Chapter 7.16
7.16 - Magnifying Glass to Remove Diseased Seeds
Andrew Treigys, University of Guelph, Canada
Suggested citation for this chapter.
Treigys,A. (2022) Magnifying Glass to Remove Diseased Seeds, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Background Information
Removing diseased seeds with the aid of a magnifying glass or sheet is relevant to African and Asian smallholder farmers as it addresses several challenges they face in their daily lives. When planting seeds, it is important to distinguish between a healthy seed and a diseased seed. Diseased seeds often have a few discolored spots that are visible to the naked eye or under low magnification. Depending on the disease, they are distinguished by discoloration (black, brown) shriveling and/or cracks (Mancini, 2020). Picking out diseased seeds can drastically impact the crop yield and overall sustainability of future crops (Pellegrino, 2010). The risk comes from pathogens spreading and infecting the soil or other crops in the field (du Toit, 2004). Pathogens also decrease the nutrient properties of certain seeds (Lee, 2015). Many farmers already search for spots on seeds as a symptom of infection solely with their eyes. However, access to eyecare is scarce amongst smallholder farmers, with eyesight often starting to decline after age 40 (Collins, 1924). It is time-consuming to manually look through seeds, but the use of magnifying glasses or sheets can help reduce time and effort in searching for pathogens.
Magnifying glass options
Magnifying glasses come in different shapes, sizes and lenses. Depending on the manufacturer and place of purchase, the prices vary. The need for the size will depend on the current eyesight of the individual or the need/want for a bigger piece of equipment. Figure 1 is the cheapest option as it is easily portable, and simple to use. It would have to be used up close rather than further away. Figure 2 is the standard option, coming in different optical sizes. Figure 3 is the most expensive option. It has a stand attached and the choice of increasing the contrast and brightness.
Step by step guide:
1. Gather your seeds in a pile or spread them out to begin sorting them.
2. Purchase and have your magnifying glass or sheet ready.
3. Start separating the seeds by sorting through them one by one while looking with the glass or sheet, making sure to dispose of the discolored seeds. Pay close attention to small or rare spots as they may be missed.
4. You can now sow using your healthy seeds.
Figure 1:
A magnifying sheet card. Approx $0.40 USD. Image from:(https://5.imimg.com/data5/ECOM/Default/2024/3/398191745/UO/GR/TT/42960663/cslms-500x500.jpg)
Figure 2:
An example of a 100 mm magnifying glass. Price can vary from $0.40 - $1.25 USD, depending on the size, materials, and if they contain a handle. Image from:(http://5.imimg.com/data5/SELLER/Default/2023/4/298776177/GK/KD/DC/12476938/magnifier-glass-lens-1000x1000.jpg)
Figure 3:
Fiber Illuminated Stand Magnifier. Different models cause the prices to vary from $45 - $115 USD.Image from:(https://5.imimg.com/data5/SELLER/Default/2024/2/383536071/IP/OC/UM/428636/illuminated-stand-magnifier-1000x1000.jpeg)
Benefits
Crop yield and quality: Removing diseased seeds is a crucial step as it can greatly improve the crop yield and quality. If diseased seeds are planted, they can drastically impact the production of food and the overall crop yield, for example soybean rust was reported to have caused 40 to 60% yield losses in the United States (Bradley, 2021), with some diseases causing a loss of 15% to 35% (Pellegrino, 2010). Profits are also negatively affected (Bradley, 2021).
Accessibility:
Many small-scale farmers live in poverty (Akpan, 2016) and are dependent on their agriculture to thrive to sustain their livelihood. The welfare of farmers is key to sustaining agricultural production in their region. Over 90 percent of farms around the world operate by families, with their food being scarce and their choice of resources being heavily constrained (Small family farmers, 2024). Economically, the choice of magnifying glasses is cheap and accessible to most farmers, making it a lucrative asset. The cost ranges from less than one U.S. dollar to more than 65 U.S. dollars for the most expensive options (e.g. stand magnifier) (Figures 1-3).Eyesight & Training:
As mentioned previously, many smallholder farmers do not have access to proper eye care. Although the government makes efforts, with low funding, and a small number of healthcare workers, it remains a challenge for many to get the proper treatment and care they need (Bechange, 2020). Because of this, identifying spotted seeds proves to be a challenge for some, as eyesight tends to drop at age 40 and so on (Collins, 1924). With the help of a magnifying glass or sheet, it helps to view spotted seeds more easily and can help reduce the time spent on carefully examining each individual seed. The use of the equipment does not require any training or expertise.Critical Analysis
While being a very cost-effective method, there are some challenges. The magnifying glass design can make it difficult to hold on for a long time as there is no support for the hands, unless the stand option is purchased or it is attached to a home-made stand. Sifting through seeds is tedious and time-consuming, and as a result it can be grueling with a lack of hand rest. When working outdoors, the sun may interfere with the glass, obstructing the visibility. In the outdoors there is a possibility of dirt and dust getting trapped within the glass. This hinders its efficacy and makes it inconvenient. The durability of the glass or sheet is dependent on the manufacturer, and the supplier. Common forms of damage might include scratches, tears, breakages, etc.. To mitigate cost, buying in bulk (e.g. within a female farmer cooperative) can help. Purchasing a glass or sheet with a stand as a collective may reduce the labour requirement and efficiency.
Conclusion
In conclusion, magnifying glasses and sheets provide a useful and cost-effective method for detecting and removing diseased seeds. It provides cost-effectiveness, an option for far-sighted individuals, and marginalized communities. There are very expensive options available. The benefits are great but also come with some problems that may deter some smallholder farmers.
Helpful Links To Get Started
The following are picture(s) of the process of identifying diseased seeds with a magnifying glass/sheet from Sakbooks.com. All versions are in the same section (8.2) apart from the North Africa & Middle East version. Sub-Saharan Africa/Caribbean version http://www.sakbooks.com/uploads/8/1/5/7/81574912/8._pests_and_disease.pdf
East/Southeast Asia version http://www.sakbooks.com/uploads/8/1/5/7/81574912/4.__sakbook_east_asia_jan_2017_english_captions_compressed.pdf
South Asia Version http://www.sakbooks.com/uploads/8/1/5/7/81574912/2.__sak_book_south_asia_jan2017_english_captions_compressed_copy.pdf
Latin America Version http://www.sakbooks.com/uploads/8/1/5/7/81574912/9._sakbook_latin_america_oct2016_english_version.pdf
North Africa & Middle East Version (Chapter 7 ~ 7.2) http://www.sakbooks.com/uploads/8/1/5/7/81574912/11._sak_nora_book.english_version_pdf.pdf
Videos(s):
The following is a video from Access Agriculture on the process of spotting diseased seeds. It may provide further context and helpful information. The video is available in multiple languages. https://www.accessagriculture.org/spotted-seed-diseased-seedOther Readings: Below are further readings on seed processing and seed quality assurance from the Food and Agriculture of the United Nations (FAO). https://www.fao.org/3/ca1492en/CA1492EN.pdf https://www.fao.org/3/ca1491en/CA1491EN.pdf
Websites to purchase from:
References
1.Akpan, S. B., Udoh, E. J., & Patrick, I. V. (2016). Sustaining small scale farming: Evidence of poverty and income disparity among rural farming households in south-south region of Nigeria. Path of Science, 2(9). https://doi.org/10.22178/pos.14-5
2.Bechange, S., Jolley, E., Virendrakumar, B., Pente, V., Milgate, J., & Schmidt, E. (2020). Strengths and weaknesses of eye care services in sub-Saharan Africa: A meta-synthesis of eye health system assessments. BMC Health Services Research, 20(1), 381. https://doi.org/10.1186/s12913-020-05279-2
3.Bradley, C., Allen, T., Tenuta, A., Mehl, K., & Sisson, A. (2021). Soybean Disease Loss Estimates from the United States and Ontario, Canada — 2020. https://doi.org/10.31274/cpn-20210607-2
4.Collins, S. D., & Britten, R. H. (1924). Variation in eyesight at different ages, as determined by the Snellen Test. A statistical study of the results of vision tests of 4,862 native white school boys and 6,479 male White Industrial Workers in the United States. Public Health Reports (1896-1970), 39(51), 3189. https://doi.org/10.2307/4577396
5.Dixon, J., Abur , A. T., & Wattenbach, H. (n.d.). Framework for analysing impacts of globalization on Smallholders. Smallholders, globalization and policy analysis. Food and Agricultural Organization, Rome. https://www.fao.org/3/y5784e/y5784e02.htm
6.du Toit, L. J. (2004). Management of diseases in seed crops. Encyclopedia of Plant and Crop Science, 675-677.
7.Lee, J. H., Hwang, S.-R., Lee, Y.-H., Kim, K., Cho, K. M., & Lee, Y. B. (2015). Changes occurring in compositions and antioxidant properties of healthy soybean seeds [Glycine max (L.) Merr.] and soybean seeds diseased by Phomopsis longicolla and Cercospora kikuchii fungal pathogens. Food Chemistry, 185, 205–211. https://doi.org/10.1016/j.foodchem.2015.03.139
8.FAO (n.d). Small family farmers | Family Farming Knowledge Platform | Food and Agriculture Organization of the United Nations. (n.d.). https://www.fao.org/family-farming/themes/small-family-farmers
9.Mancini, V., Murolo, S., & Romanazzi, G. (2016). Diagnostic methods for detecting fungal pathogens on vegetable seeds. Plant Pathology, 65(5), 691–703. https://doi.org/10.1111/ppa.12515
10.Pellegrino, C., Gilardi, G., Gullino, M. L., & Garibaldi, A. (2010). Detection of Phoma valerianellae in lamb’s lettuce seeds. Phytoparasitica, 38(2), 159–165. https://doi.org/10.1007/s12600-010-0084-x