Chrysanthemums hold potential for use as a natural pesticide

Most flower arrangements aren’t complete without the beautiful chrysanthemums. These flowers, which exist in a variety of colors, are not just for decoration, they also have many other applications. A study by researchers from the Federal University of Rio de JaneiroVila Velha University, and The Federal University of Espírito Santo revealed that one potential application of chrysanthemums (Dendranthema grandiflorum), especially the “yellow sheena” cultivar, is as a natural pesticide against the yellow fever mosquito (Aedes aegypti).

The yellow fever mosquito carries different disease-causing viruses, such as the ones responsible for Zika, dengue, chikungunya, and yellow fever. These diseases can significantly reduce a person’s quality of life since they can cause symptoms, such as fever, headaches, muscle pain, rashes, nausea, vomiting, difficulty breathing, chest pain, and rapid heartbeat. Moreover, severe cases can even lead to death.

Prevention is always better than cure, and one of the ways through which people can reduce their risk of getting mosquito-borne diseases is through proper pest control. Unfortunately, mosquitoes can develop resistance to the conventional pesticides that are widely used nowadays. This highlights the need for natural alternatives that are not just effective but are also safe to use.

In this study, which was published in The Brazilian Journal of Pharmacognosy, the researchers collected methanol and dichloromethane extracts from the yellow sheena cultivar of chrysanthemums. They then identified the active compounds present in the extracts to see if any of them have previously reported larvicidal activity. From their analysis, they found that the methanol extract contains flavonoids and caffeoylquinic acids. Meanwhile, compounds in the dichloromethane extract include triterpenoids and fatty acids, which have insecticidal activity.

The researchers also exposed yellow fever mosquito larvae to the methanol and dichloromethane extracts to determine their larvicidal activity. They based this on the 50 percent lethal concentration (LC50) values, which corresponds to the concentration needed to kill 50 percent of the larval population. Results showed that the methanol and dichloromethane extracts have LC50 values of 5.02 and 5.93 parts per million (ppm), respectively.

“Ornamental plants are abundantly cultivated in Brazilian highlands; however, after aging, they are discarded. The results of the present study demonstrate that such discarded plants could be recycled for their methanolic extracts and used to propose innovative products, as, for example, larvicides,” said the authors of the study.

Overall, these results show that chrysanthemums can be used as a natural alternative to synthetic pesticides since they contain various insecticidal compounds. (Related: Bye, bye, bugs: 12 plants to keep the bugs away.)

Harmful side effects of conventional pesticides

The detrimental effects of most conventional pesticides are not just limited to the insects they kill. These also extend to the humans who are exposed to them, either directly or through the residue they leave in food. Some of the side effects commonly associated with synthetic pesticides include the following:

  • Endocrine complications — Pesticides widely used in farming have been shown to interfere with testosterone and androgen production and functioning. Changes in these hormones can lead to reproductive problems, such as low sperm count and infertility. Studies have also shown that females exposed to high amounts of pesticides suffer from hormone-related problems like infertility, irregular menstrual cycles, no ovulation, and early reproductive senescence.
  • Brain damage — Excessive exposure to pesticides increases the risk of developing long-term brain damage and mild cognitive dysfunction, which can include speech problems and difficulty in identifying words, colors, and numbers.
  • Congenital disabilities — Even unborn babies aren’t safe from the harmful effects of pesticides. Constant exposure of expecting mothers to these chemicals increases the possibility that their child will be born with an oral cleft, neural tube defects, heart defects, or limb defects.
  • Respiratory disorders — Respiratory problems like wheezing, chronic bronchitis, and asthma are associated with pesticide exposure. However, you can reduce the risk of these health problems by wearing proper protective equipment.

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