Inducing Systemic Acquired Resistance: Helping Plants Help Themselves

Scott Titus with a basket of Impatiens ‘SunPatiens Spreading White’ with Dichondra ‘Silver Falls’

When a group of farmers I consulted with in 1987 wanted to grow certified organic apples, I started my quest for alternative growing practices. Two years later, I founded Windy Meadow Nursery. This was the same year the Sustainable Agriculture Research and Education (SARE) organization started, and I adopted its mission statement: To advance innovations that improve profitability, stewardship and quality of life by investing in state-of-the-art research and education.

The nursery has a shallow well, which is where we draw our drinking and irrigation water. Because certain products used for growing could easily infect the water, I was motivated to start researching biological and organic alternatives to conventional fungicides and greenhouse practices. The EPA also reevaluated all the pesticides used in agriculture in 1989 and banned fungicides that were known to be estrogen mimickers and endocrine disruptors.

Getting Started With Organic Products

In the winter of 2002, the growers trialed Messenger, a new agricultural crop aid that promised accelerated growth and increased resistance to disease and insects on a variety of row crops. We witnessed a surprising growth response from sun-loving Fuchsia ‘Gartenmeister Bonstedt.’ This plant’s dark bronze leaves block light from the chlorophyll, and it normally grows very slowly in the dark months of winter in the Pacific Northwest.

Spray applications of Messenger, now sold as Employ, contain Harpin protein isolated from the fire blight pathogen Erwinia amylovora that acts as an early warning. It activates the plants’ protective systems, analogous to the immune system in animals. The plant then performs as if it’s under attack and responds with increased vigor and growth. This response is accomplished by more than one mode of action and effects several synergistic changes in the plant’s physiology.

Modes Of Action Hypersensitive Reaction

The first mode of action is called the hypersensitive reaction (HR), which induces the few cells that are in direct contact with Erwinia amylovora to shrink and collapse, effectively halting the spread of the infection to a small spot on the leaf. When Harpin protein is sprayed on leaves, a slight constriction and reinforcement of cuticle cell walls and the subsequent new growth boost resistance to emerging disease infections. The
appearance of these plants differ in the same way two plants of the same variety look when one is grown under glass or outside in direct sunlight, and the other is grown in a double poly house or outside under light shade.

Systemic Acquired Resistance

Activation of HR at the local level establishes the second whole plant immune response, systemic acquired resistance (SAR). Chemical receptors in the sprayed leaves’ pathogenesis-related genes trigger a response in the plant’s DNA, which induces the SAR response throughout the entire plant. Signals travel quickly through one of three chemical transduction pathways to all parts of the plant, providing long-lasting protection against a broad spectrum of pathogens. This process is much like a vaccination that protects people from a single strain of influenza.

Plants can also use these defense mechanisms to resist invading pests. Thorns on roses evolved over millennia as a defense mechanism against foraging animals. Research conducted at Washington State University discovered the first molecular peptide signal, systemin, which activates the entire plant to produce inhibitors of the gut enzymes insects need to digest proteins from the plant sap after just one feeding. Plant-produced protease inhibitors cause digestive upset so insects stop feeding and die from starvation.

Photosynthesis

The third response is an increase in photosynthesis. This results in more efficient growth with higher nutritional levels. Studies have shown that nutritionally dense plants are not as appetizing to insects. When light levels increase rapidly after consecutive days of dark clouds to sudden bright mid-day sun, photosynthesis can stall for several hours. Plants with SAR deployed respond better to the stress of rapid and severe fluctuation in light intensity with increased photosynthetic efficiency.

One theory suggests that higher levels of antioxidant enzymes produced in the three transduction pathways in SAR plants leads to increased rates of photosynthesis. Another theory proposes that a more ordered arrangement of chlorophyll and other organelles in the photosynthesizing palisade cells is analogous to smaller computer chips with improved architecture: This arrangement operates faster and
more efficiently.

Other Methods For Inducing SAR

Other materials we use in the nursery activate pathogenesis-related gene expression and induce SAR. Silicon induces the SAR response and enables suberization (cork development in cell walls). Since most soilless mixes do not contain silicon, we add wood ash from burning tree branches from around the nursery and the mineral olivine, which is magnesium/iron silicate. As a result, the stiffening of cell walls almost eliminates the need to use PGRs on most plants.

While researching which insecticides to use in our integrated pest management program several years ago, I was drawn to a class of chemicals called neonicotinoides, or synthetic nicotine. There are several neonicotinoides on the market that contain imidacloprid, which is the active ingredient that induces the SAR response. At least one company has picked up on the SAR attributes by advertising the vigor response side effect when using this class of insecticide, which is easier than explaining systemic acquired resistance.

Ongoing scientific research suggests that using more than one method of activating SAR may employ all three of the plants transduction pathways and amplify the plant’s ability to resist pests and accelerate growth with reduced fertilizer and pesticide inputs.

With more than a decade of experience inducing systemic acquired resistance in the nursery and gaining the reputation for consistently having the best quality in the region, the advantage we enjoy is the plant health element. More robust plants with improved stress tolerance leads to a healthier, more marketable plant that is better looking and more likely to be purchased by the home gardener shopping at the independent garden centers we serve.

Leave a Reply

More From Crop Inputs...
cannabis-crop-protection

September 27, 2016

Washington State Outlines Pesticide Criteria For Cannabis Production

The state has also compiled a searchable list of pesticides that fit the criteria for use on marijuana.

Read More
Orius_June 2015

September 25, 2016

Peace Tree Farm Hosting Biocontrols Event In October

“Advanced Greenhouse Biocontrols for Ornamental and Vegetable Producers” will feature advice from biocontrol authorities Lloyd Traven and Suzanne Wainwright-Evans.

Read More
steve-larson-bayer

September 23, 2016

Bayer Continues Its Shift Into The Ornamentals Market

The company has announced its 12 distributor partners, and also recently named Steve Larson — formerly with Color Spot Nurseries — as its ornamental specialist.

Read More
Latest Stories
cannabis-crop-protection

September 27, 2016

Washington State Outlines Pesticide Criteria For Cannab…

The state has also compiled a searchable list of pesticides that fit the criteria for use on marijuana.

Read More
Orius_June 2015

September 25, 2016

Peace Tree Farm Hosting Biocontrols Event In October

“Advanced Greenhouse Biocontrols for Ornamental and Vegetable Producers” will feature advice from biocontrol authorities Lloyd Traven and Suzanne Wainwright-Evans.

Read More
steve-larson-bayer

September 23, 2016

Bayer Continues Its Shift Into The Ornamentals Market

The company has announced its 12 distributor partners, and also recently named Steve Larson — formerly with Color Spot Nurseries — as its ornamental specialist.

Read More
Biocontrols and beneficials absolutely can be used in outdoor production, with the use of banker plant systems

September 19, 2016

Learn About Biological Controls In The Greenhouse In A …

Michigan State University Extension (MSU) and Kansas State University Research and Extension are collaborating on a pre-recorded online course on “Biological Control for Greenhouse Growers.”

Read More
Bees And Pesticides

August 23, 2016

Studies Offer Conflicting Views On Neonic Effect On Bee…

How much exposure to neonicotinoids do bees need before their health becomes affected? That’s the question two research teams look to answer.

Read More
Chrysanthemum Aphid

August 22, 2016

How To ID And Manage Black Aphids In Chrysanthemums

Growers in Michigan have recently been reporting a higher presence of this pest. Here are some tips on how to control it.

Read More
Cannabis Crop Protection

August 22, 2016

Cannabis Group Stays Focused On Consistent Standards Fo…

The Foundation of Cannabis Unified Standards (FOCUS), is an independent, third-party, not-for-profit organization, is in the process of developing cannabis-specific standards for everything from cultivation and extraction to packaging and retail.

Read More
Leaf Septoria In Cannabis

August 21, 2016

Three Diseases To Watch For In Cannabis Production

The development of root rot, powdery mildew, and leaf septoria can damage cannabis to the point of complete crop loss.

Read More
Greenhouse Whitefly

August 18, 2016

Vestaron Planning For More Research And Development Of …

On the heels of launching Spear-T, its first bioinsecticide, Vestaron has received additional financing that will be used to develop new products with new modes of action.

Read More
BioWorks Mycotrol

August 17, 2016

New Organic Mycoinsecticide From BioWorks Now Registere…

BioWorks’ Mycotrol can be used to manage whitefly, thrips, aphids, and other insects in greenhouses and nurseries.

Read More
Downy mildew lesions on light coleus cultivars feature

August 12, 2016

How You Can Control Downy Mildew In Coleus, Roses, And …

Downy mildew diseases are potentially devastating to ornamental crops and at the very least can cause unsightly damage. Check out the latest research and recommendations for preventing it.

Read More
Jen Browning BASF

August 4, 2016

Horticulturist And Entomologist Jen Browning To Speak A…

Browning will discuss the use of nematodes in managing pests in greenhouses and nurseries.

Read More
Poinsettia, Heavy Whitefly Infestation -Lower Leaves, Insect - Feature

August 3, 2016

Tips For Successful Late-Season Whitefly Control

Managing late-season whiteflies successfully on poinsettia requires preventative measures put in to action early in the production cycle.

Read More
Cannabis Crop Protection

July 28, 2016

Solving The Cannabis Crop Protection Problem

A largely unregulated sector of the industry, state departments of agriculture, biocontrols companies, and other industry pros are dedicated to helping growers make the right pesticide decisions for their operations.

Read More
Aphids On Older Leaves

July 25, 2016

How You Can Stop Aphids By Understanding Their Interact…

Knowing which aphids target which crops and how aphids colonize and move on plants goes a long way toward setting up an effective management plan.

Read More
BASF Orkestra Intrinsic

June 21, 2016

New Mode Of Action From BASF Offers Deeper Disease Cont…

When it comes to disease control, you need all the help you can get. BASF recently hosted growers, Extension personnel, and trade media to present its newest fungicide with two active ingredients, offering dual modes of action.

Read More
Nematodes-feature

June 4, 2016

New Biocontrols Provide Effective Pest Control In Green…

Biological chemistry manufacturers have introduced several new products recently that offer a range of insect and disease management options. Here’s a look at some of them.

Read More
Whitefly

June 2, 2016

Breaking News: Florida Growers Reporting Major Whitefly…

Reports have come from the Florida Keys to Palm Beach County that whitefly populations in landscapes are reaching unprecedented levels and are not responding to pesticide applications. Biotype-Q has been found in four different communities. University of Florida/Institute of Food and Agricultural Science researchers are working with USDA-APHIS, USDA-ARS, the Florida Department of Agriculture, and growers and landscape professionals to manage the developing problem.

Read More
[gravityform id="35" title="false" description="false"]