BEST Practice Ecofriendly bioherbicide approach for Striga control

Abuelgasim Elzein, [email protected], and Fen Beed

Root parasitic weeds of causes annual losses of 10 years. Their intimate the genus Striga are a US$7 billion and affects interaction with different significant constraint incomes, food security, host plants prevents the to cereal and cowpea and nourishment of development of a silver production in sub- over 100 million people bullet control technology Saharan Africa. They mostly in sub-Saharan that subsistence farmers can cause total crop Africa. can adopt. Hence, it is losses particularly widely accepted that during drought, in Each Striga plant can an integrated approach infertile soils and cereal produce thousands of to Striga management monocropping. Striga seeds, viable for over is required for which biocontrol represents a crucial component. Bioherbicide innovation A bioherbicide is a plant pathogen used as a weed biocontrol agent (BCA), which is applied at sufficient rates to rapidly cause a disease epidemic that kills or severely suppresses the target weed. The use of biocontrol technology to manage Striga is a desirable control method as it is environmentally friendly, safe to farmers and crop consumers, specific to the target host, and Maize/Sorghum field infested with Striga hermonthica (pink flowers) in Bauchi State, Nigeria. Photo by A. Elzein, IITA. has the potential to be

A. Elzein is a biological control specialist, IITA Nigeria, and the Department of Agricultural Biotechnology, University of Khartoum in Sudan; F. Beed is a plant pathologist and leader of Striga biocontrol research based in IITA, Dar-es-Salaam, Tanzania.

26 economically viable. from seedling to cereal production in In addition, biological flowering shoot; protect sub-Saharan Africa, control also assists in the current crop yield; and to produce stable, the development of and prevent seed durable, and pathogenic a balance of nature, formation and dispersal. propagules. the creation of more biodiversity, and F. oxysporum f. sp. Extensive research by the sustaining of complex strigae is highly host- University of Hohenheim ecological interactions. specific to the genus (UH, Germany), Striga, and does not IITA (Benin), McGill Since the early 1990s, produce any known University (Canada), and a series of intensive mycotoxic compounds. Institute for Agricultural disease surveys in Thus, its use does not Research - Ahmadu Bello many countries of sub- pose health risks to University (Nigeria), has Saharan Africa has farmers, input suppliers, enhanced application evaluated hundreds traders or consumers of F. oxysporum f. sp. of for or threaten crops or the strigae, its formulation their pathogenicity and environment. Its unique into bioherbicidal virulence against Striga. DNA constitution differs products, and its Fusarium oxysporum from other forms of F. delivery for practical field Schlecht isolates oxysporum deposited application. The Striga have been the most in GenBank (www.ncbi. bioherbicide contains the promising. However, the nlm.nih.gov/Genbank), Striga host-specificF. discovery of a highly known to cause crop oxysporum f. sp. strigae, effective pathogen is diseases. Indeed, this applied in massive doses only one step in the ensures its biosafety to create a high infection process of developing and greatly facilitates and disease level to kill bioherbicides, for its wider application and or severely suppress which the inoculum use as a bioherbicide. Striga. mass production, formulation, delivery, In addition techniques Promotion in West Africa and storage ability must for massive production The bioherbicide is a be optimized, and the of inoculum of F. component of the IITA- mode of action, host oxysporum f. sp. strigae led project, Achieving specificity, and biosafety was optimized based sustainable Striga evaluated and fully on simple and low-cost control for poor farmers understood. methods and using in Africa, funded by inexpensive agricultural the Bill & Melinda The most widely by-products available Gates Foundation to studied and used in sub-Saharan Africa. intensively promote fungal isolate that met The chlamydospores technologies to combat all requirements for a produced by this fungus Striga in sub-Saharan potential bioherbicide for have the advantage of Africa. The project will Striga is F. oxysporum being able to survive validate the potential of Schlecht f. sp. strigae extreme environmental the bioherbicide seed Elzein et Thines (isolates events while still treatment technology Foxy2 and PSM197). remaining viable. This across major Striga- These are highly is an important feature infested agroecological virulent, attack Striga in required for a BCA zones and maize-based all growth stages—from suited to hot and dry farming systems, while seed to germination, climatic conditions of also confirming the

27 biosafety and developing plants from attack by Biosafety: To further molecular detection Striga (see next page). ensure the safety tools. Here are the The combination of of Striga BCA and highlights of the results: bioherbicide with Striga to demonstrate and susceptible variety increase awareness Technology significantly reduced among farmers, validation: Several Striga emergence by regulatory authorities, multilocation trials were 53%, resulting in 42% and stakeholders, conducted under natural reduction in number of a wide host range and artificial Striga flowering plants and in study was carried infestation across two 21% increase in grain out using 25 crops in agroecological zones yield compared to the collaboration with IAR- in northern Nigeria to susceptible control. ABU and the Nigerian evaluate the efficacy Plant Quarantine of Striga bioherbicide In addition, disease Service (NPQS) under (F. oxysporum f. sp. symptoms were field and screenhouse strigae). The inoculum recorded on emerged conditions in Nigeria. produced by UH and Striga plants parasitizing Results revealed that SUET seed company maize plants coated none of the test plants was delivered as a by the bioherbicide. showed any infection film-coat on maize The reduction in Striga by the biocontrol agent seeds (see below). emergence across maize both in the field and The application of the varieties indicates the screenhouse, and no bioherbicide technology effectiveness of the detrimental growth in combination with bioherbicide to attack effects were measured Striga resistant seeds under the soil or visual losses to plant maize reduced Striga surface. The synergistic health recorded in any emergence by 73% and effect of the bioherbicide of the inoculated crops 39%, compared to the technology combined tested, i.e., inoculation susceptible and resistant with the Striga resistant with the Striga BCA did controls, respectively, maize is expected not cause any delay and prevented 81% and to reduce the Striga in emergence, and a 58% of emerged Striga seedbank and thus the decrease in plant height, plants from reaching impact of Striga on plant vigor, chlorophyll flowering and 56% subsequent maize crops. content per leaf, shoot and 42% of the maize fresh and dry weight.

1 2 3 4

The delivery of Striga bioherbicide as a film coating onto resistant maize seeds using a professional seed treatment technology: Maize film-coated seeds with chlamydospores of F. oxysporum f. sp. strigae isolate PSM197 (1, red), isolate Foxy2 (2, yellowish), with Arabic gum (3, green); and untreated control (4, yellow). Photo by A. Elzein, IITA.

28 Hence, the Nigerian regulatory authorities (NPQS, NAFDAC) and other stakeholders were satisfied and confident that no disease was produced on plants other than Striga by the BCAs and that it is safe to use. In addition, a mycotoxin produced by Striga bioherbicide F. oxysporum f. sp. strigae was analyzed and evaluated by our project partner, the University of Stellenbosch in South Untreated maize susceptible variety - control. Africa. An evaluation of existing isolates of F. oxysporum f. sp. strigae does not produce well-known mycotoxins (e.g., Fumonisin and Moniliformin) that pose a threat to animal or human health. This finding further confirms the safety of this bioherbicide. Molecular detection tools: Development of a monitoring tool Untreated maize resistant variety - control. specific to the Striga bioherbicide is important to certify inoculum quality, monitor the presence and persistence of the BCA in soils, and validate its

Effect of the bioherbicide on Striga emergence at Gar-Alkaleri in Bauchi state in 2012: Bioherbicide was applied as a film-coat on maize seeds using Arabic gum as adhesive carrier and professional seed coating technology. Photos by A. Elzein, IITA. Bioherbicide combined with the maize resistant variety.

29 monitor its spread and by DuPont to control persistence in rhizobox Striga in sorghum), experiments under and glyphosate (an different management intensively used practices using Kenyan ). A similar soils. This promising result was also result provides a proper achieved with the baseline to further the commonly used seed existing primer set. treatment at the recommended Bioherbicide + application doses. technology: Accordingly, doses and The novel combination complementary seed and integration of the coating protocols for bioherbicide technology the three compatible plus imazapyr herbicide technologies (BCA, for Striga control with herbicide, and in a single- fungicides) have been dose seed treatment developed and IR maize to control fungal pests seeds were successfully Typical disease symptoms offers farmers with coated with a single- on Striga shoots caused by maize seed that is dose seed treatment the bioherbicide coated on able to achieve its maize seeds at Gar-Alkaleri of BCA inoculums and in Bauchi state in 2012: the yield potential. The imazapyr. The results first infection occurred on use of each technology showed that imazapyr the tip of the oldest leaves, (BCA or imazapyr) did not interfere with which turned black and has been shown to be the BCA during seed curved; the symptoms later effective when applied coating, with BCA on were extended to younger independently using leaves and growing points as growth and sporulation well which were wilted and seed coating techniques, after coating, and changed to black. Photo by A. but have not been with IR maize seed Elzein, IITA. integrated. germination. Seeds of The compatibility IR maize varieties can environmental biosafety. of Striga BCAs with thus be coated with the UH is developing a different pesticides herbicide and the BCA monitoring tool. ( and and then and fungicides with delivered to farmers The AFLP fingerprinting using the same input technique was components) was studied in vitro in pathway. Screenhouse successfully used in and field trials are developing a primer pair the laboratory. Striga BCAs showed excellent being carried out to capable of differentiating generate data on the the F. oxysporum f. sp. compatibility with imazapyr (a herbicide combined efficacy of the strigae group from other applied technologies. Fusarium species. In seed coating used in combination with IR The demonstrated addition, the monitoring compatibility of Striga tool has shown a high maize to control Striga), Metsulfuron Methyl BCA with the different specificity for isolate pesticides that contain Foxy2 and was used to (MSM) (a herbicide seed coating developed a wide range of active

30 ingredients indicate that commercial seed coating varieties or herbicides) the combination and process, developed and used separately and delivery of the Striga optimized at UH with repeatedly. bioherbicide technology SUET Seed Company with a large number of in Germany, is being The potential delivery of pesticide products is transferred and adapted coated seeds of resistant possible. These findings at IITA, Ibadan, to be maize with bioherbicide are expected to provide used as an experimental in one package to a triple action seed production unit for farmers using the coating package for capacity building and same input pathway direct control of Striga as a model for eventual will reduce transaction and fungal diseases of transfer of seed and application costs maize in sub-Saharan treatment technology to and enhances the Africa. the private sector after economic feasibility validation. and adoptability of the Suitability to African technologies. Similarly, farming systems Outlook compatibility of BCA with Our strategy for scaling- One unique advantage imazapyr and fungicides up the bioherbicide of this bioherbicide is allow seed coating of IR- innovation is based that the ability of Striga maize with bioherbicide, on using technology to become resistant to imazapyr, and fungicides appropriate to Africa to it is virtually unknown with a single-dose seed ensure that sustained as a consequence of the coating application. production of the suite of enzymes and bioherbicide is feasible secondary metabolites Future plans at a cost affordable that the BCA produce Currently, large- to African small-scale to become pathogenic scale field testing is farmers. The seed- and virulent against ongoing and is being coating treatment the target (Striga). implemented to further requires significantly Hence after validation, validate bioherbicidal less inoculums, delivering the efficacy across two establishes the BCA in bioherbicide technology agroecological zones the cereal rhizosphere, in combination with where the common i.e., the infection site of resistant maize or scenarios for maize Striga, and provides a with the herbicide infestation by Striga simple, practical, cost- imazapyr is expected in northern Nigeria effective delivery system to increase efficacy are represented. For for adoption by input in controlling Striga. understanding of suppliers to subsistence Bioherbicide and other farmers’ preferences farmers. Arabic gum compatible technologies and perceptions, as a coating material have different modes socioeconomic analysis has been shown to and sites of action and cost-benefit increase the rate of against Striga, and in analysis of bioherbicidal mycelia development a combination they will technology based on and enhance BCA have a much greater field data/surveys and sporulation. Its chance of reducing interviews, current availability in sub- the potential risk market information, and Saharan Africa at a low of development of links with other Striga price is an additional resistance to a single control strategies will economic advantage. A technology (resistant be undertaken. After

31 validation, dissemination References delivery system for controlling and commercialization Beed F.D., S.G. Hallet, J. Venne, root parasitic weed Striga with and A. Watson. 2007. Biocontrol mycoherbicide. Biocontrol will be promoted using Fusarium oxysporum; a Science and Technology, 16(1) through private sector Critical Component of Integrated 3-26. partnerships and Striga Management. Chapter 21 in Integrating New Technologies Elzein, A., F. Beed, and J. integrated with other for Striga control: Towards Kroschel. 2012. Mycoherbicide: control options such as ending the Witch-hunt (Ejeta, innovative approach to Striga G. and J. Gressel, eds). World management. SP-IPM Technical resistant varieties, IR Innovations Brief, No. 16, March varieties combined with Scientific Publishing Co. Pte. Ltd. pp 283-301. 2012. seed treatment with imazapayr, crop rotation Ciotola, M., A. DiTommaso, and Kroschel, J. and D. Müller-Stöver. A. Watson. 2000. Chlamydospore 2004. Biological control of with legumes, and soil production, inoculation methods root parasitic weeds with plant fertility management and pathogenicity of Fusarium pathogens. In: Inderjit, K. (ed.), practices, to achieve oxysporum M12-4A, a biocontrol Weed biology and management. Kluwer Academic Publishers, sustainable management for Striga hermonthica. Biocontrol Science and Technology 10: 129- Dordrecht, The Netherlands, pp. of Striga. 145. 423–438.

Partners Ejeta, G. 2007. The Striga Kroschel, J., A. Hundt, A.A. scourge in Africa: A growing Abbasher, J. Sauerborn. 1996. pandemic, In: Ejeta, G. and J. Pathogenicity of fungi collected IITA (Dr F. Beed, Dr A. in northern Ghana to Striga Elzein & Dr A. Menkir), Gressel, eds. Integrating New Technology for Striga Control: hermonthica. Weed Research 36 Institute for Agricultural Towards Ending the Witchhunt. (6), 515–520. Research – Ahmadu Bello World Scientific Publishing Co. Pte. Ltd., UK. pp. 3-16. Marley, P.S., S.M. Ahmed, J.A.Y. University (Dr A. Zarafi), Shebayan, and S.T.O. Lagoke. Nigeria; University of Elzein, A.E.M. 2003. 1999. Isolation of Fusarium Hohenheim (Prof G. Development of a granular oxysporum with potential for Cadisch, Dr F. Rasche mycoherbicidal formulation of biocontrol of the witchweed & Prof J. Kroschel), Fusarium oxysporum “Foxy Striga hermonthica in the 2” for the biological control of Nigerian Savanna. Biocontrol Germany; The Real- Striga hermonthica. In: “Tropical Science and Technology 9: IPM Company Ltd (Dr Agriculture 12– Advances in Crop 159–163. H. Wainwright), Kenya; Research (2)” (J. Kroschel, ed.). Venne J., F. Beed, A. Avocanh, University of Stellenbosch Margraf Verlag, Weikersheim, Germany, 190 pp, ISBN 3-8236- and A. Watson. 2009. Integrating (Prof A. Vilioen), South 1405-3. Fusarium oxysporum f. sp. Africa; and McGill strigae into cereal cropping University (Prof A. Elzein, A., J. Kroschel, and V. systems in Africa. Pest Management Science 65: 572– Watson), Canada. Leth. 2006. Seed treatment technology: an attractive 580.

Nitrogen 2013 Conference 18 – 22 November 2013, Kampala, Uganda The International Nitrogen Initiative (INI), African Nitrogen Centre, IITA, and Makerere University College of Agricultural and Environmental Sciences welcome scientists, agriculturalists, environmentalists, industrialists, economists, policy implementers and other practitioners to the 6th International Nitrogen Conference (N2013).

The International Nitrogen Initiative is a global effort to optimize nitrogen’s beneficial role in sustainable food production and to minimize nitrogen’s negative effects on human health and the environment.

Conference Theme: ‘Let us aim for just enough N: Perspectives on how to get there for “too much” and “too little” regions’

32