Optimizing the releasing strategy used for the biological control of the sugarcane borer Diatraea saccharalis by Trichogramma galloi with computer modeling and simulation.

One of the challenges in augmentative biological control programs is the definition of releasing strategy for natural enemies, especially when macro-organisms are involved. Important information about the density of insects to be released and frequency of releases usually requires a great number of experiments, which implies time and space that are not always readily available. In order to provide science-based responses for these questions, computational models offer an in silico option to simulate different biocontrol agent releasing scenarios. This allows decision-makers to focus their efforts to more feasible options. The major insect pest in sugarcane crops is the sugarcane borer Diatraea saccharalis, which can be managed using the egg parasitoid Trichogramma galloi. The current strategy consists in releasing 50,000 insects per hectare for each release, in three weekly releases. Here, we present a simulation model to check whether this releasing strategy is optimal against the sugarcane borer. A sensitive analysis revealed that the population of the pest is more affected by the number of releases rather than by the density of parasitoids released. Only the number of releases demonstrated an ability to drive the population curve of the pest towards a negative growth. For example, releasing a total of 600,000 insects per hectare in three releases led to a lower pest control efficacy that releasing only 250,000 insects per hectare in five releases. A higher number of releases covers a wider range of time, increasing the likelihood of releasing parasitoids at the correct time given that the egg stage is short. Based on these results, it is suggested that, if modifications to the releasing strategy are desired, increasing the number of releases from 3 to 5 at weekly intervals is most likely preferable.

Biological basis for adoption of an isoline of Telenomus remus (Hymenoptera: Scelionidae) for an augmentative biological-control program for Spodoptera frugiperda (Lepidoptera: Noctuidae).

The widely distributed, polyphagous fall armyworm, Spodoptera frugiperda (J.E. Smith, 1797), is one of the most important crop pests worldwide. The egg-parasitoid wasp, Telenomus remus Nixon, 1937, is frequently described as a possible control agent for S. frugiperda. We selected an isoline of T. remus and evaluated its parasitism potential (for 24 h) in S. frugiperda eggs, in laboratory conditions, and also its ability to fly at different temperatures and relative humidity levels, aiming to provide basic information about this isoline. The selected isoline maintained good flight capacity without affecting its parasitism efficiency or developing inefficient haplotypes for biological-control programs, compared across generations to a regularline laboratory-reared for more than 60 generations. The flight capacity of the isoline was best at 25-30 °C and relative humidity 70-90%.

A New Species of Aleiodes Wesmael (Braconidae, Rogadinae) with Potential for Biological Control of Spodoptera spp. (Lepidoptera, Noctuidae), and Notes on the Definition of the gastritor, circumscriptus, and Related Species-Groups.

A new species of Aleiodes Wesmael in the gastritor Thunberg species-group is described and illustrated. The new species, Aleiodes ceres Shimbori sp.n., occurs in Southern Brazil and Argentina. It is a potential biological control agent of caterpillars in the genus Spodoptera Guenée, namely S. cosmioides (Walker), S. eridania (Stoll), and S. frugiperda (J.E. Smith), which are serious pests on major crops including maize and soybean. The position of the new species within Aleiodes is discussed in relation to existing proposals of subdivisions of the genus into species-groups. In agreement with recent publications, the gastritor species-group is treated as separate from the circumscriptus Nees/bicolor Spinola group, as evidence suggests the latter is absent in the New World. We also propose the provisional shakirae Shimbori & Shaw species-group, to accommodate a clade of Neotropical species with geometrid hosts and morphological features similar to the gastritor and circumscriptus groups. A key to Neotropical species in the gastritor group and similar species is provided, except for species recently named without a morphological description.

Fertility Life Table, Thermal Requirements, and Ecological Zoning of Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae) in Brazil.

The boll weevil, Anthonomus grandis grandis Boh., is the most important cotton pest in Central and South America. The biological characteristics and thermal requirements of boll weevils reared on an artificial diet were assessed at seven constant temperatures (18, 20, 22, 25, 28, 30, and 32 ± 1 °C) under laboratory conditions. These data were used to determine the ecological zoning for the pest in Brazil. The development time; oviposition period; the number of eggs produced; survival of eggs, larvae, and pupae; adult longevity; and sex ratio were recorded, and additional life table parameters were calculated. The total development duration ranged from 16.1 (32 °C) to 46.2 (18 °C) days. Temperature significantly affected the number of eggs laid per female (fecundity), with the highest number of eggs observed at 25 °C (251 ± 15.8). The parameters from the fertility life table indicated the greatest population growth at 25 °C and 28 °C. The net reproductive rate (R0) at these temperatures was 22.25 times higher than at 18 °C. Based on R0 and temperature, an ecological zoning of the pest was developed for Brazil. Brazilian regions with mean temperatures above 20 °C and below 30 °C are most favorable for the population growth of the boll weevil. The most suitable crop areas were found to be the north, midwest, and part of the northeast region, although the weevil can occur throughout Brazil if the host plants are available.

Reproductive compatibility among sympatric and allopatric isofemale lines of Trichogramma pretiosum Riley, 1879.

The present study evaluated the reproductive compatibility of Trichogramma pretiosum Riley, 1879, through an integrative approach using biological data and morphometry of three isofemale lines (isolines) collected from two geographical areas. These isolines differed in sequences of mitochondrial DNA and reproductive performance in the laboratory. The wasps used to initiate the isolines were collected in different environments: two lines from a Mediterranean climate in Irvine, California, USA, and one line from a tropical climate in Piracicaba, São Paulo, Brazil. Reproductive compatibility was studied by evaluating the sex ratio and number of adult offspring produced of all mating combinations between adults from these isolines. Morphometry was studied by measuring 26 taxonomically useful characters, followed by a multivariate analysis. For the allopatric matings among Brazilian and North American isolines, a low level of crossing incompatibility was recorded, in only one direction of the crosses; whereas the sympatric North American isolines were incompatible in both directions. Multivariate analysis of the morphometric data indicated no distinct groups, suggesting that despite the genetic and biological differences, the isofemale lines are morphologically similar.

Ecological zoning of Euschistus heros in Brazil based on the net reproductive rate at different temperatures and relative-humidity levels.

The Neotropical brown stink bug, Euschistus heros (Fabricius, 1798) (Hemiptera: Pentatomidae), is one of the major insect pests in soybean crops, causing severe damage; however, some aspects of its biology that are essential for management remain unknown. To aid in the management of E. heros, the present study investigated the fertility life table of this species at 7 temperatures (18, 20, 22, 25, 28, 30, and 32 ± 1 °C) and 4 relative-humidity levels (30, 50, 70, and 90 ± 10%). Based on the net reproductive rate, R0, we developed an ecological zoning for this pest in Brazil, to identify climatically favorable areas for population growth. Our results indicated that the most favorable range is between 25 and 28 °C and above 70% RH. The ecological zoning indicated that farmers should be more concerned in the northern and Midwest regions, which include the state of Mato Grosso, the largest soybean and corn producer in Brazil. These results provide valuable information, indicating the hotspots most likely to be attacked by the Neotropical brown stink bug.

Density and Dispersal Radius of Tamarixia radiata for Control of Diaphorina citri in Citrus Groves.

Tamarixia radiata (Waterston) is the main parasitoid wasp released in abandoned, organic, and non-commercial citrus groves and in orange jasmine areas  for biological control of Diaphorina citri Kuwayama (a vector of bacteria associated with huanglongbing), as a control tactic in a strategy termed External Management. The effectiveness of parasitism is influenced by the release density and radius of action of this parasitoid. This study determined the optimal release density and radius of action of T. radiata in a commercial citrus grove. Parasitoids were released at five densities (200, 400, 800, 1,600, and 3,200 wasps/ha) at the center of circular areas with four different radii (7.5, 15, 22.5, and 30 m). The parasitism rate was assessed using 'Valencia' sweet orange seedlings, each bearing 35 D. citri fourth-instar nymphs, attached to 26-year-old 'Valencia' sweet orange trees along the perimeter of each radius. For the 7.5-m radius, the highest parasitism rate (74.1%) was observed at the density of 3,200 wasps/ha. However, for the 15-m radius, the density of 3,200 wasps/ha resulted in lower parasitism (30.7%) of D. citri nymphs. No parasitism was observed for densities lower than 800 wasps/ha and release radii above 15 m. The highest parasitoid dispersal radius and area were 18.04 m and 114.02 m2, respectively, when 3,200 wasps were released. Therefore, 3,200 wasps/ha arranged at 56 equidistant release points (approximately 57 wasps/release point) is the recommended protocol for biological control of D. citri in citrus groves.

Is Integrated Management of Gymnandrosoma aurantianum Possible with Trichogramma atopovirilia and Novel Products Used in Citrus Orchards in Brazil?

In Brazil, the citrus fruit borer, Gymnandrosoma aurantianum Lima, 1927, is a serious pest in orange orchards, causing an annual loss of 80 million US dollars, and is managed with multiple insecticide applications, often 56 in a single season. On the other hand, the parasitoid wasp Trichogramma atopovirilia Oatman & Platner, 1983 has the potential for controlling G. aurantianum by attacking its eggs. Considering the intensive insecticide applications in citrus orchards in Brazil to control the large complex of pests, especially Diaphorina citri Kuwayama, 1908, evaluation of the harmful effects of insecticides on T. atopovirilia is important to maximize efficiency in managing G. aurantianum. Here, we tested the effects of new products used in citrus orchards (cyantraniliprole, cyantraniliprole + abamectin, abamectin, sulfoxaflor, spinetoram, flupyradifure, and Cordyceps fumosorosea (Wize) Kepler, B. Shrestha & Spatafora) on adults and pupae of T. atopovirilia. Of the insecticides tested, spinetoram caused the highest impacts on T. atopovirilia parasitism, longevity, emergence, and mortality. The other products caused more sublethal than lethal effects and were classified as 1 and/or 2 in the IOBC/WPRS classification. Abamectin, cyantraniliprole, cyantraniliprole + abamectin, and the entomopathogenic fungus C. fumosorosea were classified as short-lived. Except for spinetoram, these products were classified as selective. In this study, spinetoram was considered harmful to T. atopovirilia and, therefore, should be managed carefully in IPM programs combining this parasitoid. In order to safely use this insecticide, one should respect the interval of release of the parasitoid, which is 21 days after its spraying. The novel products tested, cyantraniliprole, cyantraniliprole + abamectin, abamectin, sulfoxaflor, and the entomopathogenic fungi C. fumosorosea were selective and non-persistent to T. atopovirilia. These products are possible replacements for non-selective insecticides to achieve higher control from both chemical and biological tools.

Insect Rearing Techniques for Biological Control Programs, a Component of Sustainable Agriculture in Brazil.

This article describes the importance of rearing insects, whether on a small scale for research or a large scale for mass rearing, for use in biological control (BC) programs with macro-organisms. These inter- or multidisciplinary research programs are necessarily long-term and depend on rearing techniques for their complete development. Some successful examples of BC in Brazil are presented, including case studies of Trichogramma spp. These required broad bioecological studies that provided the basis for both mass rearing and transfer of the necessary technology to farmers. This has allowed Brazil to occupy a leadership position in biological control in "Open Fields". For example, about three million ha are being treated with Trichogramma galloi (a native parasitoid), and about three and a half million ha with Cotesia flavipes (an exotic parasitoid) to control Diatraea saccharalis, the sugarcane borer. These natural enemies are produced by commercial firms, or by laboratories in sugar and alcohol plants themselves, in the case of C. flavipes.

Determining the Minimum Temperature for Storage of Tamarixia radiata (Hymenoptera: Eulophidae) Adults for Biological Control of Asian Citrus Psyllid.

In order to control the spread of the huanglongbing (HLB) disease in citrus plants, one of the main approaches is management of its vector, the Asian citrus psyllid, Diaphorina citri Kuwayama. The intensive use of chemicals to control the psyllid has caused concern due to the damage to the environment and human health, and biological control has been a more sustainable and environmentally safe strategy. For D. citri, the parasitoid wasp Tamarixia radiata Waterston has been used successfully in the state of São Paulo, Brazil, reducing populations of D. citri nymphs by up 80% in some municipalities. Mass rearing of wasps is required to provide efficient control, which implies that quality control is required, especially in storage and transportation. In most cases, the insects are not used on the same day of emergence, which makes it necessary to develop strategies to delay development without negatively affecting the wasps. Here, we evaluated the survival of T. radiata adults over eight different exposure times (2, 4, 6, 8, 10, 12, 14, and 16 days) in three different temperatures (7, 9, and 11°C). After these periods, they were transferred to climate chambers at 25°C and their survival curves over 30 days were analyzed. We concluded that adults can be maintained at 9°C for up to 6 days without significant damage to their survival during and after the exposure period, functioning well for D. citri IPM implementation.

ß-caryophyllene emitted from a transgenic Arabidopsis or chemical dispenser repels Diaphorina citri, vector of Candidatus Liberibacters.

Production of citrus, the main fruit tree crop worldwide, is severely threatened by Huanglongbing (HLB), for which as yet a cure is not available. Spread of this bacterial disease in America and Asia is intimately connected with dispersal and feeding of the insect vector Diaphorina citri, oligophagous on rutaceous host plants. Effective control of this psyllid is an important component in successful HLB management programs. Volatiles released from the non-host guava have been shown to be repellent to the psyllid and to inhibit its response to citrus odour. By analysing VOC emission from guava we identified one volatile compound, (E)-ß-caryophyllene, which at certain doses exerts a repellent effect on D. citri. Non-host plant rejection mediated by (E)-ß-caryophyllene is demonstrated here by using Arabidopsis over-expression and knock-out lines. For the first time, results indicate that genetically engineered Arabidopsis plants with modified emission of VOCs can alter the behaviour of D. citri. This study shows that transgenic plants with an inherent ability to release (E)-ß-caryophyllene can potentially be used in new protection strategies of citrus trees against HLB.

Inga laurina trypsin inhibitor (ILTI) obstructs Spodoptera frugiperda trypsins expressed during adaptive mechanisms against plant protease inhibitors.

Plant protease inhibitors (PIs) are elements of a common plant defense mechanism induced in response to herbivores. The fall armyworm, Spodoptera frugiperda, a highly polyphagous lepidopteran pest, responds to various PIs in its diet by expressing genes encoding trypsins. This raises the question of whether the PI-induced trypsins are also inhibited by other PIs, which we posed as the hypothesis that Inga laurina trypsin inhibitor (ILTI) inhibits PI-induced trypsins in S. frugiperda. In the process of testing our hypothesis, we compared its properties with those of selected PIs, soybean Kunitz trypsin inhibitor (SKTI), Inga vera trypsin inhibitor (IVTI), Adenanthera pavonina trypsin inhibitor (ApTI), and Entada acaciifolia trypsin inhibitor (EATI). We report that ILTI is more effective in inhibiting the induced S. frugiperda trypsins than SKTI and the other PIs, which supports our hypothesis. ILTI may be more appropriate than SKTI for studies regarding adaptive mechanisms to dietary PIs.

Selectivity of plant extracts for Trichogramma pretiosum Riley (Hym.: Trichogrammatidae).

We evaluated the selectivity of three plant extracts with potential insecticidal effects for the parasitoid Trichogramma pretiosum Riley, which is commonly used in biological pest control. The plant extracts assayed were an acetone extract of Toona ciliata M. Roem., commercial neem oil, and a nanoencapsulated formulation of neem oil (NC40). The toxicity of the plant extracts to T. pretiosum was evaluated according to the recommendations of the International Organization for Biological Control- IOBC Working Group. We assessed the susceptibility of adults of the maternal and F1 generations and immature stages of T. pretiosum to the extracts. Females exposed to egg cards treated with commercial neem oil parasitized almost 70% fewer eggs than control eggs treated with water; and this extract was therefore classified as slightly harmful. When the eggs were offered to females 24h after treatment with neem oil and aqueous NC40, the parasitism rate also decreased, and the two extracts were classified as slightly harmful. Adult emergence was lower for parasitoids that fed on host eggs offered 24h after the treatment with the T. ciliata extract, which was considered slightly harmful. The emergence of T. pretiosum from eggs, larvae and pupae treated with the different plant extracts, did not decrease compared to development stages treated with the water control. The use of T. pretiosum, combined with the application of an ethanol extract of T. ciliata and a nanoencapsulated formulation of neem, appears to be feasible in view of these low toxicity indices.

Temperature-dependent development of two neotropical parasitoids of Liriomyza sativae (Diptera: Agromyzidae).

We studied two species of neotropical parasitoids that occur naturally in northeastern Brazil and are associated with Liriomyza sativae (Blanchard): Opius (Gastrosema) scabriventris Nixon (Hymenoptera: Braconidae) and Chrysocharis vonones (Walker) (Hymenoptera: Eulophidae). We evaluated the influence of seven temperatures on the duration of the egg-adult period and on the survivorship of the immature stages of the parasitoids. A temperature increase from 15 to 30°C shortened the egg-adult period of O. scabriventris and C. vonones. However, at 32°C, the developmental time for the braconid was prolonged, and no difference was observed for the eulophid, compared with 30°C. The highest temperature, 35°C, proved to be lethal for both species. At 15°C, C. vonones pupal survivorship was drastically reduced, whereas that of O. scabriventris was unaffected. At most temperatures, the eulophid had an egg-adult period shorter than or similar to the braconid, except at 15°C. The threshold temperature (Tt) of the egg-adult period for O. scabriventris was 7.3°C with a thermal constant (K) of 257.1 degree days (DD). For C. vonones the Tt was 7.4°C for the total cycle and 6.2°C for the pupal stage, with a thermal constant of 246.3 and 140.3 DD, respectively. These data allow an estimate of 29.4 annual generations for O. scabriventris and 30.5 for C. vonones in a melon production region in northeastern Brazil, values that are equivalent to 4.9 and 6.0 more generations than the host. These results demonstrate that both species have potential for application in biological control programs against the leafminer fly L. sativae.

Thermal hygrometric requirements for the rearing and release of Tamarixia radiata (Waterston) (Hymenoptera, Eulophidae)

Thermal hygrometric requirements for the rearing and release of Tamarixia radiata (Waterston) (Hymenoptera, Eulophidae). Tamarixia radiata is the main agent for the biological control of Diaphorina citri in Brazil with a parasitism rate ranging from 20 to 80%. This study investigated the influence of temperature on the development, fecundity and longevity of adults of T. radiata and the effect of relative humidity (RH) on their parasitism capacity and survival rate in the pre-imaginal period. The effect of temperature was assessed in the range between 15 and 35 ± 1ºC, 70 ± 10% RH, and a 14-h photophase. The RH effect was evaluated in the range from 30 to 90 ± 10%, temperature at 25 ± 1ºC, and photophase of 14-h. At 25ºC, circa 166.7 nymphs were parasitized, the highest parasitism capacity observed compared to other treatments. The longest longevity of females was observed at 25ºC, although the rate did not differ in the 20-30ºC temperature range. The threshold temperature (TT) was 7.2ºC, and 188.7 degrees-day were required for the development (egg-to-adult period). The parasitism rate and longevity were higher at 50 and 70% of RH. This shows that temperature and RH may affect the parasitism capacity of T. radiata on nymphs of D. citri, which can explain the great parasitism variation for D. citri observed in citrus groves in São Paulo State, Brazil.

Reflectance-based identification of parasitized host eggs and adult Trichogramma specimens.

A wide range of imaging and spectroscopy technologies is used in medical diagnostics, quality control in production systems, military applications, stress detection in agriculture, and ecological studies of both terrestrial and aquatic organisms. In this study, we hypothesized that reflectance profiling can be used to successfully classify animals that are otherwise very challenging to classify. We acquired hyperspectral images from adult specimens of the egg parasitoid genus Trichogramma (T. galloi, T. pretiosum and T. atopovirilia), which are ~1.0 mm in length. We also acquired hyperspectral images from host eggs containing developing Trichogramma instar and pupae. These obligate egg endoparasitoid species are commercially available as natural enemies of lepidopteran pests in food production systems. Because of their minute size and physical resemblance, classification is time consuming and requires a high level of technical experience. The classification of reflectance profiles was based on a combination of average reflectance and variogram parameters (describing the spatial structure of reflectance data) of reflectance values in individual spectral bands. Although variogram parameters (variogram analysis) are commonly used in large-scale spatial research (i.e. geoscience and landscape ecology), they have only recently been used in classification of high-resolution hyperspectral imaging data. The classification model of parasitized host eggs was equally successful for each of the three species and was successfully validated with independent data sets (>90% classification accuracy). The classification model of adult specimens accurately separated T. atopovirilia from the other two species, but specimens of T. galloi and T. pretiosum could not be accurately separated. Interestingly, molecular-based classification (using the DNA sequence of the internally transcribed spacer ITS2) of Trichogramma species published elsewhere corroborates the classification, as T. galloi and T. pretiosum are closely related and comparatively distant from T. atopovirilia. Our results emphasize the importance of using high-spectral and high-spatial resolution data in the classification of organism relatedness, and hyperspectral imaging may be of relevance to a wide range of commercial (i.e. producers of biocontrol agents), taxonomic and evolutionary research applications.

New method for rearing Spodoptera frugiperda in laboratory shows that larval cannibalism is not obligatory

New method for rearing Spodoptera frugiperda in laboratory shows that larval cannibalism is not obligatory. Here we show, for the first time, that larvae of the fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera, Noctuidae), can be successfully reared in a cohort-based manner with virtually no cannibalism. FAW larvae were reared since the second instar to pupation in rectangular plastic containers containing 40 individuals with a surprisingly ca. 90% larval survivorship. Adult females from the cohort-based method showed fecundity similar to that already reported on literature for larvae reared individually, and fertility higher than 99%, with the advantage of combining economy of time, space and material resources. These findings suggest that the factors affecting cannibalism of FAW larvae in laboratory rearings need to be reevaluated, whilst the new technique also show potential to increase the efficiency of both small and mass FAW rearings.

Insensitive trypsins are differentially transcribed during Spodoptera frugiperda adaptation against plant protease inhibitors.

0The fall armyworm (Spodoptera frugiperda) is an important pest insect due to high degree of polyphagia. In order to better understand its adaptation mechanism against plant protease inhibitors, bioassays were carried supplementing diet with the Kunitz trypsin inhibitor from Entada acaciifolia seeds (EATI). In vitro assays showed an increase of proteolytic activity in EATI-fed larvae midgut. Moreover, the trypsin enzymes showed insensitivity to inhibition with EATI. In order to understand what genes were overexpressed after chronic exposition to EATI, quantitative RT-PCR analyses were performed and revealed an increase in transcription of two trypsin genes, suggesting its participation in insensitivity of midgut trypsins. Another important result was the expression of one chymotrypsin gene, which is not expressed in control fed-larvae but induced in EATI-fed larvae. New regions of higher molecular weight showing proteolytic activity were visualized in inhibitor-fed larvae by zymography gel electrophoresis, proposing that the new enzymes expressed in response of inhibitor dietary would be formatting oligomers. This is a characteristic also observed in other pest insects that adapt to feed in plant protease inhibitors diet. Additional assays revealed that trypsins from EATI-fed larvae also became insensitive against Kunitz and Bowman-Birk inhibitors from soybean. This result suggests a possible involvement of the same S. frugiperda genes in adaptation against Kunitz and Bowman-Birk inhibitors in their host plants.

Natural parasitism of Diaphorina citri Kuwayama (Hemiptera, Psyllidae) nymphs by Tamarixia radiata Waterston (Hymenoptera, Eulophidae) in São Paulo orange groves / Parasitismo natural de ninfas de Diaphorina citri Kuwayama (Hemiptera, Psyllidae) por Tamarixia radiata Waterston (Hymenoptera, Eulophidae) em pomares de laranja em São Paulo

The psyllid Diaphorina citri Kuwayama 1908 has become the main citrus pest species in the state of São Paulo, Brazil, after the introduction of the huanglongbing or citrus greening. This study evaluated the parasitism of 3rd, 4th and 5th instar D. citri nymphs by Tamarixia radiata (Waterston, 1922) in citrus groves under a regimen of regular insecticide applications in ten producing regions: Araraquara, Barretos, Bauru, Botucatu, Franca, Itapetininga, Jaú, Limeira, Lins and São João da Boa Vista. Sixty-nine samples of new branches infested with nymphs of D. citri were collected from 2005 to 2008 in orange groves ranging from 1 to 20 years old, of the varieties Hamlin, Pera, Valencia and Natal. The parasitoid T. radiata is widely distributed in São Paulo orange groves, and was identified in 50 (72%) of the samples, showing a mean parasitism rate of 12.4%. The highest parasitism rate was observed in the "summer" (from January through March), with a mean of 25.7%. Nymphal parasitism was above 90% in two samples. The probable causes of the variations in parasitism of D. citri by T. radiata are discussed.

O psilídeo Diaphorina citri Kuwayama 1908 tornou-se a principal praga dos citros no estado de São Paulo após a introdução do huanglongbing ou grenning dos citros. Este estudo avaliou as proporções de ninfas de terceiro a quinto ínstares de D. citri parasitadas por Tamarixia radiata (Waterston, 1922) em pomares de laranja submetidos a pulverizações constantes de inseticidas em dez regiões produtoras, Araraquara, Barretos, Bauru, Botucatu, Franca, Itapetininga, Jaú, Limeira, Lins e São João da Boa Vista. Foram coletadas 69 amostras de ramos jovens infestados com ninfas de D. citri obtidas entre 2005 e 2008 em pomares de 1 a 20 anos de idade, das cultivares Hamilin, Pera, Valencia e Natal. O parasitóide T. radiata encontra-se amplamente distribuído em pomares de São Paulo, tendo sido observado em 50 amostras (72%), com taxa média de parasitismo de 12.4%. O maior parasitismo foi verificado no "verão" (janeiro a março) com média de 25.7%. O parasitismo de ninfas superou 90% em duas amostras. São discutidas as causas próváveis das variações entre o parasitismo de D. citri por T. radiata.

Life table of Tamarixia radiata (Hymenoptera: Eulophidae) on Diaphorina citri (Hemiptera: Psyllidae) at different temperatures.

Tamarixia radiata (Waterston, 1922) is the main parasitoid of Diaphorina citri (Kuwayama, 1907), and has been used in classical biological control programs in several countries. The current study investigated the biology and determined the fertility life table of T. radiata in different temperatures, to obtain information to support the establishment of a biological control program for D. citri in Brazil. Fifth-instar nymphs of D. citri were offered to females of T. radiata for parasitism, for 24 h. Then, the parasitoid was removed and the nymphs were placed in incubators at 15, 20, 25, 30, or 35 +/- 1 degrees C, 70 +/- 10% RH, and a 14-h photophase. The percentages of parasitism and emergence, the sex ratio, and the preimaginal period of T. radiata were determined. The fertility life table was developed from the biological data. The highest parasitism rate (77.24%) was obtained at a temperature of 26.3 degrees C, and the lowest parasitism rates occurred at 15 and 35 degrees C (23.1 and 40.2%, respectively). The highest percentages of emergence of the parasitoid occurred at 25, 30, and 35 degrees C (86.7, 88.3, and 78.8%, respectively), with the calculated peak at 30.8 degrees C (89.90%). The duration of the preimaginal developmental period for both females and males of T. radiata was inversely proportional to temperature in the thermal range of 15-35 degrees C. The development of T. radiata occurred at all temperatures studied, and the highest viability of the preimaginal period occurred at 25 degrees C. The highest values of net reproductive rate and finite growth ratio (lambda) were observed at 25 degrees C, so that in each generation the population of T. radiata increased 126.79 times, higher than the values obtained at the other temperatures.