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 <div class="title"><h3>7.19 -Marigold as a Companion Crop to Combat Pests</h3><br><h3 class="ch-owner">Jessica Witjes, University of Guelph, Canada</h3></div>
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<p>Suggested citation for this chapter.</p>
<p>Witjes,J. (2022)  Marigold as a Companion Crop to Combat Pests, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org</p>
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       <h1 class="title-bg">Background of Root-Knot Nematodes</h1>
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          <p>Root-Knot nematodes cause dramatic effects to crops and fields all around the world (Mitkowski and Abawi, 2003). Root-knot nematodes are very small (microscopic) roundworms that find habitat in soil and crop roots. They have mouths similar to needles, which are used to feed from within the roots of these affected crops (Doubrava and Blake, 2019). Crops which have been infected experience both underground and above-ground symptoms. Underground symptoms can be identified by the formation of galls, with the roots having an abundance of dried or dead root branches. Galls are formed when the nematodes enter the roots and begin to feed within (Mitkowski and Abawi, 2003). Three factors often influence the extent of root galling caused by nematodes: nematode population density, nematode species and "race," and the type of host plant. The number of galls per plant will rise in a given field in proportion to the nematode density. Larger galls will also arise from a large number of nematodes infecting nearby roots (Mitkowski and Abawi, 2003). Although most damage due to root-knot nematodes occurs below ground, some of the most visually obvious symptoms can be seen above ground. Infected plants will appear wilted or droopy, which is caused by the roots' capacity to transmit water and nutrients being harmed by the creation of these galls (Perry and Ploeg, N/A). Crop yields are decreased, and stunting is commonly reported especially on the roots of vegetable plants; furthermore, galls can break or fracture, enabling diseases transmitted by the soil to enter root systems (Dickson et al., 2020). Globally the annual yield loss of sweet potato due to root-knot nematodes was estimated to be USD 157 billion. It was responsible for 100% and 14% of the damage to citrus fruits and food crops, respectively, with a potential annual financial loss of USD 100 billion (Wendimu, 2021). </p>
<p>[[Image:Bag 34.jpg|thumb|centre|Figure 1: click for larger resolution]]</p>
<p>Figure 1: Northern root-knot nematode damage to a carrot
field in New York State. (Source: Mitkowski, 2011).</p>
<p>[[File:Bag 35.jpg]]</p>
<p>Figure 2: Roots covered in galls due to being infested with Root-knot nematodes. (Source, Allen, 2016).</p>
<p>[[File:Bag 36.jpg]]</p>
<p>Figure 3: Marigold genotypes/varieties with diverse colored petals used in the study.  </p>
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       <h1 class="title-bg">Marigold as a Companion Crop</h1>
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     <p>Marigolds are native to America and have been cultivated in Mexico for over 2000 years (Polomski and Russ, 2021). Marigolds thrive in the sunlight, are very easily cared for, and are low maintenance, making perfect additions to flower beds or even vegetable gardens. Although they are pretty contributions to a garden, they serve much more dramatic and important roles. Marigolds may be used in gardens as a pest deterrent, as the smell that is released from these plants are very undesirable to unwanted pests (Krueger et al., 2019). Alpha-terthienyl gas, which is produced by marigold plants, has the potential to decrease the number of disease-causing organisms, including bacteria, fungi, insects, and some viruses, as well as root-knot nematodes (Krueger et al., 2019). When planted close to a crop's roots, marigolds can effectively control root-knot nematodes, in part by preventing nematode eggs from developing and being released into the soil (Olabiyi and Oyadunmade, 2007).</P> 
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       <h1 class="title-bg">How marigolds can be adopted by small-scale farmers</h1>
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          <p>Marigolds can be grown from seeds or transplanted; they are also capable of living in storage containers (Ogden, N/A). Marigolds are partially annual, meaning they have the ability to last all year round; they prefer a warm season but can survive cooler weather as well. When grown, they have a seeding and production period of 85–90 days (Dalman et al, 2022). When planting marigolds, there are a few tips/tricks to keep in mind: these seeds are often planted right into the ground, in well-drained, loose soil (soil can be loosened by digging 6 inches down and mixing). Compared to pre-grown marigolds, planted seeds take longer to blossom and can have a longer-lasting blossom if dead and dried blooms are removed. The part of the marigold that protects crops from root-knot nematodes is the roots, and marigolds should not be planted near legume crops due to the antibacterial thiophenes contained in legume roots (Ogden, N/A). When marigolds are grown, although they have great nematode pest-repellent properties, they also have many other traits, including repelling many other pests with their pungent scent. Additionally, the blossoms of marigolds can be used as food colouring or natural die for many fabrics (Ogden, N/A).</p> 
<p>Marigolds should be planted directly in the vegetable beds before or while the vegetables are growing; this will ensure there isn’t a period where the nematodes can find a home in the roots of the vegetable plants before the marigolds are planted (Campbell, 2017). For optimal nematode control, dense marigold planting is recommended. It is suggested to maintain the distance between individual plants and the distance between rows to less than 18 centimetres to help avoid weeds. This is crucial because nematodes can thrive on weeds and offset the benefits of marigolds. Direct marigold sowing may require significantly greater seeding densities in order to produce a thick stand (Krueger et al., 2019).</p> 
<p>Marigolds are considered to be extremely auspicious and used as decorations for places of worship within the Hindu religion, and hence already quite prevalent in South Asia (Ghosh, 2022). Located in the Practical Resources section below, there is a tutorial on how marigold seed can be extracted from a flowering plants and reused for future purposes.</p>
<p>[[Image:Bag 37.jpg|thumb|centre|Figure 4: click for larger resolution]]</p>

<p>Figure 4: Marigolds (orange) planted as companion to many different crops in a garden. (Source: hermionesgarden.blogspot.com.)  </p>
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       <h1 style="background: #FBB03B;padding: 15px;font-weight: 600;color: #000;font-size: 22px;margin:unset;text-align:center;">Critical Analysis</h1>
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          <p>There are many health benefits when using marigolds as a treatment substitute for synthetic chemical pesticides to treat root-knot nematodes. Many pesticides that are recommended for use on crops to deter or kill pests are extremely dangerous to non-target animals and humans (Das et al., 2022). Pesticide chemicals are strong and can also be dangerous to their animal relatives, including humans (Ploeg, 2007). Using marigolds is a natural and effective nematode deterrent option for farmers and can make farmers more self-sufficient if seeds are reused and saved properly for future use. As stated above in the “Marigold as a Companion Crop” section, the part of marigolds that deter and protect crops from nematodes is the roots, which leaves the above-ground portions (stem and flower) available to be sold for extra profit as cut flowers, such as for religious ceremonies within the Hindu religion (Ghosh, 2022).</p> 
<p>Plant and crop growth when companion cropped with marigolds has been researched and shown to be much higher than crops that were not intercropped with marigolds. One study showed that tomato yields were 50% higher when using marigolds as a companion crop compared to tomato yields without marigolds. The marigolds reduced nematode galling and infestation of the tomato roots (Ploeg, 2007). Another study concluded that when marigold plants were intercropped with soybeans in the same pots, soybean shoot weight and length as well as root length increased when compared to soybean plants in separate non-intercropped pots (Hamawi et al., 2004).</p> 
<p>Training farmers to work with marigold plants is not extensive. Marigolds are a very low-maintenance plant and do not require special treatment except for preferring to be watered at the base of the plant. This would add extra work for farmers, as sprinklers may no longer be an effective method of watering. As for farmer training, while working with these plants, there are many YouTube videos like the one below in the “Practical Resources Section” to show farmers how to care for these plants. Marigold seeds may be difficult to obtain in different parts of the world, but once one marigold plant is obtained, a farmer can be self-sufficient in harvesting seeds for future years.</p>
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       <h1 class="title-bg">Helpful Links To Get Started </h1>
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          <p>	How to plant marigolds in a bed:
https://youtu.be/LWIVepvPqFA?si=c0DNxd3qKZIWIYAV</p>

<p>	How to harvest seeds for next years marigold crops from previously planted marigold plants:
https://youtu.be/qUbxK4gqNxU?si=rYAth5HI3Mas3jJI </p>

<p>	How to plant marigolds as a companion crop:
1.	https://youtu.be/AoODyDVjpv0?si=7D3tGTyodba4in0O 
2.	https://youtu.be/Pk2-1tkeGnI?si=2VbCWluWwokIosKZ</p> 
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       <h1 class="title-bg">References</h1>
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          <p>1.	Ploeg, A.T. (2007) Effects of Selected Marigold Varieties on Root-knot Nematodes and Tomato and Melon Yields. Plant Disease, 86, 505-508. https://apsjournals-apsnet-org.subzero.lib.uoguelph.ca/doi/10.1094/PDIS.2002.86.5.505 </p> 
<p>2.	Das, S., Wadud, A., Chakraborty, S., & Khokon, A. (2022,). Biorational Management of Root-Knot of Brinjal. Heliyon, 8, E09227. https://www-sciencedirect-com.subzero.lib.uoguelph.ca/science/article/pii/S2405844022005151?via%3Dihub </p> 
<p>3.	dos Santos Oliveira, A.K., Pedrosa, E.M.R., Dickson, D.W. et al. (2020) Migration and penetration of Meloidogyne enterolobii and M. incognita in soil columns with tomato and marigold. Eur J Plant Pathol 158, 591–598. https://doi-org.subzero.lib.uoguelph.ca/10.1007/s10658-019-01889-7  </p>
<p>4.	Doubrava, N., Blake, J. H., & Williamson, J. (2020, May 1). Root-knot nematodes in the vegetable garden. Home and Garden Information Center. https://hgic.clemson.edu/factsheet/root-knot-nematodes-in-the-vegetable-garden/ </p> 
<p>5.	El-Hamawi, M.H., Youssef, M.M.A. & Zawam, H.S. (2004) Management of Meloidogyne incognita, the root-knot nematode, on soybean as affected by marigold and sea ambrosia (damsisa) plants. J Pest Sci 77, 95–98. https://doi-org.subzero.lib.uoguelph.ca/10.1007/s10340-003-0034-1</p>  
<p>6.	Ghosh, D. (2022, November 27). Genda Phool: Know why Marigold Flower is considered auspicious for religious works. Times Now News. https://www.timesnownews.com/spiritual/genda-phool-know-why-marigold-flower-is-considered-auspicious-for-religious-works-article-95804310 </p> 
<p>7.	Krueger,R., Dover, K.E., WangR, K. H. (2019). For Nematode Management. University of Florida. Askifas. HTTPS://EDIS.IFAS.UFL.EDU/PUBLICATION/NG045 </p> 
<p>8.	Mitkowski, N., & Abawi, G. (n.d.). Root-knot nematode. The Plant Health Instructor.  The American Phytopathological Society. https://www.apsnet.org/edcenter/disandpath/nematode/pdlessons/Pages/RootknotNematode.aspx </p>
<p>9.	Odgen, E. (n.d.). All about marigolds. American Meadows. https://www.americanmeadows.com/content/wildflower-seeds/marigold-seeds/all-about-marigolds </p> 
<p>10.	Olabiyi., Timothy., & Oyedunmade, E. (2007). Marigold (Tagetes erecta L.) as interplant with cowpea for the control of nematode pests. African Crop Science Conference Proceedings 8, 10750-1078. https://www.researchgate.net/publication/267686298_Marigold_Tagetes_erecta_L_as_interplant_with_cowpea_for_the_control_of_nematode_pests#:~:text=The%20results%20of%20this%20experiment,per%20plant)%20and%20grain%20yield%20 </p> 
<p>11.	Perry, E.J and A.T, Ploeg. N/A, How to manage pests. California. Statewide Integrated Pest Management Program. https://ipm.ucanr.edu/PMG/PESTNOTES/pn7489.html#REFERENCE</p>  
<p>12.	Yigezu Wendimu, G. (2021). Biology, taxonomy, and management of the root-knot nematode (meloidogyne incognita) in sweet potato. Advances in Agriculture 2021, 8820211.  https://www.hindawi.com/journals/aag/2021/8820211/  
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