Branched broomrape is a parasitic plant that is an “A-listed” noxious weed in California, requiring crop destruction and a hold order to be placed on reported fields. It has been reported in several commercial tomato fields in Yolo County in recent years and is of growing concern to the California tomato industry. Until recently, there have been no registered chemistries to control branched or Egyptian broomrape in California.

Rimsulfuron, marketed as Matrix SG by Corteva, is registered on tomatoes in California is widely used both PRE and POST for nightshade and other broadleaf weed control. Based on research conducted in Italy that showed promising broomrape control with rimsulfuron applied in the irrigation water through surface drip lines (Conversa et al.), we did pilot studies in 2021 and 2022 in California.

With initially promising results, the California Tomato Research Institute submitted a 24c label (“Special Local Need”) request to California Department of Pesticide Regulation. The request was to add a chemigation application technique specifically for management of broomrape. The 24c label was approved in September 2022 and is available.

A breakdown of the 24c describing the approved chemigation application process is below.

From Corteva Matrix Label (https://ucanr.edu/blogs/UCDWeedScience/blogfiles/97715.pdf):

• For use on processing tomato for management of broomrape (Phelipanche ramosa, aka Orobanche ramosa) and Egyptian broomrape (Phelipache aegyptiaca). For management of broomrape, apply Matrix SG through buried- or surface-drip irrigation tubing to transplanted tomato. Apply at an application rate of 1.33 oz/A for up to 3 applications per season at approximately 30, 50 and 70 days after transplanting.
• Refer to product label for Matrix SG for Use Precautions, Mixing and Application directions.
• Surface or buried drip irrigation applications simulate banded applications.
• The amount of water and injection time may vary depending on soil type and irrigation system used. Introduce Matrix SG into the irrigation system at approximately the midpoint of the irrigation set to limit movement of the herbicide beyond the tomato root zone, where broomrape germination and attachment occurs, which may improve broomrape control. Factors such as soil type, irrigation system, injection timing and length, drip tape placement, etc. may affect weed control when Matrix SG is used through the drip irrigation system.
• After Matrix SG has been evenly applied across the field, flush the irrigation system prior to ending the irrigation.
• Do not apply more than a total of 4.0 oz/A Matrix SG (0.0625 lb ai/A rimsulfuron) on tomato during the same year.
• Do not make more than 3 applications of Matrix SG per year.
• Preharvest Interval: Do not apply within 45 days of harvest.  
• This label must be in the possession of the user at the time of application. Follow all recommendations and restrictions on the Matrix SG Section 3 labeling.

It is important to note that when using rimsulfuron as a chemigated material following the label, you are using the yearly maximum rate of 4 oz/acre. For growers that do not use rimsulfuron as a PRE or POST product, this will not change current weed control programs. However, if growers currently utilize rimsulfuron as a PRE or POST product in their current programs, it will need to be excluded to avoid going over the annual 4 oz/acre maximum. This may affect general weed control, as rimsulfuron is often used to target nightshade species. Research into alternatives to rimsulfuron for general weed control in processing tomatoes will begin in 2023.

As with any pesticide, it is important to read and follow the most current label instructions for application.

We would like to thank the California Tomato Research Institute for funding ongoing broomrape management research and coordinating the 24c request, Corteva Agrisciences for providing product for the research and internal data from the US and Europe to CDPR, and our cooperators who hosted herbicide research trials that support the entire processing tomato industry.

 

Matt Fatino is a UC Davis Ph.D. student with Brad Hanson's Lab.

 

A social media campaign aims to improve health of residents at low-income housing sites by encouraging vegetable intake through container gardening

The Issue 

In the U.S., vegetable intake is lowest among adults with low income. Eating the recommended daily amount of vegetables is important for overall health. Gardening has a role in promoting vegetable consumption. CalFresh Healthy Living, University of California Cooperative Extension (CFHL, UCCE) Butte Cluster and UC Master Gardeners, kicked off their second annual “Great Tomato Challenge” in 2022, a social media contest for Community Housing Improvement Program (CHIP).CHIP is a non-profit corporation that serves Butte, Glenn, Yuba and Colusa Counties by assisting low-income residents with quality, affordable housing. The goal of the “Great Tomato Challenge” event is to promote container gardening at apartment complexes through a workshop and social media contest.

How UC Delivers

The 1.5 hour Fresh from the Garden curriculum workshops took place at 5 CHIP sites, having been advertised in English, Spanish, and Hmong language flyers. Over 40 adults learned how to harvest, store, and prepare fresh tomatoes. Those who opted to sign up for the social media challenge received a tomato plant and agreed to submit photos, drawings, and recipes accessed on the CFHL, UCCE Butte Cluster Facebook page.

UC Master Gardeners partnered with CFHL, UCCE Butte Cluster to provide Facebook Live sessions to answer any questions participants had about growing their tomato plant. CFHL, UCCE Butte Cluster Educators translated questions and answers into Spanish and Hmong. 

Three winners were selected from the 36 contestants from the following categories: best photo of you and your tomato plant; best tomato drawing; and best recipe photo. Winners received a colander, whole wheat spaghetti noodles, and a jar of locally-sourced pasta sauce.

The Impact 

Eighteen participants completed an "Intent to Change" Survey for the workshop. Thirty-eight percent reported that they would: “eat more than 1 kind of vegetable each day more often within the next week.” One participant wrote “This workshop helps my family to be healthier.” Gardening has a role in promoting greater vegetable intake and variety among families with low income which improves overall health.

CalFresh Healthy Living, UCCE Butte Cluster will continue this challenge annually and is considering starting an additional annual challenge, using the same model, for a cool-season vegetable such as beets.

A child's drawing of a tomato fruit

With spring quickly approaching, many gardeners are dreaming of their garden preparations:  ordering seeds, prepping the soil, cleaning up from last year.  With all these things in mind, have you ever thought about saving the seeds from the crops you grow? There are many benefits in considering this.

• Seeds and plants saved become acclimated to our environment, climate
• There is a greater variety of vegetables to grow
• There may be more genetic diversity when growing old-time veggies
• It is can be cost effective due to higher seed prices

Hybrids vs. Heirlooms

With this in mind, there are some important things to know about what veggies to grow in order to save the seeds. 

There are two major types of seeds:   Hybrid and Heirloom seeds

• Hybrid seeds have been cross pollinated from two different varieties in the same plant species. They are crossed to produce seeds that carry desired characteristics or appearances.
  • Seeds saved from hybrid plants will revert back to their parent plants.
• Heirloom Seeds are non-Hybrid, and open pollinated.
  • Heirloom Seeds are usually more than fifty years old and have been passed down from generation to generation
  • If you plant an Heirloom seed that you have saved from an Heirloom plant, it will grow true to the parent plant.

Spacing plants to prevent cross-pollination

For the seed saving beginner, here is a list of seeds that are easy to save because they are self-pollinating.  However, despite being self-pollinating, it may still be important to space crops for guaranteed purity.  Pollinators can be attracted to the flowers and help with pollination, thus producing offspring with new characteristics. To keep seed varieties ‘pure', using ‘isolation' –planting related varieties at appropriate distance to minimize the chance of crossing.  

How long do seeds last?

This is dependent on the type of seed, but also on how they are taken care of after you save them. To ensure saved seeds will sprout in the future, store them in a cool, dry place away from moisture, heat, and light. 

Common Beans

The seed is the mature bean.  Allow the bean pod to dry on the vine. If growing more than one variety, isolate by at least 20 feet.

• Harvest the dried bean pods and place in a paper bag.
• Dry for a week or more before separating the bean from its pod.
• Grow and harvest from at least 10 plants of the same variety for diversity.  
• Seeds can last up to 4 years.

Eggplant

Allow several fruits from at least 10 plants to ripen far past the edible stage. The skin will become a dark yellow or yellowish-brown color. If growing more than one variety, isolate by at least by 50 feet.

• Mash the pulp by hand as best as you can. The seeds are hard, smooth and plump and won't damage easily.
• Toss seeds and pulp into a bucket of water and stir until pulp separates from the seeds. Seeds will sink.
• Rinse until the water comes out clear. Pour seeds through a screen, spread them in a thin layer and dry for about 3 weeks.
• Seeds can last 3-6 years

Garlic

The clove is the ‘seed', so propagation is achieved by replanting cloves. It is generally agreed that planting the largest cloves will produce the largest bulbs next year. Isolation is not necessary even if growing several varieties.

• After harvest, store garlic at room temperature to prevent premature sprouting.
• Plant from your crop every year.

Lettuce

Seeds are very easy to save.  Allow a dozen plants to grow, unharvested, through the spring and summer.  They will “bolt” (send up seed heads). Isolate by 20 feet if growing more than one variety. Once the seed heads are a yellowing-tan color and very dry, they are ready to save.

• Cut at the stem and place in a paper bag. Once dry, crush the heads and sift to separate the seeds from the chaff.
• Harvest from at least 10 plants of the same variety.
• Seeds can last 2-4 years.

Okra

Pods should be left on the plants until fully mature. Okra is self-pollinating but will cross via bees if two varieties are planted near each other. Plant one variety to ensure purity.

• Pick just as the seeds begin to split.
• Clip and store in paper bag for a few weeks.
• Seeds can last up to 3 years.

Peas

Peas are self-pollinating, however, keep favored plant 20 feet away if growing more than one variety.

• Allow pods to slightly dry on the vine before harvesting.
• When picked, place in a paper bag and allow to dry further for a week or two.
• Thresh them from the pod, and store in a jar or envelope.
• Seeds can last up to 5 years

Peppers

Peppers are very easy to save. Once ripe, it's time to harvest the seeds. Peppers are self-pollinating but will occasionally cross via bees if two varieties are planted near each other. Plant varieties 100 feet away.

• Cut open the ripe fruit, scrape out the seeds and let dry on a paper plate for a week before storing in a jar. 
• Seeds can last up to 2 years.

Tomatoes

Tomatoes are mostly self-pollinating, but to ensure purity, separate the favored plant by 10 feet. Allow the fruit to fully ripen on the stem before harvesting. 

• Cut the tomato open and scoop out the seeds.
• Place the seeds in a jar of water and allow to ferment until a white mold forms on top of the water.
• During this process, cover the top of the jar with paper towel to keep flies out.
• Rinse the contents of the jar with water until it comes out clear.
• Allow seeds to settle between rinses. Good seeds will sink to the bottom each time.
• Spread seeds out on a paper plate and allow to dry for 3-4 days before storing in a paper envelope.
• Seeds can last up to 5 years.
• Watch our Tomato Seed Saving Video at https://www.youtube.com/watch?v=FvTCfcpLQgw&t=1s

Hopefully, these suggestions will inspire you to begin the exciting adventure of saving your own seeds from the crops you grow.  Happy Gardening!!!

Heidi Aufdermaur has been a UCCE Stanislaus County Master Gardener since 2019; Heidi took all photos used in this article.

Resources

California Master Gardener Handbook.

Seeds Matter. www.seedmatters.org

The Heirloom Life Gardener.  Bake Creek Heirloom Seed Company.  Jere and Emilee Gettle.

 

Conventional processing tomato weed management in California often includes pre-plant herbicides (trifluralin and/or s-metolachlor), followed by cultivation, and hand hoeing. Rimsulfuron herbicide can also be used in conventional systems and can be applied either pre or post transplanting. Post-transplant applications of rimsulfuron can selectively remove nightshades if applied when the weeds are very young, no more than 2 true leaves, however, long plant-back restrictions may limit its use. Therefore, the use of hand crews is often needed to remove weeds that emerge in the plant row, where standard cultivation equipment is ineffective.

Automated weeders, or robotic weeders, use cameras and computers to distinguish crops from weeds. They are equipped with either spray nozzles or cultivators to remove weeds within the crop row. Commercially available for about 10 years, these complex machines are very expensive but have shown promising results in transplanted crops in Salinas, CA and Yuma, AZ. Gaining popularity in the Central Valley is the finger weeder, a relatively simple and low-priced mechanical cultivator designed to remove weeds within the crop row. The mechanism was developed by K.U.L.T.-Kress in Germany. The system uses interlocking rubber fingers (Figure 1) to remove small weeds in the plant row once transplants are established. Finger weeders can also be adapted to and added to existing cultivators and modified for individual grower needs.

While both robotic cultivators and finger weeders have been used and evaluated in many vegetable crops, there has been little research evaluating these tools in processing tomatoes and how well they may complement or replace a traditional herbicide program. The main objective of this project was to evaluate crop safety, weed control, time, and costs associated with using mechanical cultivators as part of a conventional weed management program in processing tomatoes. This work is supported by the California Tomato Research Institute, with assistance from grower cooperators.

 

Methods

This project was conducted in 2020 and 2021 in both Colusa and Merced counties.UCCE Vegetable Crops Advisor, Scott Stoddard, led project efforts in Merced County. Only the Colusa site data will be presented here. The Colusa County field site was located just north of Colusa, CA and the same site was used both years. The field was transplanted to double row tomatoes, on 60” beds. Plot size was 5 beds by 250 ft length, except for Control (Treatment 4) which was 5 beds by 100 ft length to minimize impact. Each treatment was replicated three times. The following treatments were evaluated:

1. Rimsulfuron at 2oz/A (grower standard)
2. Automated cultivator (1 bed/pass)
3. Finger weeder mechanical cultivator (5 beds/pass)
4. Control: no in-row cultivation, no post-transplant herbicide.

The entire field, including trial plots, received a pre-plant application of s-metolachlor/trifluralin, standard cultivation to remove weeds outside of plant row, and s-metolachlor/trifluralin lay-by. Operations were the same for 2021. Plant stands were assessed before and after cultivator passes. Weeds were counted before treatment, 2 weeks, and 4 weeks after treatment in the center bed of each plot. Crews hand-weeded one month before harvest in 2020 and 7 weeks before scheduled harvest in 2021. Weeds were counted before and after hand-weeding passes. Cultivators and hand-weeding crews were timed as they moved through the field. Ten feet from the center bed of each plot was harvested by hand and sorted for red, green and culled fruit. Steve Fennimore, UCCE Weed Specialist, provided the Robovator automated cultivator, made by F. Poulsen Engineering ApS in Denmark (Figure 2). The finger weeder was a 2020 purchase by the grower cooperator (Figure 3). The main weeds present in the field included bindweed, lambsquarters, pigweed, puncturevine and thorn apple (Figure 4).

 

Results

Weed control results are shown in Figure 5. In 2020, the Robovator and finger weeder did an excellent job of weed control on all plots. In 2020, the Robovator worked very well, providing up to 85% control on average two weeks and four weeks after it was run, and we saw very little crop injury (Figure 6). However in 2021, due to heavy winds in early May, the young tomato plants were not upright, and the robotic weeder had difficulty distinguishing where the stem of the plant was compared to the top of the plant. These plots suffered 11-19% crop loss, which also occurred at the Merced site in 2020 (Figure 7). Despite the crop injury, average weed control was 71% after 2 weeks in 2021 and there was no negative impact on yield. The finger weeder provided 66% on average two weeks post-treatment in 2020. It is worth noting that by plot, the finger weeder provided over 90% control post-treatment in two of the plots. The third plot showed poor control due to heavy bindweed pressure, therefore bringing the average down. The finger weeder also provided excellent control at the Merced site in 2020. In 2021, the finger weeder provided an average of 56% control two weeks after treatment and 66% control four weeks after treatment. The grower standard herbicide treatment of rimsulfuron provided 34% and 44% control on average at two and four weeks after application in 2021, but it is worth noting this field did not have heavy nightshade pressure. Despite the numeric differences between treatments shown in Figure 5, there was no significant difference between the cultivator treatments and the grower standard (rimsulfuron) for weed control in either year, due to high variation in weed pressure between plots, which can be seen from the high standard error values.

 

In general, hand weeding provided 60-100% control between 2020 and 2021. Hand weeding times and costs were not significantly different between the grower standard (rimsulfuron), finger weeder or robotic weeder treatments in both years and all treatments significantly decreased time and costs compared to the control plots (Table 1). Weed pressure increased in 2021 leading to higher weed counts and longer hand weeding times and associated costs compared to 2020. There were no significant differences in yield between plots in 2020 or 2021.

 

Summary

Field variation and weed species influenced weed pressure and control, some plots had >300 weeds and others only had 10. There was poor bindweed control from cultivators and hand-weeding crews, which was expected based on the biology of bindweed. Both in-row cultivators provided decent control in 2020. The finger weeder was able to cover five beds per pass and moved quickly through the field compared to the Robovator. All treatments significantly reduced hand weeding costs and time compared to the control in 2020. Despite the crop injury issues with the automated cultivator in 2021, the Robovator plots resulted in the highest % weed control and fastest hand-weeding times.

The finger weeder is gaining popularity in the Sacramento Valley and provides an option for in-row mechanical cultivation without the expense of an automated weeder. Timing is key when using either type of in-row cultivator. The size of the tomato plant and the size of emerging weeds needs to be just right to avoid crop injury while also removing young weeds. The finger weeder provided excellent weed control in Colusa and Merced in 2020, despite poor bindweed control. The automated weeder provided excellent weed control at the Colusa site, but with high crop injury and technological challenges. When working correctly, automated weeders provide accurate and precise weed control, though issues can arise when conditions are not as favorable. In-row mechanical cultivators, like the finger weeder, are more economical, but automated weeders are becoming more prevalent in California for vegetable production systems.

Many thanks to the California Tomato Research Institute, Steve Fennimore, Scott Stoddard, and our grower cooperators for working with us on this project.

 

Amber Vinchesi-Vahl is the UC Cooperative Extension Vegetable Crops Advisor for Colusa, Sutter and Yuba counties.

This article was published in the March/April 2022 issue of Progressive Crop Consultant.