Green Blog

Grow cover crops to attract beneficial insects, add nutrients, suppress weeds and build soil

George Washington, the father of our country, said it well when he proclaimed he grew “crops to eat and sell” and “crops to replenish the soil.”

Generations of farmers follow his footsteps.

Cover crops (also known as green manures) are plants primarily grown for the benefit of the soil rather than for crop yield. With autumn only a few months away, now's a good time to think about planting cool-season cover crop seed mixes for your farm or garden.

Why grow cover crops?

The benefits of cover cropping include reduced soil erosion, adding organic matter, nutrients, and mycorrhizae to the soil, and weed and nematode suppression. Cover crops also increase nutrient retention and water infiltration. And some, such as radish, break into compacted soil layers, making it easier for the following crop's roots to develop more fully. Flowering cover crops on farms also increase beneficial insects, including bees and natural enemies, that provide pollination and pest control services in crop production.

How do cover crops benefit natural enemies?

Beneficial insects need nectar and pollen to survive and reproduce. For example, adult parasitoid wasps feed on flowers, while the parasitoid larvae prey on pests such as aphids, caterpillars, and stink bugs. Lady beetle, aka ladybugs, feed on flowers, especially during times of prey scarcity. In addition to flowers, cover crops, such as vetch and bell (fava) beans, have extra-floral nectaries or spurs at the base of the leaves. These secrete a sugary syrup that attracts beneficial insects, such as syrphid flies to control aphids.

Insectary cover crop seed mixes.

Winter mixes that attract beneficial insects (aka Insectary Plants) and fix nitrogen include bell beans, clovers, field peas, and vetch. Other insectary plants to add to a cover crop mix include forbs such as baby blue eyes, poppies, phacelia, purple Chinese houses, sweet alyssum, and tidy tips. Small grains (triticale, barley, and rye) are good pollen sources for beneficial insects. It's a good idea to order insectary cover crop mixes from local sources to avoid potential introduction of non-native forb-type plants from other areas.

Cover crops to perhaps avoid in some crop rotations.

Avoid cover crop species that host arthropod pests or plant pathogens that can damage nearby crops. For example, bell beans are a key host for tomato spotted wilt virus vectored by thrips insects, UC IPM. Mustards attract beneficial insects, but are significant hosts for pests such as stink bugs, cucumber beetles, flea beetles, and lygus bugs. Alfalfa has extra-floral nectaries, but is not a recommended insectary plant because it hosts pathogens, including alfalfa mosaic virus that infects a number of crops, including tomatoes (UC IPM).

How important are floral resources for natural enemies?  

In a 1998 research article, Beneficial insects move from flowering plants to nearby crops, published in California Agriculture journal, I pointed out that beneficial insects extensively use flowering cover crops. In a mark-and-recapture study in an almond orchard with a cover crop, 80 percent of the syrphid flies and 40 percent of the lacewings (both aphid feeders) trapped in the trees fed on flowers and extra-floral resources that the insectary plants provided, as did 10 percent of the parasitoid wasps, which prey on peach twig borer.

Balancing multiple needs of cover crops.

Note that legumes need to be mowed or disked prior to full bloom for maximum nitrogen fixation, limiting floral resources. To favor beneficial insects, don't mow or disk all of your cover crop at once; instead, leave occasional strips of flowering plants on your farm. Beneficial insects will find the flowers, as they move around (at least 600 feet for many natural enemies and over a mile for bees). If frost is a concern in your orchard, consider planting strips of low-growing insectary plants, such as tidy tips and other forbs listed above. Be sure to select seed mixes that work with surrounding crops.

George Washington used cover crops to replenish the soil; they're also good for the soul when you savor the benefits, especially all the flowers and beneficial insects attracted to them. Why not play a game of “I Spy” in your cover crop and see if you can find a bumble bee or one of the myriad of natural enemies featured in the UC IPM poster, Meet the Beneficials. 

 

Additional reading

Flowering cover crops support wild bees and a regional sustainability agenda, part of the June 2018 research update in California Agriculture journal.

UC ANR publications on cover crops:

Cover crops for California Agriculture

Cover Cropping for Vegetable Production

Cover Cropping and Conservation Tillage in California Processing Tomatoes

Small Grain Cover Crops

Cowpea Production: Sample Costs and Benefits as a Summer Cover Crop

Cover Cropping in Vineyards: A Grower's Handbook

Cover Crops for Walnut Orchards

UCCE helps farmers see the potential in agricultural use of drones

In the late 1800s, when automobiles started replacing horses in the United States, farmers were likely pondering how the new technology could be adapted for agricultural production. Before long, tractors revolutionized the industry.

A similar scenario unfolded in June at a UC Cooperative Extension field day in Merced County. Farmers, scientists and entrepreneurs gathered at Bowles Farm in Los Banos to learn how drones may be deployed on farms of the future to improve irrigation, fertilization and pest management practices and monitor the crop to maximize yield and profit.

Instead of driving a pickup truck around the perimeter of the field, pushing through hip-high row crops, or meticulously sampling dozens of tree leaves, a quick fly-over with the right equipment could provide farmers all the data they need to make production decisions.

This won't happen tomorrow. Regulations still hamper drone use and the cost of some equipment is prohibitive. But UCCE advisor David Doll is working with scientists at UC Merced and Fresno State to find low-cost alternatives for data collection and analysis that will make the information collected by drones of value to farmers.

“We were able to get good correlation with plant water stress using a thermal camera, however the platform is too expensive,” Doll said.

Doll's research, funded by a grant from UC Agriculture and Natural Resources, uses data from hundreds of drone flights over an almond orchard. The project has shown that monitoring perennial cropping systems from the sky presents challenges.

“Perennial crops will have water stress before the crops show stress,” Doll said. “We need to find an algorithm to identify water stress before it's too late for the orchard.”

Bowles Farming Company, which hosted the field day, flies drones over its farms three days a week, said Justin Metz of the company's technology integration team. The high-definition imagery is shared with the on-staff agronomist, who can diagnose emerging issues.

“Our use of drones is in its infancy, but we're ahead of others,” Metz said. “Knowing the capabilities is really exciting. Drones are here, and they're going to stay.”

UCCE agronomy and weed science advisor Lynn Sosnoskie attended the drone field day to gather ideas and make contacts. She believes drones have the potential to monitor crops for herbicide injury.

“I want to ground truth drone images to see if they can predict yield loss,” Sosnoskie said.

Retired pest control adviser Richard Stewart, one of about 100 attendees, is considering how drones could be used to monitor for rodent damage in irrigation ditch banks.

“I've never see anyone do that,” he said. “I'm just looking into it. It's a new idea.”

Reduce food waste to combat world hunger and slow global climate change

One-third of the world's food is spoiled or tossed rather than eaten, a fact that is tragic when nearly one billion people go hungry. The injustice of food waste is worsened by the fact that food decomposing in landfills emits greenhouse gases that contribute to climate change.

The conventional management of municipal waste in landfills places discarded food and plant matter into an anaerobic environment, initiating a chemical reaction that turns biomass into biogas – specifically methane, a greenhouse gas that's 28 times more potent than carbon dioxide.

Reducing the volume of the California waste stream and reducing the emission of greenhouse gases into the atmosphere are objectives that have spurred state lawmakers to enact regulations, such as Assembly Bill 939, which in 1985 mandated a 50 percent diversion of solid waste away from landfills. A 1989 update to the law also required municipalities to reach out to residents with training on greenwaste etiquette and waste diversion.

UC Cooperative Extension is working closely with the cities and county of Santa Clara in a far-reaching program to divert organic matter – food and green waste – from landfills by composting and using the product to enrich soil in the home garden.

In early June, UC Master Composter Don Krafft conducted a class on composting in a Palo Alto community center, one of 22 sessions to be offered in the spring and summer of 2018. A retired telecommunications professional, Krafft's interest in composting stemmed from his work as a Master Gardener for UC Cooperative Extension.

“I live in a townhouse, so I do worm composting. The No. 1 reason,” Krafft said, “is because it's fun.”

The composting workshops are just one component of the UC Cooperative Extension's composting efforts in Santa Clara County, led by UCCE staff research associate Cole Smith. The Environmental Protection Agency has a food recovery hierarchy, he said, which has source reduction at the top, followed by feeding the hungry, feeding animals, industrial uses, then composting, and finally delivery to a landfill.

“By diverting and recycling at the source, we reduce the diesel footprint for hauling,” Smith said. “We want to tighten the nutrient loop and the backyard is the closest place.”

The classic composting technique involves layering “browns” – dry leaves, sawdust, woody cuttings, straw, shredded newspaper and cardboard – with “greens” – grass clippings, food scraps, coffee grounds, egg shells, green plant cuttings and manure.

“Start and end with browns to keep the fruit flies down,” Krafft said. “It's like making lasagna.”

Certain foods should not be added to the home compost heap – including meat, whole eggs and dairy products.

The mix of greens and browns should be maintained evenly moist, but not soaked, and turned at regular intervals, the more often, the faster the materials decompose.

“Maintenance is completely adaptable. You can do a lot or a little and it gets easier with time,” Krafft assured the audience.

The compost is ready when the components are no longer recognizable and the pile is cold. Once composted, the former waste becomes a stable soil amendment with a pleasant earthy smell. It's then ready to be applied in the garden.

UCCE Santa Clara has also developed a three-acre composting demonstration site at Martial Cottle Park in San Jose, where volunteers are composting animal waste generated by the 4-H animal program in a project made possible by a grant from the Santa Clara Valley Water District.

The facility includes a variety of commercial and homemade compost containers, including one built by a volunteer that employs bicycle power to mix compost.

The issue of food waste is capturing significant attention not only in Santa Clara County and not only in the garden. Food waste reaches across multiple disciplines, including agriculture, environment, and public health, key areas of UC Agriculture and Natural Resources' efforts.

“Food waste is a symptom of our food systems and food practices going astray,” said Wendi Gosliner, a project scientist in the UC ANR Nutrition Policy Institute, co-founder of California Food Waste Prevention Week, which was held for the first time in March 2018.

“Addressing the issue requires researchers, practitioners, policy makers, communities and individuals to innovate and develop new solutions,” Gosliner said.

UC ANR programs that have a hand in food waste prevention include:

• Nutrition education programs – UC CalFresh and the Expanded Food and Nutrition Education Program – which teach families how to eat right and economize
• The UC Master Food Preserver Program, which offers training on canning, freezing, drying, fermenting and other techniques to preserve a summertime food bounty to eat later
• The 4-H Youth Development program, which trains youth in recycling and is providing animal manure for the Santa Clara compost demonstration site
• The UC Master Gardener Program, which endorses the use of homemade compost
• Nutrition Policy Institute, which conducts research that informs nutrition policy and programs for healthy children, families and communities

“UC ANR translates research to practice in helping communities manage food resources, learn to preserve food and compost – all parts of the food waste solution,” Gosliner said. “Thinking about these and other UC ANR activities under the umbrella of food waste prevention can help to better nourish people, protect the environment and conserve human, natural and financial resources.

National Pollinator Week: Open house at UC Davis Bee Garden

June 18-24 is National Pollinator Week.

Do you know where your pollinators are? Think bees, birds, butterflies, bats and beetles.

And think flies. Especially syrphid flies, also known as "flower flies" and "hover flies."

The UC Davis Department of Entomology and Nematology is hosting an open house during National Pollinator Week from 11 a.m. to 2 p.m. at its bee garden, Häagen-Dazs Honey Bee Haven on Bee Biology Road, west of the central UC Davis campus.

Here's what you can expect to see or do:

• learn how to catch and observe bees up close
• see honey bees at work in an observation beehive
• learn about bee diversity and identification
• learn about what and how to plant for bees
• learn about growing and good pollination in home fruit gardens
• see easy-to-grow bee plants and solitary bee houses available for a donation to the garden.

The Häagen-Dazs Honey Bee Haven, installed in the fall of 2009 and located next to the Harry H. Laidlaw Jr. Honey Bee Research Facility on Bee Biology Road, off Hopkins Road, is a half-acre garden devoted to bee pollinator conservation and education. It was founded and sprang to life during the term of interim department chair, Professor Lynn Kimsey, director of the Bohart Museum of Entomology, who coordinated the entire project. Kimsey was singled out for her work when the Pacific Branch of the Entomological Society of America honored her and four others – "The Bee Team"– with the 2013 outstanding team award. 

A Sausalito team – landscape architects Donald Sibbett and Ann F. Baker, interpretative planner Jessica Brainard and exhibit designer Chika Kurotaki – won the design competition. The judges were Professor Kimsey; founding garden manager Missy Borel (now Missy Borel Gable), then of the California Center for Urban Horticulture; David Fujino, executive director, California Center for Urban Horticulture at UC Davis; Aaron Majors, construction department manager, Cagwin & Dorward Landscape Contractors, based in Novato; Diane McIntyre, senior public relations manager, Häagen-Dazs ice cream; Heath Schenker, professor of environmental design, UC Davis; Jacob Voit, sustainability manager and construction project manager, Cagwin and Dorward Landscape Contractors; and Kathy Keatley Garvey, communications specialist, UC Davis Department of Entomology and Nematology.

Others with a key role in the founding and "look" of the garden included the UC Davis Art/Science Fusion Program, founded and directed by the duo of entomologist/artist Diane Ullman, professor and former chair of the UC Davis Department of Entomology, and self-described "rock artist" Donna Billick of Davis. Miss Bee Haven, a six-foot long worker bee sculpture, the work of Billick, anchors the garden. The art in the garden is the work of their students, ranging from those in Entomology 1 class to community residents. Eagle Scout Derek Tully planned, organized and built a state-of-the-art fence around the garden.

Why are pollinators so crucial? Take it from the Xerces Society for Invertebrate Conservation:

"Pollinators are essential to our environment. The ecological service they provide is necessary for the reproduction of over 85 percent of the world's flowering plants, including more than two-thirds of the world's crop species. The United States alone grows more than 100 crops that either need or benefit from pollinators, and the economic value of these native pollinators is estimated at $3 billion per year in the U.S. Beyond agriculture, pollinators are keystone species in most terrestrial ecosystems. Fruits and seeds derived from insect pollination are a major part of the diet of approximately 25 percent of all birds, and of mammals ranging from red-backed voles to grizzly bears. In many places, the essential service of pollination is at risk from habitat loss, pesticide use, and introduced diseases."

So, on Saturday, June 23, you won't see any red-backed voles or grizzly bears. But you'll see bees, butterflies, birds and beetles.

And flies. Syprhid flies.

For more information on the open house, access https://hhbhgarden.ucdavis.edu/wp-content/uploads/2018/01/Pollinator-week-flyer-2018-1.pdf

 

UC Cooperative Extension farm advisors launch “Growing the Valley” podcast

A new UC Cooperative Extension podcast that focuses on growing orchard crops in the San Joaquin and Sacramento valleys is now available free at http://growingthevalleypodcast.com, Apple iTunes and Google Play Music.

The hosts are Phoebe Gordon, UCCE orchard systems advisor in Madera and Merced counties, and Luke Milliron, UCCE orchard systems advisor for Butte, Tehama and Glenn counties. The pair conduct research and extension programs that cover tree crops, with a focus on almonds, pistachios, walnuts, prunes, figs and cling peaches.

The podcast is a new extension format for UCCE. Podcasts are essentially audio files posted on the internet that can be downloaded and heard at the listener's convenience.

“Many of us in the ag world spend a lot of time in our trucks and it's a great time to learn new things,” Gordon said.

The podcast will feature brief research reports and timely topical information from the hosts, plus interviews with other UCCE farm advisors, specialists and professors, researchers from the USDA, other universities and industry representatives. It is intended for current and future farmers, pest control advisors, industry representatives and the public.

The first full-length episode is a 20-minute segment with veteran UCCE weed science advisor Kurt Hembree. Hembree, who is based in Fresno County, discusses herbicide resistant weeds that are a concern in orchard systems.

“As things get going, we'll be experimenting with podcast length and format,” Milliron said “We'd like to hear from listeners about the sorts of things they are interested in.”

Milliron and Gordon have posted a survey where listeners can weigh in about their content preferences and program length. In time, the dialog between the hosts and listeners will be expanded on the website to allow for questions and comments from the audience.

“Who knows, we might even set up a voice mailbox for people to call in with questions, too,” Milliron said.

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