What is Neem Good for as a Biopesticide: An Overview

Saqib Ali Ateel & 

Dr. Salman Ahmad, PhD. Agronomy

[email protected]

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.

What is neem good for as a Pesticide?

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.

Neem, A Tree of 21st Century

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

Repellent Effects of Neem Extract on Desert Locust

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.

Table 1: Major pesticidal compounds of Neem and their Mode of Action

Scientific evidence of neem as biopesticides

• Tanh et al. (2002) observed the effect of neem-based biopesticide on aphid in different crops. They reported significant effects on aphid control by disturbing the lifecycle in several ways like decreasing larval growth, reducing feeding potential and disrupting the insect's digestive system.
• Neem extract sprays significantly control the cotton aphid nymph population by decreasing the number of molts which makes it unable for the larva to become adult and hence decreases the aphid population (Santos et al., 2004). Scientists also reported similar results on faba beans, lettuce, strawberry and sweet pepper.
• Yang et al. (2006) sprayed the neem-based azadirachtin on grasshopper control in grasslands and found more than 90% control on grasshoppers.
• Singh and Yadav (2007) reported 42% mortality of American bollworm on chickpea crop when sprayed with neem-based biopesticides.
• Ogah et al. (2007) studied the comparative effect of synthetic pesticide and neem-based biopesticide on rice and reported a higher yield and more population of friend insects in the plot where biopesticide was used. Although synthetic pesticides gave more control over the borer population than biopesticides, the final yield was less than biopesticide-treated plants due to harmful effects on friendly insects and plant health.
• Bhavani and Rao (2013) sprayed neem-based biopesticide against sugarcane whitefly and reported 80% whitefly mortality when sprayed and removed infested leaves.
• Mungbean seed treated with neem seed powder has longer shelf life due to fewer attacks of mungbean beetle. A dose of 1.5mg neem leaf powder per 100 grams of grain seeds significantly reduced the egg-laying capacity and mortality of adult store grain beetle (Amhad et al., 2015).
• Noonari et al. (2016) reported a considerable effect of neem seed extract on cotton thrips (67%) and jassid (71.97%) under field conditions in Tandojam Sindh, Pakistan.
• Shah et al. (2017) observed a markable effect of neem seed extract on wheat aphids compared with moringa leaf extract and Imidacloprid. Neem seed extract also has minimum effect on mortality of friend insects coccinellids and syrphids.

Some Additional Agricultural Benefits of neem

 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.

Future thrust of Neem as a Biopesticide

 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.

References

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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