Spodoptera frugiperda (J.E.Smith), also known as the "fall army worm(FAW)," belongs to the Noctuidea family of owlet worms in the Lepidoptera order (Gobernment of Wetern Australia, 2020) FAW undergoes total metamorphosis. The egg is dome-shaped, measuring roughly 0.4 mm in diameter and 0.3 mm in height, with a mass that ranges from 100 to 200 (Bhusal & Chapagain, 2020). Total egg production per female averages about 1500 with a high of over 2000, and the egg stage only lasts two to three days throughout the summer (Bhusal & Chapagain, 2020). The second stage, which has six instars, is the larvae (Bhusal & Chapagain, 2020), the most harmful to host plants (Kumela et al., 2019). Larvae are greenish with a black head in their first instar; by their second instar, the head has turned orange. The body's dorsal surface turns brownish in the third instar, and lateral white lines start to appear. The head is reddish brown and white-marbled in the fourth to sixth instars, and the brownish body has white sub-dorsal and lateral lines (Bhusal & Chapagain, 2020; Navasero & Navasero, 2020). The brightest part of the day is when larvae tend to hide (Rojas et al., 2004). The larvae stage lasts for around 14 days in the summer and 30 days in the cooler months (Volp & Myron, 2022). Typically, pupation occurs in the earth, 2 to 8 cm below the surface. Reddish brown is the hue of the pupa. The transition from the pupa stage to the adult stage typically takes 20 days (Bhusal & Chapagain, 2020). The adult moths have a lifespan of 15 days on average (Benson, 2017).
In 2016 FAW was first discovered in Africa in the countries of Nigeria and the Democratic Republic of S. Tomé and Principe, (Goergen et al., 2016). It is a pest that is extremely polyphagous and preys on a variety of plant species, including vegetables, sorghum, millet, and maize (Yigezu & Wakgari, 2020). The immature larvae of FAW eat mostly on the epidermal leaf tissue, which results in dead hearts, and make open windows in the leaves, which result in a skeletal structure (Goergen et al., 2016).
Globally, it was predicted that 170,000 ha of India's maize farmland were impacted by FAW, which spread to 10 states across the nation (Sagar et al., 2020). According to Gu and Woo (2019), the Yunnan region of China is the most severely affected by FAW, with 80,000 ha of land affected and major damage to crops like maize, sorghum, sugarcane, and ginger crops. 98.6% of the 11,1992.17 hectares of affected land in China is covered in maize (FAO, 2019). More than 10,000 acres of maize in other provinces, like Cambodia, were impacted by FAW in 2019 (Cambodia News). With an infestation rate ranging from 0.5 to 32%, FAW was found in Bangladesh in 8 regions, 22 districts, and 71 administrative regions.
According to FAO (2019), the expected yield loss from FAW in Thailand ranged from 130 million to 260 million dollars. Given the favorable climatic circumstances in Nepal that allow for the growth of FAW populations, the potential crop loss in maize is estimated to be up to 100% if this pest is not appropriately handled. Similar reports of FAW infestations include about 10,000 ha of land in Indonesia, 16,200 ha of land in Myanmar, and 46,000 ha of land in Vietnam (et al., 2020) (Sagar et al., 2020).
While no steps were taken, numerous African nations, including Ghana and Zambia, suffered losses estimated at 8.5 to 21 million tons, or around 250-630 million US dollars (Sagar et al., 2020). In both Ghana and Zambia, the percentage of maize lost to FAW was estimated to be 45% and 40%, respectively. A total of 30.54 million US dollars' worth of corn was lost by Ethiopia, and the FAW had an impact on around 250,000 ha of agricultural land, or 11% of Kenya's entire maize cultivation area due to FAW attacks, yield losses in Tanzania and Uganda totaled 3.2 million tons and 13.91 million tons, respectively (Sagar et al., 2020).
The use of synthetic pesticides is the main method of controlling FAW, according to a study on small-holder farmers' management techniques against the disease that was carried out in Ghana, Rwanda, Uganda, Zambia, and Zimbabwe. Farmers were not employing protective equipment while handling these pesticides, despite the fact that some of them are exceedingly toxic and are forbidden by agro input authorities (Kenko & Kamta, 2021). According to the World Health Organization (WHO), about 1,000,000 people are affected by acute poisoning by contact with the pesticide(Dad et al., 2022).
The relationship between exposure to synthetic pesticides and human health is thoroughly examined in a survey of the epidemiological literature published between May 2018 and May 2019, starting with agricultural workers, this study found a link between agricultural workers' exposure to synthetic pesticides and poor health outcomes (Jallow et al., 2017). The results are closely tied to various malignancies, genetic damage, oxidative stress, neurological problems, respiratory, metabolic, and thyroid effects, but pesticides in water resources also have a negative impact on human health as well as the health of the overall environment (Ayilara et al., 2023). Because synthetic pesticides are less biodegradable, they have a longer lasting impact on the environment, endangering microbial life and reducing soil respiration by 35%, among other effects. Additionally, they directly exterminate helpful organisms like bees and aquatic organisms (Carvalho, 2017).
In agricultural areas, synthetic pesticides have contaminated about 90% of the water supplies (Wahaab & Badawy, 2004). The bioaccumulation and bio magnification of large amounts of pesticides endangers the aquatic and terrestrial food systems (Carvalho, 2017; Wahaab & Badawy, 2004).According to studies, pesticide exposure is endangering biodiversity and species. In recent decades, European countries have recorded a 70% reduction in insect biomass and a 50% decline in farmland bird (Raven & Wagner, 2021).
Synthetic pesticides have also increased production costs among farmers indicating no significant returns in agriculture as a business, countries on the African continent have increasingly been adopting the use of synthetic pesticides making their import costs higher than before as many don’t have active chemical ingredients that produce synthetic pesticides. The Food and Agriculture Organization of the United Nations (FAO) indicate that in terms of trade, Uganda’s total pesticide import value increased by about 13 times, from US$6.5 to US$82.6 million, between 1994 and 2018 (FAO, 2020), as shown in the figure below(Sustainable & Goals, 2021). With the World Health Organization estimates of about three million cases of acute synthetic pesticide poisoning worldwide and approximately 220,000 death per year (., 2014; Jeyaratnam, 1990; Pandey et al., 2023). It creates an urgent need for research to discover more safe and sustainable approaches for pest control.
Botanical extracts, which are natural extracts derived from pesticidal plants and are either employed as crude extracts or the isolated active components, have the potential to be a safe and sustainable alternative to synthetic pesticides (Samada & Tambunan, 2020). Such botanicals have multiple modes of action, such as repelling, anti-feeding, and anti-oviposition, which makes them less susceptible to pesticide resistance, they are also target specific, less toxic to mammals, and biodegradable as their rate of decomposition increases under solar radiation (Divekar, 2023). Small-holder farmers with limited resources can easily use botanical pesticides because they are affordable, readily available locally, and don't require sophisticated preparation techniques or technology (Grzywacz et al., 2014; Samada & Tambunan, 2020).
To manage field and storage pests, a number of plants, including Azadirachta indica, Phytolaca dodecandria, Lantana camara, Tithonia diversifolia, and Tephrosia vogelii, have been utilized traditionally in Africa (Samada & Tambunan, 2020). The bioactivity of several botanicals has been tested in studies, and the findings indicate that they are successful in controlling pests in both the field and storage (Samada & Tambunan, 2020).
A. indica and T. vogelii are two of the most extensively researched botanical pesticides in the world. In Africa, A. indica contains azadirachtin, which has anti-feeding, repellent, anti-oviposition, and anti-molting properties and is effective in controlling over 250 species of pests (Luntz & Nisbet, 2000). Farmers in the Masaka region of Uganda utilize neem leaf extracts to manage field pests including aphids (Julius, 2002; Kamatenesi et al., 2008). According to Asogwa et al. (2010), A. indica leaf and seed powder extracts are efficient against weevils in stored maize, improve seed vigor, and lessen fungal attack and infections on stored seeds.
Traditional names for T. vogelii (fish bean) include "Maluku" in Luganda and "Ekiluku" in Runyankore (Julius, 2002). The primary bioactive phytochemicals in T.vogelii are rotenoids, which include rotenone, deguelin, and tephrosin. They are highly concentrated in the leaves and have potent insecticidal properties against a variety of pests, as well as anti-feeding and anti-ovipositional properties (Zhang et al., 2020). Furthermore, Tephrosia vogelli is heavily promoted in Africa as an agroforestry tree due to its ability to fix nitrogen and as green manure. When grown in Malawi alongside maize, it produced more yield per acre than fertilized monoculture maize (Akinnifesi et al., 2009).
T.vogelli is traditionally used in Malawi and Zimbabwe to protect stored maize and beans against Sitophilus ssp (Kamanula et al., 2011). In Zimbabwe, Tephrosia vogelii is used to control ticks in dairy animals, a study was done to test its efficacy and it was found that there was no significant difference between T. vogelii and Triatix dip at 5% level (Gadzirayi et al., 2009). It is effective in controlling bruchid beetles (Grzywacz et al., 2014) T. vogelii and A. indica extracts were tested against Padagrica species and investigated in Hibiscus sabdariffa in Nigeria, it exhibited high efficacy (59-80%) and a combination of the two was effective as synthetic pesticide delfamethrine (Journal & June, 2013). T. vogelli is also effective in controlling field pests in watermelon (Citrullus lanatus) (Alao & Adebayo, 2015).
In Africa, Azadirachta indica is also frequently used as a pesticide (Luntz & Nisbet, 2000)with itsmain active component, Azadirachtin, is contained in the seed and tuber . Through a number of different mechanisms of action, azadirachtin is efficient at controlling pests in both the field and storage. According to Ajenifujah-Solebo et al. (2019), it has characteristics that repel, prevent oviposition, and prevent feeding. By preventing the production of morphogenetic peptides and causing sterility by changing ecdysteroid, azadirachtin inhibits molting and decreases the quantity of viable eggs and line progeny (Luntz & Nisbet, 2000).
In Uganda, smallholder farmers have long used a mixture of plant extracts, including A. indica, T. vogelii, hot paper, lantana camara, and garlic (Julius, 2002). Tephrosia vogelii has been utilized as an organic manure in Uganda due to its high phosphorus content (Nakuru, 2013). However, Spodoptera frugiperda has not been thoroughly researched in terms of the efficiency of botanical combinations (Julius, 2002). Thus, the purpose of this study is to evaluate the effectiveness of a mixture of Tephrosia vogelii and Azadirachta indica in controlling Spodoptera frugiperda in a lab setting.