2026-03-02
Daniel Ameyaw, Vincent Yao Eziah, Laith Khalil Tawfeeq Al-Ani, Patricia Akua Sitsofe Nyahe, Candice Anne Coombes, Medetissi Adom, Ken Okwae Fening, Maxwell Kelvin Billah, Michael Yao Osae, Drauzio Eduardo Naretto Rangel, Dalia Sukmawati, Owusu Fordjour Aidoo, Mavis Agyeiwaa Acheampong
The false codling moth (FCM, Thaumatotibia leucotreta Meyrick) is a major constraint on chilli pepper production and export in Ghana. Although chemical pesticides remain the main control strategy, their effectiveness is limited and export restrictions on synthetic residues highlight the need for sustainable alternatives. To address this challenge, the virulence of seven native Metarhizium isolates (UGKAP1, UGJKCS9, UGJKCS10, UGNAKC1, UGAFMF20, UGAFMF8 and UGSUHC1) obtained from agricultural fields in Ghana against final instar FCMs at 1 × 10 8 conidia/mL was evaluated via conidial-sand assays, and compared with that of two USDA ARSEF isolates ( Beauveria bassiana ARSEF 252 and Metarhizium anisopliae sensu lato ARSEF 4570). As abiotic environmental factors can affect fungal efficacy, the influence of humidity on the infectivity of four selected isolates (UGJKCS9, UGJKCS10, UGSUHC1 and UGAFMF20) was assessed. All seven native isolates caused > 80% pupal mortality within 21 days. The pupal mortality rates of ARSEF 252 and ARSEF 4570 were 49% and 57%, respectively. The most virulent isolate, UGJKCS9, exhibited an LC 50 of 2.7 × 10 6 conidia/mL and an LT 5 0 of 3 days. High pupal mortality (82–100% at 10 5 and 10 7 conidia/mL) occurred across all tested humidity levels (43%, 75% and 98% RH) for all four isolates. These results indicate that the tested isolates, particularly UGJKCS9, exhibit strong potential as sustainable alternative control agents for FCMs in Ghana, warranting further evaluation under field conditions for integration into chilli pepper pest management programmes.
2026-02-15
Emma Stirk, Megan Mulcahy, Sean Thackeray, Sean Moore, Martin Hill
The generalist egg parasitoid Trichogrammatoidea cryptophlebiae (Nagaraja, 1979) (Hymenoptera: Trichogrammatidae) is mass-reared in South Africa on Thaumatotibia leucotreta (false codling moth). However, alternative tortricid hosts may improve or enhance production. This study assessed the suitability of Cydia pomonella , Cryptophlebia peltastica and Lobesia vanillana as alternative hosts for the parasitoid through no-choice and choice trials. Host acceptance, emergence, superparasitism, unsuccessful emergence, sex ratio, and offspring morphology were measured. In no-choice assays, T. leucotreta and L. vanillana yielded the highest parasitism, while C. peltastica showed significantly less parasitism. Emergence was highest from C. pomonella and C. peltastica , but high superparasitism in these species resulted in increased unsuccessful development compared to the other species. Lobesia vanillana, the smallest host, classified by egg size, produced significantly smaller offspring of the parasitoid. Morphological analyses showed limited differences in forewing length, but significant host- and sex-dependent variation in hind tibia length. Choice trials revealed a consistent preference for T. leucotreta , particularly eggs that had been irradiated, suggesting its continued suitability for mass production of T. cryptophlebiae . These findings highlight key host-related traits affecting T. cryptophlebiae biology and rearing potential and confirm L. vanillana and C. peltastica as physiological hosts.
2025-08-25
Dewidine van der Colff, Leanne Dreyer, Alex Valentine, Francois Roets
In this study we assessed how an invasive tree ( Acacia mearnsii ) and an ecologically equivalent native species ( Virgilia divaricata ) interact with their insect pests and fungal pathogens in sympatric populations along forest edges in the Cape Floristic region of South Africa. We determined how insect herbivore abundance and fungal disease development differ between the two species across a moisture gradient and whether observed differences can be explained by moisture availability and/or plant nutrient levels. The two host plants had similar foliar nutrient content, but measurements of δ12C / δ13C isotope ratios in leaves indicated that only the native plant experienced drought stress at drier sites. The degree of disease development after tree wounding was similar for both species and was not correlated with soil moisture content in either species. As predicted by the biotic release hypothesis, herbivore numbers were significantly higher on the native plant. Herbivore numbers on A. mearnsii were unaffected by moisture availability, but herbivore numbers on V. divaricata increased at drier sites. Consequently, under conditions of increased drought, V. divaricata may experience higher levels of drought stress than the invasive A. mearnsii and may suffer from increased insect herbivory, rendering it a weaker competitor. Herbivore abundance and disease development were significantly influenced by plant nutrient content for A. mearnsii , but not for V. divaricata . Relatively nutrient-poor A. mearnsii trees experienced higher herbivore loads but slower disease development than nutrient-rich trees. Therefore, the susceptibility of A. mearnsii seems to be determined by plant nutrient levels, a factor that varies independently from water availability.
2025-08-18
Liezl Whitehead, Vaughn Swart, Marieka Gryzenhout, Lizette Koekemoer
Mosquitoes substantially impact human and animal health as vectors of disease and consequently take a heavy toll on the economy. In order to effectively investigate the evolutionary history of vectors of disease and understand their associated biological tendencies, it is vital to correctly identify and classify the relevant species. Since phylogenetic studies on South African species are currently markedly underrepresented in the literature, the current study aimed to investigate the placement of South African Anopheles Meigen mosquito species within the genus’ extensive taxonomic framework based on the cytochrome oxidase subunit 1 (COI), internal transcribed spacer 2 (ITS2) and 28S ribosomal DNA sequences. Maximum likelihood and Bayesian phylogenetic analyses were performed for each of the COI, ITS2 and 28S DNA datasets, as well as a concatenated analysis for all three DNA regions combined. Upon examination, several phylogenetic findings were corroborated by analyses based on multiple DNA regions. These findings supported the non-monophyly of several taxa relevant to the region (subgenus Anopheles , Laticorn Section, and the Funestus Group) and may indicate the non-monophyly of several South African species [ An. coustani Laveran, An. tenebrosus Dönitz, An. parensis Gillies, An. funestus Giles and An. longipalpis C (Theobald) (Type C) (Koekemoer et al. 2009)]. The results reveal numerous challenges within the current systematic framework of the genus Anopheles and provide a novel focus on the phylogeny of South African taxa.
2025-07-03
Inam Yekwayo, Asabonga Mngeni
In the Eastern Cape, natural landscapes that are adjacent to rivers and the sea are threatened by illegal sand mining, which occurs without prior assessment of biodiversity. Sand mining activities lead to the reduction of vegetation cover and plant species richness. Generally, species richness of arthropods correlates positively with plant species richness. Thus, it is important to test the effect of sand mining on arthropod diversity. In this study we compared species richness, abundance, Shannon-Wiener diversity and composition of ants, beetles and spiders between sand-mined areas and the surrounding grassland. Arthropods were collected using pitfall traps in eight plots in the sand-mined area and eight plots in the surrounding grassland. The sand-mined area and the grassland supported similar species richness and abundance of arthropods. However, significantly greater diversity was in the surrounding grassland than the sand-mined area. Furthermore, species composition of arthropods between the two areas was significantly different. Additionally, there were 13 morphospecies that were indicators of the sand-mined area, and ten morphospecies that were indicators of the surrounding grassland, while there were no shared indicator species between the two study areas. As such, disturbance-tolerant species that prefer open habitats may have replaced specialist arthropods. Given that our study showed that illegal sand mining changes species composition and reduce the diversity of arthropods, sand mining should be restricted to designated areas to reduce the impact of mining on arthropods and improve conservation.
2025-03-03
Muano Netshipise, Pieter Schalk Schoeman, Reinette Gouws-Meyer, Shandukani Rudolf Netshifhefhe
A survey of the coconut bug, Pseudotheraptus wayi damage on litchi fruits was conducted on eight farms in the Limpopo and Mpumalanga provinces to assess infestation levels. Ten Mauritius litchi trees per study site/farm were randomly selected and monitored in November and December 2023. Fallen/aborted immature fruits were collected from the mature litchi trees. A total of 11 083 fruits were collected and inspected for coconut bug damage. A total of 5 262 fruits were found to be damaged by coconut bugs. The results of the predicted percentage means from the GLMM modelling of the damage caused by the coconut bugs ranged from 19.71% to 62.41% on aborted fruit from farms, with 33.77% and 57.53% in Limpopo and Mpumalanga provinces, respectively. An indication that the coconut bug caused an average annual loss of 45.65% on immature fruit that were subsequently aborted in production from the two provinces. These findings point towards the fact that there is a considerable presence of coconut bug on the farms and also that litchi is a very good host of the coconut bug. The coconut bug damage increased when other host plants are cultivated in close proximity. Further research to evaluate economic impact of this pest is therefore needed.
2025-02-27
DJAKARIDJA BERTE
The sleeping sickness focus of Bonon was the last one still active at a low endemic level in Côte d’Ivoire. An entomological survey carried out in June 2015 during the rainy season using “Vavoua” traps guided subsequent control activities. Indeed, it improved knowledge of tsetse fly ecology. All the tsetse flies caught (i.e. 1909) belonged to the subspecies Glossina palpalis palpalis (Robineau-Desvoidy, 1830), the major vector of Human African Trypanosomiasis (HAT) in Côte d’Ivoire. In this paper, we looked at the relationship between the apparent density (AD, flies/trap/day) and biotopes. The AD significantly varied according to biotopes, with high density around villages. The trypanosomes overall infection rate (mature and immature) according to microscopic observation was 23.2%. When considering mature infections, the infection rate was 5.5 %. Polymerase chain reaction (PCR) analyses confirmed the presence of Trypanosoma brucei s.l. and Trypanosoma congolense “forest type”. Blood meals analysis using cytochrome b gene sequences revealed that tsetse flies fed on pigs. The edges of the villages seem to constitute preferred habitats for tsetse flies where they are protected from insecticide pressure in the fields, and where they can easily take bloodmeals from free-ranging pigs. The findings of this study provided a baseline in decision-making for subsequent vector control activities.
2023-11-24
Colin Morrison, Robert Plowes, Ivy Ng’iru, Aaron Rhodes, Dino Martins, Lawrence Gilbert
Invasive species are the second largest contributor to biodiversity loss and drivers of ecosystem change. Buffelgrass is a C4, perennial grass native to Africa and Asia that was widely introduced across tropical and subtropical rangelands as livestock forage. Buffelgrass reduces native biodiversity and ecosystem stability in its introduced range when it escapes livestock pastures. Understanding the ecology of insects associated with buffelgrass in its native range may provide an understanding of invasion processes and biological control opportunities where buffelgrass has become an invasive challenge. Here, we present the results of a six-year survey of herbivorous arthropods of a native buffelgrass population from Kenya. Buffelgrass was examined for externally and internally feeding insects of vegetative and reproductive tissues. We also categorised buffelgrass detritivores and parasitoids that may use buffelgrass herbivores as hosts. The samples were photographed and Sanger sequenced to identify them to the lowest possible taxonomic ranking. We collected information on sample abundances, phenologies, tissues consumed, and putative diet breadths. We identified 25 morphospecies representing seven orders and 16 families. The putative host plant specialisation was as high as 67% for Diptera. Phenological variation in herbivore presence correlated with seasonal rainfall and provided a guide for when to conduct follow-up biological control agent searches. The most abundant herbivore was a gall midge (Diptera: Cecidomyiidae) that inhabits buffelgrass culms. Additional research should focus on bringing this species into containment where host choice trials can be conducted to determine if it is truly monophagous and assess its impact on buffelgrass growth.