Tamarixia radiata global distribution to current and future climate using the climate change experiment (CLIMEX) model.

The phloem-limited bacteria, "Candidatus Liberibacter asiaticus" and "Ca. L. americanus", are the causal pathogens responsible for Huanglongbing (HLB). The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the principal vector of these "Ca. Liberibacter" species. Though Tamarixia radiata Waterston (Hymenoptera: Eulophidae) has been useful in biological control programmes against D. citri, information on its global distribution remains vague. Using the Climate Change Experiment (CLIMEX) model, the potential global distribution of T. radiata under the 2050s, 2070s, and 2090s for Special Report on Emissions Scenarios A1B and A2 was defined globally. The results showed that habitat suitability for T. radiata covered Africa, Asia, Europe, Oceania, and the Americas. The model predicted climate suitable areas for T. radiata beyond its presently known native and non-native areas. The new locations predicted to have habitat suitability for T. radiata included parts of Europe and Oceania. Under the different climate change scenarios, the model predicted contraction of high habitat suitability (EI > 30) for T. radiata from the 2050s to the 2090s. Nevertheless, the distribution maps created using the CLIMEX model may be helpful in the search for and release of T. radiata in new regions.

Efficacy and Residual Toxicity of Insecticides on Plutella xylostella and Their Selectivity to the Predator Solenopsis saevissima.

We evaluated the efficacy and residual toxicity of nine commercial insecticides on Plutella xylostella and their selectivity to the predator ant Solenopsis saevissima under laboratory and field conditions. First, to test the insecticides' effectiveness and selectivity, we conducted concentration-response bioassays on both species and the mortalities were recorded 48 h after exposure. Next, rapeseed plants were sprayed following label rate recommendations in the field. Finally, insecticide-treated leaves were removed from the field up to 20 days after application and both organisms were exposed to them as in the first experiment. Our concentration-response bioassay indicated that seven insecticides caused mortality ≥80% of P. xylostella: bifenthrin, chlorfenapyr, chlorantraniliprole, cyantraniliprole, indoxacarb, spinetoram, and spinosad. However, only chlorantraniliprole and cyantraniliprole caused mortality ≤30% of S. saevissima. The residual bioassay indicated that four insecticides had a long-lasting effect, causing mortality of 100% to P. xylostella 20 days after application: chlorantraniliprole, cyantraniliprole, spinetoram, and spinosad. For S. saevissima, bifenthrin caused mortality of 100% during the evaluated period. Additionally, mortality rates below 30% occurred four days after the application of spinetoram and spinosad. Thus, chlorantraniliprole and cyantraniliprole are safe options for P. xylostella management since their efficacy favor S. saevissima.

Modeling climate change impacts on potential global distribution of Tamarixia radiata Waterston (Hymenoptera: Eulophidae).

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an efficient vector of "Candidatus Liberibacter" species, the causative agents implicated in citrus greening or huanglongbing (HLB). HLB is the most devastating citrus disease and has killed millions of citrus trees worldwide. Classical biological control using Tamarixia radiata Waterston (Hymenoptera: Eulophidae) against ACP has been successful in some regions. Climatic conditions are critical in determining suitable areas for the geographical distribution of T. radiata. However, paucity of information on climate change impacts on the global spread of T. radiata restricts international efforts to manage ACP with T. radiata. We investigated the potential global distribution of T. radiata using 317 native and non-native occurrence records and 20 environmental data sets (with correlation coefficients (|r| > 0.7)). Using the Maximum Entropy model, these data were analyzed for two shared socioeconomic pathways (SSPs) and two time periods (2030s and 2050s). We showed that habitat suitability for T. radiata occurred in all continents except Antarctica. However, the highly suitable areas for T. radiata were found in parts of the Americas, Asia, Africa and Oceania. The climate suitable areas would increase until the 2050s. The predictions showed that mean temperature of coldest quarter and precipitation of warmest quarter were the most important environmental variables that influenced the distribution of T. radiata. The model reliably predicted habitat suitability for T. radiata, which can be adapted in classical biological control programs to effectively manage ACP in an environmentally friendly manner.

Spatial-temporal distribution of Dalbulus maidis (Hemiptera: Cicadellidae) and factors affecting its abundance in Brazil corn.

BACKGROUND: Since the last decade, Dalbulus maidis has become the primary pest in cornfields, particularly due to its ability to transmit plant pathogens. Dalbulus maidis is the main vector of the corn stunt spiroplasma and maize bushy stunt phytoplasma. However, there is little information available on this pest. Understanding its spatial dynamics may allow us to determine how its infestations begin and to identify its colonization patterns, dispersal, and the role of landscape structure on D. maidis dynamics. Thus, this study aimed to investigate within-field spatial distribution and the factors associated with D. maidis abundance in five commercial fields. RESULTS: In all fields, higher infestations occurred at the boundaries of the central pivot, showing a clear edge-biased distribution. Ranges varied from 100.4 to 611.8 m, and our models' overall fit indicated strong to moderate spatial dependency. Additionally, correlation analyses indicated a positive effect of air temperature on the population of D. maidis. Conversely, rainfall negatively affected D. maidis. CONCLUSION: This study provides essential guidance for improving D. maidis integrated pest management at regional and local scales. Based on its high dispersal ability, our study suggests the need for a legislative or regulatory method of control for D. maidis, especially in regions where corn has more than one growing season. © 2022 Society of Chemical Industry.

Forecasting the seasonal dynamics of Trichoplusia ni (Lep.: Noctuidae) on three Brassica crops through neural networks.

The cabbage looper, Trichoplusia ni Hübner (Lep.: Noctuidae), is a destructive pest of Brassica crops. Their larvae defoliate plants, leading to reduced crop yield. Understanding and modeling pest seasonal dynamics is central to management programs because it allows one to set up sampling and control efforts. This study aimed to train, with field-collected data, artificial neural networks (ANN) for T. ni forecasting on Brassica crops. ANNs were used due to their suitability to fit complex models with multiple predictors. Three weather variables (air temperature, rainfall, and relative humidity lagged at different intervals from the day of pest assessment) and three host plants (broccoli, cabbage, and cauliflower) along with another plant-related variable (days after transplanting) were used as input variables to build ANNs with different topologies. Two outputs (T. ni eggs or larvae) were tested to verify which one would yield more precise models. ANNs forecasting T. ni eggs performed better, based on Pearson's correlation (rv) of observed with fitted values. The winning ANN (rv = 0.706) had weather data lagged by 15 days, 2 neurons in the hidden layer, hyperbolic tangent as the activation function, and resilient propagation as the learning algorithm. Broccoli and cauliflower were the hosts with major contributions for T. ni occurrence. Rainfall was the primary environmental predictor and affected T. ni negatively. Therefore, the winning ANN may be used to forecast T. ni egg densities 15 days in advance, allowing for timely management of this pest.

Seed treatment for managing fall armyworm as a defoliator and cutworm on maize: plant protection, residuality, and the insect life history.

BACKGROUND: The highly polyphagous and invasive fall armyworm (FAW, Spodoptera frugiperda) can feed on different plant parts of host crops, damaging whorls and stalks in early maize growth stages. Systemic insecticide seed treatment (IST) could minimize this damage, although the residual efficacy may vary with the plant tissue damaged. Using damage rating scales and artificial infestation in controlled conditions, we determined the potential of IST against FAW attacking maize whorl leaves or the stalk base. RESULTS: Chlorantraniliprole, cyantraniliprole, or thiodicarb + imidacloprid IST similarly killed > 80% FAWs for 1 or 2 weeks after plant emergence depending on the plant tissue attacked. The residual efficacy (i.e. time after plant emergence sustaining > 80% larval mortality) lasted from the first to the eleventh day (VE-V3 maize growth stages), while for cutworm on the maize stalk base, it lasted 3-7 days after plant emergence (V1-V2 stages). In terms of damage, the ISTs lasted 15 days after emergence (V4 stage) for FAW on whorl leaves and 10 days (V3 stage) for FAW feeding on the stalk base. The larvae surviving on the seed-treated plants underwent sublethal effects in growth and development, reducing insect fitness. CONCLUSION: Diamide or carbamate + neonicotinoid seed treatments kill FAW larvae on maize whorls or stalks in favorable edaphoclimatic and insecticide-susceptibility conditions. The cumulative impacts of systemic IST on aboveground insect pests go beyond mortality. The ISTs studied can be valuable against FAW in maize, for instance, to help protect varieties that may not express sufficient insect resistance in maize early growth stages.

Insecticide seed treatment against corn leafhopper: helping protect grain yield in critical plant growth stages.

BACKGROUND: The corn leafhopper, Dalbulus maidis (Hemiptera: Cicadellidae), spreads maize stunt pathogens and requires timely and effective crop protection. We determined the interaction between maize phenology and the vector feeding/infection period by stunt pathogens with the residual efficacy of neonicotinoid insecticidal seed treatments. Greenhouse- and field-grown maize plants, seed-treated with clothianidin or imidacloprid insecticides, were infested during seven growth stages with corn leafhoppers reared under controlled conditions on maize plants displaying infection symptoms by both spiroplasma (corn stunt spiroplasma, Spiroplasma kunkelii) and phytoplasma (maize bushy phytoplasma) pathogens. RESULTS: In the greenhouse and field settings, seed treatment reduced the stunt disease symptoms and corn yield loss during the VE-V4 maize growth stages and caused no phytotoxicity. The neonicotinoid seed treatment reduced 20-60% of the yield losses from the corn stunt disease until the V4 growth stage. Infestation by infective corn leafhoppers in the V12 maize growth stage caused a 25-30% yield loss irrespective of seed treatment, yet no stunt disease symptom was evident. Nonetheless, corn yield losses and visual stunt symptoms as rated by a nine-category ordinal scale were strongly correlated (r = 0.79, P < 0.01). CONCLUSION: These results reinforce that maize plants are more susceptible to leafhopper stunt disease during the VE-V4 growth stages (emergence to the fourth-leaf stage). Seed treatment helps reduce the damage in the early growth stages (VE-V2), although supplemental control measures depending on leafhopper population density may be needed from VE-V12 to protect yield losses from the maize stunt condition. © 2021 Society of Chemical Industry.

The seasonal dynamic of Tuta absoluta in Solanum lycopersicon cultivation: Contributions of climate, plant phenology, and insecticide spraying.

BACKGROUND: A variety of abiotic and biotic factors promoting seasonal variation in the population of insect pests. Knowledge of the timing and magnitude of these factors is important for the study of population dynamics and the development of efficient pest management programs. Currently, there are few studies regarding Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) seasonal dynamics in tomato cultivation under open field conditions, either with or without insecticide application. This study aimed to investigate the effects of tomato phenology, climatic factors, and insecticide spraying on the seasonal dynamics of T. absoluta in tomato cultivation under open field conditions, using data from monitoring performed for 3 years. RESULTS: Insecticide, host plant, and climatic conditions can affect T. absoluta life cycles directly over time, resulting in shifts of peaks of the pest. Insecticides for T. absoluta control reduced injury caused by larvae; however, this was not enough to reduce the density below economic injury levels (EIL) during periods of climatic conditions more suitable for population growth. Tuta absoluta densities surpassed EIL more frequently during the tomato plant fruiting stage. The highest densities of mines and damaged fruits occurred during periods of August to January and September to January in crops without and with the application of insecticides, respectively. Regarding the climatic factors, the highest densities of T. absoluta occurred during periods of increasing air temperature and low rainfall. CONCLUSION: This study provides relevant insights into the factors that regulate the dynamics of T. absoluta in tomato cultivation and the decision-making process of control of this pest. © 2021 Society of Chemical Industry.

Plant Resistance in Some Modern Soybean Varieties May Favor Population Growth and Modify the Stylet Penetration of Bemisia tabaci (Hemiptera: Aleyrodidae).

Complaints of severe damage by whiteflies in soybean fields containing genetically engineered (GE) varieties led us to investigate the role of transgenic soybean varieties expressing resistance to some insects (Cry1Ac Bt toxin) and to herbicide (glyphosate) on the population growth and feeding behavior of Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae). In the laboratory, the whiteflies reared on the GE Bt soybeans had a net reproductive rate (R0) 100% higher and intrinsic rate of population increase (rm) 15% higher than those reared on non-GE soybeans. The increased demographic performance was associated with a higher lifetime fecundity. In electrical penetration graphs, the whiteflies reared on the GE soybeans had fewer probes and spent 50% less time before reaching the phloem phase from the beginning of the first successful probe, indicating a higher risk of transmission of whitefly-borne viruses. Data from Neotropical fields showed a higher population density of B. tabaci on two soybean varieties expressing glyphosate resistance and Cry1Ac Bt toxin. These results indicate that some GE soybean varieties expressing insect and herbicide resistances can be more susceptible to whiteflies than non-GE ones or those only expressing herbicide resistance. Most likely, these differences are related to varietal features that increase host-plant susceptibility to whiteflies. Appropriate pest management may be needed to deal with whiteflies in soybean fields, especially in warm regions, and breeders may want to consider the issue when developing new soybean varieties.

Biological performance and oviposition preference of tomato pinworm Tuta absoluta when offered a range of Solanaceous host plants.

The tomato pinworm Tuta absoluta (Lepidoptera: Gelechuidae) is native to South America and has now become the main tomato pest in Europe, Africa and Asia. The wide range of host plants attacked by this pest has been reported as one of the main reasons for the success of this important insect species. However, the information currently available on the biological performance of T. absoluta on Solanaceae has been obtained from a limited number of host species. The Solanaceae family is composed of thousands of species, many of which are potential hosts for T. absoluta. Our results showed that the highest oviposition rates occurred on cultivated tomato plants, potato and wild tomato. The lowest rates occurred on "gilo", "jurubeba", green pepper and pepper. The highest survival rates of the immature stages occurred on potato and the lowest on pepper, green pepper and "jurubeba". Female fertility, following infestation of the different plant species, was highest for insects that developed on tomato or potato and the lowest rates were seen on American black nightshade. The net reproductive rate and the intrinsic growth rate were highest on potato and tomato. Cluster analysis grouped tomato and potato as highly susceptible to attack, American black nightshade, juá, eggplant, gilo and wild tomato as moderately susceptible, whilst pepper, green pepper and jurubeba were categorized as resistant to T. absoluta. These results clearly demonstrate that the choice of solanaceous host plant species has a direct impact on the fitness parameters of the tomato pinworm as well as survival potential, dispersion and establishment at new sites. These results are important for the planning of integrated pest management strategies.

Spatial distribution and colonization pattern of Bemisia tabaci in tropical tomato crops.

BACKGROUND: In precision integrated pest management, management tactics are implemented only where and when needed, by identifying the sites where the pest population has reached economic thresholds. Tomato, Solanum lycopersicum (Linn.), is a vegetable cultivated worldwide, but its production is reduced by insect pests such as the whitefly, Bemisia tabaci (Genn.). To improve management, there is a need to understand B. tabaci spatial dynamics in tomato fields, which will elucidate colonization patterns and may improve management of this pest. Thus, this study was conducted to assess the spatial autocorrelation, distribution, and colonization patterns of B. tabaci in 19 commercial tomato fields through the growing season. RESULTS: A total of 69 isotropic variograms were fit for B. tabaci. The insect distribution was aggregated with a strong level of spatial dependence. Ranges of spatial dependence varied from 0.53 to 19.05 m and 0.5 to 20 m for adults and nymphs, respectively. Overall, densities of adults and nymphs were higher and reached the economic threshold mainly at the field edges. CONCLUSION: Our results suggest a colonization pattern for B. tabaci starting at the edges and spreading inwards in to the tomato fields. This study can improve B. tabaci management in tomato fields, especially scouting and decision-making to treat fields. Scouting for this pest should be directed to the field edges, with sample points at least 20 m apart from each other for independent insect counts. © 2020 Society of Chemical Industry.

Lethal and antifeedant effects of Bordeaux mixture on the marsh slug (Deroceras laeve).

The marsh slug, Deroceras laeve (Müller), is a generalist pest of agricultural crops. Slugs are mainly managed with synthetic pesticides that can also have high toxicity toward vertebrates and nontarget arthropods. Besides, they are not labeled for use in organic crop systems. Bordeaux mixture (BM) is an alternative product often used in organic crops for controlling plant diseases. The molluscicidal activity of BM has been reported; however, to our knowledge, no study has determined its efficacy to control D. laeve. This study aimed to determine the lethal (concentration- and time-mortality curves, and foliar persistence) and antifeedant (reduction in leaf consumption) effects of BM-treated cabbage leaves on D. laeve. The LC50 of BM was 28.15%, and the LT50 was 8.83 h. The BM LC25 reduced D. laeve leaf consumption by 3.31-fold. Furthermore, high control effectiveness (mortality > 90%) was attained until the 7th day after spraying. These findings reveal that BM reduces damage by killing D. laeve in a fast faction and by reducing foliar consumption. Therefore, BM can be an alternative to D. laeve management in both conventional and organic systems.

Spatial Distribution of Frankliniella schultzei (Thysanoptera: Thripidae) in Open-Field Yellow Melon, With Emphasis on the Role of Surrounding Vegetation as a Source of Initial Infestation.

Frankliniella schultzei (Trybom) is a serious pest of melon crops and is commonly found in the main producing areas of melon in Brazil (North and Northeast regions). This pest causes significant losses, damaging plants through feeding and tospovirus vectoring. Thus, the proper management of F. schultzei is crucial to prevent economic losses, and knowledge of the within-field distribution patterns of F. schultzei can be used to improve this pest management. This study aimed to determine the within-field distribution (through semivariogram modeling and kriging interpolation) and the factors associated with F. schultzei abundance in open-field yellow melon crops. We surveyed four yellow melon fields located in Formoso do Araguaia (Tocantins state, North Brazil) for thrips abundance in various crop stages (vegetative, flowering, and fruiting) in 2015 and 2016. Twelve models were fitted and it was determined that F. schultzei counts were strongly aggregated. The median spatial dependence was 4.79 m (range 3.55 to 8.02 m). The surface maps generated by kriging depicted an edge effect in fields 3 and 4. In addition, correlation analyses indicated that air temperature and presence of surrounding cucurbits are positively associated with F. schultzei abundance in yellow melon fields. Altogether, these insights can be combined for spatially based pest management, especially when the conditions (cucurbits in the surroundings and warmer periods) are favorable to F. schultzei.

Practical Sampling Plan for Liriomyza huidobrensis (Diptera: Agromyzidae) in Tomato Crops.

The pea leafminer, Liriomyza huidobrensis (Blanchard), is an important pest of tomato crops worldwide. Conventional sampling plans are the starting point for the development of pest control decision-making. The present study aimed to develop a conventional sampling plan for L. huidobrensis during the vegetative and reproductive stages of tomato (Solanum Lycopersicum L.). The best sampling unit for vegetative and reproductive stages of tomato crops was determined. The frequency distributions of L. huidobrensis densities in tomato crops were assessed, and the ideal number of samples to constitute the sampling plan was determined. The basal leaf of the middle section of the plant canopy was the best plant part for sampling. Pea leafminer densities were fitted to the negative binomial distribution with a common aggregation parameter (Kcommon = 0.7289) that represents all tomato fields. The sampling plan consists of 73 samples per field, irrespective of field size (1, 5, or 10 ha). Evaluations using this sampling plan were performed in 47 min, 1 h 9 min, and 1 h 25 min at a cost of US$1.74, US$2.54, and US$3.12 per sampling in fields of 1, 5, and 10 ha, respectively. The sampling plan developed in this study may lead to more well-informed decision-making for controlling L. huidobrensis in tomato fields up to 10 ha. Additionally, it is inexpensive (up to US$3.12 per sampling area), fast (up to 1 h 25 min per sampling area), and practical (it can be used in tomato crops at the vegetative and reproductive stages).

Conventional Sampling Plan for Scouting Neoleucinodes elegantalis (Lepidoptera: Crambidae) Eggs on Tomato Fruits.

The small tomato borer, Neoleucinodes elegantalis (Guenée), is an important pest of tomato (Solanum lycopersicum L.) in South and Central America. This pest is a potential threat for many tomato-producing areas and was listed in 2014 as an A1 quarantine pest by the European and Mediterranean Plant Protection Organization. Soon after hatching, the neonate N. elegantalis larvae penetrate the fruits where they feed until pupation. Therefore, effective N. elegantalis management relies on the timely scouting of egg densities to allow decision-making prior to penetration of neonates into fruits. This study aimed to develop a conventional sampling plan for scouting N. elegantalis eggs on tomato plants. The most representative and precise sampling unit was the most basal fruit cluster for plants bearing up to three clusters (S1 plants). For plants with more than three fruit clusters (S2 plants), the most representative and precise sampling unit was the combination of the second and third fruit clusters. Among the four variables evaluated (eggs/fruit, egg masses/fruit, percentage fruit with eggs, and percentage clusters with eggs), the percentage of clusters with eggs was the most economical for N. elegantalis sampling based on the number of samples and cost required. For this variable, the number of samples determined at the 25% error level was 42 and 36 samples for S1 and S2 plants, respectively. The sampling plan developed for scouting N. elegantalis is fast, reflects pest infestation in tomato fields, and costs less than US$1.50 per field scouted.

Assessing the impact of climate change on the worldwide distribution of Dalbulus maidis (DeLong) using MaxEnt.

BACKGROUND: For the first time, a model was applied at the global scale to investigate the effects of climate change on Dalbulus maidis. D. maidis is the main vector of three plant pathogens of maize crops and has been reported as one of the most important maize pests in Latin America. We modelled the effects of climate change on this pest using three Global Climate Models under two Representative Concentration Pathways (RCPs) using MaxEnt software. RESULTS: Overall, climate change will lead to a decrease in suitable areas for D. maidis. In South America, climate change will decrease the areas suitable for the pest, especially in Brazil. However, Argentina, Chile, Colombia, Ecuador, Peru and Venezuela will have small areas that are highly suitable for the corn leafhopper. Outside the pest's range, Ethiopia, Kenya, Rwanda, Burundi and South Africa also should be concerned about the risk of corn leafhopper invasions in the future because they are projected to have conditions that are highly suitable for this insect in some areas. CONCLUSION: This study allows the relevant countries to increase their quarantine measures and guide researchers to develop new Zea mays varieties that are resistant or tolerant to D. maidis. In addition, the maize-stunting pathogens for the areas are highlighted in this modelling. © 2019 Society of Chemical Industry.

Negative cross-resistance between structurally different Bacillus thuringiensis toxins may favor resistance management of soybean looper in transgenic Bt cultivars.

High adoption rates of single-gene Bacillus thuringiensis (Bt) Cry1Ac soybean impose selection pressure for resistance in the soybean looper, Chrysodeixis includens, a major defoliator in soybean and cotton crops. To anticipate and characterize resistance profiles that can evolve, soybean looper larvae collected from field crops in Brazil in 2013 were selected for resistance to Cry1Ac. Using two methods of selection viz., chronic exposure to Cry1Ac cotton leaves and the seven-day larval exposure to purified Cry1Ac on the artificial diet, 31 and 127-fold resistance was obtained in 11 and 6 generations of selection, respectively. The resistance trait had realized heritability of 0.66 and 0.72, respectively, indicating that most of the phenotypic variation in Cry1Ac susceptibility of the soybean looper larvae was due to additive genetic variation. The Cry1Ac-selected populations showed positive cross-resistance to Cry1Ab (6.7-8.7 fold), likely because these Bt toxins have a very similar molecular structure. Importantly, the Cry1Ac-selected populations became more susceptible to Cry2Aa and Cry1Fa, showing negative cross-resistance (up to 6-fold, P < 0.05). These results indicate that Cry1Ac, Cry1Fa, and Cry2A are compatible in a multi-toxin approach to minimize the risk of rapid adaptation of the soybean looper to Bt toxins.

Toxicity and Sublethal Effects of Phthalides Analogs to Rhyzopertha dominica.

Phthalides and their precursors have demonstrated a large variety of biological activities. Eighteen phthalides were synthesized and tested on the stored grain pest Rhyzopertha dominica. In the screening bioassay, compounds rac-(2R,2aS,4R,4aS,6aR,6bS,7R)-7-bromohexahydro-2,4-methano-1,6-dioxacyclopenta[cd]pentalen-5(2H)-one (15) and rac-(3R,3aR,4R,7S,7aS)-3-(propan-2-yloxy)hexahydro-4,7-methano-2-benzofuran-1(3H)-one (17) showed mortality similar to the commercial insecticide, Bifenthrin® (≥90 %). The time (LT50 ) and dose (LD50 ) necessary to kill 50 % of the R. dominica population were determined for the most efficacious phthalides 15 and 17. Compound 15 presented the lowest LD50 (1.97 µg g-1 ), being four times more toxic than Bifenthrin® (LD50 =9.11 µg g-1 ). Both compounds presented an LT50 value equal to 24 h. When applied at a sublethal dose, both phthalides (especially compound 15), reduced the emergence of the first progeny of R. dominica. These findings highlight the potential of phthalides 15 and 17 as precursors for the development of insecticides for R. dominica control.

Natural mortality factors of tomato leafminer Tuta absoluta in open-field tomato crops in South America.

BACKGROUND: Little importance has been given to the role of natural mortality factors (biotic and abiotic) in the regulation of tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae) populations. The present study determined the action of mortality factors on T. absoluta populations infesting cultivated tomato crops. Eighty ecological life tables for T. absoluta in field cultivated tomato plants were constructed and analyzed. RESULTS: Total T. absoluta mortality was 99.08%, with 38.76% mortality during the egg phase, 57.20% in the larva phase and 3.12% in the pupal phase. The main mortality factors during the egg stage were predation, parasitism and egg inviability. In the larval stage, the main mortality factors were predation, parasitism, entomopathogenic agents and physiological disorders. In the pupal stage, the main mortality factor was predation. The larvae of the third and fourth instar were more susceptible to the action of mortality factors and the predatory wasp, Protonectarina sylveirae, was the main insect predator of these larvae. CONCLUSIONS: The T. absoluta population is regulated under field conditions by the action of natural enemies of the larvae. The predatory wasp P. sylveirae is very important in the regulation of T. absoluta populations in open-field tomato crops in Brazil. © 2018 Society of Chemical Industry.