Marigold Tagetes is more than just a vibrant addition to gardens; it is a powerful ally in the fight against pests. The Marigold as insecticide has been the subject of numerous studies, which have revealed their effectiveness against a diverse range of agricultural and household pests.

The effectiveness of Tagetes as an insecticide is evident across a range of pest species, offering a natural alternative to synthetic chemicals.

Marigold as Insecticide

This list includes the pests and/or larvae that have been found to be killed or repelled by various Tagetes species, along with the specific parts of the plant used and the form in which they were administered.

Aphids

Aphids are small sap-sucking insects that can cause significant damage to crops. Tagetes have been found to produce a deterrent effect on aphids, helping to protect plants by preventing aphid infestation. The effectiveness of Tagetes against aphids has been documented, providing a natural alternative to chemical pesticides.^[1]https://pdfs.semanticscholar.org/a21e/eba9c5719d37f9aff99b8f8aa2b206d826d9.pdf

Tagetes Marigold for Aphids (Aphis spp.)

• Additional common names: Plant lice
• Effective Tagetes variety: Tagetes minuta
• Parts of the plant used: Whole plant
• Form of Tagetes solution: Essential oil
• Administration: Applied as a spray
• Pest control method: Repels aphids

Bed Bugs

Bed bugs are a growing concern in many urban settings. Tagetes extracts have shown potential in controlling bed bug populations, offering a natural pest control solution. The use of Tagetes in combating these pests is supported by research findings, which suggest a promising avenue for natural bed bug management.^[2]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/#pone.0233511.ref029

Marigold for Bed Bugs (Cimex lectularius)

• Effective Tagetes variety: Tagetes patula (dwarf marigold)
• Parts of the plant used: Essential oil
• Form of Tagetes solution: Essential oil (EO)
• Administration: Exposure to dry residues by the Impregnated Paper Disk Test (IPDT)
• Pest control method: Exterminates bed bugs with a 100% elimination rate at a concentration of 100 mg/mL and an LC50 value of 15.85 mg/mL

Caterpillars

Caterpillars are known for their destructive feeding habits on foliage and various crops. Research has indicated that Tagetes has larvicidal effects on some caterpillars, which could be instrumental in protecting crops from their damage.^[3]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/#pone.0233511.ref031

Cabbage Maggot (Delia radicum)

• Effective Tagetes varieties: Tagetes erecta (African marigold) and Tagetes patula (French marigold)
• Parts of the plant used: Roots
• Form of Tagetes solution: Fresh tissue extracts
• Administration: Application to soil where cabbage maggot eggs are present
• Pest control method: Causes mortality in first instar larvae, with T. patula extract showing up to 100% effectiveness

This study discusses the susceptibility of the cabbage maggot, Delia radicum, to fresh tissue extracts from two species of marigold, Tagetes erecta and Tagetes patula. The study highlights the effectiveness of root extracts from these plants, with a noted increase in mortality rates when extracts from flowering plants were used.

The combination of Tagetes extracts with the entomopathogenic nematode Steinernema feltiae also showed potential as an effective control method under both laboratory and greenhouse conditions. This suggests that Tagetes spp. could be integrated into pest management programs for the cabbage maggot, offering a reduction in pest populations without the use of synthetic chemicals.^[4]https://www.tandfonline.com/doi/abs/10.1080/10440040802394992

Fall Armyworm (Spodoptera frugiperda)

• Effective Tagetes variety: Tagetes erecta (African marigold)
• Parts of the plant used: Leaves
• Form of Tagetes solution: Organic leaf extracts in n-hexane, acetone, and ethanol
• Administration: Application of leaf extract at various concentrations to the food source
• Pest control method: Exhibits antifeedant effects, reduces larval weight, and kills larvae and pupae with an LC50 ranging from 152.2 to 312.2 ppm

This study indicates that organic extracts from the leaves of T. erecta can act as an antifeedant and are lethal to both larvae and pupae stages of the fall armyworm. The varying concentrations and types of extracts (n-hexane, acetone, and ethanol) demonstrate different levels of efficacy, with the ethanol leaf extract showing the highest mortality rate.

These findings suggest that T. erecta leaf extracts could be a viable eco-friendly alternative to synthetic insecticides for protecting maize crops.^[5]https://journals.flvc.org/flaent/article/view/79302/76646

Mites

Mites are pests that can cause extensive damage to plants and soil health. Tagetes has been recognized for its insecticidal properties as a natural alternative to chemical acaricides.

One study revealed Mexican marigold (Tagetes minuta) in hexane solvent to be 89% effective as acaricide against the spider mite, Tetranychus truncatus, which was 12% more effective than neem oil.

Marigold Acaricide for Spider Mites (Tetranychus truncatus)

• Effective Tagetes variety: Tagetes minuta (Mexican marigold)
• Parts of the plant used: Dried and pulverized plant
• Form of Tagetes solution: Solvent fractions (hexane, chloroform, and water extracts)
• Administration: Laboratory evaluation of ovicidal and adulticidal activities at various concentrations
• Pest control method: Exhibits significant ovicidal action at higher concentrations and adulticidal effect, with hexane fraction showing over 90% adult mortality

This study revealed the efficacy of different solvent fractions of Mexican marigold, Tagetes minuta, against the spider mite, Tetranychus truncatus. The research involved using hexane, chloroform, and water to extract substances from the dried and pulverized botanical, which were then tested for their ability to kill eggs (ovicidal) and adult mites (adulticidal).

The findings revealed that the hexane extract was particularly effective, with the highest concentrations achieving complete egg mortality and more than 90% adult mortality. The hexane tagetes solution was found to be more effective than neem oil.

REFERENCE: Vannathara, Ashish et al. “Acaricidal effects of Tagetes minuta L. (Asteraceae) against Tetranychus truncatus Ehara (Prostigmata: Tetranychidae).” International Journal of Acarology 49 (2023): 325 – 333.^[6]https://www.semanticscholar.org/paper/Acaricidal-effects-of-Tagetes-minuta-L.-against-Vannathara-Bhaskar/d5c226efb401f24f7256460e17a41852d2981bd8

Mosquitocidal / Larvicidal

Mosquitoes are not only annoying but also vectors for diseases. The species T. erecta, T. minuta, and T. patula have been identified as having mosquito-repellent and larvicidal activities, which could be critical in disease control efforts.^[7]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3609190/^[8]http://www.ijps.ir/&url=http:/www.ijps.ir/article_1860.html.

Marigold for Mosquitoes (Various species)

• Additional common names: Mozzies
• Effective Tagetes variety: Tagetes minuta
• Parts of the plant used: Leaves and flowers
• Form of Tagetes solution: Essential oil and crushed plant parts
• Administration: Oil applied as a spray, crushed parts used in the environment
• Pest control method: Repels mosquitoes

Tagetes for Nematodes (Various genera)

The Tagetes species, particularly Tagetes patula and Tagetes erecta, have been recognized for their ability to offer an effective natural solution for managing nematode infestations.

• Effective Tagetes variety: Tagetes patula, Tagetes erecta
• Parts of the plant used: Roots, foliage
• Form of Tagetes solution: Plant extracts and decomposed plant material
• Administration: Soil incorporation of plant material and extracts
• Pest control method: Kills nematodes

The roots and foliage of these plants contain compounds that are toxic to various nematode genera. When incorporated into the soil, either as plant material or in extract form, these marigold species can significantly reduce nematode populations.

Root-Knot Nematodes (Meloidogyne spp.)

• Effective Tagetes variety: Tagetes minuta
• Parts of the plant used: Roots
• Form of Tagetes solution: Plant material and extracts
• Administration: Soil incorporation of plant material
• Pest control method: Exterminates root-knot nematodes

The roots and foliage of these Tagetes plants contain compounds that are toxic to various nematode genera. When incorporated into the soil, either as plant material or in extract form, these marigold species can significantly reduce nematode populations.

This method of pest control not only helps in exterminating nematodes but also enriches the soil as the decomposed plant material adds nutrients back into the earth.

Sand Flies

Sand flies are known for spreading leishmaniasis, a tropical and subtropical disease spread by sand fly bites. Research has shown that Tagetes may offer a natural means to control sand fly populations, which is a significant step towards combating this disease.^[9]https://pubmed.ncbi.nlm.nih.gov/24717195/

Termites

Termites can undermine structural integrity by damaging wood. The insecticidal properties of Tagetes provide a potential method for termite management, which is a boon for pest control strategies. ^[10]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/#pone.0233511.ref027^[11]http://researchjournal.co.in/upload/assignments/5_29-31_2.pdf^[12] jQuery('#footnote_plugin_tooltip_546254_1_12').tooltip({ tip: '#footnote_plugin_tooltip_text_546254_1_12', tipClass: 'footnote_tooltip', effect: 'fade', predelay: 0, fadeInSpeed: 200, delay: 400, fadeOutSpeed: 200, position: 'top center', relative: true, offset: [-7, 0], });/journal/paperinformation.aspx?paperid=124278" target="_blank" rel="noreferrer noopener">https://www.scirp.org/(S(351jmbntvnsjt1aadkozje))/journal/paperinformation.aspx?paperid=124278))

Ticks

Ticks are ectoparasites that can transmit diseases to humans and animals. Tagetes has been found to have acaricidal effects, making it a valuable tool in tick control, which is essential for preventing tick-borne diseases.^[13]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/#pone.0233511.ref033^[14]http://researchjournal.co.in/upload/assignments/5_29-31_2.pdf^[15]https://pubmed.ncbi.nlm.nih.gov/23778081/

Western Tarnished Plant Bug

The western tarnished plant bug is a significant pest in agriculture. Studies suggest that Tagetes could be used to manage these pests effectively, which could lead to more sustainable pest management practices.^[16]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/#pone.0233511

Marigold Insecticide for Western Tarnished Plant Bug (Lygus hesperus)

• Effective Tagetes variety: Tagetes patula (French marigold)
• Parts of the plant used: Foliage
• Form of Tagetes solution: Aqueous and methanolic foliar extracts
• Administration: Direct contact with plants and incorporation into the diet of pests
• Pest control method: Reduces survival of L. hesperus, with mortality being concentration-dependent

This study indicates that the French marigold, Tagetes patula, exhibits bio-insecticidal toxicity against the western tarnished plant bug, Lygus hesperus, which is a significant pest affecting various crops in the western United States and Mexico.

The study’s assays demonstrated that both direct contact with T. patula plants and the inclusion of its foliar extracts in the pests’ diet significantly reduced their survival. The concentration-dependent nature of the mortality suggests the presence of toxic compounds within the marigold extracts that are lethal to these pests.

Whitefly

Whiteflies cause harm by feeding on plant sap and transmitting plant viruses. Research supports the use of Tagetes in controlling whitefly infestations, which could be a significant advantage in agricultural pest control. (NCBI Study on Whitefly)^[17]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/^[18]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/#pone.0233511.ref034^[19]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237031/#pone.0233511

Mechanism of Action and Application

The bioactive compounds in Marigold Tagetes, such as alpha-terthienyl, are toxic to many pests. These compounds disrupt the life cycle of insects, acting as repellents, antifeedants, or growth inhibitors.

Tagetes can be integrated into pest management programs through companion planting, direct application of extracts and oils, and crop rotation to reduce soil-dwelling nematode populations.^[20]https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/decision_PC-176602_22-Mar-12.pdf

Environmental and Health Benefits

The use of Marigold Tagetes as an insecticide aligns with sustainable agriculture and pest management practices. It reduces reliance on synthetic chemicals, thereby minimizing environmental and health risks. This approach supports biodiversity and promotes ecological balance.

Fortunately, the diverse applications and benefits of Marigold Tagetes in pest control are well-supported by scientific research. Far beyond yard and garden beauty, Tagetes stands out as a promising candidate for natural pest management in addition to the other many useful Marigold benefits.