Marigold (Tagetes spp.) as a Service Plant for Sustainable Agriculture
Service plants like Tagetes spp. (marigold) contribute significantly to agroecosystems, providing benefits such as pest control, soil protection, and improved fertility, making them valuable tools for sustainable agriculture.
Tagetes spp., the most species used in cropping system : Tagetes erecta, Tagetes patula, Tagetes minuta (also known as African, French, Mexican marigolds), are widely recognized for their role in integrated pest management (IPM). These plants offer antifungal, insecticidal, and nematicidal properties, making them essential in both gardens and farms. They combat pests like root-knot nematodes (RKNs), whiteflies, aphids, caterpillars, ants, and more. Additionally, Tagetes produce allelopathic compounds, particularly thiophenes, that reduce nematode populations through inhibition and toxicity.
Why Choose One Over the Other (T.erecta vs T.patula vs T.minuta)?
Tagetes erecta: Ideal for farmers looking to maximise nematode control with a plant with high ornamental value. It's suited for warm climates and provides strong protection through its bioactive thiophenes. Farmers looking for larger flowers and a long bloom period would benefit most from this variety.
Tagetes patula: A more versatile and hardy option, perfect for farmers in cooler climates or with variable weather. It's highly adaptable, economical, and easy to cultivate, making it a favorite for small-scale farms and home gardens. It attracts a wide range of beneficial insects, aiding in integrated pest management.
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Tagetes minuta: Best for larger, more functional applications, especially for farmers facing significant weed and pest pressure. It has strong allelopathic properties, making it excellent for weed suppression. While less ornamental, it offers effective protection for crops and is useful in larger field settings.
Case study: Why are Tagetes effective against nematodes (eg. Root-knot nematodes)?
Meloidogyne incognita damages for example on tomato shoots and roots :
Tagetes, like Tagetes erecta (African marigold), produce natural compounds called thiophenes, which act as natural nematicides.
These compounds, located in the roots of the plant, affect the nervous system of soil parasites such as nematodes, impairing their ability to feed and move. As a result, the population of nematodes in the soil is significantly reduced. Thiophenes, particularly α-terthienyl, become more effective when exposed to sunlight, enhancing the plant’s natural ability to protect the soil. These substances hinder the development of nematodes, thereby protecting vulnerable crops from root damage. Thiophenes prevent nematode growth and reproduction by interfering with their development, providing effective protection against root harm.
Where to Use Tagetes?
Tagetes spp. can be used in a variety of agricultural settings, depending on the goals of the farmer.
- Vegetable Gardens: Between crop rows or as a border plant.
- Orchards: Around the base of fruit trees to deter soil pests.
- Field Crops: In strips or patches to protect larger areas.
- Greenhouses: In pots or directly in beds to create a pest-repellent barrier.
When to Use them?
To maximize the benefits of marigolds, it’s important to plant them at the right time.
- Planting Season: Sow marigolds in spring (February-March) when soil temperatures exceed 18°C.
Bloom Period: From May to October, offering natural pest protection during the peak growing season.
How to Use Those Service Plants?
1. Direct Planting:
Best Practices:
Intercropping: Plant marigolds between rows of tomatoes, cabbage, potatoes, parsley or orchards productions.. This helps in repelling pests and reducing nematode populations.
- Spacing: Maintain 30-40 cm between marigold plants to ensure sufficient growth without overcrowding.
- Duration: Leave marigolds in the ground for the full growing season to maximize nematode control.
2. Trap Crop:
Use Tagetes erecta as a trap crop around vegetable plots to lure nematodes away from the main crops. Harvest and remove marigolds before the nematodes complete their life cycle, effectively reducing the pest load.
In both the field and the greenhouse, choosing the appropriate species and variety of Tagetes depends on the specific pests you're dealing with and the characteristics of your crop ecosystem. Below is a table, from Hooks et al.2010, outlining optimized strategies based on pest types, region, and the methods employed :
| Crop Studied | Nematode Targeted | Cultivar | Tactic | Findings | Country | Reference |
|---|---|---|---|---|---|---|
| Carrot | Meloidogyne javanica | T. patula Happy Days | Grown in rotation | Reduced galls, improved carrot yield compared to fallow or okra. | Brazil | Huang (1984)PMID: 19294045 |
| Taro | M. javanica | Unknown | Cover crop | Reduced nematodes before taro planting. | USA, Hawaii | Sipes and Arakaki (1997)
PMID: 19274275 |
| Lettuce | M. hapla | T. patula, Nemagone, Polyema | Micro-plots, incorporation | Reduced root galls, effective M. hapla control | USA | Abawi and Vogel (2000) |
| Great Burdock | R. reniformis | T. erecta | Field infestation | Marked reduction in nematode populations. | Japan | Nakasone (1973) |
| Cabbage, Cauliflower | T. brassicae | T. tenuifolia, T. lucida | Incorporation | Inhibited nematode buildup. | India | Siddiqui and Alam (1987) |
| Pineapple | R. reniformis | T. patula, Boy-O-Boy | Inter-cycle rotation | Similar nematode reduction to clean fallow. | USA, Hawaii | Ko and Schmitt (1996)
PMID: 19277173 |
| Water Spinach | M. incognita | F590 | Rotation | Reduced root-knot nematodes in spinach. | Taiwan | Tsay et al. (2004)
PMID: 19262785 |
| Soybean | M. incognita | T. erecta and T. patula mix | Co-planted in pots | Increased yield, reduced nematodes. | Egypt | El-Hamawi et al. (2004) |
| Snapbeans | H. galeatus, P. thornei | T. patula, Rusty Red | Rotation | Increased snapbean yield by 57%. | USA | Rhoades (1980)https://journals.flvc.org/nematropica/article/view/63725 |
| Mulberry | M. incognita | T. patula (unknown variety) | Intercropping | Reduced root-galling on mulberry. | India | Govindalah et al. (1991)
https://www.indianjournals.com/ijor.aspx?target=ijor:ijn&volume=21&issue=1&article=017 |
| Strawberry | P. penetrans | Single Gold | Grown in rotation | Reduced nematode density, improved yield and quality. | Netherlands | Evenhuis et al. (2004) |
| Potato | P. penetrans | T. tenuifolia, T. patula spp. | Rotation | Reduced nematodes, better yields post-marigold. | Canada | Kimpinski et al. (2000)
PMID: 19271006 |
| Potato, Tomato | P. penetrans | T. erecta × T. patula | Rotation/double cropping | Effective population suppression. | USA | LaMondia (2006)
PMID: 19259461 |
| Tomato | T. claytoni, T. christiei | T. minuta | Rotation | Suppressed nematodes significantly. | USA | Hackney and Dickerson (1975)
PMID: 19308137 |
| Tomato | M. incognita | T. patula, Single Gold | Intercrop and experiment | Reduced nematode species in tomato plots | USA | Ploeg (2000) |
Use and Management
To ensure optimal growth and effectiveness of Tagetes spp., follow these guidelines:
- Soil Requirements: Use fertile soil with at least six hours of sunlight. Marigolds thrive in well-drained soil.
- Watering: In hot regions like northern Florida, regular watering is essential, but avoid overwatering as this can cause dwarf varieties to rot.
- Fertilization: Too much nitrogen or excessive shade may result in leafy plants with few flowers. Aim for balanced fertilization to encourage blooms.
- Pests: Common pests include mites, which may attack during hot weather, causing webbing on the foliage. Use appropriate pest control measures, such as insecticidal soaps or organic sprays.
- Transplanting: Large marigolds can be transplanted if the root system is well dug out.
- Seed Germination: Germination occurs in a week at 21°C to 25°C. Avoid overly hot conditions, as they can cause leggy growth. Planting slightly deeper than the pot depth is recommended for stability.
Pro Tips for Farmers :
- Companion Planting: Pair marigolds with high-value crops like tomatoes, beans, or cucumbers for both pest control and soil benefits.
- Soil Assessment: Use marigolds in areas with known nematode issues to test soil health and adjust subsequent planting strategies.
Monitoring: Observe pest and soil health regularly to determine the effectiveness and adjust practices accordingly. For severe nematode issues, rotate crops with Tagetes every 2-3 years for long-term soil health benefits.
The Advantages (for the Farmer and Environment):
- Pest Control:
- Reduces nematode populations by acting as a non-host or poor host, producing allelopathic compounds(Thiophenes) that inhibit their development.
- Effective against aphids, whiteflies, caterpillars, and certain fungal pathogens.
- Thiophenes disrupt nematode growth and reproduction by blocking their development, protecting sensitive crops from root damage.
- Improvement of Soil Health:
- Enhances soil structure through root biomass, increasing organic matter after decomposition.
- Acts as a cover crop, preventing erosion and maintaining soil moisture.
- Provides natural protection without using chemical pesticides.
- Increased Biodiversity:
Attracts beneficial insects, like pollinators and predatory insects, supporting a balanced agroecosystem.
The Limits (for the Farmer and Environment):
- Climate Sensitivity: Not frost-resistant; requires indoor sowing or protection in colder climates.
- Nutrient Competition: May compete with main crops for nutrients if not managed properly.
- Space Usage: Ensure proper spacing to avoid overcrowding with main crops, which can hinder growth
- Products derived from Tagetes, such as maceration sprays, have a short shelf life, requiring immediate use for maximum effectiveness. Additionally, marigolds have a limited growing season, particularly in colder climates, where frost can kill plants, necessitating replanting each year.
- Rotating Tagetes with other control strategies enhances its efficacy and reduces resistance risks.
Safety For Humans :
- Thiophenes, especially α-terthienyl, are naturally occurring secondary metabolites in marigolds. They are highly reactive but not known to be toxic to humans at the concentrations naturally present in the plants.
- In traditional and modern uses, Tagetes spp. are commonly grown in gardens and around crops, with no reported risks to human health from handling, growing, or even using their extracts as sprays.
- However in a product like a biopesticide having active compounds from Tagetes plant extract, could have concentrated forms or synthetic derivatives of thiophenes and those forms could potentially cause irritation or toxicity if ingested or directly exposed to skin in large amounts. But this is rarely a concern with the natural use of Tagetes spp.
Safety For animals :
Toxicity to Insects and Pests
- Thiophenes are highly toxic to nematodes, certain insects (e.g., aphids, whiteflies), and fungi. They disrupt pest growth and reproduction by interfering with cellular or nervous system functions.
- They are not broad-spectrum pesticides but rather target specific pests, making them valuable in sustainable pest management.
- Beneficial insects (like pollinators) are usually not harmed by marigolds, as the toxic thiophenes are mainly concentrated in the roots and not in the nectar or flowers.
Cost of production (Simulation case):
1. Seed or Plant Material
- Purchase Tagetes seeds at garden centers, nurseries, or online shops. Look for organic seeds if prioritizing sustainable practices. Seed Cost: Marigold seeds typically range from €3 to €5 for 100-300 seeds, depending on the variety (e.g., Tagetes erecta, Tagetes patula, Tagetes minuta).
- For 1 hectare (10,000 m²), let's assume that the farmer needs to plant about 20,000 to 30,000 seeds (depending on planting density).
- Estimated cost: €60–€150 for seeds per hectare.
- For 1 hectare (10,000 m²), let's assume that the farmer needs to plant about 20,000 to 30,000 seeds (depending on planting density).
- Transplants: If the farmer uses transplants (young plants) instead of seeds, the cost could be €0.10 to €0.30 per plant.
- For 30,000 plants, this could cost between €3,000–€9,000 depending on the source.
2. Labor
- Planting and Maintenance: Marigolds require labor for sowing seeds, transplanting (if applicable), watering, pruning, and pest management.
- Planting Labor: Depending on local wage rates, labor costs for planting can range from €200 to €500 per hectare.
- Ongoing Maintenance: Weeding, irrigation, and pest monitoring can require €500 to €1,000 per hectare over the growing season.
3. Fertilization and Soil Preparation
- Marigolds prefer fertile, well-drained soil with good organic matter content. Fertilization costs can depend on the soil's initial nutrient levels and whether organic or synthetic fertilizers are used.
- Organic Fertilizer: Organic compost, manure, or other fertilizers can cost around €200–€500 per hectare.
- Synthetic Fertilizer: Use of synthetic fertilizers could cost about €100–€300 per hectare depending on the nutrient requirements and soil condition.
- Soil Preparation: Plowing, leveling, and amending the soil could cost €100–€300 per hectare depending on the equipment and labor availability.
4. Watering/Irrigation
- Marigolds are fairly drought-tolerant but require regular watering, especially during dry spells or in regions with low rainfall.
- Irrigation Costs: If the farmer is using a drip irrigation system or sprinkler system, water costs may vary depending on water availability, rates, and system maintenance. Typical costs for irrigation could range from €200 to €500 per hectare.
5. Pest and Disease Management
- Marigolds are relatively pest-resistant but still require monitoring for aphids, whiteflies, and root diseases..
- Organic Treatments: If the farmer uses organic pest control, the cost might be around €100–€200 per hectare. Synthetic pesticides would be more expensive.
- Integrated Pest Management (IPM): The cost of implementing IPM programs might be slightly higher due to monitoring and using non-chemical pest control measures, but this would typically cost between €100–€300 per hectare.
6. Harvesting
- Marigolds generally need to be harvested regularly during their flowering period, depending on the variety.
- Labor Costs for Harvesting: Harvesting marigolds typically involves cutting flowers or uprooting the entire plant. The labor cost for harvesting could range from €200 to €500 per hectare, depending on how labor-intensive the process is.
7. Packaging and Marketing (if selling)
- If the farmer intends to sell marigolds (e.g., as cut flowers or seeds), there will be additional costs for packaging and marketing.
- Packaging: Simple packaging for cut flowers or marigold seeds can cost €100–€300 per hectare, depending on the scale and packaging type (e.g., bouquets, boxes, or bags).
Marketing and Distribution: Costs for reaching markets (local or export) may range from €100–€500 per hectare depending on transportation and sales channels.
| Cost Item | Estimated cost (per hectare) |
|---|---|
| Seeds or transplants | €60–€9,000 (seeds or transplants) |
| Labor (planting & maintenance) | €700–€1,500 |
| Soil Preparation & Fertilization | €300–€800 |
| Watering/Irrigation | €200–€500 |
| Pest & Disease Management | €100–€500 |
| Harvesting | €200–€500 |
| Packaging & Marketing | €100–€800 (if selling) |
Additional Considerations:
- Scale of Production: The cost per hectare might decrease as the scale of production increases due to economies of scale. For larger farms, labor costs per unit of area may be lower, and bulk seed purchasing can reduce overall seed costs.
- Climate and Region: Water availability, soil fertility, and local labor costs will also affect the overall production costs. For example, farms in arid regions with irrigation requirements will have higher water costs.
Market Conditions: If the marigolds are intended for sale, market demand will determine the profitability. For pest control, the cost might be justified by the savings on chemical pesticides and the potential for long-term sustainability.
General guiding table for farmers:
| Criteria | Tagetes erecta
(African Marigold) |
Tagetes patula
(French Marigold) |
Tagetes minuta
(Mexican marigold) |
|---|---|---|---|
| Size & Growth Habit | Tall (up to 90-120 cm),
bushy with large flowers |
Short (15-30 cm), compact, bushy growth | Tall (up to 120-180 cm), upright, more weedy appearance |
| Flower Characteristics | Large,
dense flowers (orange, yellow) |
Small to medium-sized flowers (variety of colors) | Small flowers, less ornamental, yellowish-green |
| Aesthetic Value | High ornamental value;
large blooms |
High ornamental value; diverse colors | Low ornamental value; more functional than decorative |
| Bloom period | Long bloom period
(May to October) |
Blooms prolifically throughout the summer | Blooms in summer; shorter bloom period |
| Climate adaptation | Warm climates;
not frost-resistant |
More adaptable to varying climates; some frost tolerance | Warm climates; prefers full sun and well-drained soils |
| Ease of Cultivation | Easy to grow;
requires regular watering |
Very easy; hardy, grows well in various conditions | Moderate; needs space to thrive, less ornamental |
| Drought Tolerance | Moderate;
requires regular watering |
High drought tolerance | High drought tolerance |
| Soil Benefits | Enhances soil structure;
improves organic matter |
Good for soil health; decomposes easily | Strong allelopathic effect; good for weed suppression |
| Key Bioactive Compounds | Rich in thiophenes (e.g., α-terthiényle),
photo-toxic |
Moderate levels of thiophenes | High levels of essential oils (terpenes), strong bioactivity |
| Pest Control | Effective against nematodes,
aphids, and whiteflies |
Known for controlling nematodes, especially root-knot nematodes | Strong repellent effect on nematodes, insects, and some fungal diseases |
| Trap Crop Potential | Effective for trapping nematodes away from main crops | Good as a trap crop; dense root system | Very effective; strong pest deterrent |
| Allelopathic Properties | Moderate allelopathy (affects certain weed seeds) | Mild allelopathic effect | High allelopathic effect; suppresses weed seed germination |
| Attracts Beneficial Insects | attracts pollinators | Excellent for attracting pollinators and beneficial insects | Attracts beneficial insects; moderate pollinator attraction |
| Cost of Seeds | €3-5 for 100-300 seeds (moderately priced) | €2-4 for 100-300 seeds (economical) | €4-7 for 100-200 seeds (slightly higher cost) |
| Seed availability | Widely available | Widely available | Less common; may require specialty seed suppliers |
| Use Cases in Agriculture | Best for nematode control and soil improvement | Ideal for small-scale farms, gardens, and polyculture | Ideal for small-scale farms, gardens, and polyculture |
| Disadvantages | Sensitive to overwatering; nutrient competition | Smaller flowers, may compete for nutrients | Can be invasive if not managed; less attractive flowers |
Testimony (Youtube videos)
These Magic Flowers Will Repel Pests and Feed Your Plants from 10:00 to 11:00 minutes
The Ultimate Companion Flower! - YouTube
Science-Based Companion Planting Combinations That WORK from 1:23 to 2:24 minutes
Acknowledgements :
Special thanks to the researchers from the Sophia Agrobiotech Institute (INRAE) of Sophia Antipolis, France, including Caroline Djian-Caporalino (Research Engineer), Anne-Violette Lavoir (Maître de Conférences), and Cliven Njekete (PhD) for their invaluable contributions to the study of plant-parasitic nematodes, sustainable pest management,service plants and integrated ecological practices. center|thumb|Book about service plants, soon in english version, coordonné par Caroline Djian-Caporalino et Anne-Violette Lavoir [1]
Webography :
https://www.johnnyseeds.com/flowers/marigold/
https://www.dianeseeds.com/marigold.html
Bibliography :
- Cerruti, R.R., Hooks, A.P., Wang, K.H., Ploeg, A., & McSorley, R. (2017). Using marigold (Tagetes spp.) as a cover crop to protect crops from plant-parasitic nematodes. The Pharma Journal, 6(11), 823-831. Retrieved from https://www.thepharmajournal.com/archives/2017/vol6issue11/PartA/6-9-72-823.pdf
- Djian-Caporalino, C., & others. (2010). Plantes nématicides et résistantes aux nématodes [Nematicidal and nematode-resistant plants]. ScienceDirect. Retrieved from https://www.sciencedirect.com/science/article/pii/S092913931000168X#tbl0005
- Desmedt, W., Mangelinckx, S., Kyndt, T., & Vanholme, B. (2020). A phytochemical perspective on plant defense against nematodes. Frontiers in Plant Science, 11, 602079.doi: 10.3389/fpls.2020.602079
- Djian-Caporalino, C., & others. (2008). Plantes nématicides et résistantes aux nématodes [Nematicidal and nematode-resistant plants]. Bulletin of Insectology, 61(1), 95-102.
- Marahatta, S. P., Wang, K.-H., Sipes, B. S., & Hooks, C. R. R. (2012). Effects of Tagetes patula on Active and Inactive Stages of Root-Knot Nematodes. Journal of Nematology, 44(1), 26-30. https://journals.flvc.org/jon/article/view/79250
- Parolin, P., Bresch, C., Desneux, N., Brun, R., Bout, A., Boll, R., & Poncet, C. (2012). Secondary plants used in biological control: A review. Plant Pathology, 61(4), 510-520. https://ijpp.areeo.ac.ir/article_37321.html?lang=en
- Reynolds, L. B., Potter, J. W., & Ball-Coelho, B. R. (2002). Crop Rotation with Tagetes sp. is an Alternative to Chemical Fumigation for Control of Root-Lesion Nematodes. Journal of Nematology, 34(3), 319-324. https://ijpp.areeo.ac.ir/article_37321.html?lang=en
- Renčo, M., Sasaneli, N., & Maistrello, L. (2010). Plants as Natural Sources of Nematicides. Agricultural Nematology Journal, 12(4), 455-465.https://ijpp.areeo.ac.ir/article_37321.html?lang=en
- Ploeg, A. T. (2002). Effects of Selected Marigold Varieties on Root-Knot Nematodes and Tomato and Melon Yields. Plant Disease, 86(5), 505-508. https://ijpp.areeo.ac.ir/article_37321.html?lang=en
- Yang, G., Zhou, B., Zhang, X., Zhang, Z., Wu, Y., Zhang, Y., Lü, S., Zou, Q., Gao, Y., & Teng, L. (2010). Effects of Tomato Root Exudates on Meloidogyne incognita. Plant Pathology Journal, 59(2), 233-239. https://ijpp.areeo.ac.ir/article_37321.html?lang=en
- Rajasekaran, T., Madhusudan, R., & Ravishankar, G. A. (2006). Elicitation of Thiophene Production by Cultured Hairy Roots of Tagetes patula. Plant Cell Biotechnology, 13(2), 112-117. https://ijpp.areeo.ac.ir/article_37321.html?lang=en
- Hooks, C. R. R., Wang, K.-H., Ploeg, A., & McSorley, R. (2010). Using marigold (Tagetes spp.) as a cover crop to protect crops from plant-parasitic nematodes. Applied Soil Ecology, 46(3), 307-320. https://doi.org/10.1016/j.apsoil.2010.09.005
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