten the food security of communities around the globe, and research must be conducted to develop management strategies to reduce yield and economic losses . Branched broomrape is a parasitic plant native to the Mediterranean region of Eurasia. It is a holoparasite that parasitizes a host plant’s root system resulting in loss of vigor, yield reduction, and even death to the host . In the United States, there are four species of weedy broomrapes known to parasitize economically important agricultural crops: small broomrape, Louisiana broomrape , Egyptian broomrape, and branched broomrape . In the past several years, branched broomrape and Egyptian broomrape have been reported in California, including Yolo, Solano, and San Joaquin counties . In California, branched broomrape is “A” classified, being “an organism of known economic importance subject to California State enforced action involving eradication, quarantine regulation,containment, rejection, or other holding action,” while Egyptian broomrape is classified as a “Qlisted” noxious weed .

A field reported to be infested with an “A-listed” pest such as branched broomrape will be evaluated by the local county agriculture commissioner, quarantined, and that season’s crop destructed. For at least two years following this discovery, a hold order is placed on the field and only approved non-host rotational crops may be planted. Broomrape has been discovered in conventional, intensely managed fields, suggesting that conventional weed control practices and currently registered herbicides do not provide adequate broomrape control. Currently there are no proven management practices to selectively control branched broomrape in tomato, making this parasitic weed a serious threat to the California processing tomato industry. Branched broomrape was first discovered in California in 1903 in Butte County, followed by discoveries in Alameda, Colusa, Sacramento, San Benito, Santa Clara, San Joaquin, Ventura, and Yolo Counties . After a severe infestation was discovered in the Sacramento Valley in 1959, an intense industry wide eradication effort began at a cost of $1.5 million funded by a marketing order program . From 1973-1982, field scouting combined with fumigation with methyl bromide reduced broomrape seed banks and eradication was thought to have been successful . Branched broomrape is considered to be one of the most common and destructive broomrape species, infesting 2.6 million hectares of crops across Asia, North Africa, and the Mediterranean . Branched broomrape’s reemergence in California is extremely concerning to the viability of the California processing tomato industry for several reasons. California’s Mediterranean climate is similar to branched broomrape’s native range,agronomic practices make the proliferation and spread of broomrape’s minute seeds in and among fields highly likely, while broomrape’s phenological development make it inaccessible to conventional weed control practices and infestations difficult to detect. California’s regulatory environment make soil disinfetation via fumigation difficult and costly and there are no registered herbicides for broomrape control. Broomrape control strategies should focus on preattachment or very early during their lifecycles, when they are most vulnerable and before yield loss occurs . Broomrape’s unique phenology, specifically how it develops below the soil surface for 2/3 of its lifecycle, makes it unavailable to many conventional weed management techniques such as cultivation, post emergent herbicides, hand rogueing, etc. In addition, vertical farming racks rapid progression from emergence to flowering and relatively small stature make scouting for the parasite in tomato fields extremely difficult. Broomrape seeds are extremely small . Their small size results in limited seed carbohydrate reserve and broomrape species have evolved mechanisms to ensure successful host attachment. Broomrapes require several specific conditions for germination: a stratification period, sufficient soil moisture, and detection of specific root exudates .

Broomrape respond to a group of hormones known as strigolactones which include orobanchol, didehydroorobanchol, and solanacol . The detection of these exudates ensures the seed is within an acceptable distance to a host plant so that the broomrape radicle can intercept a host root and begin to form a haustorium. A haustorium is a modified rootstructure that connects parasitic plants to the host plant’s root vascular system, allowing the broomrape to become a sink for water and nutrients . After sufficient nutrients have accumulated, the broomrape will form a swollen nodule known as a tubercle to store nutrients and water . As the parasite matures, shoots will form from this tubercle, emerge above the soil surface, develop flowers that selfpollinate, and produce seed. Egyptian broomrape is the most limiting factor in tomato production in Israel and many neighboring countries accounting for 30% of total losses caused by all agronomic constraints and resulting in annual losses of up to $5 million . In Ethiopia, as of 2009, state sponsored farms had given up growing processing tomatoes in historically fertile regions because of broomrape infestations . In northern Israel, increasing infestations of broomrape over the last 30 years caused many growers to abandon tomato in lieu of less profitable non-host crops . Chile has historically faced challenges with broomrape in processing tomatoes , and the parasite has become increasingly widespread in that country. Researchers in Israel have developed a decision support system, named PICKIT, to manage Egyptian broomrape in processing tomatoes . The PICKIT system relies on a growing degree day based model to inform precise applications of targeted chemical applications. The PICKIT system has various herbicide programs related to different infestation levels and relies on pre-plant incorporated treatments , chemigation treatments , and foliar treatments. The PICKIT system utilizes two acetolactate synthase herbicides to control broomrape; a sulfonylurea applied preplant in conjuction with low dose applications of an imidazolinone. These herbicides include sulfosulfuron and imazapic . These applications are made according to the GDD model to target specific broomrape development stages, specifically when it is a nutrient sink on the tomato plant, resulting in rapid translocation of herbicide from the host to the parasite. In 2016, commercial tomato growers in Israel deployed the PICKIT system and achieved 95% Egyptian broomrape control in 33 fields . Israeli researchers have partnered with Chilean researchers to adapt the PICKIT system to Chilean processing tomato growing conditions. Chile, like California, has infestations of branched broomrape Branched broomrape has been found in several counties in California, including two of the top five producing counties . While currently an “A-list” quarantine pest requiring crop destruction, there is a high likelihood this pest will become widespread enough to require management programs like any other weed. The PICKIT system developed in Israel could provide similar management in California. However, because there are differences between the Israeli and California processing tomato systems and broomrape species , the PICKIT program must be evaluated and calibrated for use in California cropping systems. Imazapic is registered in the southern United States for use as an early post-emergence herbicide in peanuts but is not registered in California for use on any crops. Sulfosulfuron is registered in many states for use as a selective systemic herbicide on broadleaf weeds in wheat and is registered in California for non-crop use but not in tomato . In order for these herbicides to potentially be registered under an emergency use authorization for broomrape control or an indemnified label under California production conditions, there must be research on their performance and crop safety. The overall goal of this study was to determine if there was potential to adapt the PICKIT decision support system for branched broomrape control in California processing tomatoes and to provide herbicide registration support data needed to register PICKIT herbicides for special use in California. To evaluate the PICKIT system under California conditions, a series of crop safety and efficacy field experiments were conducted in 2019 and 2020.