Climate change, human activities and transportation of goods and persons across territorial boundaries have exacerbated movement of insect species between continents and hemispheres. Insects such as the africanized honey bee, Apis mellifera scutellata Lepeletier (Eimanifar et al. 2018), small hive beetle, Aethina tumida Murray (Neumann et al. 2016), longhorn crazy ant, Paratrechina longicornis (Latreille) (Deyrup et al. 2000), and the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (De Meyer 2005) hitherto endemic to Africa, have become established in North America. Similarly, the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) native to the tropical and sub-tropical regions of the Americas has spread to Asia and also first observed in Africa in early 2016 (Goergen et al. 2016; Tindo et al. 2017). Spodoptera frugiperda with its devastating feeding habits currently occurs in Africa, Asia, Australia, North and South America (Nagoshi et al. 2017; Cock et al. 2017; FAO. 2018; Uzayisenga et al. 2018). The fall armyworm is endemic to the Neotropics, attacking vegetables, row, and turf crops (Luttrell and Mink, 1999; Braman et al. 2000; Nuessly et al. 2007; Souza et al. 2013). The pest has the potential to cause maize yield losses between 21–53% in low-input smallholder farming systems (Abrahams et al. 2017).
Maize, Zea mays L. (Poaceae), the cereal with highest production worldwide can be grown commercially as an industrial and/or food crop. It is grown across a wide range of agro-ecological zones, from wet to hot semi-arid lands and in different soil types (Shiferaw et al. 2011). In Africa, More than 300 million people depend on maize as their main food crop (IPBO. 2017). The crop is also valuable as feed for farm animals and for alcohol (biofuel) production. In most of Africa, the crop is often produced by resource-constrained smallholder farmers (Odendo et al. 2001; Cairns et al. 2013), exacerbating the importance to adapt pest control measures, and monitoring procedures to this influential category of crop producers.
In sub-Saharan Africa (SSA), maize is the most widely grown staple food crop providing food and livelihood for about 208 million people in the region (Parihar et al. 2011; Macauley. 2015; FAOSTAT. 2019) and accounting for 73% of calorific intake (Shiferaw et al. 2011). However, production is constrained by drought, diseases and several pests, including lepidopteran stemborers, such as Busseola fusca (Fuller) (Noctuidae), Sesamia calamistis (Hampson) (Noctuidae) and invasive Chilo partellus (Swinhoe) (Crambidae). Recently, the impact of fall armyworm Spodoptera frugiperda on maize has been a great challenge for the continent since it is a major threat to food and nutrition security for millions of people (Huesing et al. 2018). Maize losses due to S. frugiperda damage range from 8.3 to 20.6 million tons, with annual financial losses of US$2,481–6,187 million (Abrahams et al. 2017). In Cameroon, the pest exists in all the major maize producing agro-ecological zones of the country, with the highest severity and infestation recorded in the Sahelian and Highland savanna zones (Tindo et al. 2017; Kuate et al. 2019).
The popyphagous S. frugiperda feeds on approximately 353 crop species from 76 plant families mainly Poaceae Asteraceae and Fabaceae in its native range (Montezano et al. 2018). Maize, rice, sugarcane, and sorghum are known to be the major hosts of S. frugiperda whereas vegetables and cotton are the minor hosts (Prasanna et al. 2018). The caterpillars of the destructive larval stage of FAW feed on young leaf whorls, stems, branches, and reproductive organs, such as tassels and ears inflicting substantial damage to maize crops and causing high grain yield loss (De Almeida et al. 2002; FAO. 2018). Damage by first instar larvae on maize appear as silvery patches called “windowpanes” because one side of the leaf is eaten, leaving the opposite epidermal layer intact. Damage by the third and fourth instar larvae is more significant with holes appearing on the edges and with characteristic row of perforations visible due to feeding on the whorl of the growing plants. The larvae also migrate from the leaves to the tassels and the developing ears/grains causing grain yield losses and exposing the grains to mycotoxin contamination.
The pest in Africa is threatening the livelihood of indigenous smallholder farmers who rely on maize production for income and food security (Goergen et al. 2016; Abrahams et al. 2017). The sporadic spread of the pest and its potential to travel 1600 km over a 30-h period (Prasanna et al. 2018) signifies more danger for grain producers in Africa. Genetically modified maize hybrids expressing Bacillus thuringiensis insecticidal proteins has been used to control S. frugiperda (Blanco et al. 2010; Okumura et al. 2013; Huang et al. 2014), but the indigenous African smallholder grain producers rely on synthetic pesticides as a control measure for maize pests (Cook et al. 2007; Khan et al. 2010; Midega et al. 2018; Tanyi et al. 2020). However, the use of synthetic pesticides has exacerbated the effect of poisonous substances in non-target areas with devastating consequences on the environment (Perez et al. 2000; Xu et al. 2010). This underscores the need to develop S. frugiperda management strategies based on the local farmers’ needs and priorities (Kumela et al. 2019) since they are the major grain producers in most African countries. There is therefore an urgent need for a reliable low-cost technology for early detection of the pest and its sustainable management for resource-constrained smallholder farmers.
Knowledge of the seasonal variation of the pest in different locations (De Almeida et al. 2002) as well as early detection, monitoring, surveillance, and scouting are key tools to aid a successful integrated pest management program that includes biological control, resistant varieties, and cultural control strategies (McGrath et al. 2018). Monitoring reveals the presence, population size, spread and movement of a pest. Monitoring the fall armyworm is often done using pheromone-based traps that attract male moths (McGrath et al. 2018). However, there have been conflicting results across geographic regions on the use of varied blends of the synthetic analogues of the natural sex pheromones as lures in different trap types in monitoring FAW (Meagher et al. 2019).
CABI and FAO in 2019 advocated for monitoring FAW using this technique to give advance warning to farmers at the beginning of the maize-cropping season. The FAO Fall Armyworm Monitoring and Early Warning System (FAMEWS) mobile application tool requires users to input both field scouting and pheromone trap data (FAO and CABI. 2017). In addition, FAO and Pennsylvania State University jointly developed an innovative talking mobile app called Nuru (Swahili for “light”) in several African countries (FAO and CABI. 2017). Although the technologies are good, implementation by farmers is problematic since most of them are often not educated and/or cannot use mobile telephones and hence lack the skills needed for effective use of the technology. The adoption of commercially available pheromones by indigenous smallholder farmers in Africa is also constrained by the scarcity of the pheromone lures and traps and their high-cost.
FAW pheromone trap data can be used to estimate, a week in advance, the subsequent abundance of larvae in pastures (Silvain 1986) though McGrath et al. 2018 observed no relationship between the number of FAW males caught in traps and the number of females laying eggs in the same locality. Thus, catches of male moths in traps should simply be used to estimate the presence of potential egg-laying females in the area. Some researchers have reported similarities in moths captured with locally produced low cost traps made from repurposed materials such as plastic containers as compared to bucket traps (Critchley et al. 1997). Therefore, there is vital and urgent need for local lures that can attract high numbers of male and female moths into traps to directly reduce the egg laying potential and resultant number of the destructive larvae in the farm as well as used as a monitoring technique. Consequently, the aim of this study was to test indigenous low-cost lures in low-cost traps for monitoring and control of the fall armyworm as a component of the Indigenous Integrated Management of this pest.