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Thermal tolerance in Spodoptera frugiperda: Influence of age, sex, and mating status

Mbande, Abongile

Title: Thermal tolerance in Spodoptera frugiperda: Influence of age, sex, and mating status Authors: Mbande, Abongile; Mutamiswa, Reyard; Chidawanyika, Frank Abstract: Temperature plays a key role in shaping the physiology and behavior of ectotherms where responses can depend on age, sex and ontogeny. We investigated the effects of age, sex and mating status on thermal tolerance of Spodoptera frugiperda 3-, 6- and 9-days old adults heat shocked at adult, pupal and larval stages, at 40 °C for 2 h. Our results showed varied significant critical thermal maxima across mating status, age, sex and life stage in tested insects after heat shock. The virgin females CTmax increased with age while it fluctuated in males and 6 days old virgin females had higher CTmax than males. The 3 day old mated females had the highest heat tolerance while 6 days old virgin males the lowest heat tolerance. There was no significant difference in CTmax recorded between virgin males and females aged 3 and 9 days as well as 3, 6 and 9 day mated males and females. There was also no significant interaction between mating status and sex but there was a significant interaction effect between life stage and age. Mated males had higher CTmax than females across all heat shocked developmental stages. The results show a high level of fitness and survival in S. frugiperda females, which may be advantageous in invasion. This study also showed “carry over” effects in adults heat shocked at juvenile stage, with aged adults showing decline in CTmax. This study suggests that plasticity of thermal tolerance may be an important approach for S. frugiperda invasion.

Effects of Different Combinations of Sterile and Fertile Thaumatotibia leucotreta on Fruit Infestation and Population Growth Rate

Michael M. Githae — 2025-01-01T00:00:00Z

Title: Effects of Different Combinations of Sterile and Fertile Thaumatotibia leucotreta on Fruit Infestation and Population Growth Rate Authors: Michael M. Githae; Candice A. Coombes; Mutamiswa, Reyard; Sean D. Moore; Martin P. Hill Abstract: Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a key phytosanitary pest of citrus in South Africa. The pest damages fruit by burrowing and feeding on the pulp, thus causing yield losses and export rejections. There are several T. leucotreta management strategies, such as orchard sanitation, mating disruption, attract-and-kill, the use of biocontrol agents, and the sterile insect technique. A laboratory cage study was conducted to examine the impact of different combinations of treated (sterile) and untreated (fertile) T. leucotreta adults on fruit damage and reproduction rate. Thaumatotibia leucotreta adults were grouped into different combinations of treated (T) and untreated (U) male (M) and female (F): UM × UF (control), TM × UF, UM × TF, TM × TF, and UM × UF × TM × TF. These combinations were released into cages to mate and oviposit on the Navel oranges. Each treatment was replicated three times, and the experiment was repeated three times. After 4 weeks, the number of damaged fruit and larval entries per fruit per cage were recorded. Damaged fruit per treatment were then incubated until all emerging F1 progeny were collected and outcrossed with fertile T. leucotreta. Fecundity and fertility per treatment were recorded. Cages with sterile T. leucotreta had significantly fewer damaged fruit, larval entries, and emerged F1 adults compared to the control, except for UM × UF × TM × TF treatments. Similarly, control cages and UM × UF × TM × TF treatments had significantly higher fecundity and fertility compared to other treatments involving sterile T. leucotreta. The TM × UF combination exhibited the lowest rate of increase per generation (< 0.57× from the parental to F1 generation), demonstrating a reduction in the fertile population. The results demonstrated that the release of sterile T. leucotreta leads to sterile-fertile matings rather than fertile-fertile matings, thereby aiding in pest suppression in the T. leucotreta SIT programme.

Parallel concepts and future opportunities across the biological control and invasion sciences

Ross N. Cuthbert — 2026-01-01T00:00:00Z

Title: Parallel concepts and future opportunities across the biological control and invasion sciences Authors: Ross N. Cuthbert; Nompumelelo Baso; Tressia Chikodza; Candice Coombes; Jane Doherty; Michael Githae; Tamzin C. Griffith; Marco R. Hernandez; Karla M. Jaschke; Michael D. Jukes; David Kinsler; Hugh J. MacIsaac; Hlumelo T. Mantshi; Pippa Muskett; Mutamiswa, Reyard; Anthony Ricciardi; Guy F. Sutton; Deric V. Tanka; Jaqui van Dyk; Clarke van Steenderen; Jaimie T.A. Dick; Julie Coetzee Abstract: The biological control and invasion sciences are long-standing research fields that have accrued enormous fundamental and applied interest. However, their theoretical and practical integration remains in its infancy. Utilizing an expert elicitation process with participants spanning these sciences, we identify conceptual parallels and future opportunities to strengthen links and address future challenges in both fields. We found that the biological control and invasion sciences face pervasive context-dependencies that must be understood to improve outcome predictions, including climatic changes, spatiotemporal scales, and ‘ecological surprises’. Both sciences would further benefit from terminological streamlining to improve communication, sharing of emerging technologies, and mitigation of the taxonomic decline. The two fields are strongly affected by social perceptions and awareness by decision makers, requiring more effective engagement and translation efforts. Our exercise promotes cross-cutting interdisciplinary advances to improve understanding of fundamental ecological and evolutionary processes, socio-ecological challenges, and management efficacy across the biological control and invasion sciences.

A Framework for Multidimensional Management of Invasive Alien Insect Pests in Sub-Saharan Africa

Klaus Birkhofer — 2026-01-01T00:00:00Z

Title: A Framework for Multidimensional Management of Invasive Alien Insect Pests in Sub-Saharan Africa Authors: Klaus Birkhofer; Frank Wätzold; Ruben Remelgado; Pia Addison; Pascal Aigbedion-Atalor; Anna F. Cord; Sunday Ekesi; Mutamiswa, Reyard; Rwomushana, Ivan; Martin Paul Tabe-Ojong Jr; Nyamukondiwa, Casper Abstract: Invasive alien insect pests pose a significant threat to achieving sustainable food systems in sub-Saharan Africa, where reliance on synthetic pesticides has led to unsustainable practices due to high costs and health and environmental risks. This article presents a multidimensional framework for managing invasive alien insect pests in sub-Saharan Africa, specifically directed at researchers, policymakers, non-governmental organisations and other institutions responsible for invasive pest management as well as extension services for farmers. Invasive pests, such as the Oriental fruit fly and the fall armyworm, and a highly damaging native species for comparison are central to the framework. The framework considers the environmental, socio-economic, and regulatory dimensions of pest management decisions. It reviews different control strategies used against invasive alien pests, highlighting their limitations and environmental impacts. By considering farmer characteristics, institutional support, market demands, and regulatory policies, the article emphasises the need for integrated pest management approaches. The aim is to contribute to the development of sustainable, effective pest management strategies that will ensure long-term agricultural productivity and food security in sub-Saharan Africa.