Southern Forests: a Journal of Forest Science

Advancements in double-stranded RNA (dsRNA) technology for effective management of forest insect pests

Mon, 26 May 2025 00:00:00 +0000

The emergence of forest insects as a result of climatic changes presents traditional management strategies with significant challenges. RNA interference (RNAi) has attracted attention as a possible innovative forest conservation strategy. By eliciting gene silencing with double-stranded RNA (dsRNA), RNAi can effectively control insect pests, especially those belonging to the order Coleoptera. However, RNAi implementation in forest pest management is hindered by varying efficacy, target gene selection, dsRNA design and delivery techniques, particularly for long-lived endophagous insects such as bark beetles and Asian long-horned beetles. This review examines the development of forest pest-combating RNAi delivery systems such as nanoparticles, symbiont-mediated, cationic liposome-assisted and plant-mediated delivery. The study highlights the need for risk assessments of forest protection products (FPPs) using double-stranded RNA and suggests integrating off-target prediction capabilities based on sequence complementarity analysis. Despite obstacles, RNAi shows promise for controlling wood-boring beetles, and additional research could boost its effectiveness against these insects.

The use of suitability models and remote sensing to map forest suitability: A systematic review

Mon, 26 May 2025 00:00:00 +0000

The rapid decline of vegetated landscapes jeopardises vital ecosystem services underpinning climate change mitigation efforts. Restoring and repurposing these landscapes presents a powerful opportunity to recover lost services and strengthen the fight against climate change. This study undertook a comprehensive review of the scientific literature, focusing on suitability models and remote sensors used to identify areas suitable for forest vegetation. An exhaustive search and analysis of publications across the globe made over a 15-year period from 2008 to 2022 across three major databases (Scopus, ScienceDirect, and Web of Science) yielded 80 relevant publications. This analysis revealed a significant upward trend in research output, particularly since 2020. This surge reflects the increasing urgency of global landscape restoration initiatives. Additionally, the analysis of the reviewed articles revealed a rising preference for medium- to high-resolution remote sensing data, with Landsat emerging as the dominant sensor for forest suitability assessments. Notably, Maximum Entropy (MaxEnt) emerged as the most widely used model, followed by the increasingly popular Random Forest (RF). However, a concerning geographical disparity in research was identified. Publications were heavily concentrated in the Americas and Asia, while developing nations showed a significant research gap. This discrepancy highlights the critical need for increased research efforts in developing countries to equip them with the robust suitability models and advanced sensor technologies necessary for effective and targeted forest rehabilitation and restoration initiatives. Investing in research capacity building within developing nations holds immense potential to accelerate global landscape restoration efforts.

DNA sequence data confirms the presence of two closely related cypress-feeding aphid species on African cypress (Widdringtonia spp.) in South Africa

Mon, 26 May 2025 00:00:00 +0000

Aphids in the genus Cinara (Hemiptera: Aphididae) are pests of coniferous trees globally. Some of these aphids have become invasive in various parts of the world and have led to significant economic and environmental damage. During surveys conducted as part of a sentinel plant project, severe aphid infestations were observed on Widdringtonia trees in the Kirstenbosch National Botanical Garden, Cape Town, South Africa. In addition, planted Widdringtonia wallichii Endl. ex Carrière trees within their natural range of the Cederberg Wilderness Area, Western Cape, South Africa were found infested with aphids. In this study, we investigated the species identity of the aphids using DNA sequence data for the mitochondrial cytochrome c oxidase (COI) gene. The results revealed the presence of two closely related aphid species, the cypress aphid, Cinara cupressi (Buckton) and the cypress pine aphid, Cinara tujafilina (Del Guercio) infesting Widdringtonia spp. in South Africa. Both aphid species are alien to South Africa. While this is not the first report for either species in the country, the current study provides evidence of impact, with severe infestations leading to branch dieback and tree death. This finding supports the regulation of Cinara spp. in South Africa and highlights that management is urgently needed.

Exploring the diversity of leafrollers (Lepidoptera: Tortricidae) associated with eucalypts in South African forestry nurseries and plantations, with a new report of Strepsicrates sp.

Privilege T Makunde, Bernard Slippers , Brett P Hurley — Mon, 26 May 2025 00:00:00 +0000

A number of insect pests cause damage to eucalypts in South Africa. Their accurate identification is a key part of managing and controlling these pests. The aims of this study were to identify leafroller insect species in South African eucalypt nurseries and plantations, and to determine whether the species were native insects that had developed new host associations with eucalypts or introduced non-native species. A section of the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene of multiple specimens from nurseries and plantations was sequenced. The sequence data were compared and validated using sequences available in BOLD systems and GenBank databases. Results revealed the presence of an introduced non-native Strepsicrates sp. in both nurseries and plantations. In addition, the native species Choristoneura occidentalis and Eccopsis incultana were confirmed as present in plantations only and the native species Lozotaenia capensana was confirmed as present in one of the nurseries. Eucalypts are reported as host plants of C. occidentalis, E. incultana and Lozotaenia capensana for the first time. The findings contribute valuable insights into the identification and diversity of leaf rollers in eucalypt plantations in South Africa, with potential implications for pest management.

Coastal carbon storage in degraded, natural, and restored mangrove ecosystems of Guyana

Sabrina Dookie , Sirpaul Jaikishun , Abdullah Adil Ansari — Mon, 26 May 2025 00:00:00 +0000

Mangroves are among the most carbon-rich forests in the tropics due to their capacity to sequester and store carbon within their ecosystems. However, the combination of natural and human-induced phenomena causes changes in these ecosystems which can affect the flow of carbon within them. In the wet and dry seasons, we examined and compared the carbon content stored in aboveground biomass, standing litter, and soil in natural, degraded, and restored mangrove ecosystems located along the Guyana coastline. During a one-year period, a point-centred quartered method was used for tree sampling, while a randomised block design was used for standing litter and soil sampling. Our study revealed that the natural ecosystems exhibited higher carbon pool levels (29.58–35.14 Mg ha⁻¹), followed by the degraded ecosystems (30.49–32.27 Mg ha⁻¹), and then the restored ecosystems (22.81–27.63 Mg ha⁻¹). Significant differences were documented only in carbon found in aboveground biomass between ecosystem states, particularly within the natural ecosystems, due to the presence of mature trees with larger diameters at breast height. While seasonal fluctuations exist between the various carbon pools, particularly within the degraded ecosystems, our findings yielded insignificant differences between seasonality for all three carbon pools. However, linear mixed-effect models revealed that seasonality may influence the soil and standing litter carbon concentrations to an extent. Positive correlations in the restored ecosystems suggest that the larger carbon stocks in aboveground biomass may be associated with carbon stocks in soil and standing litter, unlike the negative correlations seen in the natural and degraded ecosystems. Our study provides some evidence that the overall carbon storage capacity of mangroves is influenced by the current state of their ecosystem, that is, ecosystems characterised by minimum disturbances may possess a greater capacity for carbon storage in comparison to ecosystems that are currently experiencing or have recovered from disturbances.

Floristic and structural changes in a neotropical urban novel forest over 13 years

Mon, 26 May 2025 00:00:00 +0000

The ecological importance of non-native species is the main characteristic of novel ecosystems. Pinus elliottii species is highly invasive in tropical forests and is commonly found in secondary forests in Brazil. We investigated the floristic and structural changes in an urban novel forest dominated by P. elliottii over a 13-year period (2011–2023). Based on the knowledge about novel forests ecology, we hypothesised that the community will remain stable without significant changes in tree structure and composition over the study period. We studied a small urban forest fragment (2 ha) in Juiz de Fora municipality, south-eastern Brazil. We measured all trees with diameter at breast height (DBH) ≥ 50 mm in a sample of 15 permanent plots (20 × 20 m) in 2011, 2016 and 2023, and calculated the changes in phytosociological and species diversity parameters for each period. As hypothesised, we did not observe significant changes in community structure and composition. Species richness increased from 63 to 80 over the period, but without changes in the phytosociological hierarchy. The non-native species P. elliottii remained as the most important species (importance value, IV) in 2011 (15.1%), 2016 (14.9%) and 2023 (14.2%). The following 12 hyperdominant species in the phytosociological hierarchy, which accounted for more than 70% of IV over the periods, remained dominant with no or small changes in the species hierarchy. The species diversity indices (H’) and multivariate analysis (ANOSIM) did not show significant differences over the periods. We concluded that the community is likely to remain with no significant changes in the coming decades due of the self-regenerating structure of the main populations. To the best of our knowledge, this is the first dynamic analysis of an urban novel forest in the neotropics, providing valuable insights for a better understanding of its ecology and functioning.

First report of the giant conifer aphid, Cinara pinivora (Wilson) and the Monterey pine aphid, Essigella californica (Essig) (Hemiptera: Aphididae) in South Africa

Privilege T Makunde, Bernard Slippers, Brett P Hurley — Mon, 26 May 2025 00:00:00 +0000

Pine aphids represent a significant group of insect pests in coniferous ecosystems worldwide. To assess pine aphid prevalence and potentially new introductions in South Africa, aphid samples from various pine-growing regions were collected through national surveys conducted by the Tree Protection Co-operative Programme (TPCP) and directly sent from landowners to the FABI Diagnostic Clinic. Morphological examination and DNA barcoding confirmed two previously unreported aphid species as Cinara pinivora and Essigella californica. To our knowledge, this is the first report of these North American native aphids in South Africa. This study provides an important reference for future research aimed at safeguarding South Africa’s pine plantations against emerging threats from invasive aphid species.