Pest Of Citrus Research Articles

Impact of Insecticide Treatments for Phyllocnistis citrella (Lepidoptera: Gracillariidae) on Growth and Yield of Young Citrus reticulata Mandarins.

The citrus leafminer, Phyllocnistis citrella Stainton, is an invasive pest of citrus whose larvae damage developing leaves, which can impact tree photosynthetic capacity and may ultimately reduce tree growth and yield. Damage is most pronounced in young trees due to their greater propensity for production of new foliage, which supports P. citrella oviposition and larval development. We studied P. citrella damage and tree growth and yield among different insecticide treatment regimes to gauge their effectiveness at protecting young citrus trees. Three levels of insecticide treatments were applied over 3 yr to 'Tango' mandarin (Citrus reticulata Blanco) citrus trees planted in the prior summer, which were inspected regularly along with untreated trees. Leaves suitable for oviposition by P. citrella were available during all census dates, though their numbers fluctuated in the summer months. Phyllocnistis citrella were suppressed for 2-3 wk by systemic or foliar treatments of insecticides. The higher number of treatments provided more sustained suppression of larvae. Trunk diameter was unchanged and canopy volume affected by only the most aggressive treatment regime. However, citrus yield was 2-2.5 times higher following the second year of treatments and 1.2- to 1.8-fold times following the third year of treatments for trees in the treatment regimes that included systemic imidacloprid plus 2-3 or 4-5 foliar applications, respectively, relative to untreated controls. Suitable leaf flush and larval densities declined over the 3 yr of the study. These data support the use of insecticidal control of P. citrella to protect young 'Tango' mandarin trees, but demonstrated that frequent applications are necessary to suppress populations.

Ants affect citrus pests and their natural enemies in contrasting ways

Ants are one of the most abundant insect groups in citrus orchards. They help in controlling pests, but they can also facilitate the outbreak of other pests, such as those that produce honeydew. Moreover, ants can also affect natural enemies of pests. Here, we review how ants affect pest abundance, considering whether the pest produces honeydew and whether it spends part of its life-cycle in the soil (edaphic stages). We also investigated the effects of the presence of ants on natural enemies with a meta-analysis and how this effect is modified by honeydew production by the pest, the most abundant ant species, and the specialization and mode of dispersal (winged or wingless) of the natural enemy. The presence of ants decreased the abundance of non-honeydew producing pests, but increased the abundance of honeydew producers. Ants increased the abundance of pests without edaphic stages, but decreased pests with such stages. In addition, the identity of the most abundant ant species affected the abundance of natural enemies; the ants Iridomyrmex rufoniger and Lasius grandis had a negative impact whereas other ant species did not affect the abundance of natural enemies. Moreover, the presence of ants decreased the abundance of generalist and winged natural enemies of honeydew-producing pests. Our review provides crucial information on the effects of ants on biological control practices in citrus orchards, and increases our understanding of the relationships between ants, pests and their natural enemies.

Exploring non‐host plant‐based management strategy with lemongrass, garlic and guava volatiles for the African citrus triozid

AbstractThe African citrus triozid (ACT), Trioza erytreae, is an important pest of citrus. Both nymphs and adults damage the plant by feeding on the sap causing young shoots to die. Trioza erytreae also vectors Candidatus Liberibacter africanus, the bacteria that cause citrus greening disease. Since certain non‐host plants are known to repel insect pests, it is important to investigate how such plants can be exploited to manage T. erytreae. Here, we screened effects of odours of three non‐host plants namely guava (Psidium guajava), garlic (Allium sativum) and lemongrass (Cymbopogon citratus) against T. erytreae's location of a common host plant, rough lemon (Citrus jambhiri) and showed that repellence varied interspecifically with the plants. Using cage assays, we found that guava and garlic decreased the attraction of females but not males of T. erytreae to rough lemon volatiles. Chemical analysis by coupled gas chromatography/mass spectrometry (GC/MS) showed that volatiles of three of the plants were dominated by terpenoids; guava (69% comprised of limonene, 34%, (E)‐β‐ocimene, 29% and (Z)‐β‐Ocimene, 6%), lemongrass (56% comprised of geranial, 26%, neral, 19% and myrcene, 11%) and rough lemon (74% comprised of limonene, 53%, sabinene, 11% and (E)‐β‐ocimene, 10%). On the other hand, the volatile profile of garlic was dominated by benzenoids and saturated compounds (85% comprised of benzaldehyde, 12%, benzyl alcohol, 17%, nonanal, 31%, decanal, 13% and hexadecane, 12%). Our results suggest that non‐host plant volatile composition and richness in specific compounds may contribute to influencing T. erytreae response to its host, with garlic and guava as potential non‐host plants that can be exploited in the management of the pest.

Isolation, characterization, culturing, and formulation of a new Beauveria bassiana fungus against Diaphorina citri

The Asian citrus psyllid, Diaphorina citri, is a worldwide destructive citrus pest. It aids in the transmission of a group of phloem-limited bacteria (Candidatus Liberibacter spp.) that leads to Huanglongbing (HLB) disease. In this study, a new Chinese native fungal strain (F-HY006) was isolated from the cadavers of D. citri collected from Ganzhou, Jiangxi in China (114°94′ E, 25°87′ N). The isolate was virulent towards adult female D. citri with corrected mortality of 76% and LT50 of 4.09 d after application of a suspension containing 107 conidia/ml (400 µl/citrus seedling). Morphologic and phylogenetic analyses identified this isolate as Beauveria bassiana. Based on its virulence against D. citri and growth characteristics (2.89 ± 0.28 × 105 conidia/cm2) on the PDA plate, biphasic (liquid–solid) cultivation for conidia production of B. bassiana F-HY006 was optimized using several nutritional and environmental factors. Soybean meal + cottonseed powder (1:1) and continuous fluorescent light resulted in the highest conidial production (5.7 × 109/g dry substrate). Moreover, the oil-based conidial formulation was optimized using sesame oil as an effective carrier, which resulted in a significant enhancement of the conidial shelf life, tolerance to thermal stress, and virulence against D. citri compared to unformulated conidia. Therefore, we have prepared a potential mycopesticide for the biological control of D. citri based on the optimized biphasic culture growth and formulation of an isolated virulent fungus, B. bassiana F-HY006.

Field Ecology and Food Suitability of Tarsonemus spp. (Acari: Tarsonemidae).

Tarsonemus bakeri Ewing (Acari: Tarsonemidae) is a species of mite commonly associated with citrus in many countries including the United States. A short report in 1942 suggested this species is phytophagous, but it has not been reported as a pest in citrus or any other crop since then. A single survey of 78 orchards in three growing regions in California demonstrated that Tarsonemus spp. mites were only associated with leaf samples that had visible sooty mold. A seasonal population study in one citrus orchard showed that all life stages of Tarsonemus spp. were present year-round on leaves and fruit, with the population on fruit reaching a peak in December (59.7 ± 15.2 mites per fruit). Results from a food suitability study showed that the population declined sharply on both plastic and leaf substrate when the mites were not provided a supplementary food source. When supplementary food was provided in the form of Alternaria, honeydew, molasses, or combinations of these, mites survived and multiplied throughout the 29-d study, irrespective of the substrate. Tarsonemus bakeri were found on excised, decaying leaves collected from an orchard. These studies verify that Tarsonemus spp. are associated only with sooty mold in citrus orchards. T. bakeri populations cannot sustain themselves on leaf tissue alone, indicating that they are nondamaging to citrus and therefore need not be considered a phytosanitary concern by importing countries.

Detection of common citrus pests in northern Iran using an artificial neural network

Detection of common citrus pests in northern Iran using an artificial neural network

Evaluating the potential of flowering plants for enhancing predatory hoverflies (Syrphidae) for biological control of Diaphorina citri (Liviidae) in California

Diaphorina citri (Hemiptera: Liviidae) is a notorious citrus pest that vectors a bacterium that causes huanglongbing, a lethal citrus disease. Studies evaluating the potential of buckwheat (Fagopyrum esculentum), alyssum (Lobularia maritima), phacelia (Phacelia tanacetifolia), and California poppy (Eschscholzia californica) as insectary plants for conservation biological control of D. citri were conducted in California citrus orchards. Field studies assessed flowering phenology and attractiveness to hoverflies and other natural enemies, hoverfly oviposition on D. citri colonies, and the effect of potted alyssum and predation from hoverflies on the mortality of D. citri nymphs. Laboratory studies quantified lifetime consumption of D. citri nymphs by individual Allograpta obliqua (Diptera: Syrphidae) larvae, the only hoverfly species attacking D. citri in the field. Results indicated that alyssum and buckwheat possessed a short sowing to flowering time (30–33 days when sown in March) and attracted 10–20 times more syrphids than California poppy. No hoverflies were observed feeding from phacelia. California poppy was marginally attractive to hoverflies, and failed to attract ladybugs, parasitoids, or predatory wasps. When alyssum was present in an unsprayed citrus orchard, the number of hoverfly eggs laid on D. citri colonies and abundance of predators was 3.5 times and 2.5 times higher, respectively, when compared to control plots lacking alyssum. Consequently, 10% more D. citri nymphs survived to adulthood in the control plots compared to alyssum plots. In the laboratory, individual A. obliqua larvae consumed, on average, 421 D. citri nymphs before pupation. Results demonstrate that A. obliqua is an important and voracious predator of D. citri nymphs, and that alyssum and buckwheat show potential as insectary plants for conservation biological control of D. citri.

Comparative transcriptome analysis of different developmental stage of Bactrocera minax (Diptera: Tephritidae): Implication of the molecular basis of its obligatory diapause induction

The Chinese citrus fruit fly, Bactrocera minax (Enderlein), a devastating pest in citrus, has an obligatory diapause at the pupal stage. Although the physiology of obligatory diapause has been well described, the molecular mechanisms underlying the process remain unknow. Here we investigated the molecular mechanisms of obligatory diapause induction in B. minax using high-throughput RNA-Seq data from second-instar larva (2L), third-instar larva (3L) and pupa (P) stages. A total of 116,402 unigenes were obtained, of which 54,781 unigenes were successfully annotated in public databases, and the differentially expressed genes in the 3L vs 2L, P vs 2L, and P vs 3L comparisons were identified. The cluster co-expression patterns of the differentially expressed genes revealed that significantly differentially-expressed genes in the pupal stage were predicted to be related to diapause induction. All differentially expressed genes were investigated by GO functional and KEGG pathway analysis, and the results showed that genes involved in processes such as 20-hydroxyecdysone (20E) biosynthesis, cell cycle and metabolic pathways are likely related to obligatory diapause induction in B. minax. These results provide important information on the transcriptome of the Chinese citrus fruit fly that can be used for further functional studies as well as contributing to our understanding of the molecular basis of obligatory diapause induction and suggesting potential molecular targets for the control of this pest.

Molecular, morphometric and digital automated identification of three Diaphorina species (Hemiptera: Liviidae).

Diaphorina is a species-rich genus, native to the tropics and subtropics of the Old World, particularly of more arid regions. One of the species, Diaphorina citri, is the economically most important pest of citrus. Diaphorina species are morphologically similar which makes their identification difficult. In this study, the accuracy of DNA barcoding, using mitochondrial cytochrome c oxidase subunit 1 (COI), geometric morphometrics of the forewing and digital image processing methods were tested for identification of the three Diaphorina species: D. chobauti, D. citri and D. zygophylli. Moreover, the published COI sequences of D. citri, D. communis and D. lycii obtained from Genbank were used for cluster analyses. DNA barcodes for D. chobauti and D. zygophylli are deposited in Genbank for the first time. The results of the molecular and geometric morphometric analyses are congruent and place D. chobauti as the sister taxon of the other Diaphorina species. The geometric morphometric analysis shows that in D. zygophylli the fore margin is slightly curved proximally and sharply bent distally, while in D. chobauti and D. citri it is straight proximally and weakly bent distally. The results of digital image processing show that the distribution of the dark pattern differs consistently in the three studied species.

Analysis of limiting fators of RGL citrus fruit productivity (study case in Pal VII Village, Bermani Ulu Raya Subdistrict, Rejang Lebong District)

Environmental factors, especially climate, soil and pest attack, are limiting factors in citrus production. The purpose of this study was to determine the limiting factors on RGL citrus productivity. This research was carried out in 2019 in Pal VII Village, Bermani Ulu Raya District, Rejang Lebong Regency, Bengkulu Province with seven farmers at the research location. Data was collected from primary and secondary data consist of 10 years climate data, soil characteristics and citrus pest and diseases identification, which are then analyzed descriptively. The results showed that the productivity of RGL citrus in the research location was influenced by high rainfall during the fruiting period. Another limiting factor is the relatively low soil nutrient content because farmers generally do not apply fertilization technology that based on crop needs. Pests and diseases that had been potential reduced the productivity and quality of citrus fruits were fruit borers, fruit flies and scurvy, and climate factors also influenced the quality.

Biological Control of a Phytosanitary Pest (Thaumatotibia leucotreta): A Case Study.

Thaumatotibia leucotreta, known as the false codling moth, is a pest of citrus and other crops in sub-Saharan Africa. As it is endemic to this region and as South Africa exports most of its citrus around the world, T. leucotreta has phytosanitary status for most markets. This means that there is zero tolerance for any infestation with live larvae in the market. Consequently, control measures prior to exporting must be exemplary. Certain markets require a standalone postharvest disinfestation treatment for T. leucotreta. However, the European Union accepts a systems approach, consisting of three measures and numerous components within these measures. Although effective preharvest control measures are important under all circumstances, they are most critical where a standalone postharvest disinfestation treatment is not applied, such as within a systems approach. Conventional wisdom may lead a belief that effective chemical control tools are imperative to achieve this end. However, we demonstrate that it is possible to effectively control T. leucotreta to a level acceptable for a phytosanitary market, using only biological control tools. This includes parasitoids, predators, microbial control, semiochemicals, and sterile insects. Simultaneously, on-farm and environmental safety is improved and compliance with the increasing stringency of chemical residue requirements imposed by markets is achieved.

Effects of the entomopathogenic fungus Clonostachys rosea on mortality rates and gene expression profiles in Diaphorina citri adults

Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a serious pest of citrus. The insect also transmits Candidatus Liberibacter asiaticus, the pathogen of a devastating citrus disease called Huanglongbing. Clonostachys rosea is a versatile fungus that possesses nematicidal and insecticidal activities. The effect of C. rosea against D. citri remains unclear. Here we examined the pathogenicity of C. rosea against D. citri adults. A mortality rate of 46.67% was observed in adults treated with 1 × 108 conidia/mL spore suspension. Comparative transcriptomic analyses identified 259 differentially-expressed genes (DEGs) between controls and samples treated with fungi. Among the DEGs, 183 were up-regulated and 76 down-regulated. Genes with altered expression included those involved in immunity, apoptosis and cuticle formation. Our preliminary observation indicated that C. rosea is virulent against ACP adults and has the potential as a biological control agent for ACP management in the field.

A degree-day model for predicting adult emergence of the citrus gall wasp, Bruchophagus fellis (Hymenoptera: Eurytomidae), in southern Australia

The citrus gall wasp, Bruchophagus fellis, is a serious pest of citrus in southeast Australia and the ability to accurately predict its highly synchronised adult emergence periods is critical for its effective management. We monitored emergence of the citrus gall wasp for six years during 2010–2017 in southern Australia, yielding a total of 22 site-by-year datasets from two citrus production regions and multiple citrus varieties. For each dataset, the proportions of emerged wasps on different monitoring dates were related to the corresponding degree-days using a 2-parameter Weibull function. The two degree-day parameters, the lower development threshold temperature and biofix date, were estimated at 8 °C and August 1 respectively by cross-validation of a series of candidate values using the sum of squared differences between the predicted and observed median emergence dates as the performance indicator. According to the final fitted Weibull function, 5, 50, and 95% emergence occur when 560, 723 and 835 degree-days above 8 °C have accumulated after August 1. The predicted median emergence dates differed from the corresponding observed median emergence dates by an average of 2.8 days across the 22 datasets. The average deviations for 5 and 95% emergence were slightly larger, at five and four days, respectively. Observed degree-days for median emergence did not differ significantly between the two citrus production regions, indicating there is no need for separate degree-day models for different regions. Based on the degree-day model, an interactive, online timing tool has been developed, allowing growers to use local weather station data to predict when the gall wasp is likely to emerge in average, warm, and cool years.

Comparative transcriptome analysis of thiamethoxam susceptible and resistant Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), using RNA-sequencing.

Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), transmits the causal pathogen of huanglongbing and is a global pest of citrus. D. citri populations exhibit resistance to multiple insecticide modes of action in areas where these chemicals have been overused. We performed genome-wide transcriptional analysis for two field populations of D. citri (Wauchula and Lake Alfred, Florida, USA) that exhibit 1300-fold resistance to the neonicotinoid insecticide, thiamethoxam, and compared it to that of susceptible psyllids collected from the same area and without imposed selection. The Lake Alfred population responded to insecticide resistance by up-regulation of 240 genes and down-regulation of 148 others. The Wauchula population exhibited similar patterns to the Lake Alfred population with up-regulation of 253 genes and down-regulation of 115 others. Gene Ontology annotation associated with cellular processes, cell, and catalytic activity were assigned to differentially expressed genes (DEGs). The DEGs from Lake Alfred and Wauchula populations were mapped to Kyoto Encyclopedia of Gene and Genomes pathways and implicated enrichment of metabolic pathways, oxidative phosphorylation, extracellular matrix-receptor interaction, terpenoid backbone biosynthesis, and insect hormone biosynthesis in the resistant populations. Up-regulation of 60s ribosomal proteins, UDP-gluscoyltransferases, cytochrome c oxidases, and CYP and ABC transporters among thiamethoxam-resistant D. citri implicates a broad array of novel and conventionally understood resistance mechanisms.

Pest categorisation of Diaphorina citri.

The EFSA Panel on Plant Health performed a pest categorisation of Diaphorina citri (Hemiptera: Liviidae) (Asian citrus psyllid) for the EU. D. citri is a key pest of citrus in several countries as it is a vector of serious bacterial pathogens, the putative causal agents of Huanglongbing (HLB) also known as citrus greening. Eggs are laid on tips of growing shoots on and between unfurling leaves. Females may lay more than 800 eggs during their lives. Nymphs pass through five instars. The life cycle requires from 14 to 49 days, depending upon the season. There is no diapause, but populations are low in winter. It overwinters as an adult which may live for several months. The species completes 9–10 generations/year; however, under protected conditions, up to 16 generations have been recorded. Commission Implementing Regulation (EU) 2019/2072 (Annex IIA) regulates D. citri, as a quarantine pest not known to occur in the EU territory. Fruits and plants for planting provide potential pathways for entry into the EU. Climatic conditions and the availability of host plants provide conditions to support establishment in the EU. The introduction of D. citri would have an economic impact in the EU through direct but mainly indirect effects due to potential transmission of HLB. Phytosanitary measures are available to reduce the likelihood of entry. D. citri satisfies the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. D. citri does not meet the criteria of occurring in the EU, nor plants for planting being the principal means of spread, for it to be regarded as a potential Union regulated non‐quarantine pest.

Insecticidal Potential of Indigenous Flora of Soon Valley against Asian Citrus Psyllid Diaphorina citri Kuwayama and Cotton Aphid Aphis gossypii Glover

Diaphorina citri Kuwayama (Psyllidae: Hemiptera) and Aphis gossypii Glover (Aphididae; Hemiptera) are destructive sap-feeding pests of citrus and cotton, respectively. This study assessed the toxicity potential of indigenous flora of Soon valley and surrounding salt range (Punjab, Pakistan) against D. citri and A. gossypii. Among acetone extracts of 40 plant species, the extracts of Mentha longifolia (L.) Huds., Melilotus officinalis (L.) Pall., Nerium indicum Mill., Datura alba L. and Salvia officinalis L. showed highest psyllid mortality (i.e. 93, 91, 89, 88 and 81%, respectively). Bioassay with most effective extracts further revealed that the most toxic extracts were S. officinalis, N. indicum and M. longifolia with LC50 values of 18.59, 20.27 and 20.73%, respectively. Similar trend of toxicity was observed in case of their LT50 values. These results suggest the putative effectiveness and further biochemical characterization of these plant extracts for the management of D. citri and A. gossypii and other sap-feeding insect pests.

Assessing potentiality of safer ways to manage citrus leaf miner and lemon butterfly

Effectiveness of two safer pest management modules was tested against the important pests of citrus namely, citrus leaf miner and lemon butterfly. Natural components like neem oil, vegetable oil, asafoetida, acetylsalicyclic acid, pheromone trap, mechanical removal of infested plant parts and a naturolyte, spinetoram were incorporated into the modules. The components worked effectively to check the build up of the pest populations and their damages and the modules showed good effectiveness against the targeted pests and sponsored good yields. The standard chemical check also registered at par yields but the safer treatments were more cost-effective and environment friendly than standard chemical check.

Endosimbiontes asociados a Diaphorina citri, vector de Candidatus Liberibacter asiaticus

iaphorina citri is considered the most dangerous citrus pest because it transmits Candidatus Liberibacter asiaticus, the causal agent of Huanglongbing (HLB). Like other hemiptera insects, D. citri has developed mutualistic interactions with prokaryotic organisms known as endosymbionts. This symbiosis can be obligatory, when the interaction occurs with a primary endosymbiont, or facultative, when it is a secondary endosymbiont. Symbiosis is essential for various physiological functions, but some endosymbionts can adversely affect the psyllid's abilities. D. citri is associated with a great diversity of endosymbionts, with Candidatus Carsonella ruddii, Candidatus Profftella armatura, Candidatus Wolbachia spp. and Candidatus Liberibacter spp standing out. The aim o symbiotic relationship, prokaryotes, Candidatus Wolbachia, transmission of Candidatus Liberibacter asiaticus.

A Brief Review ofResseliella citrifrugis(Diptera: Cecidomyiidae), a Lesser-Known Destructive Citrus Fruit Pest

AbstractThe gall midge, Resselielia citrifrugis Jiang (Diptera: Cecidomyiidae), is a major citrus pest in China. The pest occurs widely in regions with tropical, subtropical, and temperate climates. Larvae feed inside the fruit, leading to premature fruit drop or damaged fruits. An infested fruit can have hundreds of larvae in it. The extent of losses varies, usually between 10 and 100%, depending on the grove management level. Resselielia citrifrugis hosts include common citrus varieties. China has no area-wide management program against the pest. Field pest management measures include grove sanitation, fruit bagging, and pesticide applications. This review identifies three scientific and technological gaps that need to be filled to protect the U.S. citrus industry from this pest. First, the taxonomical and systematic status of R. citrifrugis needs to be clarified and validated before the pest can be effectively regulated. Second, traps and/or lures for early detection of the pest need to be developed before the pest arrival. Third, pest risk mitigation measures against the pest need to be evaluated and strengthened.

Impact of the Invasive Argentine Ant in Citrus Agroecosystems: Effects on the Diversity and Frequency of Native Ant Species Foraging on Tree Canopy.

Simple SummaryWe aimed at assessing the impact of the Argentine ant invasion on the native ant community in citrus ecosystems. We compared the Argentine ant’s invaded and uninvaded citrus orchards in the south of Portugal, estimating species richness and the frequency of ant assemblages foraging on the tree canopy. The results suggest that the Argentine ant has a negative impact on the native ant community structure, markedly reducing the diversity and frequency of native species. This impact was more or less pronounced depending on the season. Possible implications for citrus pest management are discussed.The invasion of the Argentine ant, Linepithema humile (Mayr) (Hymenoptera, Formicidae) can alter the entire ecosystem with serious impacts on the native community structure (e.g., ant diversity) and processes (e.g., trophic interactions) leading to biodiversity loss and pest outbreaks. Most studies addressing these impacts have been conducted in natural or semi-natural areas, few are those conducted in agricultural ecosystems, such as citrus orchards. These are dominant agricultural ecosystems in Mediterranean landscapes. Furthermore, most studies have been conducted in a short span, not evidencing seasonal fluctuations. In this work, we assessed the ecological impact of the Argentine ant on the native ant communities in citrus orchards, in the region of Algarve, southern Portugal. By using principal response curve, we compared seasonal variation on ant assemblages in invaded and uninvaded citrus orchards foraging on tree canopy from a two-year sampling. The Argentine ant had a marked negative impact on the native ant community foraging on citrus canopy. In the uninvaded orchards, the native ant community had a rich assemblage composed of 16 ant species, in its majority (72%) controlled by the dominant species Lasius grandis Forel, Tapinoma nigerrimum (Nylander) and/or Pheidole pallidula (Nylander). In the invaded orchards, the native ant community was poorer and highly modified, mostly dominated by the Argentine ant (80%). Apparently, the only native ant species not affected by the presence of the Argentine ant was Plagiolepis pygmaea (Latreille). A significant negative effect was found between the proportion of infested trees by L. humile and the number of native ant species per orchard. Differences in the native ant community in the invaded and uninvaded orchards persisted over seasons and years. However, negative impacts were higher in the spring and summer, and less pronounced in the autumn. We discuss implications for citrus pest management.