Salicylic acid for plants. 38

Salicylic Acid for Plants.

Salicylic acid (SA) is an important plant hormone and plays a vital role in plant health. It impacts plant growth and development, and the ability of plants to resist both biotic and abiotic stresses.

• SA supercharges plant defense mechanisms. It makes plants less vulnerable to fungal and bacterial attack.
• SA improves root growth, flowering time, and protects aging and stressed plants from oxidative damage.
• The role of salicylic acid in plants is as a defence signal from inside the plant.
• Plants make Salicylic acid as a trigger for a natural defence against pathogens. However, they often do not manufacture SA quickly enough to prevent pathogens from causing damage. Foliar SA speed up this process.
• Even when conditions are ideal, inefficiencies exist that affect the production of free radicals and anti-oxidants.
• Free radicals are the “bad guys” and disrupt plant functions. Anti-oxidants are the ‘good guys” and deactivate or neutralise the free radicals.
• The production of anti-oxidants is natural but if carbohydrates are low or conditions are not favourable, anti-oxidants become limited.
• Its like a car engine. Even when a car engine runs perfectly it still produces toxic chemicals. In a plant, the by-products of chemical processes must be dealt with for the plant to remain healthy.
• When conditions are not ideal there are more of these toxic by-products. For example, photochemical efficiencies of optimised turf canopies are around 0.7. This contrasts with stressed turf which is at 0.55 or less.

This blog dovetails with our article on DIY pest control, and research into two novel bioactive compounds.

Salicylic Acid (SA) is a key component of aspirin, and extracts from Witch Hazel have been used to treat pain and inflammation for thousands of years. In 1933, SA was first proposed to develop acquired immunity after disease infection.

SA Affects Plant Processes.

Exogenous applications of Salicylic Acid on plants has several benefits to plants. It regulates plant processes depending on the concentration that you apply, with low concentrations tending to induce a response and high concentrations of SA inhibiting them.

• Abiotic stresses. SA impacts on several abiotic stresses that include a plants cold tolerance, its ability to cope with temperature extremes, its drought and UV radiation tolerance, and its tolerance to soil salinity.
• SA induces disease resistance.

Foliar applications of SA affect several aspects of plant growth and development¹Hayat Q, Hayat S, Irfan M, Ahmad A. Effect of exogenous salicylic acid under changing environment: A review. Environ Exp Bot. 2009;68:14–25. doi: 10.1016/j.envexpbot.2009.08.005. ²Khan MIR, Fatma M, Per TS, Anjum NA, Khan NA (2015) Salicylic acid-induced abiotic stress tolerance and underlying mechanisms in plants. Front Plant Sci 6:462. ³Malamy, J., Hennig, J., and Klessig, D. F. (1992). Temperature-dependent induction of salicylic acid and its conjugates during the resistance response to tobacco mosaic virus infection. Plant Cell 4, 359. doi: 10.1105/tpc.4.3.359.

Exogenous applications of SA on plants affect:

• Seed germinaton.
• Plant growth.
• Root development.
• Photosynthesis.
• Plant respiration and
• the Krebs cycle.

Salicylic Acid vs Other Plant Hormones/Bio-stimulants:

We have written a detailed overview of Bio-stimulants in these two articles. Article 1 and Article 2. However, SA has some unique properties in comparison to other plant hormones or bio-stimulants.

Salicylic Acid.

SA has roles in a plants ability to cope with abiotic stresses like salinity, drought, cold, heavy metals and heat stress. Plant physiological processes that SA regulates include:

• Photosynthesis.
• The opening and closing of stomata.
• Enzyme function.
• Nutrient uptake and
• Overall plant growth and development (seed germination, vegetative growth, flowering, and senescence).

Table Showing Properties of Salicylic Acid vs Common Organic Compounds.

Systemic Acquired Resistance (SAR).

• Systemic Acquired Resistance (SAR) is a long lasting and broad spectrum plant defence mechanism. SAR occurs when a pathogen infects a turf grass plant.
• After infection, a pathogen triggers what the SA pathway.
• This then induces defence response genes in the plant.
• This results in PR protein production.
• These proteins play an important role in plant defence.

The other role of SA in turf grass management, is as a plant hormone that helps regulate various physiological processes.

Here are a few key roles of SA in turf grass:

Disease Resistance with Salicylic Acid for Plants:

SA boosts a plant’s immune system. It enhances a plant’s resistance to several diseases, and in particular to fungi or bacteria.

It activates defence mechanisms inside the plant, and so makes the plant less prone to infection. For example, foliar applications of SA cause SAR in plants, and provide protection against various biotic stresses.⁴Yang Y, Shah J, Klessig DF. 1997. Signal perception and transduction in plant defence responses. Genes ant1 Develop 11:1621-39.

When a plant becomes infected, SA tends to build up in the locally infected tissue. After this it then moves around the plant to induce SAR in the non-infected parts of the plant.

Fungal diseases.

• SA improves turf resistance against diseases such as Dollar Spot and Brown Patch, by activating defence responses in the plant. This includes the production of antimicrobial compounds, and the reinforcement of cell walls. The end result is that it makes it more difficult for fungi to infect the turf grass.
• SA is very effective against grey leaf spot on perennial ryegrass. It significantly reduces this disease when you apply it as a foliar ⁵Rahman A, Kuldau GA, Uddin W. Induction of salicylic acid-mediated defence response in perennial ryegrass against infection by Magnaporthe oryzae. Phytopathology. 2014 Jun;104(6):614-23..

Bacterial diseases.

• SA  helps turf grass combat bacterial diseases like bacterial wilt and bacterial leaf blight. Research shows that preventative treatments with SA, reduce bacterial wilt in both ‘Penn-A4’ and ‘Tyee’ creeping bentgrass.
• SA reduces bacterial disease in both ideal and high temperature treatments. At 23 °C and 35 °C, disease severity in SA treated plants is less than in the untreated control.⁶Sha Liu, Joseph Vargas, Emily Merewitz, Jasmonic and salicylic acid effects on bacterial etiolation and decline disease of creeping bentgrass, Crop Protection Volume 109, July 2018, Pages 9-16
• SA stimulates the plant’s immune system to produce defence-related proteins, enzymes, and chemicals. All of these inhibit bacterial growth and limit disease progression.

Viral diseases.

While SA doesn’t directly target viruses, it indirectly enhances turf grass resistance to them. It activates SAR, and helps the plant to produce antiviral proteins that slow down the spread and replication of viruses.

Nematode Resistance using Salicylic Acid:

• SA increases turf grass resistance against nematodes. Nematodes are microscopic worms that damage turf grass roots, and result in stunted growth and decline.
• SA induces defence mechanisms in the plant, and this includes nematode-repellent chemicals which deter nematode feeding⁷Molinari S, Salicylic acid as an elicitor of resistance to root-knot nematodes in Tomato, ISHS Acta Horticulturae 789: XV Meeting of the EUCARPIA Tomato Working Group ⁸El-Sherif, A.G.;* Gad, S. B.; **Khalil, A.M. & ***Mohamedy, Rabab H.E. 2015. Impact of Four Organic Acids on Meloidogyne Incognita Infecting Tomato Plants under Greenhouse Conditions, Global Journal of Biology, Agriculture and Health Sciences, Vol.4(2):94-100.
• SA treated Tomato plants show a 20 to 25% reduction in root knot egg numbers in comparison to an untreated control⁹Molinari, Sergio. (2008). Salicylic Acid as an Elicitor of Resistance to Root-Knot Nematodes in Tomato. Acta horticulturae. 789. 119-125. 10.17660/ActaHortic.2008.789.15. . Similar results were seen in 2017 by Martínez-Medina et al¹⁰Martínez-Medina A., Fernandez I., Lok G. B., Pozo M. J., Pieterse C. M. J., Van Wees S. C. M. (2017). Shifting from priming of salicylic acid- to jasmonic acid-regulated defences by Trichoderma protects tomato against the root knot nematode Meloidogyne incognita. New Phytol. 213, 1363–1377. 10.1111/nph.14251.

Insect effects.

• Research shows SA repels certain insects such as thrips¹¹O. Ozinger, Effects of methy salicylate, methyl jasmonate and Cis-Jasmone on thrips Tabaci Lindeman, 2012,University of Natural Resources and Life Sciences, Vienna Division of Plant Protection , caterpillars¹²Iversonlo A, Inverson L, and Eshita S, The Effects of Surface-Applied Jasmonic and Salicylic Acids on Caterpillar Growth and Damage to Tomato Plants, OHIO J SCI 101 (5):S)O-94, 2001, and has indirect effects on mite mortality¹³Homayoonzadeh M, Moeini P, Khalil Talebi K, Allahyari H,Torabi E, Michaud JP, Physiological responses of plants and mites to salicylic acid improve the efficacy of spirodiclofen for controlling Tetranychus urticae (Acari: Tetranychidae) on greenhouse tomatoes, Exp Appl Acarol. 2020 Nov;82(3):319-333 .¹⁴Vilela de Resende JT, Rafael Matos R, Zeffa DM, Constantino LV, Alves SM, Ventura MU, Resende NCV, Youssef K, Relationship between salicylic acid and resistance to mite in strawberry, Folia Hort. 33(1) (2021): 107–119.

Stress Tolerance with Salicylic Acid:

Turf grass often faces stressors, such as drought, heat, or cold. SA helps plants cope with these as it regulates various stress-responsive genes and biochemical pathways. It improves the resilience of turf grass,and allows it to withstand adverse conditions more effectively.

Seed Germination.

Foliar applications of SA improve seed germination and promote protein synthesis. These proteins that are vital for germination to successfully occur.

Growth Regulation.

SA influences the growth and development of turfgrass. It promotes root growth, and results in a healthier and more robust root system. Additionally, it regulates shoot growth, helps to maintain a balanced growth pattern and increases overall turf quality.

Photosynthesis and Chlorophyll Production.

SA also enhances photosynthesis, which is crucial for energy production and to maintain turf grass health. It increases chlorophyll content, which leads to greener and more vibrant turf.

Drought Stress.

SA plays a major role in how plants cope with drought stress. It does this by influencing several growth parameters when plants are under drought stress.

When you make foliar applications of SA it helps synthetize soluble sugars and the amino acid, proline, and so maintains the moisture status of plants.

Temperature Stress.

SA increases plant tolerance to both high and low temperature stress. It does this by activating enzymes that protect the plant from damage.

For example, in Tall Fescue, foliar SA reduces high temperature stress by increasing photosynthetic pigments, and the build up of proline¹⁵Hayat, Q., S. Hayat, M. Irfan and A. Ahmad, 2010: Effect of exogenous salicylic acid under changing environment: A review. Environmental and Experimental Botany 68, 14-25..

The role of SA in abiotic and biotic factors¹⁶Rossi CAM 1, Marchetta EJR, Kim JH, Castroverde CDM, Molecular regulation of the salicylic acid hormone pathway in plants under changing environmental conditions, Trends in Biochemical Sciences, Volume 48, Issue 8, August 2023, Pages 699-712 (credits: Rossi et al. 2023; DOI: 10.1016/j.tibs.2023.05.004).

Salicylic Acid on Cool Season Turf.

Cool-season turf is susceptible to temperature extremes and this has a major impact on growth. Research shows that SA increases heat tolerance on Kentucky Bluegrass and Tall Fescue, and increases turfgrass quality.¹⁷Larkindale, J, and Huang, B. (2004). Thermotolerance and antioxidant systems in Agrostis stolonifera: involvement of salicylic acid, abscisic acid, calcium, hydrogen peroxide, and ethylene. J. Plant Physiol. 161, 405–413.

In a 2019 study¹⁸Zhang X and Goatley M, Evaluating the effects of SA and pigment sources, 2019 https://issuu.com/leadingedgepubs/docs/va-turfgrass-2019-jan-feb/s/10135194, salicylic acid plus a Copper based pigment improved the colour of creeping bentgrass under heat and mild drought stress at 42 and 56 d after treatment.

These results show:

• The role of SA in plants with the pigment is to block UV-B radiation. This protect the plants photosynthetic function from UV-B injury.
• There is a synergy between SA and the pigment resulting in an improvement in turf quality under heat and mild drought conditions.

How to Apply Salicylic Acid to Plants?

There have been two issues associated with SA and its use on plants.

• How to apply an amount that actually works? It is not water soluble so you can’t simply dissolve this in water, and apply it to vegetation. You will not be able to apply enough to get a result.
• How to apply high loads of SA without any damage to the plant.

The Delopment of a Salicylic Acid Bio-stimulant.

In 2019 we began to investigate how to apply high loads of SA, and in 2021 we developed a way to dissolve 200 g in 1 L of liquid. To achieve the equivalent loading at home you will need to dissolve over 650 aspirin in a litre of water.

Currently this high load of SA is only available in Vertmax Duo. However in the future we are looking at this being available as a standalone product with no pigment.

Vertmax Duo: A Premium Turf Pigment with Salicylic Acid.

The development of Vertmax Duo began shortly after the launch of Bayer’s Stressgard products. The Stressgard range offers a colourant and biostimulant that are pre-mixed with certain fungicides.

Vertmax Duo was developed to offer the same plant health benefits plus complete flexibility when it comes to your choice of tank mix partner. You can use Vertmax Duo as a stand alone application or tank mix it with all turf pesticides.

Why Vertmax Duo?

Vertmax Duo turf pigment is the only product on the market that contains 200g/L of salicylic acid. One application gives an immediate colour response together with all the potential benefits listed below.

It’s formulation also contains adjuvants and stickers to help with coverage, longevity and uptake.

Benefits of Vertmax Duo.

• Because of its tank compatibility you can mix this with all fungicides, fertilisers and insecticides. You have not got to use one brand to get the benefits of SA.
• Salicylic acid increases disease resistance plus heat and drought tolerance of turf.
• No stain formulation.
• Increases root growth and lateral branching.
• There is a contimual program of turf pigment research and improvement.
• Use results in higher quality playing surfaces.

Please feel free to check out more information on Vertmax Duo or contact us directly. To put it another way, why prevent your playing surface from being at its best?

Vertmax Duo label

Vertmax Duo presentation.

Buy Vertmax Duo.

Vertmax Duo comes in 1 L containers.

Buy Here If you wish to purchase this unique colourant and biostimulant packed full of the plant health benefits of Salicylic Acid.