Template:Chapters 8.3
8.3 - Neem to combat pests during grain storage and the field
Gryphon Theriault-Loubier, University of Guelph, Canada
Suggested citation for this chapter.
Theriault-Loubier,G(2022) Neem to combat pests during grain storage and the field. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Introduction
Neem (Azadirachta indica) is a fast growing, drought tolerant deciduous, evergreen tree of Indo-Malay origin but now widely grown throughout the tropics and subtropics including in Africa (World Agroforestry Centre, 2011). Neem leaves and fruit have been in use since pre-history for a variety of purposes including ethnobotanical, medicinal, cultural and agricultural (Jamir, 1999; Harbant, & Mohamed, 2012). The plant or its extracts can be used as a multi-functional natural pesticide, for example as a seed coating to maintaining food quality during storage (Nisar, 2009), as a spray on field crops (Baidoo, 2012), and even as an adjunct prophylactic (preventative medicine) in aquaculture (Kumar, 2013). Neem can be used as an effect biopesticide in tropical vegetable gardens (e.g. kale and cabbage in Thailand) which often use large amounts of commercial pesticides (Tran 2003). The functionality of neem is due to some 35 active ingredients, among which are anti-feedants, deterrents, growth and reproduction limiting (sterility) compounds. Azadirachtin (Fig.1),
a complex terpenoid, is widely considered to be the most active insecticidal ingredient (Schmutterer, 1990). While the seeds have the highest concentration of azadirachtin, the fruit, leaves and bark also contain the compound (Bramachari, 2004).
Use of Neem as a Field Spray
Neem extracts can be used as a bio-pesticide spray for field crops. Bramachari reported that neem has been found to be effective against 413 different species of insects in 16 different insect orders including beetles, caterpillars, aphids, leafhoppers, leaf miners, psyllids, thrips, mealy bugs and whiteflies. Research has shown some efficacy in application to mite species (V. jacobsoni) that commonly infest honey bee hives (Melathopoulos et al., 2000). Baidoo (2012) found that neem extract significantly reduced the population of cabbage pests, and increased cabbage weight (See Critical Analysis). Neem is particularly effective at the juvenile insect stage, as it disrupts a common insect hormone ecdysone, preventing moulting. As a result, the larvae remain in an immature stage and die (Bramachari, 2005). Therefore, the extract works best on the second generation of insects and a delayed response in the field is a common observation, and this should be explained to farmers in advance to prevent disappointment (Schmutterer 1990). Similarily, food products which require a high visual quality or do not recover from insect feeding might not be best suited for neem compounds (Schmutterer 1990).
Use of Neem to Prevent Food Storage Losses
The pesticidal property of azadirachtin means an extract of the seed or pulverized seed powder can be applied to jute bags for storage of grain, and can serve doubly as an insect deterrent; alternatively neem leaves are sometimes directly added to grain storage bags (Melathopoulous, 2000, Brahmachari 2004).
Possible Benefits
The neem tree is exceptionally hardy – suitable growing conditions include those that experience >400 mm rainfall, extended drought and poor soil, including saline (salty) soils (Schmutterer 1990). Obara (2004) describes the potential of Kenyan neem trees as a supply of excellent quality carving wood. It is considered highly desirable for this purpose as it is easy to work with has an aesthetically pleasing grain. While this is a benefit on the side of productivity, it should be considered that in areas of limited wood supply, these trees might need protection from poachers (Obara, 2004).
Extract of the neem tree has the potential to reduce reliance on commercial pesticides. Neem extract has the potential to be a low cost, long-term solution that may reverse conventional income flow from farmer to input manufacturer (Tran, 2003). Neem has potential as a small-medium local business enterprise, and the reader is encouraged to read Tran (2003) who has explored this subject. There may be significant market demand for the product in the future given the wealth of research and possible applications of neem compounds, including as a treatment for dengue fever, as a contraceptive and analgesic, and for rheumatism (Bramachari, 2004).
In terms of environmental impact, neem has been reported to disturb aquatic life at lower rates than many synthetic pesticides since it degrades rather quickly (36-48 hrs) following application if exposed to sunlight (Scott, 2003). While aquatic invertebrates were unharmed at full agricultural applicable concentrations of neem, some benthic (bottom feeding) populations were disturbed (Scott, 2003).
Critical Analysis
Tree propagation time:
Neem is propagated from seeds (see below). It is estimated that approximately 10 years (minimum) of growth is required for a tree to produce ~10 kg of fruit, of which only a portion is neem kernel (Schmutterer 1990). Development projects may find this to be outside of their project timelines. Therefore, trees must be locally pre-existing or a long-term plantation program must be implemented. There may also be regulations on importing neem seed if not locally available (see below).Spraying frequency: Schmutterer (1990) states that neem compounds are generally less effective in the short-term than synthetic commercial alternatives. While ecologically beneficial, the relatively short half-life of 36-48 hours is a practical challenge, meaning that the compound will need reapplication every 5-7 days. However, it is noted that some conventional pesticides also have similar application requirements (Schmutterer 1990).
Impact on plant growth: While Baidoo (2012) noticed increased cabbage weight as a result of neem spraying, Egho (2011) noted delayed development of the cowpea plant at 5% neem extract concentration.
Impact on human health: Though neem extracts are generally considered to be safe by advocates, Bramachari (2004) found that there were some human health concerns related to neem application. Toxicity in mammals from neem has been reported at relatively high dosages (Bramachari, 2004). Long-term controlled studies do not appear to have been conducted, and hence the possible effects of prolonged exposure to low doses of neem extract are not clear. As with any effective pesticide, safety equipment is preferable, but according to Raizada (2001), this may not be necessary after the neem extract has dried.
Environmental impact: As neem is a wide spectrum pesticide (Bramachari), it may harm beneficial insects. Prolonged over-spraying of neem extract may also lead to insect resistance, and hence neem should be incorporated into integrated pest management (IPM) programs that promote good ecology to reduce pests (e.g. crop rotations) (Appropriate Technology, 2006).
Patent rights:
An ongoing legal battle exists between W. R. Grace & Co. and advocate Jeremy Rifkin. W.R. Grace has patented a method of extracting an active ingredient from neem for use in commercial pesticides, whereas Rifkin contends that the traditional use of neem means that such a technology cannot be patented (Wolfgang, 1995).How to make the extract: Small-Scale Production (Neem Foundation)
Preparing Neem Kernel Extract: The process for making a neem kernel extract is relatively simple. Following harvesting, neem kernels are ground, then the powder is usually gathered in a simple muslin cloth pouch and soaked overnight in water. The next morning, the pouch is squeezed to remove as much of the extract as possible. The ratio for an effective concentration of compounds is 50 g of neem kernel to 1 L of water. To increase surface area and decrease the time necessary for extraction, the outer coat of the neem kernel is removed, and the kernel is pounded gently. Some reports indicate that the outer coat is an effective addition to fertilizer. If the means do not exist locally to remove the seed coat, the ratio of the extract from (intact) neem kernels should be increased to 75 g per 1 L of water. The age of the neem kernels after harvesting is important; the seeds should be at least 3 months in age, and no older than 8 months to assure maximum azadirachtin content. For purposes of application onto leaves, an emulsifier is usually added, such as soap oil, soap cake powder, sandovit, or teepol, which are sometimes sold commercially. An emulsifier assists the active compounds in sticking to the leaves that will receive application.
Preparing Neem Leaf Extract: The concentrations of the active compounds are highest in neem kernels, but they are also present in the leaves (Bramachari, 2004). It is estimated that for 1 ha of land, nearly 80 kg of leaves would be required which is substantial. For practical purposes, it is therefore suggested that neem leaf extract should be applied to seedlings in nurseries and kitchen gardens. The process of making the leaf extract is nearly the same as producing the seed extract: the leaves are soaked overnight, then the next day the leaves are ground and the extract is filtered: 1 kg of green neem leaf is required per 5 L of water. As above, an emulsifier is added to facilitate better adhesion to applied leaf surfaces.
How to Spray Neem Extract or Commercial Neem Oil
As the active compounds break down fastest in extended bright light, the compound should be applied in the evening or very early morning. During high temperatures, the frequency of spraying should be increased. Since the compound is washed away by water, daily spraying is recommended in the rainy season. As insects lay eggs on the underside of the leaves, it is important to spray neem extract on the underside of the leaves. Optimally, each acre of land can be sprayed with approximately 60 L of ready-to-use solution (see below).
As an alternative, neem oil can be purchased commercially. To apply onto crops or seeds, 30 ml of neem oil is added to 1 L of water, along with an emulsifier. The resultant product needs to be mixed thoroughly and applied before oil droplets start floating on the water surface. Backpack sprayers have been found to be more effective than hand sprayers as they often have a built-in mixing agitation technology.
Picture Based Lesson to Train Farmers
For the South Asian version (pictures only, text for you to insert), click this link for lesson 9.3:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.3_south_asian.pdf
For the East/South Asian version (pictures only, text for you to insert), click this link for lesson 9.3:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.3e.s.a.pdf
For the Sub-Saharan Africa/Caribbean version (pictures only, text for you to insert), click this link for lesson 9.3:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.3subsaharan_africa_carribean.pdf
For the Latin-America version (pictures only, text for you to insert), click this link for lesson 9.3:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.3latin_america.pdf
Source: MN Raizada and L Smith (2016) A Picture Book of Best Practices for Subsistence Farmers. eBook, University of Guelph Sustainable Agriculture Kit (SAK) Project, June 2016, Guelph, Canada.
Further Information
Sources of seed and information on propagating neem trees
The trees are typically planted from seed. In India, there are commercial suppliers of neem seed including JDG Seeds which sell neem seeds for $1.10 USD per kg. Please refer to the Tree Seed Supplier Directory on the website of the World Agroforestry Center for local suppliers of neem seeds.
The Neem Foundation states that: “The seeds should be as fresh as possible as older seeds often do not germinate. Provided that only a few trees are to be planted, and there is sufficient moisture available, with minimum weeds, the seeds may be sown directly into the ground. Two to three seeds are placed together about 1 cm deep in loose soil. After germination, only the strongest plant should be retained. When planting a large number, it is advisable to cultivate young plants first in pots, trays or plastic bags. After 3 months, they should be transplanted into the ground. When using bags or pots care should be taken that the plants are not allowed to develop to a stage where the taproot has pierced the bottom and has to be shortened before transplantation. This weakens the trees and substantially slows their growth.”
References
1. Adarkwah, C., et al. "Bio-Rational Control of Red Flour Beetle Tribolium Castaneum (Herbst) (Coleoptera: Tenebrionidae) in Stored Wheat with Calneem Registered Oil Derived from Neem Seeds." Journal of Pest Science 83.4 (2010): 471-9.
2. Baidoo, P. K., and J. I. Adam. "The Effects of Extracts of Lantana Camara (L.) and Azadirachta Indica (A. Juss) on the Population Dynamics of Plutella Xylostella, Brevicoryne Brassicae and Hellula Undalis on Cabbage." Sustainable Agriculture Research 1.2 (2012): 229-34
3. Bramachari, Goutam. (2005). Neem – An omnipotent Plant: A retrospection. ChemBioChem 2005(4), 408 – 421.
4. Egho, E. O., and E. M. Ilondu. "Seeds of Neem Tree (Azadirachta Indica A. Juss). Promising Biopesticide in the Management of Cowpea Insect Pests and Grain Yield in the Early Cropping Season at Asaba and Abraka, Delta State, Nigeria." Journal of Agricultural Science 4.1 (2012): 181-9.
5. Harbant, & Mohamed. (2012). Evaluating eco-friendly botanicals (natural plant extracts) as alternatives to synthetic fungicides. Annals of Agricultural and Environmental Medicine : AAEM, 19(4), 673-676.
6. Hummel, H., Hein, D.F., and Schmutterer (2012). The Coming of Age of Azadirachtins. Journal of biopesticides, 5(sup.) 82.
7. Isman, Murray B., Saber Miresmailli, and Cristina MacHial. "Commercial Opportunities for Pesticides Based on Plant Essential Oils in Agriculture, Industry and Consumer Products." Phytochemistry Reviews 10.2 (2011): 197-204. Biological Sciences.
8. Kumar, S., Raman, R. P., Pandey, P. K., Mohanty, S., Kumar, A., & Kumar, K. (2013). Effect of orally administered azadirachtin on non-specific immune parameters of goldfish carassius auratus (linn. 1758) and resistance against aeromonas hydrophila. Fish & Shellfish Immunology, 34(2), 564-573.
9. Melathopoulos, A. P., Winston, M. L., Whittington, R., Smith, T., Lindberg, C., Mukai, A., & Moore, M. (2000). Comparative laboratory toxicity of neem pesticides to honey bees(hymenoptera: Apidae), their mite parasites varroa jacobsoni(acari: Varroidae) and acarapis woodi (acari: Tarsonemidae), andBrood pathogens paenibacillus larvae and ascophaera apis. Journal of Economic Entomology, 93(2), 199-209.
10. Neem: The bitter truth. (2006). Appropriate Technology, 33(3), 29-29.
11. Nisar, K., et al. "Pesticidal Seed Coats Based on Azadirachtin-A: Release Kinetics, Storage Life and Performance." Pest Management Science, 65 (2) pp.175-182, 2009 (2009)Biological Sciences
12. Obara, A. O., Hoeft, M. G., & Hoeft, R. (2004). Neem, azadirachta indica A. juss. (meliaceae), and its potentialfor sustainable woodcarving in kenya. Economic Botany, 58(1), 98-111.
13. R. B. Raizada, M. K. Srivastava, R. A. Kaushala, R. P. Singh, Food Chem. Toxicol. 2001, 39(5), 477 ± 483.
14. Scott, I. M., and N. K. Kaushik. "The Toxicity of a Neem Insecticide to Populations of Culicidae and Other Aquatic Invertebrates as Assessed in in Situ Microcosms." Archives of Environmental Contamination and Toxicology 39.3 (2000): 329-36. Biological Sciences; Environmental Sciences and Pollution Management.
15. Schmutterer, H. (1990.) Properties and Potential of the Natural Pesticides from the Neem Tree, Azadirachta Indica. Annu. Rev. Entomol. 1990. 35:271-97.
16. Tran, V. M., & Perry, J. A. (2003). Challenges to using neem (azadirachta indica var. SianensisValenton) in thailand. Economic Botany, 57(1), 93-102.
17. T, T. Jamir, K. Sharma H, and K. Dolui A. "Folklore Medicinal Plants of Nagaland, India." Fitoterapia 70.4 (1999): 395-.ProQuest Agriculture Journals
18. Wolfgang, Lori. "Patents on Native Technology Challenged." Science 269.5230 (1995): 1506-. ProQuest Agriculture Journals.
19. World Agroforestry Centre (2011). A tree species reference and selection guide: Azadirachta indica. Available online at < http://www.worldagroforestrycentre.org/sea/products/afdbases/af/asp/SpeciesInfo.asp?SpID=271>