The groundnut leaf miner (GLM),
Aproaerema modicella, also known as the soya bean moth in Australia (
Aproaerema simplexella) was predominantly a significant pest of groundnut (
Arachis hypogaea) and soya bean (
Glycine max) in Asia. It was first reported in Africa in 1998
(Page et al., 2000). Its presence has since raised concerns in groundnut and soya bean production. The GLM is distributed across multiple countries in Asia, Africa and Australasia (
CAB International, 2014;
Buthelezi et al., 2021). The pest’s ability to thrive in diverse agroecological environments, ranging from regions with warm summers and cold winters to those with consistently warm climates, indicates its adaptability to various climatic conditions
(Buthelezi et al., 2021). Groundnut leaf miner larvae cause significant damage by feeding on the leaf mesophyll, leading to leaf browning, abscission and reduced photosynthetic capacity, which directly affects crop yields
(Kolhe et al., 2015; Kenis and Cugala, 2006). In India, GLM infestations were reported to cause up to 90% losses in groundnut yield
(Reddy et al., 1978; Sumithramma, 1998). In Africa, 100% losses in groundnut and soybean crops have been recorded in countries such as Uganda, Mozambique and South Africa
(Cugala et al., 2010; Buthelezi et al., 2013;
Ibanda et al., 2018).
Groundnut is a crucial legume crop for smallholder farmers in Africa, providing both subsistence and income
(Janila et al., 2013). Soya bean is an essential source of protein for human consumption as well as for animal feed. Its susceptibility to GLM poses a serious threat to food security
(Bhor et al., 2014; Tukamuhabwa and Oloka, 2016).
This review synthesizes management strategies for GLM in Africa and Asia, focusing on biological, cultural, resistant cultivar screening and chemical controls. The majority of studies on GLM management have been conducted in Asia, although efforts to manage the pest in Africa are ongoing through similar approaches.
The distribution of GLM
The prevalence of GLM has been documented across various regions in Asia, Africa and Australasia. In Asia, it has been reported in India, Bangladesh, Cambodia, China, Indonesia, Java, Malaysia, Myanmar, Nepal, Pakistan, the Philippines, Sri Lanka, Thailand, Vietnam and the Indian state of Orissa. In Africa, GLM is known to occur in Uganda, the Democratic Republic of Congo (DRC), Malawi, Mozambique, Kenya, South Africa, Egypt, as well as on the Indian Ocean islands of Madagascar, Réunion and Mauritius. In Australasia, GLM is prevalent in Australia specifically in Western Australia, the Northern Territory, Queensland, New South Wales, Victoria, Tasmania, South Australia and Norfolk Island and in New Zealand (
CAB International, 2014;
Buthelezi et al., 2021).
The biology of GLM
Groundnut leaf miner is classified under family Gelechiidae and the subfamily Anacampsinae within the Lepidoptera order. Among the 12 species in the genus
Aproaerema,
A.
modicella is the most studied due to its pest status on groundnut and soya bean in Asia and Africa
(Hall et al., 1993; Jyothi et al., 2008).
Description and damage symptoms of GLM on the leaves of the host plant
The GLM adult moth is grey, with a wingspan reaching up to 18 mm
(Shanower et al., 1993a). Female GLM moth lays small, shiny white eggs that are oval in shape. The larva of GLM is greyish-green with a glossy black head and feed on the leaf mesophyll, forming winding mines that eventually expand into blotches
(Chanthy et al., 2010). These mines result in leaf distortion, browning and desiccation, causing early leaf drop and yield losses (
Kenis and Cugala, 2006). In its lifetime, one larva can destroy 34.8 to 179.3 cm² of leaf area (
Shanower, 1989). In South Africa, GLM infestations correspond with the flowering and pegging stages of groundnut, typically occurring 5 to 6 weeks after the crop emerges
(Buthelezi et al., 2017; 2021).
Groundnut leaf miner life cycle
Female GLM moths lay between 87 and 473 eggs on the underneath surface of leaves, stems, or petioles (
Cherian and Basheer, 1942). The life cycle duration depends on environmental conditions, particularly temperature, ranging from 15 to 80 days
(Shanower et al., 1993b). Under warmer conditions, the full life cycle can take 15-28 days, while in cooler conditions, it extends to 37-45 days (
Cherian and Basheer, 1942;
Sandhu, 1978). In South Africa, GLM has a generation cycle of 28-30 days, with two peaks per season
(Buthelezi et al., 2017).
Effects of climatic factors on GLM incidence
Climatic factors like temperature, humidity and rainfall significantly influence GLM populations. Studies in South Africa showed higher moth catches during periods of high temperatures and low rainfall, while rainy periods saw a drop in population density
(Buthelezi et al., 2017). These findings align with observations in India, where GLM infestation peaks coincide with high temperatures and reduced humidity (
Arunachalam and Kavitha, 2012). Furthermore, GLM infestations in India have also been predominantly recorded in rainfed cropping systems
(Reddy et al., 1978).
Host plants of GLM
Soya bean is the primary shared host for GLM populations in Asia, Australasia and Africa (
Common, 1990;
Bailey, 2007;
Buthelezi et al., 2013). In Africa and India, GLM also infests groundnut
(Buthelezi et al., 2013). In Australia, it affects
Cullen tenax,
Psoralea patens and clover (
Trifolium spp.) (
Bailey, 2007). In South Africa, GLM infests various leguminous crops and wild hosts but not in winter
(Buthelezi et al., 2013). Table 1 details the known host plants of
A.
modicella in India
(Shanower et al., 1993a) and South Africa (
Van der Walt, 2007;
Buthelezi et al., 2013), showing shared hosts between Asian and African populations. Groundnut leaf miner is generally absent during winter months in South Africa. Studies have shown that it reappears in high numbers during the rainy season, suggesting an unknown overwintering strategy
(Buthelezi et al., 2013). In India, there is no documented evidence on how GLM survives the off-season, warranting future research into its survival strategies during non-cropping periods.
Economic imapct of the GLM
Groundnut leaf miner is a significant pest for groundnut and soya bean in South and Southeast Asia and Africa
(Shanower et al., 1993a; Kenis and Cugala, 2006). In regions like India, GLM causes up to 90% yield loss, particularly in the absence of natural predators, resulting in prevalent outbreaks
(Reddy et al., 1978; Sumithramma, 1998). Africa has also reported severe damage, with total crop loss in countries such as Mozambique, Uganda and South Africa
(Cugala et al., 2010; Buthelezi et al., 2013; Ibanda et al., 2018). The established economic threshold for GLM in South Africa is 2 larvae per plant, while in Mozambique, it is 38 larvae per plant (
Kenis and Cugala, 2006; Van der
Walt et al., 2009). These threshold levels, along with environmental conditions, guide control measures for managing GLM outbreaks.
Control measures for GLM
Cultural control
Crop rotation
Rotating groundnut with non-leguminous crops, such as maize, cotton or sorghum, reduces GLM infestations. These crops disrupt the pest’s lifecycle and decrease populations (
Thakur, 2013).
Intercropping
Mixed cropping systems, like groundnut with sorghum or cowpea, have shown reduced GLM populations (
Rajagopal and Hanumanthaswamy, 2000).
Irrigation
Drought stress exacerbates GLM infestations. Irrigated crops display lower infestation rates, as seen in South Africa
(Buthelezi et al., 2017).
Planting dates
Adjusting planting times reduces GLM attack. In South Africa, early planting (November) is less vulnerable than late planting (January)
(Buthelezi et al., 2017).
Biological control
Predators
Several predators of GLM have been documented in India, with some of these species listed in Table 2. Polyphagous predators such as lacewings (
Chrysoperla carnea) and ladybirds (
Cheilomenes sexmaculata) have been reported to feed on GLM (
Crop Pest Compendium, 2005). However, their effects on GLM populations in Africa have yet to be thoroughly studied (
Kenis and Cugala, 2006).
Parasitoids
The number of GLM parasitoids which have been recorded in different countries are listed in Table 3. Several parasitoids, particularly from the families Braconidae, Ichneumonidae, Hymenoptera, Pteromalidae, Eupelmidae, Bethylidae, Chalcididae, Eurytomidae and Trichogrammatidae are effective against GLM larvae in South Africa and India
(Murugasridevi et al., 2022; Van der
Walt et al., 2009; Shanower et al., 1993a). However, more research is needed to explore their potential in Africa.
Pathogens and nematodes
Entomopathogenic fungi like
Beauveria bassiana (
Joshi and Patel, 2011) and nematodes such as
Steinernema have been observed to attack GLM larvae
(Rajagopal et al., 1988). Their use as biological control agents in Africa requires further investigation.
Chemical control
There are several insecticides used to provide control for GLM. Some of these are listed in Table 4. Several chemicals previously reported as effective for controlling GLM in India, such as Dimethoate 30 EC, Monocrotophos 36 EC, Carbaryl 50 WP, Endosulfan 35 EC, Methoxyfenozide 24 SC and Profenofos, are now banned or have restricted usage in various regions.
Pazhanisamy and Hariprasad (2013) evaluated newer alternatives for GLM control, whereas
Pavviya and Muthukrishnan (2016) confirmed the effectiveness of Methoxyfenozide 24 SC in controlling GLM (Table 4). In Africa, cypermethrin has been effective in Mozambique and South Africa
(Cugala et al., 2010; Buthelezi et al., 2013). However, the indiscriminate use of chemicals could lead to resistance, emphasizing the need for integrated pest management approaches.
Monitoring GLM populations using pheromones
Sex pheromones are chemicals emitted by one sex to attract the other. Sex pheromones are crucial in managing GLM, as they aid in monitoring pest activity (
Ghewande and Nandagopal, 1997).
Nandagopal and Reddy (1990) identified the female sex pheromone of GLM and is used in traps as a blend of three chemical components; [(Z)-7, 9-decadienyl acetate, (E)-7-decenyl acetate and (Z)-7-decenyl acetate in the ratio10:2:1.4]. This mixture has been used effectively in monitoring flight activity of GLM in India (
Das, 1999;
Radhika et al., 2014) and South Africa
(Buthelezi et al., 2013; 2017).
Screening groundnut and soya bean genotypes for resistance to GLM
Several groundnut breeding lines resistant to GLM have been released by ICRISAT in Hyderabad, India (
Nigam, 2014). Groundnut varieties like ICGV 86031 show resistance to GLM. These genotypes could be used in breeding programs to develop more resistant groundnut lines, particularly in high-risk regions (
Reddy, 2001).
In India, soya bean varieties MAUS 62-2, DS 97-12 and HIS 01 were most resistant to GLM. Groundnut leaf miner infestation recorded in these cultivars ranged from 5.2%, 6.74% and 7.44% respectively (
Shirale and Uttamrao, 2010). In Uganda, a soya bean screening study revealed that three soya bean genotypes were resistant to GLM; VI046160, VI046165 and VI046167
(Ibadan et al., 2018). It was proposed that these varieties could serve as parents in breeding programs aimed at developing resistance to GSLM in soya bean
(Ibadan et al., 2018).
Integrated pest management (ipm) methods for GLM
Integrated Pest Management (IPM) employs various methods to reduce or replace synthetic pesticides. Effective approaches to managing GLM in India include using trap crops like soya bean, pheromone traps and intercropping groundnut with suitable soya bean varieties. Additionally, timed insecticide applications at 30-35, 45-50 and 60-65 days after sowing and botanical insecticides, such as 2% crude neem oil, have proven to be effective (
Nandagopal and Ghewande, 2004).
Muthiah (2000) highlights other successful methods, including the use of GLM sex pheromones,
Bacillus thuringiensis and an insecticide combination of phosphamidon (0.02%), endosulfan (0.04%) and neem oil (2%), which can be applied alone or with pheromone traps in both base and trap crops.
Agurla et al., (2024) evaluated IPM strategy to control GLM which comprised of practices such as summer deep ploughing, soya bean as a trap crop and pheromone traps for GLM control. This strategy effectively managed the GLM, resulting in reduced pest incidence and increased yields.
Recommendations for future research
Future studies should focus on:
• Identifying GLM overwintering strategies across different agroecological zones.
• Investigating the genetic basis for host preferences in GLM populations from Australia, New Zealand, South Africa and Asia.
• Exploring indigenous biological control agents for potential use in classical or augmented biological control.
• Determining GLM infestation threshold levels for better pest management.
• Developing and screening GLM-resistant cultivars.
