Broomrape in California Processing Tomatoes
With an initial 10 years of aggressive effort and funding support from the entire California processing tomato industry, the goal being eradication of this rapidly spreading and invasive pest, this parasitic weed has received little attention since 1982. Although eradication was successfully achieved during this period of aggressive research, surveying and fumigation broomrape has made a reemergence in the last decade - with reports in San Benito County in 2009, San Joaquin County in 2014, Solano County in 2014, 2016 and 2021 and Yolo County, where there has been sustained and a growing number of reports, from 2017 - present. This is an area of concern which the entire industry must mobilize around. Broomrape will not go away on its own. We do not want this weed to spread throughout the state.
Some considerations around Broomrape:
- Broomrape is classified as a Class A pest by the CDFA. Because of this classification, although the outcome for any given processing tomato field which is infested with broomrape is up to the Ag Commissioner of the county in which the find is made, the State of California strongly suggests a "hold" order on the field in question for a period of at least 2 years. In practice this means that the entire crop revenue will be lost in the year of the find and in subsequent years only those rotational crops designated by the Ag Commissioner may be grown, harvested and sold.
- Broomrape is easily spread by equipment, boots and water.
- Broomrape is a prolific seed producer. One plant can produce over 100,000 seeds; each seed only 0.3 mm long. Broomrape seed has been documented to last in the soil for at least 25 years, and is expected to last even longer.
- The host range of Branched broomrape covers a number of economically important rotational crops in the Central Valley: safflower, sunflower, carrot, bell pepper, several brassica species, lettuce, several bean crops (chick pea, faba bean, vetch, clover), melon, potato, hemp, and many common weeds.
- Although broomrape is a weed which other processing tomato producing regions outside of the U.S. deal with (recent studies from Chile and Greece suggest a potential 80% crop loss) there has been no findings to date of easily transferable resistance genes. The methods of control which are in use elsewhere are complicated, costly and use chemistries which are not yet registered for use in tomatoes in the state of California.
If Broomrape is discovered in a field the below specific actions should be taken to reduce the risk of future spread and to drive the needed research work forward:
- The grower should be contacted immediately.
- As an industry we have the resources and the plan to do the needed research but we need more field sites and an accurate infestation baseline. If you, or someone you knows, has an impacted field please encourage them to get in contact with the CTRI (530-405-9469) prior to field burn-down.
- A designated area for cleaning should be assigned and solely utilized. This area will be an at risk location for future broomrape emergence and should be monitored carefully.
- Soil and plant debris should be knocked off of all equipment in areas of high concern using scrapers, air compressors and pressure washers (in that order).
- Quaternary ammonium, NOT BLEACH, is the cleaning agent which is proven to inhibit seed germination. Locally this can be bought under the labels: Clorox Pro Quaternary or MG 4-Quat. A solution of 1% is necessary for efficacy and should be used to spray down the equipment after soil and plant debris has been knocked off and pressure washing is completed. To provide maximum germination inhibition washed equipment should be left to sun dry, not sprayed down with water or other cleaning agents. These quaternary ammonium products can be purchased at local farm supply outlets.
- It is recommended that field workers use disposable coveralls and clean shoes by brushing off dirt and debris and then disenfecting soles similar to the equipment decontamination procedures described above.
The above procedure is time consuming and expensive, but in areas of high concern it is necessary to reduce the risk of spread to growers own fields and the fields of others by equipment movement.
As an industry we are working on both short and long term solutions in the following areas:
- Working with the USDA to get instances related to broomrape included under Federal Crop Insurance,
- Funding research around both spread reduction and long term management (multiple CTRI, CDFA, and IR4 funded projects from 2019 - present),
- Have submitted an emergency use exemption for and are eagerly awaiting approval from CDPR on the use of rimsulfuron via SSDI (a mitigation technique proven effective for long term management elsewhere),
- Determining the most effective route towards eradication of broomrape seed in known infested fields,
- and finally; developing a long term, statewide program - something like the BCTV Control Board with a non-voluntary assessment shared equally by both growers and processors - with a focus on just this issue.
Although these industry efforts are important, the most effective means to control the spread of this pest is active concern for the presence of this parasitic weed in processing tomato fields.
CTRI Funded Research:
Links to Other Information: