French bean [Phaseolus vulgaris (L.)] is one of the most important introduced vegetable crops in the socioeconomic farming systems of eastern Africa. It is a crop with great potential for addressing food insecurity, income generation, and poverty alleviation in the region (Monda et al., 2003). In Kenya, French bean is the most important export vegetable crop. Estimates indicate that up to 50,000 small-holder families are involved in French bean production in the country (HCDA, 2011). In the year 2010, the crop accounted for 54% of the total volume of vegetables exported from the country at a total value of Kshs. 4.3 billion ($5 million) (HCDA, 2011). Other east African countries with an increasing potential for French bean production are Uganda, Tanzania, and Rwanda (Kimani et al., 2004).
In most of these countries, production of the crop is dominated by rural small-scale farmers with most of them being women and children. French bean is therefore a major source of income and employment among these groups (Wahome et al., 2011). Besides east Africa, French bean is widely cultivated in temperate and subtropical regions and in other parts of the tropics (Purseglove, 1987). Apart from its lucrative market, the vegetable is generally popular for its high nutritional content, being rich in protein, calcium, iron, and vitamins (Kelly and Scott, 1992). However, despite all the impressive statistics, realization of maximum benefits by French bean growers is hampered by various challenges. Among the major challenges cited for French bean production are unfavorable environmental conditions and insect pest problems (Monda et al., 2003) with the latter further confirmed by a bean value chain analysis study conducted in Kenya by The Netherlands Development Organization and Fineline Systems in 2012.
In the past, indiscriminate application of pesticides has been the norm among many growers in a bid to realize higher yield (Dinham, 2003). However, emerging food safety and quality issues in the European market (EU) have led to stringent standards for fresh fruits and vegetables entering the EU. The EU, which is Kenya’s largest market, has placed some Kenyan horticultural products including French bean on “high-risk” status and implemented inspection and sampling at European designated points of entry where samples are to be analyzed for the presence of pesticide residues before the consignments are released into the market (HCDA, 2011). This testing revealed that a majority of small-holder French bean producers were noncompliant with market requirements, resulting in interception of their produce in the international market. In addition, fear of maximum residue level (MRL) noncompliance discourages exporters from buying French bean from small-holders (Henson et al., 2008). Thus, with the amount of insecticide used becoming increasingly unacceptable, alternative measures of pest control need to be implemented if French bean is to maintain its vital position in improving livelihoods of the rural poor. The use of agronets represents a technology with a potential of not only providing resource-poor farmers with low cost pest control, but also for better crop performance through modified crop microclimate. Studies in Benin–West Africa have reported lower populations of diamondback moth [Plutella xylostella (L.)], aphid [Lipaphis erysimi (Kaltenbach)], and borer [Hellula undalis (Fabricius)] on cabbage grown under nets compared with the use of foliar insecticide or unsprayed controls (Licciardi et al., 2008; Martin et al., 2006). In Kenya–East Africa, net covers have also proved effective in reducing insect pest pressure and modifying the nursery microclimate leading to improved tomato [Solanum lycopersicum (L.)] (Gogo et al., 2012) and cabbage [Brassica oleracea (L.) var. capitata (L.)] (Muleke et al., 2013) seedling growth and quality. Martin et al. (2013, 2014) showed higher efficacy against aphids and whitefly with an alpha-cypermethrin-treated net compared with a non-treated net. We also showed the potential of agronet in modifying microclimate conditions and improving yields and quality of tomato under tropical field conditions (Saidi et al., 2013). The use of agronets increased both total and marketable yields compared with open-field production. Fruit from plants covered with agronets had higher total soluble solids, lower titratable acidity, and higher sugar-to-acid ratio.
Increasing yield and supplying French bean with quality characteristics demanded by target markets is vital in increasing the consumption and export value of the crop (Kimani et al., 2007). However, as a result of the new requirements relating to environmental sustainability of pesticides and the changing consumer requirements for quality currently demanded by the international market for French bean and other fresh produce, there is need to evaluate other technologies that can help address some of these concerns.
This study evaluated whether growing French beans under agronet (treated or non-treated with an insecticide) covers could reduce insect pest infestation on the crop and the subsequent need for insecticide spray as well as whether agronets positively modified the microclimate leading to improved pod yield and quality.
Antignus, Y. & Ben-Yakir, D. 2004 Ultraviolet-absorbing barriers, an efficient integrated pest management tool to protect greenhouses from insects and virus disease. In: Rami Horowitz, A. and I. Ishaaya (eds.). Insect pest management: Field and protected crops. Springer, New York, NY
Dinham, B. 2003 Growing vegetables in developing countries for local urban populations and export markets: Problems confronting small-scale producers Pest Mgt. Sci. 59 575 582
Gogo, E.O. 2013 Influence of eco-friendly nets and floating row cover on microclimate modification, pest infestation, growth and yield of tomato [Lycopersicon esculentum (Mill.)]. MSc thesis, Egerton University, Egerton, Kenya
Gogo, E.O., Saidi, M., Itulya, F.M., Martin, T. & Ngouajio, M. 2012 Microclimate modification using eco-friendly nets for high quality tomato transplant production by small-scale farmers in east Africa HortTechnology 22 292 298
Gogo, E.O., Saidi, M., Itulya, F.M., Martin, T. & Ngouajio, M. 2014 Eco-friendly nets and floating row covers reduce pest infestation and improve tomato [Solanum lycopersicum (L.)] yields for smallholder farmers in Kenya Agronomy 4 1 12
HCDA 2011 Horticulture validated report. Agricultural Information Resource Centre, Nairobi, Kenya
Henson, S., Jaffee, S., Cranfield, J., Blandon, J. & Siegel, P. 2008 Linking African smallholders to high-value markets: Practitioner perspectives on benefits, constraints and interventions. Policy Research Working Paper 4573. Agriculture and Rural Development Department, The World Bank
Jaetzold, R. & Schmidt, H. 2006 Farm management handbook of Kenya. Natural conditions and farm information. Vol.11/ C. 2nd Ed. Ministry of Agriculture, East Kenya, Kenya
Kelly, J.F. & Scott, M.K. 1992 The nutritional value of snap beans versus other vegetables. In: Proc. of an International Conference held in Cali, Colombia, 16–20 Oct. 1989
Kimani, J.M., Kimani, P.M., Githiri, S.M. & Kimenju, J.W. 2007 Mode of inheritance of common bean [Phaseolus vulgaris (L.)] traits for tolerance to low soil phosphorus Euphytica 155 225 234
Kimani, P.M., van Rheenen, H., Mathenge, P. & Ndegwa, A. 2004 Breeding snap beans for smallholder production in east and central Africa, p. 49–51. In: Bean improvement for the tropics, annual report 2004. CIAT, Cali, Colombia
Licciardi, S., Assogba-Komlan, F., Sidick, I., Chandre, F., Hougard, J.M. & Martin, T. 2008 A temporary tunnel screen as an eco-friendly method for small-scale farmers to protect cabbage crops in Benin International Journal of Tropical Insect Science 27 152 158
Lloyd, A.E., Hamacek, A.P., George, R.J. & Waite, G. 2004 Evaluation of exclusion netting for insect pest control and fruit quality enhancement in tree crops International Journal of Tropical Insect Science 27 3 4
Martin, T., Assogba-komlan, F., Houndete, T., Hougard, J.M. & Chandre, F. 2006 Efficacy of mosquito netting for sustainable small holder’s cabbage production in Africa J. Econ. Entomol. 99 450 454
Martin, T., Chandre, F., Ochou, G., Vaissayre, M. & Fournier, D. 2002 Pyrethroid resistance mechanisms in the cotton bollworm [Helicoverpa armigera (Lepidoptera: Noctuidae)] from west Africa Pestic. Biochem. Physiol. 74 17 26
Martin, T., Gogo, E.O., Saidi, M., Kamal, A., Delétré, E., Bonafos, R., Simon, S. & Ngouajio, M. 2014 Repellent effect of an alpha-cypermethrin treated net against the whitefly [Bemisia tabaci (Gennadius)] J. Econ. Entomol. 107 684 690
Martin, T., Palix, R., Kamal, A., Delétré, E., Bonafos, R., Simon, S. & Ngouajio, M. 2013 A repellent treated netting as a new technology for protecting vegetable crops J. Econ. Entomol. 106 1699 1706
MOA and JICA (Ministry of Agriculture in Conjunction with Japan International Co-operation Agency) 2000 Local and export vegetables growing manual. Agricultural Information Resource Centre, Nairobi, Kenya
MOARD (Ministry of Agriculture and Rural Development) 2003 Fruits and vegetable technical hand book. Agricultural Information Resource Centre, Nairobi, Kenya
Monda, E.O., Munene, S. & Ndegua, A. 2003 French beans production constraints in Kenya. African Crop Science Society. African Crop Science Conference Proc. 6:683–687
Moreno, D.A., VƑ’llora, G., Soriano, M.T., Castilla, N. & Romero, L. 2002 Floating row covers affect the molybdenum and nitrogen status of chinese cabbage grown under field conditions Funct. Plant Biol. 29 585 593
Muleke, E.M., Saidi, M., Itulya, F.M., Martin, T. & Ngouajio, M. 2013 The Assessment of the use of eco-friendly nets to ensure sustainable cabbage seedling production in Africa Agronomy 3 1 12
Purseglove, J.W. 1987 Tropical crops. Dicotyledons. Longman, New York, NY. p. 132–136
Saidi, M., Gogo, E.O., Itulya, F.M., Martin, T. & Ngouajio, M. 2013 Microclimate modification using eco-friendly nets and floating row covers improves tomato [Lycopersicon esculentum (Mill)] yield and quality for small holder farmers in East Africa Agricultural Sciences 4 577 584
Tanny, J., Cohen, S., Grava, A., Naor, A. & Lukyanov, V. 2003 The effect of shading screens on microclimate of apple orchards Chilean Journal 4 347 359
van Bruggen, A.H.C., Whalen, C.H. & Arneson, P.A. 1986 Emergence, growth and development of dry bean seedlings in response to temperature, soil moisture, and Rhizoctonia Solani Phytopathology 76 568 572
Wahome, S.W., Kimani, P.M., Muthomi, J.W., Narla, R.D. & Buruchara, R. 2011 Multiple disease resistance in snap bean genotypes in Kenya African Crop Science Journal 19 289 302
Waterer, D., Bantle, J. & Sander, T. 2003 Evaluation of row covers treatments for warm season crops. Saskatchewan Agriculture and Food, University of Saskatchewan, Saskatchewan, Canada. 8 Oct. 2014. <http://www.usask.ca/agriculture/plantsci/vegetable/resources/veg/2003_microclimate_ziptunnel.pdf>