High population levels lead Glycaspis brimblecombei (Hemiptera: Aphalaridae) to unrecorded feeding and oviposition behaviors on Eucalyptus urograndis plants / Altos níveis populacionais levam Glycaspis brimblecombei (Hemiptera: Aphalaridae) a diferentes comportamentos de alimentação e oviposição em plantas de Eucalyptus urograndis

The red gum lerp psyllid, Glycaspis brimblecombei Moore, 1964 (Hemiptera: Aphalaridae), an insect pest originating in Australia and which feeds only on Eucalyptus L'Hér. (Myrtales: Myrtaceae) plants, has spread to several countries. The populations of this insect commonly reach high populations on Eucalyptus plants since its entry into Brazil, and also indicated an unrecorded behavioral. The objectives of this study were to describe a peculiar adaptation in the feeding habit of G. brimblecombei and to register the new habit. The oviposition and feeding by G. brimblecombei, commonly, on the leaves of Eucalyptus, started to occur, also, on lignified twigs. This suggests a not yet recorded adaptation of this insect to reduce insect × plant intraspecific competition.

O psilídeo de concha, Glycaspis brimblecombei Moore, 1964 (Hemiptera: Aphalaridae), um inseto praga originário da Austrália e que se alimenta apenas de plantas de Eucalyptus L'Hér. (Myrtales: Myrtaceae), se espalhou por vários países. Esse inseto, geralmente, atinge grandes populações em plantas de Eucalyptus desde sua entrada no Brasil e, também, indicou um comportamento diferente. Os objetivos deste estudo foram descrever uma adaptação peculiar no hábito alimentar de G. brimblecombei e registrar o novo hábito. A oviposição e alimentação por G. brimblecombei, geralmente, nas folhas de Eucalyptus, passaram a ocorrer, também, em ramos lignificados. Isso sugere uma adaptação diferente desse inseto para reduzir a competição intraespecífica inseto × planta.

Entomopathogenic fungi as the microbial frontline against the alien Eucalyptus pest Gonipterus platensis in Brazil.

The eucalyptus snout beetle (ESB), Gonipterus platensis, is endemic to Australia but has become a major invasive, destructive pest of Brazilian eucalyptus plantations. Efforts to develop insecticides based on entomopathogenic fungi against ESB are limited by the lack of known virulent strains. We therefore explored the virulence of indigenous Brazilian strains of major entomopathogenic fungi-Beauveria spp. and Metarhizium anisopliae-against ESB adults. We found widely varying virulence and later capacities for conidial production on infected adult cadavers. Two strains stood out, B. bassiana IBCB-240 and M. anisopliae IBCB-364, as especially lethal for ESB adults under laboratory conditions, sporulated abundantly on infected insects, and also outperformed comparable strains used in commercial mycoinsecticides. Notably, B. bassiana IBCB-240 exhibited lower LT50 values at low inoculum levels (≤ 107 conidia mL-1) and smaller LC50 values than M. anisopliae IBCB-364. Taken together, this study emphasizes natural variation in virulence among indigenous Beauveria and Metarhizium strains against ESB adults and identifies fungal strains with superior lethality to existing commercialized strains for managing this eucalyptus pest in Brazil.

Insect egg-induced physiological changes and transcriptional reprogramming leading to gall formation.

Gall-inducing insects and their hosts present some of the most intricate plant-herbivore interactions. Oviposition on the host is often the first cue of future herbivory and events at this early time point can affect later life stages. Many gallers are devastating plant pests, yet little information regarding the plant-insect molecular interplay exists, particularly following egg deposition. We studied the physiological and transcriptional responses of Eucalyptus following oviposition by the gall-inducing wasp, Leptocybe invasa, to explore potential mechanisms governing defence responses and gall development. RNA sequencing and microscopy were used to explore a susceptible Eucalyptus-L. invasa interaction. Infested and control material was compared over time (1-3, 7 and 90 days post oviposition) to examine the transcriptional and morphological changes. Oviposition induces accumulation of reactive oxygen species and phenolics which is reflected in the transcriptome analysis. Gene expression supports phytohormones and 10 transcription factor subfamilies as key regulators. The egg and oviposition fluid stimulate cell division resulting in gall development. Eucalyptus responses to oviposition are apparent within 24 hr. Putative defences include the oxidative burst and barrier reinforcement. However, egg and oviposition fluid stimuli may redirect these responses towards gall development.

Phytophthora Species Associated with Roots of Native and Non-native Trees in Natural and Managed Forests.

Roots act as a biological filter that exclusively allows only a portion of the soil-associated microbial diversity to infect the plant. This microbial diversity includes organisms both beneficial and detrimental to plants. Phytophthora species are among the most important groups of detrimental microbes that cause various soil-borne plant diseases. We used a metabarcoding approach with Phytophthora-specific primers to compare the diversity and richness of Phytophthora species associated with roots of native and non-native trees, using different types of soil inocula collected from native and managed forests. Specifically, we analysed (1) roots of two non-native tree species (Eucalyptus grandis and Acacia mearnsii) and native trees, (2) roots of two non-native tree species from an in vivo plant baiting trial, (3) roots collected from the field versus those from the baiting trial, and (4) roots and soil samples collected from the field. The origin of the soil and the interaction between root and soil significantly influenced Phytophthora species richness. Moreover, species richness and community composition were significantly different between the field root samples and field soil samples with a higher number of Phytophthora species in the soil than in the roots. The results also revealed a substantial and previously undetected diversity of Phytophthora species from South Africa.

Selectivity of mycoinsecticides and a pyrethroid to the egg parasitoid Cleruchoides noackae (Hymenoptera: Mymaridae).

Plants of the genus Eucalyptus, cultivated in many countries, have great importance for the world economy. In Brazil, this culture occupies a total of 5.7 million hectares, but native and exotic insect pests can reduce its productivity. Thaumastocoris peregrinus Carpintero & Dellapé (Hemiptera: Thaumastocoridae), an exotic Australian pest, damages Eucalyptus plants. Biological control using the egg parasitoid Cleruchoides noackae Lin & Huber (Hymenoptera: Mymaridae), Heteroptera predators and entomopathogenic fungi, such as Beauveria bassiana and Metarhizium anisopliae, have potential for managing T. peregrinus. Chemical insecticides, including bifenthrin and acetamiprid + bifenthrin, also control this insect. The compatibility of chemical and biological control methods favors integrated pest management. The objective of this study was to evaluate the selectivity of commercial products based on B. bassiana, M. anisopliae and the chemical bifenthrin on the parasitoid C. noackae and its parasitism on T. peregrinus eggs. The selectivity test followed the standards recommended by the International Organization for Biological Control (IOBC). Beauveria bassiana has selectivity to parasitism as well as viability, but was slightly harmful to C. noackae adults; M. anisopliae was innocuous to adults and to the viability of the offspring of this parasitoid, but it reduced the parasitism rate; and bifenthrin did not show selectivity to this parasitoid.

Multivariate ratio analysis and DNA markers reveal a new Australian species and three synonymies in eucalypt-gall-associated Megastigmus (Hymenoptera: Megastigmidae).

The genus Megastigmus Dalman, 1820 (Hymenoptera: Megastigmidae) contains potential biocontrol agents of the invasive eucalypt galling chalcid Leptocybe spp. (Hymenoptera: Eulophidae), with several species reported in various parts of the world. Species discrimination is challenging due to intraspecific morphological variation, difficulty in measuring sizes of body parts, and the lack of information regarding the global distribution of parasitic Megastigmus. We used two species commonly associated with Leptocybe in its native range to review taxonomic methods and determine the most reliable morphological characters in species delimitation. We examined size variation of body characters, and conducted species discrimination using multivariate ratio analysis, mitochondrial Cytochrome c oxidase subunit 1 (COI) and nuclear 28S rDNA (28S) sequences. Morphological traits were effective in species delimitation yet revealed high variation in several characters employed in current keys. Knowledge generated on morphology and DNA justified the description of a new species, M. manonae, sp. n., the first record of M. pretorianensis in Australia, and revised diagnostic characters for M. zvimendeli. Based on these diagnostic characters and molecular data, we synonymize three species (M. judikingae, syn. n., from Australia, M. sichuanensis, syn. n., from China and M. icipeensis, syn. n., from Kenya) with M. zvimendeli. Our findings highlight the importance of molecular markers in assisting taxonomic decision-making and the need for coordinated work in identifying Megastigmus associated with Leptocybe spp.

Chemical vs entomopathogenic control of Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) via aerial application in eucalyptus plantations.

The Thaumastocoris peregrinus spread to eucalyptus plantations in many countries. Chemical control is a questionable measure, mainly due to the environmental impact, high cost and moreover has the use restricted by the forest certifications. Bio-insecticides may have similar efficiency to chemical products to control T. peregrinus. The chemical thiamethoxam, thiamethoxam + lambda-cyhalothrin, acephate and the microbial Beauveria bassiana and Metarhizium anisopliae insecticides were tested at different doses to manage T. peregrinus. The products were sprayed on eucalyptus plants using aircraft and populations of this insect were counted before application and at 1, 14 and 21 days afterwards (DAA). Ten eucalyptus trees were evaluated per plot, with the collection of ten leaves from the middle third of the crown of each tree, and the number of T. peregrinus nymphs and adults obtained per leaf was determined. All the chemical insecticides had similar control at 1 DAA for T. peregrinus nymphs and adults. At 14 DAA, the number of T. peregrinus nymphs and adults on eucalyptus leaves was similar for the chemical and microbial insecticide treatments. At 21 DAA the control efficiency of T. peregrinus nymphs and adults was higher than 80% with all insecticides. The entomopathogenic insecticides have potential for aerial application to control T. peregrinus nymphs and adults and provide viable and environmentally-friendly alternative to manage this pest.

Biological traits of Quadrastichus mendeli (Hymenoptera, Eulophidae), parasitoid of the eucalyptus gall wasp Leptocybe invasa (Hymenoptera, Eulophidae) in Thailand.

Quadrastichus mendeli Kim & La Salle, a parasitoid of Leptocybe invasa Fisher & La Salle, is a uniparental species. This study assessed the biological traits of Q. mendeli in the laboratory at a temperature of 27 ± 1 °C. Diets had a highly significant effect on the mean longevity of female Q. mendeli. Feeding honey solution prolonged the mean longevity of the parasitoid to 4.80 days. The estimated 50% survival period was 3 days. The mean potential fecundity in all ages was 8.85 eggs per female. Age had a highly significant effect on the mean egg load. There was a positive relationship between egg load and female size. The mean of realized fecundity throughout the life span was 2.47 progenies per female. The mean developmental time of Q. mendeli from the egg to adult stage was 27.06 days. The shorter developmental time of Q. mendeli in comparison to its host can be considered a reason for the successful control of L. invasa in Thailand.

Ophelimus mediterraneus sp. n. (Hymenoptera, Eulophidae): a new Eucalyptus gall wasp in the Mediterranean region.

We report here for the first time the presence of Ophelimus mediterraneus sp. n. in Mediterranean Europe. This species appears to be closely related to Ophelimus maskelli, a well-known invasive pest of Eucalyptus. Based on molecular (cytochrome oxidase I, 28S), morphological (multivariate ratio analysis) and bio-ecological investigations, our study gives unambiguous relevant criteria that allow the discrimination between these two species. A full description of O. mediterraneus sp. n. is also provided. The geographic distribution of O. mediterraneus sp. n. as well as its impact on Eucalyptus species needs to be more widely assessed since its presence may have been confused with O. maskelli in their sympatric introduced areas. Further investigations of potential parasitoids in the native area may thus be welcomed to evaluate classical biological control achievability.

Structure and Sense Organs of Ovipositors of an Endoparasitoid Aprostocetus causalis and an Ectoparasitoid Quadrastichus mendeli in Leptocybe spp.

Little is known of the olfactory mechanisms of host detection in the ovipositors of endoparasitoids and ectoparasitoids. An endoparasitoid Aprostocetus causalis La Salle & Wu (Hymenoptera: Eulophidae) and an ectoparasitoid Quadrastichus mendeli Kim & La Salle (Hymenoptera: Eulophidae: Tetrastichinae) are the two parasitoids of the eucalyptus gall wasp Leptocybe spp. Structures and sense organs of ovipositors of A. causalis and Q. mendeli were studied using scanning and transmission electron microscopy, which provided essential information for exploring the mechanism of host detection by endoparasitoid and ectoparasitoid. The ovipositors of two parasitoids consisted of the first and second valvulae and ended in a pointed tip. There were three types of microtrichia, two types of sensilla chaetica, and one type of sensilla campaniformia on the ovipositors of A. causalis and Q. mendeli. However, Q. mendeli has the fourth type of microtrichia on the ovipositor. The morphology, types, distribution, length, and width of these sensilla and microtrichia were described, and their possible functions are discussed in conjunction with the stinging, oviposition, and the host selection process.

Parasitoids of the eucalyptus gall wasp Leptocybe spp.: a global review.

The genus Leptocybe Fisher & La Salle (Hymenoptera: Eulophidae) and its type species L. invasa were first described in 2004. Leptocybe spp. are global pests of eucalyptus plantations, and parasitoids play an important role in their control. In this review, we describe the species, distribution, biology, ecology and parasitism levels of Leptocybe spp. parasitoids and the problems associated with biological control programmes against Leptocybe spp. Additionally, prospects for the use of conservation or augmentative biological control programmes against Leptocybe spp. are discussed. Worldwide, approximately 23 species of parasitoids of Leptocybe spp. in 7 families and 10 genera have been found to date. Comparing the parasitism levels of the parasitoids showed that Quadrastichus mendeli, Selitrichodes neseri and several (approximately 4) native Megastigmus spp. could be exploited to manage Leptocybe spp. Available information on the Leptocybe spp. parasitoids is expected to improve our understanding related to ongoing studies of biological control programmes against Leptocybe spp.

When taxonomy and biological control researchers unite: Species delimitation of Eadya parasitoids (Braconidae) and consequences for classical biological control of invasive paropsine pests of Eucalyptus.

The invasive eucalyptus tortoise beetle, Paropsis charybdis, defoliates plantations of Eucalyptus nitens in New Zealand. Recent efforts to identify host specific biological control agents (parasitoids) from Tasmania, Australia, have focused on the larval parasitoid wasp, Eadya paropsidis (Braconidae), first described in 1978. In Tasmania, Eadya has been reared from Paropsisterna agricola (genus abbreviated Pst.), a smaller paropsine that feeds as a larva on juvenile rather than adult foliage of Eucalyptus nitens. To determine which of the many paropsine beetle hosts native to Tasmania are utilized by E. paropsidis, and to rule out the presence of cryptic species, a molecular phylogenetic approach was combined with host data from rearing experiments from multiple locations across six years. Sampling included 188 wasps and 94 beetles for molecular data alone. Two mitochondrial genes (COI and Cytb) and one nuclear gene (28S) were analyzed to assess the species limits in the parasitoid wasps. The mitochondrial genes were congruent in delimiting four separate phylogenetic species, all supported by morphological examinations of Eadya specimens collected throughout Tasmania. Eadya paropsidis was true to the type description, and was almost exclusively associated with P. tasmanica. A new cryptic species similar to E. paropsidis, Eadya sp. 3, was readily reared from Pst. agricola and P. charybdis from all sites and all years. Eadya sp. 3 represents the best candidate for biological control of P. charybdis and was determined as the species undergoing host range testing in New Zealand for its potential as a biological control agent. Another new species, Eadya sp. 1, was morphologically distinctive and attacked multiple hosts. The most common host was Pst. variicollis, but was also reared from Pst. nobilitata and Pst. selmani. Eadya sp. 1 may have potential for control against Pst. variicollis, a new incursion in New Zealand, and possibly Pst. selmani in Ireland. Our molecular data suggests that Pst. variicollis is in need of taxonomic revision and the geographic source of the beetle in New Zealand may not be Tasmania. Eadya sp. 2 was rarely collected and attacked P. aegrota elliotti and P. charybdis. Most species of Eadya present in Tasmania are not host specific to one beetle species alone, but demonstrate some host plasticity across the genera Paropsisterna and Paropsis. This study is an excellent example of collaborative phylogenetic and biological control research prior to the release of prospective biological control agents, and has important implications for the Eucalyptus industry worldwide.

Genomic analysis of a cypovirus isolated from the eucalyptus brown looper, Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae).

The eucalyptus brown looper, Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae), is the main lepidopteran defoliator of eucalyptus plantations in Brazil. Outbreaks of this insect pest are common in Brazil and can affect the productivity of planted forests severely. T. arnobia caterpillars from a laboratory colony with viral infection symptoms were analyzed by electron microscopy that revealed polyhedral occlusion bodies (OBs) with several icosahedral virus particles embedded. Analysis of its genetic material showed ten segments of dsRNA, which confirmed this virus as a possible member of the genus Cypovirus. Phylogenetic analysis of the whole genome sequence revealed its close relationship with other isolates of Cypovirus 14 species and according to these results we proposed the name Thyrinteina arnobia cypovirus 14 (TharCPV-14) for this new virus isolate. Further research will be necessary in order to analyze the potential of this virus as a biopesticide.

Terpenes associated with resistance against the gall wasp, Leptocybe invasa, in Eucalyptus grandis.

Leptocybe invasa is an insect pest causing gall formation on oviposited shoot tips and leaves of Eucalyptus trees leading to leaf deformation, stunting, and death in severe cases. We previously observed different constitutive and induced terpenes, plant specialized metabolites that may act as attractants or repellents to insects, in a resistant and susceptible clone of Eucalyptus challenged with L. invasa. We tested the hypothesis that specific terpenes are associated with pest resistance in a Eucalyptus grandis half-sib population. Insect damage was scored over 2 infestation cycles, and leaves were harvested for near-infrared reflectance (NIR) and terpene measurements. We used Bayesian model averaging for terpene selection and obtained partial least squares NIR models to predict terpene content and L. invasa infestation damage. In our optimal model, 29% of the phenotypic variation could be explained by 7 terpenes, and the monoterpene combination, limonene, α-terpineol, and 1,8-cineole, could be predicted with an NIR prediction ability of  .67. Bayesian model averaging supported α-pinene, γ-terpinene, and iso-pinocarveol as important for predicting L. invasa infestation. Susceptibility was associated with increased γ-terpinene and α-pinene, which may act as a pest attractant, whereas reduced susceptibility was associated with iso-pinocarveol, which may act to recruit parasitoids or have direct toxic effects.

Homogenization and impoverishment of taxonomic and functional diversity of ants in Eucalyptus plantations.

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 (ß diversity).

The first identification of genomic loci in plants associated with resistance to galling insects: a case study in Eucalyptus L'Hér. (Myrtaceae).

Genomic loci related with resistance to gall-inducing insects have not been identified in any plants. Here, association mapping was used to identify molecular markers for resistance to the gall wasp Leptocybe invasa in two Eucalyptus species. A total of 86 simple sequence repeats (SSR) markers were screened out from 839 SSRs and used for association mapping in E. grandis. By applying the mixed linear model, seven markers were identified to be associated significantly (P ≤ 0.05) with the gall wasp resistance in E. grandis, including two validated with a correction of permutation test (P ≤ 0.008). The proportion of the variance in resistance explained by a significant marker ranged from 3.3% to 37.8%. Four out of the seven significant associations in E. grandis were verified and also validated (P ≤ 0.073 in a permutation test) in E. tereticornis, with the variation explained ranging from 24.3% to 48.5%. Favourable alleles with positive effect were also mined from the significant markers in both species. These results provide insight into the genetic control of gall wasp resistance in plants and have great potential for marker-assisted selection for resistance to L. invasa in the important tree genus Eucalyptus.

The beetle Costalimaita ferruginea (Coleoptera: Chysomelidae) in Eucalyptus plantations in transition area of Amazon and Cerrado Biomes / O besouro Costalimaita ferruginea (Coleoptera: Chysomelidae) em plantios de Eucalyptus em áreas de transição dos Biomas Amazon e Cerrado

Abstract Costalimaita ferruginea (Coleoptera: Chrysomelidae) attacks Eucalyptus plants causing severe damage through netting of the leaves. Recently, this Coleoptera has been reported attacking Myrtaceae in Mato Grosso State and, studies about the occurrence of this beetle in commercial plantations of eucalypts has been the subject of researchers through monitoring programmes in the forest protection area. With the beginning of the rainy season, adults were observed causing damage in eucalypt plantations in four cities that are part of the transition region of Amazon and Cerrado Biomes. The spots where these insects were observed are located in Feliz Natal, Lucas do Rio Verde, Sorriso and Vera. The purpose of this study was to report the new occurrences and to characterize the attack period of the beetle C. ferruginea in Eucalyptus plantations in Middle-North region of Mato Grosso State, region of Biomes Transition.

Resumo Costalimaita ferruginea (Coleoptera: Chrysomelidae) ataca plantas de Eucalyptus provocando intensos danos através do rendilhamento das folhas. Recentemente, esse Coleoptera tem sido relado atacando Myrtaceae no Estado de Mato Grosso e, estudos sobre a ocorrência desse besouro em plantios comerciais de eucaliptos tem sido alvo de pesquisadores através de programas de monitoramento na área de proteção florestal. Com o início do período chuvoso, adultos foram observados causando danos em plantios de eucalipto em quatro municípios que fazem parte da região de transição dos Biomas Amazônia e Cerrado. Os pontos onde foram observados esses insetos estão localizados em Feliz Natal, Lucas do Rio Verde, Sorriso e Vera. O objetivo deste trabalho foi relatar as novas ocorrências e caracterizar o período de ataque do besouro C. ferruginea em plantios de Eucalyptus na região Médio-Norte do Estado de Mato Grosso, região de transição de Biomas.

The beetle Costalimaita ferruginea (Coleoptera: Chysomelidae) in Eucalyptus plantations in transition area of Amazon and Cerrado Biomes.

Costalimaita ferruginea (Coleoptera: Chrysomelidae) attacks Eucalyptus plants causing severe damage through netting of the leaves. Recently, this Coleoptera has been reported attacking Myrtaceae in Mato Grosso State and, studies about the occurrence of this beetle in commercial plantations of eucalypts has been the subject of researchers through monitoring programmes in the forest protection area. With the beginning of the rainy season, adults were observed causing damage in eucalypt plantations in four cities that are part of the transition region of Amazon and Cerrado Biomes. The spots where these insects were observed are located in Feliz Natal, Lucas do Rio Verde, Sorriso and Vera. The purpose of this study was to report the new occurrences and to characterize the attack period of the beetle C. ferruginea in Eucalyptus plantations in Middle-North region of Mato Grosso State, region of Biomes Transition.

The gall wasp Leptocybe invasa (Hymenoptera: Eulophidae) stimulates different chemical and phytohormone responses in two Eucalyptus varieties that vary in susceptibility to galling.

Gall-inducing insects produce various types of galls on plants, but little is known about the gall-induction mechanism of these galling insects. The gall wasp Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) forms galls of different sizes on several Eucalyptus species. To clarify the physiological responses of Eucalyptus to L. invasa infestation, we measured the dynamics of nitrogen (N), carbon (C), total phenolics, total tannins and four types of phytohormones (zeatin [Z] + zeatin riboside [ZR], gibberellins [GA], indole-3-acetic acid [IAA] and abscisic acid [ABA]) in galled and ungalled leaf tissues of two Eucalyptus horticultural varieties (DH201-2 [Eucalyptus grandis × Eucalyptus camaldulensis] and EA [Eucalyptus exserta]) with different susceptibility to galling throughout the larval developmental stages. Nitrogen, total phenolics, tannins and four kinds of phytohormones strongly accumulated in tissues galled by L. invasa (especially during early larval feeding stages). While N, Z + ZR and GA levels were higher, tannins and ABA levels were lower in the galled tissues on the highly susceptible variety. Nitrogen, total phenolics, GA, Z + ZR and IAA levels in the galled tissues gradually decreased during gall development, but ABA and tannins conversely increased in the galled tissues of the less susceptible variety. Our results suggest that the effects of gall-inducing insects on plants depend not only on the susceptibility of the plant infested but also on the developmental stage of galled tissues. Gall formation process is thus synergistically influenced by both gall-inducing insect and plant genotypes.