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Several key tree genera are used in planted forests worldwide, and these represent valuable global resources. Planted forests are increasingly threatened by insects and microbial pathogens, which are introduced accidentally and/or have adapted to new host trees. Globalization has hastened tree pest emergence, despite a growing awareness of the problem, improved understanding of the costs, and an increased focus on the importance of quarantine. To protect the value and potential of planted forests, innovative solutions and a better-coordinated global approach are needed. Mitigation strategies that are effective only in wealthy countries fail to contain invasions elsewhere in the world, ultimately leading to global impacts. Solutions to forest pest problems in the future should mainly focus on integrating management approaches globally, rather than single-country strategies. A global strategy to manage pest issues is vitally important and urgently needed.

The gall wasp Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is a major limiting factor in the cultivation of eucalyptus both in Brazil and across the world. This insect induces a gall formation on the principal veins of leaves, apices and petioles. This study investigated the impact of inoculating the fungus T. harzianum on plant growth and defense responses of Eucalyptus to Leptocybe invasa. Two hybrid eucalypt clones (Eucalyptus tereticornis Sm. × Eucalyptus camaldulensis Dehnh.) were used to produce seedlings. Plants were inoculated by spraying the T. harzianum conidial suspension onto the fourth, fifth and sixth fully expanded leaves. Evaluations of ovipositions and galls were carried out 7 and 44 days after infestation (d.a.i), and growth parameters were assessed at six points during the experiment: 15, 30, 45, 60, 75 and 90 d.a.i. Our findings show that susceptible and resistant non-inoculated Eucalyptus plants infested by L. invasa developed galls. However, only oviposition marks were observed in inoculated plants without gall formation, indicating that T. harzianum inoculation enhances Eucalyptus resistance to L. invasa. Additionally, inoculated plants showed increased height, leaf count and branch growth. The findings of this study suggest that T. harzianum has significant potential for controlling L. invasa infestations in susceptible Eucalyptus plantations and the added advantage of enhanced plant growth.

Despite its negative impacts on the environment and biodiversity, tree plantations can contribute to biodiversity conservation in fragmented landscapes, as they harbor many native species. In this study, we investigated the impact of Eucalyptus plantations on the taxonomic and functional diversity of ant communities, comparing ant communities sampled in managed and unmanaged (abandoned for 28 years) Eucalyptus plantations, and native Atlantic rain forests. Eucalyptus plantations, both managed and unmanaged, reduced the functional diversity and increased the similarity between ant communities leading to functional homogenization. While communities in managed plantations had the lowest values of both taxonomic and functional ant diversities, ant communities from unmanaged plantations had similar values of species richness, functional redundancy and Rao’s Q compared to ant communities from forest patches (although functional richness was lower). In addition, communities in unmanaged Eucalyptus plantations were taxonomically and functionally more similar to communities located in managed plantations, indicating that Eucalyptus plantations have a severe long-term impact on ant communities. These results indicate that natural regeneration may mitigate the impact of Eucalyptus management, particularly regarding the functional structure of the community (α diversity), although it does not attenuate the effects of long term homogenization in community composition (β diversity).

Thyrinteina arnobia (Lepidoptera: Geometridae) is a native American species. Despite its historical importance as an insect pest in Eucalyptus plantations, more information is needed regarding the population diversity, demography, and climatic variables associated with its distribution in different regions of Brazil. We used a phylogeographic approach to infer the genetic diversity, genetic structure, and demographic parameters of T. arnobia . We also conducted an ecological niche modeling (ENM) to predict suitable areas for T. arnobia occurrence in Brazil and other countries worldwide. Although T. arnobia populations have low genetic diversity in Brazil, we identified mitochondrial haplogroups predominating in different Brazilian regions and high Ф ST and Ф CT values in AMOVA, suggesting a low frequency of insect movement among these regions. These results indicate that outbreaks of T. arnobia in Eucalyptus areas in different regions of Brazil are associated with local or regional populations, with no significant contribution from long-distance dispersal from different regions or biomes, suggesting that pest management strategies would be implemented on a regional scale. In Brazil, the demographic and spatial expansion signals of T. arnobia seem to be associated with the history of geographical expansion of Eucalyptus plantations, a new sustainable host for this species. ENM indicated that isothermality and annual rainfall are critical climatic factors for the occurrence of T. arnobia in tropical and subtropical areas in the Americas. ENM also suggested that T. arnobia is a potential pest in Eucalyptus areas in all Brazilian territory and in regions from Africa, Asia, and Oceania.

The Eucalyptus snout beetle ( Gonipterus sp. n. 2) is a destructive invasive pest of Eucalyptus plantations, responsible for significant defoliation and wood yield losses globally. Native to Australia, this beetle has adapted to thrive on diverse Eucalyptus hosts, overcoming their chemical defences. However, the mechanisms by which Gonipterus tolerates or utilises these plant defence metabolites remain poorly understood. In South Africa, Gonipterus sp. n. 2 poses a significant threat to Eucalyptus plantations by causing extensive defoliation and leading to substantial reductions in growth and wood production. This study investigates the relationship between diet, host Eucalyptus species, and the gut microbiome of Gonipterus sp. n. 2. Using controlled feeding experiments, beetles were reared on artificial, semi-artificial, and natural diets, as well as two Eucalyptus genotypes with distinct secondary metabolite profiles. High-throughput 16S rDNA sequencing and gas chromatography-mass spectrometry (GC–MS) revealed significant shifts in gut bacterial diversity and composition across diets. Natural diets supported the most diverse microbial communities, while artificial diets fostered a homogenised microbiome dominated by opportunistic taxa like Serratia . Host-specific effects were observed in frass microbiota, with substantial biotransformation of monoterpenes into less toxic derivatives. The results highlight the plasticity of Gonipterus gut microbiota, which enables metabolic adaptability and resilience in diverse environments. This microbial flexibility underpins the invasiveness of Gonipterus , emphasising the role of gut symbionts in overcoming host chemical defences. Understanding these interactions offers novel insights for microbiome-targeted pest management strategies, providing a sustainable approach to mitigate the impact of Gonipterus on global Eucalyptus forestry.

Abstract Leptocybe invasa Fisher & La Salle, 2004 (Hymenoptera: Eulophidae) forms galls in tips, young branches, central veins, and petioles of Eucalyptus spp. leaves. This insect reproduces primarily through thelytokous parthenogenesis, with males being rare. The parasitism of L. invasa by Quadrastichus mendeli Kim & La Salle, 2008 (Hymenoptera: Eulophidae), with short life cycle and rapid dispersion, is high. The objective was to record the first occurrence of L. invasa males and its parasitoid Q. mendeli in galls of this pest in Paraguay. Branches of the grancam clone PL 113 (Eucalyptus grandis × Eucalyptus camaldulensis) with L. invasa galls were collected from February to April 2022 in the Maciel District, Caazapá Department, Paraguay. These branches were put in plastic bags, preserved in 70% ethanol and the insects emerged sent to the Laboratory of Biological Control of Forest Pests (LCBPF) at FCA/UNESP in Botucatu, São Paulo state, Brazil. Morphological characteristics confirmed the presence of L. invasa males at a ratio of 38:1 (females to males). Morphological and molecular analysis identified Q. mendeli and its samples deposited in GenBank (OR248672.1). The parasitism rate of L. invasa by Q. mendeli was 26.8%, marking the first record of this occurrence in Paraguay. Resumo Leptocybe invasa Fisher & La Salle, 2004 (Hymenoptera: Eulophidae) forma galhas nos ponteiros, ramos jovens, nervuras centrais e pecíolos das folhas de Eucalyptus spp. Este inseto se reproduz predominantemente por partenogênese telítoca, sendo os machos raros. O parasitismo de L. invasa por Quadrastichus mendeli Kim & La Salle, 2008 (Hymenoptera: Eulophidae), que apresenta ciclo de vida curto e rápida dispersão, é elevado. O objetivo deste estudo foi registrar a primeira ocorrência de machos de L. invasa e de seu parasitoide Q. mendeli em galhas dessa praga no Paraguai. Ramos do clone grancam PL 113 (Eucalyptus grandis × Eucalyptus camaldulensis), com galhas de L. invasa, foram coletados entre fevereiro e abril de 2022, no Distrito de Maciel, Departamento de Caazapá, Paraguai. Esses ramos foram acondicionados em sacos plásticos, preservados em etanol a 70% e os insetos emergidos foram enviados ao Laboratório de Controle Biológico de Pragas Florestais (LCBPF), da FCA/UNESP, em Botucatu, estado de São Paulo, Brasil. As características morfológicas confirmaram a presença de machos de L. invasa em uma proporção de 38:1 (fêmeas: machos). Análises morfológicas e moleculares identificaram Q. mendeli, com amostras depositadas no GenBank (OR248672.1). A taxa de parasitismo de L. invasa por Q. mendeli foi de 26,8%, constituindo o primeiro registro dessa ocorrência no Paraguai.

The blue-gum chalcid Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) is a gall wasp pest of Eucalyptus species, likely native to Australia. Over the past 15 years it has invaded 39 countries on all continents where eucalypts are grown. The worldwide invasion of the blue gum chalcid was attributed to a single thelytokous morphospecies formally described in 2004. Subsequently, however, males have been recorded in several countries and the sex ratio of field populations has been found to be highly variable in different areas. In order to find an explanation for such sex ratio differences, populations of L. invasa from a broad geographical area were screened for the symbionts currently known as reproductive manipulators, and both wasps and symbionts were genetically characterized using multiple genes. Molecular analyses suggested that L. invasa is in fact a complex of two cryptic species involved in the rapid and efficient spread of the wasp, the first recovered from the Mediterranean region and South America, the latter from China. All screened specimens were infected by endosymbiotic bacteria belonging to the genus Rickettsia. Two closely related Rickettsia strains were found, each infecting one of the two putative cryptic species of L. invasa and associated with different average sex ratios. Rickettsia were found to be localized in the female reproductive tissues and transovarially transmitted, suggesting a possible role of Rickettsia as the causal agent of thelytokous parthenogenesis in L. invasa. Implications for the variation of sex ratio and for the management of L. invasa are discussed.

The gall wasp, Leptocybe invasa, poses a significant global threat to Eucalyptus cultivation, by causing substantial economic losses. The objective of this study was to differentiate between resistant and susceptible genotypes by morphological characteristics using image analysis based on the damage caused by the gall wasp. In addition, consensus sequences derived from transposable elements (TEs) and the genome of Eucalyptus spp. Were identified by in silico analysis. Furthermore, another objective was to discriminate Eucalyptus genotypes in response to Leptocybe invasa by conducting molecular analyses involving transposable elements and inter simple sequence markers. For image analysis, the GroundEye ® system was used to collect images of 60 leaves from six genotypes, three of which were resistant and three susceptible. Eucalyptus spp. sequences were obtained from the GenBank database by in silico analysis and pairwise alignments with TE sequences were conducted using BLASTN. Multiple sequence alignment was performed with Clustal Omega, followed by the identification of conserved regions in Jalview. A motif signature was generated using Weblogo. For molecular characterization using ISSR markers and TEs, samples of young leaves were obtained from a total of 80 Eucalyptus seedlings, of which 50 were classified as resistant and 30 as susceptible to L. invasa. It was possible to distinguish gall wasp susceptible and resistant genotypes by image analysis. In silico analysis enabled the identification of conserved regions in the Eucalyptus spp. genome, which were associated with proteins involved in secondary metabolite production, e.g., terpenes, which play a role in the response to L. invasa. The discrimination capacity of TEs and ISSR primers was demonstrated and bands were generated that could be used to identify resistant genotypes. However, increasing the number of markers required to discriminate genotypes in both cases is suggested.

Abstract Galls by Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) reduce the productivity of Eucalyptus spp. plantations and Quadrastichus mendeli Kim & La Salle (Hymenoptera: Eulophidae) parasitizes this pest. This study aimed to evaluate, under laboratory conditions, two biological control strategies against Leptocybe invasa using the parasitoid Quadrastichus mendeli: (i) inundative biological control (referred to here as applied biological control), consisting of the release of five mated females per seedling, and (ii) natural biological control, representing the action of naturally occurring populations of the parasitoid already established in the environment. Ninety-day-old seedlings of the clone 3025 (Eucalyptus grandis × E. camaldulensis), naturally infested by L. invasa, were placed individually in cages under controlled conditions (25 ± 2 °C; 70 ± 10% RH; 12 h photoperiod) in a completely randomized design with 22 replicates per treatment. The number of insects was adjusted using zero-inflated mixed nonlinear regression models. The emergence of L. invasa adults (p>0.05) was similar between treatments, but that of Q. mendeli greater with the release of five females of this natural enemy per seedling compared to the applied biological control. The controlled release of Q. mendeli reduced L. invasa damage on Eucalyptus seedlings, increasing the importance of applied biological control to manage this pest in cultivated forests. Resumo Galhas formadas por Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) reduzem a produtividade de plantações de Eucalyptus spp., e Quadrastichus mendeli Kim & La Salle (Hymenoptera: Eulophidae) parasita essa praga. Este estudo teve como objetivo avaliar, em condições laboratoriais, duas estratégias de controle biológico contra Leptocybe invasa utilizando o parasitoide Quadrastichus mendeli: (i) controle biológico inundativo (denominado aqui como controle biológico aplicado), consistindo na liberação de cinco fêmeas acasaladas por muda, e (ii) controle biológico clássico, representando a ação de populações naturalmente ocorrentes do parasitoide já estabelecidas no ambiente. Mudas com 90 dias de idade do clone 3025 (Eucalyptus grandis × E. camaldulensis), naturalmente infestadas por L. invasa, foram colocadas individualmente em gaiolas sob condições controladas (25 ± 2 °C; 70 ± 10% UR; fotoperíodo de 12 h) em delineamento inteiramente casualizado, com 22 repetições por tratamento. O número de insetos foi ajustado por meio de modelos de regressão não linear mistos com inflação de zeros. A emergência de adultos de L. invasa (p>0,05) foi semelhante entre os tratamentos, mas a de Q. mendeli foi maior com a liberação de cinco fêmeas desse inimigo natural por muda, em comparação ao controle biológico aplicado. A liberação controlada de Q. mendeli reduziu os danos causados por L. invasa em mudas de Eucalyptus, ressaltando a importância do controle biológico aplicado para o manejo dessa praga em florestas cultivadas.

The defoliator Physocleora dukinfeldia Schaus 1897 (Lepidoptera: Geometridae) was recently reported attacking Eucalyptus urograndis (Myrtaceae) plantations in Brazil, raising concerns about its potential impact on commercial forestry. In this context, early characterization of pest biology plays a critical role in understanding host-use patterns and forecasting potential impacts on forest ecosystems. This study aimed to characterize the biology and foliar consumption of P. dukinfeldia on E. urograndis and its native host, Schinus terebinthifolia (Anacardiaceae), by recording molting, mortality, pupation, and emergence of imago, measuring larval head capsule width, pupal weight, and size, and calculating stage duration and viability under controlled conditions. The insect completed its life cycle on both host plants, with significantly longer development time and reduced pupal viability observed on E. urograndis . Although larval survival was low on both host species, nearly one-third of the individuals successfully reached adulthood. No significant differences in leaf consumption were detected between the two eucalyptus species evaluated in this study. These findings indicate that P. dukinfeldia has the biological capacity to adapt to eucalyptus and should be closely monitored in forest production areas. This is the first report to detail the life cycle and feeding behavior of this species on eucalyptus, providing critical baseline information for future pest management strategies.