Butterflies, nematodes, and marigold

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Miguel Braganza

A rose by any other name may smell as sweet, but the Konkani term ‘rosam’ has nothing to do with the Latin ‘rosa’ and the English ‘rose’. Rosam is the local word for marigold. This is the flower most commonly associated with Dussehra. The festival of Dussehra is still a month away because the ‘Adhik Maas’ of the Ashwin month follows the ‘Poshan Maah’ of September and precedes the normal month of Ashwin this year. The ‘Tulsi Vivah’ is celebrated on November 26, and the wedding season that uses an abundance of marigold flowers for decorating the mandaps starts thereafter. So, we have approximately two months to grow marigolds and earn money.

Marigold flowers now find application in petals therapy and aroma therapy. In the COVID-19 era, this can help one overcome depression due to the lockdown, loss of income, etc. The dried petals are used to extract yellow pigment to be used in food colouring, clothing dyes, or as a powder that is mixed in chicken feed to produce a more intense colour to egg yolks. The powder is also used in rangoli and during the Holi festival. As the years go by, more and more applications are being found for the flower that is truly worth its weight in gold.

The bobbing orange, butter yellow, ochre and lemon-yellow heads of marigold flowers are a sight to see on the borders of fields filled with green and ripening red chilies and tomatoes. Many centuries ago, farmers on the Mediterranean coast found that tomatoes grew better when grown near plots of marigold plants. They did not know why and how but they knew that there was a tangible benefit. So, they grew marigold in other fields where traditionally only tomatoes were grown and gained economically through better yields of tomatoes.

Some people were curious to know why tomato plants did better when grown together with marigold plants. The first thing they noticed was that butterflies preferred the large, showy flowers of marigold to the small, dull, and unattractive flowers of tomatoes and chilies. The butterflies laid their eggs on the marigold plant and the leaf-miner caterpillar infestation on the nearby tomato, chili, and capsicum plants was greatly reduced. The plants had more active leaf area for photosynthesis and produced a bigger harvest. The role of the marigold in attracting the insects to itself is now known as trap cropping.

What is visible is often only the tip of the iceberg. The rest of the picture is hidden from view. And it was exactly the same case with the benefits of the marigold or the Tagetes erecta plant. Scientists discovered that the roots of the marigold plants produced exudates that suppressed the microscopic root-knot nematodes in the soil that infest the roots and retard the plants. Just growing the marigold plant is enough to change all this for the better. This is one form of nurse cropping using the pest suppressant property of marigold.

Marigold flowers are used across religions and even by agnostics to welcome comrades in various spheres of civil society. The marigold’s warm yellow, orange, or saffron colour signifies both warmth and sacrifice. It is a plant that we can grow easily in Goa and gain by having both flowers as well as protection for our chilies and tomato plants.