Search

Since 2016, the invasive insect Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) from the Americas has made maize production unattainable without pesticides in parts of Sub-Saharan Africa and Asia. To counteract this pest, farmers often resort to the use hazardous pesticides. This study aimed to investigate botanicals, microbials, and semi-synthetic insecticides in Ghana for pest control without harming local ecosystems. Under laboratory and on-station conditions, the present study evaluated the acute and sublethal responses of S. frugiperda to: (i) Pieris rapae Granulovirus (PrGV) + Bacillus thuringiensis sub sp. kurstaki (Btk) 5 WP, (ii) Btk + monosultap 55 WP, (iii) ethyl palmitate 5 SC, (iv) azadirachtin 0.3 SC, (v) acetamiprid (20 g/l) + λ-cyhalothrin (15 g/l) 35 EC, (vi) acetamiprid (30 g/l) + indoxacarb (16 g/l) 46 EC, and (vii) emamectin benzoate 1.9 EC. The results showed that at 96 hours post-exposure emamectin benzoate-based formulation has the highest acute larvicidal effect with lower LC50 values of 0.019 mL/L. However, the results suggested strong sublethal effects of PrGV + Btk, azadirachtin, and ethyl palmitate on the bionomics of S. frugiperda. Two seasons on-station experiments, showed that the semi-synthetic emamectin benzoate and the bioinsecticide PrGV + Btk are good candidates for managing S. frugiperda. The promising efficacy of emamectin benzoate and PrGV + Btk on the bionomics of S. frugiperda in the laboratory and on-station demonstrated that they are viable options for managing this pest. [ABSTRACT FROM AUTHOR]

The aphids Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) pose serious threats to the production of cruciferous crops in the tropics. Understanding their population dynamics is important for developing integrated pest management programmes to minimize their damage to crops. This study investigated the effects of climatic factors, natural enemies and plant age on the population dynamics of these pests. The population density of aphids and their natural enemies in 20 cabbage plants, and weather conditions were monitored for five cropping seasons from 2019 to 2021 in two agroecological zones of Ghana (Coastal Savannah and Deciduous Forest zones). The highest population density of L. e pseudobrassicae was recorded in January (dry season) in both agroecological zones, while the highest population density for M. persicae occurred in September (minor rainy season) and August (dry spell) in the Coastal Savannah and Deciduous Forest zones, respectively. The highest aphid densities were noted to occur during periods with low relative humidity and low rainfall. The population density of L. e. pseudobrassicae was significantly negatively related to plant age, air temperature and relative humidity, and positively related to syrphids (Paragus borbonicus) and spiders in the Coastal Savannah zone, while in the Deciduous Forest zone, it was significantly positively related to coccinellids. On the other hand, M. persicae population density was significantly positively related to syrphids and coccinellids in the Deciduous Forest zone. Rainfall negatively affected syrphids in the Coastal Savannah zone, while air temperature positively affected syrphids and negatively affected spiders in the Deciduous Forest zone. Coccinellids had a significant positive relationship with relative humidity in the Deciduous Forest zone. This study provides important insights into the key factors that regulate aphid population densities on cabbage and will support development of timely interventions to manage these pests. [ABSTRACT FROM AUTHOR]

We investigated the susceptibility of five cabbage varieties ('Oxylus', 'Super Cross', 'Vantar F1 Hybrid', 'Santa'F1 and 'Fortune') to aphids. Trials were set up in the Accra plains for two rainy seasons in 2017. The first trial examined aphid infestation and the second included weekly blanket spray of neem oil at 0.48 L/ha (60 ml/15 L water) during the second rainy season. Five systematically sampled cabbage leaves per plot were examined for the numbers of aphids and associated natural enemies (predators). Symptoms of aphid attack (incidence and severity of infestation) were also recorded. Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) (Hemiptera: Aphididae) were the two aphid species observed and their numbers differed significantly between varieties in both seasons during the first but not the second trial. Few aphids settled on 'Oxylus', while more occurred on 'Fortune'. L. e. pseudobrassicae was the most abundant aphid on all the varieties. Aphid numbers were significantly decreased by neem application. Occurrence of natural enemies did not differ significantly between varieties, except for spiders during the major rainy season. There was no significant difference in aphid infestation between varieties during the first season as all of them completely succumbed to the infestation, while in the second season aphid incidence and severity of infestation was highest on 'Fortune', with 'Oxylus' being the least attacked by aphids. The crop yield was zero during the first season without protection for all the varieties. However, in the second season, lower yields (0.19–3.66 t/ha) was obtained with cabbage without protection, and much higher yields (14.8–21.1 t/ha) were obtained on neem-treated plots. [ABSTRACT FROM AUTHOR]

The infestation of the fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in Africa since 2016 has been a major threat to maize production. Previous studies in Togo and Ghana from 2016 to 2018 did not correlate FAW infestation to yield losses. Thus, the aim of this study which assesses the impact of FAW infestation by inspecting 150 maize farms throughout the five Agro-Ecological Zones (AEZs) of Togo for FAW plant damage, and third instar larvae were used to infest 10-day-old maize plants in netted plots under controlled conditions at an experiment station (Station d'Expérimentations Agronomiques de Lomé) in 2019 and 2020. As control plots at the experiment station, plots were both netted and treated with emamectin benzoate, simply netted, or open to natural infestation. The number of larvae, egg masses, percent damaged plants, and damage proportions of leaves and ears were scored until harvest. Infestations and damages on maize plant throughout Togo were similar between the two years but were higher in the southern part of the county (AEZ5). At the experiment station, the yield losses were significantly considerable and increased from 25% infestation. The losses were 0.37 t ha−1 for 25% infestation, 0.34 t ha−1 for 30%, 0.59 t ha−1 for the open plots, 0.70 t ha−1 for simple netted and 50% infestation, 1.03 t ha−1 for 75%, and 1.27 t ha−1 for 100% infestation. This current study suggested thorough inspection on maize farms to set off management practices from 25% of infestation. [ABSTRACT FROM AUTHOR]

The necessity of cold storage for mycoinsecticides poses a logistical challenge in tropical Africa, where maintaining consistent refrigeration is a major obstacle. To investigate alternative preservation methods, our study evaluates conidial-based freeze-dried formulations of Beauveria bassiana (IMI 389521), Metarhizium acridum (IMI 330189), and mycelial-based freeze-dried formulations of Hirsutella thompsonii (IMI 327488 and IMI 391722). Propagules were cryoprotected with lactose, mannitol, and raffinose, encapsulated, and freeze-dried in plastic and glass vials. Bioformulations in glass vials were cryoprotected with mannitol only. Viability (CFU/g each day) of bioformulations, following 16-weeks-storage, and their virulence (at 1 × 107 conidia mL−1 in six days) against key pests of maize and cassava in Africa (larger grain borer, variegated grasshopper and cassava green mite) were determined under ambient laboratory conditions in Ghana. Our results show that non-freeze-dried conidia of B. bassiana and M. acridum had significantly higher viability and efficacy than freeze-dried versions, when stored under non-refrigerated conditions (averaging 27.7°C, 78.8% RH). Freeze-dried H. thompsonii mycelia were neither viable nor virulent against cassava green mite. Freeze-dried B. bassiana and M. acridum in plastic vials remained viable for 12 weeks, while in glass vials they were viable for seven weeks. Freeze-dried B. bassiana in both plastic and glass vials caused 38–43% mortality in larger grain borer, and M. acridum caused 45–82% mortality in variegated grasshopper. Further, conidia cryoprotected with lactose had significantly higher viability and mortality than raffinose and mannitol. Our research contributes to mycoinsecticide development, particularly in the context of storage and application challenges in tropical climates. [ABSTRACT FROM AUTHOR]

Invasive alien species (IAS) continue to shape the global landscape through their effects on biological diversity and agricultural productivity. The effects are particularly pronounced in Sub-Saharan Africa, which has seen the arrival of many IAS in recent years. This has been attributed to porous borders, weak cross border biosecurity, and inadequate capacity to limit or stop invasions. Prediction and early detection of IAS, as well as mechanisms of containment and eradication, are needed in the fight against this global threat. Horizon scanning is an approach that enables gathering of information on risk and impact that can support IAS management. A study was conducted in Ghana to establish two ranked lists of potential invasive alien plant pest species that could be harmful to agriculture, forestry, and the environment, and to rank them according to their potential threat. The ultimate objective was to enable prioritization of actions including pest risk analysis, prevention, surveillance and contingency plans. Prioritisation was carried out using an adapted version of horizon scanning and consensus methods developed for ranking IAS worldwide. Following a horizon scan of invasive alien species not yet officially present in Ghana, a total of 110 arthropod and 64 pathogenic species were assessed through a simplified pest risk assessment. Sixteen species, of which 14 were arthropods and two pathogens, had not been recorded on the African continent at the time of assessment. The species recorded in Africa included 19 arthropod and 46 pathogenic species which were already recorded in the neighbouring countries of Burkina Faso, Côte d'Ivoire, and Togo. The majority of arthropod species were likely to arrive as contaminants on commodities, followed by a sizable number which were likely to arrive as stowaways, while some species were capable of long distance dispersal unaided. The main actions suggested for species that scored highly included full pest risk analyses and, for species recorded in neighbouring countries, surveys to determine their presence in Ghana were recommended. [ABSTRACT FROM AUTHOR]

Simple Summary: The fall armyworm (FAW) is a serious threat to maize production in Africa following its outbreak in 2016. Fortunately, some beneficial insects that could control FAW are already present in Africa, including Telenomus remus which parasitizes FAW eggs. Telenomus remus has been used in South America for biological control of FAW for several decades. Though T. remus is already present in Africa, little is known about its potential to be used for augmentative biological control of FAW under ecological conditions and agricultural systems in Africa. This study contributed to addressing this knowledge gap by conducting replicated field release trials of T. remus for FAW control in large maize plots in Ghana. In the major and minor rainy seasons, T. remus parasitized up to 33% and 100% of FAW egg masses, respectively, in the release plots. However, similar effectiveness of T. remus was recorded in non-treated control and farmers' plots located at 150–400 m distance from release plots, indicating high dispersion of the parasitoid. A single application of Emamectin benzoate did not significantly affect the parasitism rates of T. remus, and could be considered in IPM strategies against FAW. In response to the threat caused by the fall armyworm to African maize farmers, we conducted a series of field release studies with the egg parasitoid Telenomus remus in Ghana. Three releases of ≈15,000 individuals each were conducted in maize plots of 0.5 ha each in the major and minor rainy seasons of 2020, and compared to no-release control plots as well as to farmer-managed plots with chemical pest control. No egg mass parasitism was observed directly before the first field release. Egg mass parasitism reached 33% in the T. remus release plot in the major rainy season, while 72–100% of egg masses were parasitized in the minor rainy season, during which pest densities were much lower. However, no significant difference in egg mass parasitism was found among the T. remus release plots, the no-release control plots and the farmer-managed plots. Similarly, no significant decrease in larval numbers or plant damage was found in the T. remus release fields compared to the no-release plots, while lower leaf and tassel damage was observed in farmer-managed plots. Larval parasitism due to other parasitoids reached 18–42% in the major rainy season but was significantly lower in the minor rainy season, with no significant differences among treatments. We did not observe significant differences in cob damage or yield among the three treatments. However, the lack of any significant differences between the release and no-release plots, which may be attributed to parasitoid dispersal during the five weeks of observation, would require further studies to confirm. Interestingly, a single application of Emamectin benzoate did not significantly affect the parasitism rates of T. remus and, thus, merits further investigation in the context of developing IPM strategies against FAW. [ABSTRACT FROM AUTHOR]