Saqib Ali Ateel &
Dr. Salman Ahmad, PhD. Agronomy
Increasing demand for organic foods has reverted the attention of researchers toward plant extracts which indeed have some effects on various pests. One such extract is neem leaves and oil. It is a common question from many farmers, "What is neem good for?"
The conventional agriculture production system starts with synthetic fertilizers and pesticides and ends with them. The injudicious use of synthetics not only increases the cost of production but also makes agriculture poison part of our bodies. Europe and the Middle East allow the lowest levels of "maximum residue limits" (MRLs), making excessive use of synthetic chemicals counterproductive.
Biopesticides can pave a path for minimizing synthetic agrochemicals. They not only save plants from the harmful effects of pests but also supports the ecosystem to create a balance between harmful insects and beneficial ones, commonly called predators.
The biopesticides never intend to kill all harmful pests. Instead, they intend to keep pests under control, so they can't harm the crop beyond Economic Threshold Level (ETL) while providing food to the predators.
During cotton season 2019-20, we faced the worst cotton production in South Punjab (Pakistan). Our biggest problems were pink bollworm and whitefly. When farmers treated PBW with synthetic pesticides, they were able to kill the larva and flying insects which came in touch with the poisons but also killed more than 70% of predators. The next application was considered necessary within a week to crush PBW for the current crop. In some situations, the PBW was controlled. However, it was followed by colonies of pesticide-resistant whiteflies to make cotton leaves oily and black. The situation worsened on rainy days.
The situation led us to study various studies to find good words about some plant extracts, including Neem leaves. To verify those studies, the professors and scholars of a highly esteemed university, MNSUA, Multan, supported us with their experiments of various plant extracts on resistant whiteflies. Neem oil and leaf extract helped control whiteflies without heavily harming predators.
We were not the first to know what neem is good for as a biopesticide. Our ancestors have been using the leaves and fruit of this plant for centuries. Our mothers used to give us neem juice to drink to avoid some diseases around. The evidence found in the ruins of Harrap and Mohenjodaro proves that our ancestors were aware of its miraculous characteristics 4500 years ago.
Neem can be grown in sub-humid to arid climates. It is mainly found in the Indian subcontinent and Africa. It is a fast-growing plant that may grow up to 20 feet in just three years from seed. It may grow under limited water conditions and tolerate extreme heat and temperatures up to 1200C. It has a production life from 150 to 200 years.
Our experiments of neem leaf extract over whiteflies have shown some benefits over the plant itself. The neem leaves have some medicinal effects too. (figure 1).
Figure1: Agricultural and other uses of Neem
Scientists observed the repellent effects of neem extract on desert locusts, which provides a trigger for further research to explore the pesticide effects of neem (Schmutterer, 1995). Neem has proven pesticidal effects, and neem-based biopesticides have been recognized as one of the best biopesticides around the world. Neem extract contains more than 300 compounds (Li et al., 2019). Among them, a compound abundantly found in neem seed oil and leaf extract is "Azadirachtin (\ ə-ˌza-də-ˈrak-tən\) " which is effective against 400 species of pest. Some major compounds having pesticidal properties found in neem extract are shown in table 1.
Sr. No. |
Name of compound |
Mode of action |
Reference |
1 |
Azadirachtin |
|
Chaudhary et al. (2017) |
2 |
Nimbin |
Antifeedent |
Simmonds et al. (2004) |
3 |
Nimbolin |
Anti-termite |
Sarah et al. (2019) |
4 |
Salannin |
|
Govindachari et al. (1996) |
5 |
Meliantriol |
Feeding inhibitor |
Lin et al. (2021) |
6 |
Quercitin |
Antifeedent |
Upasani et al. (2003) |
7 |
Mehmoodin |
Antibacterial |
Atawodi and Atawodi (2009) |
8 |
Meliantriol |
Antifeedant |
Jacobson (1995) |
9 |
Salannol |
Inhibit larval growth |
Koul et al. (2004) |
10 |
Nimbosterol |
Antifungal |
Govindachari et al. (1998) |
11 |
Gedunin |
|
Braga et al. (2020) |
Table 1: Major pesticidal compounds of Neem and their Mode of Action
Neem leaves also act as a feed. In vermicomposting process (formation of vermicompost by using earthworms), the addition of neem leaves in feed increase the population and efficiency of earthworms to produce more vermicompost.
Neem leaves and neem cake (seed after extracting oil) contain many nutrients, fibre, protein and organic acids and are also used as biofertilizers.
Nitrogen use efficiency of urea fertilizer can be increased markedly by mixing it with neem seed powder. Blend the urea fertilizer with neem seed powder 20% by weight or mix urea with Gypsum and neem seed powder in a ratio of 5:4:1, which results in a slow and steady release of nitrogen and hence increases the nitrogen efficiency of urea fertilizer.
We recently observed neem extract's killing and inhibiting effects on Pink Bollworm and Whiteflies when the latter had become resistant to currently available pesticides in the market. This lab experiment helped us use neem and other plant extracts as IPM tools while reducing the number of chemicals by more than 70% in South Punjab, Pakistan cotton crop.
Neem-based biopesticides have less shelf life when exposed to sunlight (mainly due to UV light). Latest techniques like the use of nanotechnology should be focused on tackling this issue.
The effect of neem extract on ecologically important organisms should be investigated.
Mixing neem extract with other herbal extracts, synergistic and antagonistic effects should be thoroughly studied.
Neem dosage for the same insect pest on different crops should be determined.
Ahmad, K., Adnan, M., Khan, M. A., Hussain, Z., Junaid, K., Saleem, N., et al. (2015). Bioactive neem leaf powder enhances the shelf life of stored mungbean grains and extends protection from pulse beetle. Pak. J.Weed Sci. Res 21, 71–81.
Atawodi SE, Atawodi JC (2009) Azadirachta indica (neem): a plant of multiple biological and pharmacological activities. Phytochem Rev 8:601–620
Bhavani, B., & Rao, C. V. N. (2013). Management of sugarcane white fly (Aleurolobus barodensis Mask.) in north coastal districts of Andhra Pradesh, India. International journal of social science & interdisciplinary research, 2, 112-115.
Braga, T. M., Rocha, L., Chung, T. Y., Oliveira, R. F., Pinho, C., Oliveira, A. I., ... & Cruz, A. (2020). Biological activities of gedunin—A limonoid from the Meliaceae family. Molecules, 25(3), 493.
Chaudhary, S., Kanwar, R. K., Sehgal, A., Cahill, D. M., Barrow, C. J., Sehgal, R., & Kanwar, J. R. (2017). Progress on Azadirachta indica based biopesticides in replacing synthetic toxic pesticides. Frontiers in plant science, 8, 610.
Govindachari TR, Suresh G, Gopalakrishnan G, Banumathy B, Masilamani S (1998) Identification of antifungal compound from the seed oil of Azadirachta indica. Phytoparasitica 26:109–116
Govindachari, T. R., Narasimhan, N. S., Suresh, G., Partho, P. D., & Gopalakrishnan, G. (1996). Insect antifeedant and growth-regulating activities of salannin and other C-seco limonoids from neem oil in relation to azadirachtin. Journal of chemical ecology, 22(8), 1453-1461.
Jacobson M (1995) In: Schmutterer H (ed) The neem tree: source of unique natural products for integrated pest management, medicine, industry and other purposes. VCH, New York, pp 484–495
Koul O, Singh G, Singh R, Singh J, Singh J, Daniewski WM, Berlozecki S (2004) Bioefficacy and mode-of-action of some limonoids of salannin group from Azadirachta indica A. Juss and their role in a multicomponent system against lepidopteran larvae. J Biosci 29:409. https://doi. org/10.1007/BF02712112
Li, L., Song, X., Yin, Z., Jia, R., & Zou, Y. (2019). Insecticidal activities and mechanism of extracts from neem leaves against Oxya chinensis. Arquivo Brasileiro de Medicina Veterinária e Zootecnia, 71, 1-10.
Lin, M., Yang, S., Huang, J., & Zhou, L. (2021). Insecticidal Triterpenes in Meliaceae: Plant Species, Molecules and Activities: Part Ⅰ (Aphanamixis-Chukrasia). International Journal of Molecular Sciences, 22(24), 13262.
Noonari, A. M., Abro, G. H., Khuhro, R. D., & Buriro, A. S. (2016). Efficacy of bio-pesticides for managegement of sucking insect pests of cotton, gossipium hirsutum (L.). Journal of Basic and Applied Sciences, 12, 306-313.
Ogah, E. O., Omoloye, A. A., Nwilene, F. E., & Nwogbaga, A. C. (2011). Effect of neem seed kernel extracts in the management of rice stem borers in the field in Nigeria. Nigerian Journal of Biotechnology, 23.
Santos, T. M. D., Costa, N. P., Torres, A. L., & Boiça Júnior, A. L. (2004). Effect of neem extract on the cotton aphid. Pesquisa Agropecuária Brasileira, 39(11), 1071-1076.
Sarah, R., Tabassum, B., Idrees, N., & Hussain, M. K. (2019). Bio-active Compounds isolated from Neem tree and their applications. In Natural bio-active compounds (pp. 509-528). Springer, Singapore.
Schmutterer, H. (1995). The neem tree, Azadirachta indica A. Juss, and other meliaceous plants: source of unique natural products for integrated pest management, medicine, industry and other purposes, 1st edition. VCH, Weinheim. ISbN 3Y527Y30054Y6. 696 pp.
Shah, F. M., Razaq, M., Ali, A., Han, P., & Chen, J. (2017). Comparative role of neem seed extract, moringa leaf extract and Imidacloprid in the management of wheat aphids in relation to yield losses in Pakistan. PLoS One, 12(9), e0184639.
Simmonds, M. S., Jarvis, A. P., Johnson, S., Jones, G. R., & Morgan, E. D. (2004). Comparison of anti‐feedant and insecticidal activity of nimbin and salannin photo‐oxidation products with neem (Azadirachta indica) limonoids. Pest Management Science: formerly Pesticide Science, 60(5), 459-464.
Singh, S. S., & Yadav, S. K. (2007). Comparative efficacy of insecticides, biopesticides and neem formulations against Helicoverpa armigera on chick pea. Annals of Plant Protection Sciences, 15(2), 299-302.
Upasani, S. M., Kotkar, H. M., Mendki, P. S., & Maheshwari, V. L. (2003). Partial characterization and insecticidal properties of Ricinus communis L foliage flavonoids. Pest Management Science: formerly Pesticide Science, 59(12), 1349-1354.
Yang et al. (2006) investigated the impact of neem based azadirachtin on grass hopper in grasslands and found more than 90% control on grass hopper population.
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