Toxicity of an Annonin-Based Commercial Bioinsecticide Against Three Primary Pest Species of Stored Products.

The effects of a bioinsecticide formulation based on extract of Annona squamosa L. (Annonaceae) containing 10,000 mg L-1 of acetogenin annonin as the main active ingredient were investigated against three primary pest species of stored grains in Brazil [maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), Mexican bean weevil Zabrotes subfasciatus (Boheman) (Coleoptera: Chrysomelidae: Bruchinae), and cowpea weevil Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae: Bruchinae)] by means of residual contact bioassays. In a concentration-dependent manner, the annonin-based commercial bioinsecticide caused significant adult mortality of C. maculatus (LC50 = 6890 µL kg-1), S. zeamais (LC50 = 2781 µL kg-1), and Z. subfasciatus (LC50 = 2120 µL kg-1) after 120 h of residual contact exposure. In addition to acute toxicity, the tested bioinsecticide also promoted a significant reduction of the number of eggs laid by females of C. maculatus (EC50 = 5949.7 µL kg-1) and Z. subfasciatus (EC50 = 552.7 µL kg-1). Moreover, the bioinsecticide significantly reduced the number of emerged insects (F1 generation) of C. maculatus (EC50 = 2763.0 µL kg-1), S. zeamais (EC50 = 1380.8 µL kg-1), and Z. subfasciatus (EC50 = 561.5 µL kg-1). The bioinsecticide also reduced the percentage of damaged grains for the three pest species studied, and its grain-protectant properties are comparable to or superior in efficacy in relation to a diatomaceous earth-based insecticide (Insecto® at 1000 mg kg-1) used as a positive control. Thus, this standardized formulation has promising bioactivity against stored insect species and can be a useful component for IPM of stored grains in Brazil and elsewhere.

Acute and Chronic Toxicities of an Annonin-Based Commercial Bioinsecticide and a Joint Mixture with a Limonoid-Based Formulation to the Fall Armyworm.

The bioactivity of a newly registered annonin-based formulation (Anosom® 1 EC) was investigated for use against the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), both singly and mixed with a limonoid-based formulation (Azamax® 1.2 EC) using dietary exposure bioassays. Anosom® 1 EC caused significant mortality in S. frugiperda larvae exposed to treated artificial media, with the activity level dependent on both the concentration and the exposure time. In addition to exhibiting acute toxicity, this formulation (tested at LC50) also caused growth inhibition of S. frugiperda, as demonstrated by a significant reduction in pupal weight and viable larval and pupal phases and an increase in the duration of the larval stage. Moreover, the bioinsecticide caused an increase in the proportion of deformed or defective pupae; these were characterized by the retention of exuvia from the last larval instar. The bioinsecticide (at the previously estimated LC90) was, in a time-dependent manner, equally as toxic as the limonoid-based biopesticide (Azamax® 1.2 EC), which was tested at concentrations recommended for the management of S. frugiperda in Brasil. Moreover, the binary mixture (1/2 LC90 of Anosom® 1 EC + 1/2 the recommended rate of Azamax® 1.2 EC) of both bioinsecticides caused a similar level of mortality compared to the bioinsecticides tested individually (full concentration), demonstrating an additive effect of these commercial bioinsecticides. In light of these findings, this standardized formulation based on extract of Annona squamosa can constitute a useful component in the framework of S. frugiperda management, mainly in organic food production systems.

Toxicity of Secondary Metabolites from Meliaceae Against Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae).

The study was carried out to evaluate the bioactivity of secondary metabolites from Trichilia pallida, Trichilia pallens, and Toona ciliata against fall armyworm Spodoptera frugiperda (J. E. Smith) larvae. The studied compounds included (+/-)-catechins, a triglyceride, and cedrelone isolated from T. ciliata branches, fruits, and stems, respectively; dammaradienol isolated from T. pallida leaves; and scopoletin isolated from T. pallens branches. The compounds' activity was evaluated through ingestion and topic treatment. Treated artificial diet was offered to first instar larvae to evaluate ingestion effect, while an application on the dorsal thoracic region of third instar larvae was used to evaluate the topic effect. Mortality was assessed daily, and larval weight was recorded after 7 days for ingestion and 5 days for topic application. Scopoletin and triglyceride caused low mortality rates and reduction in larval weight by ingestion, (+/-)-catechins caused larval weight reduction by ingestion, and scopoletin reduced survival by topic treatment. The most effective compound was cedrelone that affected larval survival and development mainly by ingestion. The estimated LC50, LC90, and EC50 for cedrelone were 0.0365, 0.0659, and 0.0095%, respectively. Further, cedrelone-treated corn leaf discs were offered to fourth instar larvae during 16 h in choice and no-choice tests. The deterrence indexes obtained in the choice tests were 23.5 and 36.3% at concentrations of 0.0365 and 0.0659, respectively. Consumption of cedrelone-treated leaf discs at the concentration of 0.0659% was lower compared to the control in the no-choice test. Thus, cedrelone caused lethal and sublethal effects and phagodeterrence on S. frugiperda and should be further studied.

Threshold Concentration of Limonoids (Azamax) for Preventing Infestation by Mediterranean Fruit Fly (Diptera: Tephritidae).

This study identified the threshold concentration of limonoids for the complete inhibition of oviposition of Ceratitis capitata (Wiedemann) in grapes 'Itália.' Choice and no-choice experiments with the insect were performed. The three no-choice bioassays were conducted following a completely randomized design with 18 treatments (three densities of insects [one, two, or three females]×five concentrations of limonoids and control) and 20 replicates. In a free choice bioassay, two fruits per cage (a treatment grape and a control) were provided for ovipositing. Three densities of insects (one, two, or three females) were used, with 15 replicates. Bioassays were conducted at 25±2°C, 60±10% relative humidity, and a photoperiod of 14:10 (L:D) h. The inhibition of oviposition of C. capitata was concentration dependent, with infestation occurring at lower concentrations of azadirachtin (+3-tigloylazadirachtol) and complete inhibition occurring at concentrations at or exceeding 100 ppm azadirachtin (+28.5 ppm of 3-tigloylazadirachtol), maintaining protective effects even at the most densely populated treatment (three females per fruit). When the pest had a free choice of host grapes (treatment vs. control), severe inhibition was observed at concentrations≥50 ppm azadirachtin (+14.3 ppm of 3-tigloylazadirachtol). We conclude that a threshold concentration of 100 ppm azadirachtin (+28.5 ppm of 3-tigloylazadirachtol) is capable of preventing grape infestation. This concentration is likely to provide a reliable level of protection, as the experimental population density of three females per fruit usually does not occur in the field and wild flies usually have more host options.

No Correlation of Morpho-Agronomic Traits of Phaseolus vulgaris (Fabaceae) Genotypes and Resistance to Acanthoscelides obtectus (Say) and Zabrotes subfasciatus (Boheman) (Coleoptera: Chrysomelidae).

Resistance of common bean (Phaseolus vulgaris) varieties is an important tool to control Acanthoscelides obtectus (Say) and Zabrotes subfasciatus (Boheman) (Coleoptera: Chrysomelidae: Bruchinae) worldwide. However, bioassays to characterize the resistance of a genotype can be difficult to perform. Therefore, the current study sought to correlate the morpho-agronomic traits of P. vulgaris genotypes with their resistance to A. obtectus and Z. subfasciatus to facilitate genotype characterization. Bean samples of each genotype were infested with newly emerged insect couples, and the number of adults obtained in each genotype was quantified (value used as a resistance parameter). The resistance index was calculated by dividing the number of adults obtained in each genotype by the one obtained in the cultivar Bolinha, used as the standard for susceptibility. Fifty genotypes were evaluated for A. obtectus and 202 for Z. subfasciatus. All genotypes were characterized according to their resistance to each insect and 18 other morpho-agronomic traits, for a total of 19 descriptors. Principal component analyses did not show any correlation between insect resistance and the morpho-agronomic traits of the genotypes. Further, the thousand seeds weight (TSW), which is indicative of the genotype center of origin was tested considering genotypes from Mesoamerican with low TSW, while those from Andean with high TSW. Thus, the lack of correlation between genotype resistance and TSW indicates that resistance to A. obtectus and Z. subfasciatus in P. vulgaris is not related to the host center of origin.

Pimenta pseudocaryophyllus Derivatives: Extraction Methods and Bioactivity Against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae).

Plant-based insecticides can play an important role in integrated insect pest management (IPM), especially in protecting stored grains. The aim of this study was to evaluate the bioactivity of derivatives (powder, ethanolic extract, and essential oil (EO)) from the leaves of Pimenta pseudocaryophyllus (Myrtaceae), a Brazilian native species, against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), the main insect pest of stored corn. The powder and essential oil prepared from leaves showed a repellent effect. Moreover, the EO exhibited promising insecticidal activity through residual contact (LC50 = 1522 mg kg(-1)) and significantly decreased the F 1 progeny and the percentage of damaged grains. However, the essential oil obtained from P. pseudocaryophyllus leaves did not result in significant mortality of S. zeamais adults after 72 h of exposure by fumigation in concentrations up to 400 µL L(-1) of air. Based on GC-MS analysis, 20 compounds were identified in the essential oil of P. pseudocaryophyllus leaves, being chavibetol (38.14%), methyl eugenol (11.35%), and terpinolene (9.17%) as the major constituents. Essential oil from P. pseudocaryophyllus leaves is an interesting source of compounds with grain-protectant properties and should be analyzed in future studies aiming to develop new bioinsecticides to use in the IPM of stored grains.

Resistance of Citrus and Related Genera to Diaphorina citri Kuwayama (Hemiptera: Liviidae).

The present study was developed to evaluate the resistance of the following genotypes of Citrus and related genera to this pest: 'Pera,' 'Natal', and 'Washington Navel' oranges (Citrus sinensis), 'Marsh Seedless' grapefruit (Citrus paradisi), hardy orange 'Rubidoux' (Poncirus trifoliata), kumquat (Fortunella margarita Swingle), citrumelo 'Swingle' (C. paradisi x P. trifoliata), and citrange 'Troyer' (P. trifoliata x C. sinensis). The experiments were performed in greenhouses with plants grafted onto 'Rangpur' lime (Citrus limonia) and placed individually in voile cages. The preference for oviposition in a no-choice test, and the effect of genotype were evaluated. The egg-adult cycle was monitored to determine the effect of genotype on the biology of the insect. Poncirus 'Rubidoux' was the least preferred genotype for oviposition; reduced number of eggs was also found to occur on citrange 'Troyer', and 'Marsh Seedless' was the genotype with the most eggs. No significant variation in the duration of the embryonic period was observed; however, a difference in the viability of eggs was found, with the lowest egg viabilities on 'Swingle.' Kumquat and 'Marsh Seedless' genotypes were correlated with increased durations of the nymphal phase, however, there was no difference in the survival of this phase. Fecundity of females on 'Troyer', 'Swingle', and kumquat was reduced. Considering all of the evaluated parameters, it was concluded that cultivars of sweet orange are the most susceptible genotypes to Diaphorina citri. Regarding oviposition, P. trifoliata 'Rubidoux' showed resistance of the antixenosis type.

Tropical Plant Extracts as Sources of Grain-Protectant Compounds Against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae).

The toxicity of organic plant extracts to Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) was assessed for three tropical plant species: branches, leaves, and seeds of Annona montana (Annonaceae), branches of Aristolochia paulistana (Aristolochiaceae), and leaves and branches of Casearia sylvestris (Salicaceae). The screening assay resulted that the extracts of A. montana seeds obtained with hexane (LC50 = 534.75 mg kg(-1) and LT50 = 6.10 days) and with dichloromethane (LC50 = 424.67 mg kg(-1) and LT50 = 5.03 days) were the most promising treatments, followed by the extract prepared from A. montana leaves with hexane (LC50 = 837.70 mg kg(-1) and LT50 = 4.90 days). Moreover, extracts (at 1,500 mg kg(-1)) prepared from C. sylvestris branches with dichloromethane and A. paulistana with hexane caused significant mortality (37% and 41.5%, respectively) beyond sublethal effects on S. zeamais. Therefore, based on the biological assays, extraction yield, and evaluation of the chromatographic profile of the crude extracts by TLC, the hexane extract of A. montana seeds was selected and fractioned using liquid-liquid partitioning. The hydroalcoholic fraction caused mortality of 55.5%, significantly superior to dichloromethane fraction, which caused 35.5% of mortality. Chemical analyses ((1)H NMR, HPLC, and TLC) were performed, and the results showed the presence of alkaloids and acetogenins in both active fractions, which have been associated with bioactivity. Therefore, extracts prepared from A. montana seeds (especially) is an interesting source of new compounds with promising grain-protectant properties.

Neem derivatives are not effective as toxic bait for tephritid fruit flies.

Neem derivatives have been widely touted as replacements for pesticides. A feasible replacement of synthetic insecticides in the management of fruit flies could be to use neem products in baits. This study evaluated the bioactivity of neem (Azadirachta indica A. Juss) derivatives in bait for adults of Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann). The estimated LCs50 values for A. fraterculus and C. capitata were 7,522 ppm (18.40 ppm of azadirachtin) and 1,368 ppm (3.35 ppm of azadirachtin), respectively, using an aqueous extract of neem seeds in bait after 10 d of experimentation. No significant differences in the mortality of A. fraterculus and C. capitata adults exposed to baits made from different extracts and neem oil were observed after 3 h or 2 or 6 d; differences among the treatments were observed only on the 10th day of the evaluation. We conclude that neem derivatives applied as a bait spray over citrus plants did not demonstrate a toxic effect on A. fraterculus and C. capitata. The reasons for the low efficacy of the neem bait on Tephritid fruit flies are discussed.

Resistance of citrus genotypes to Phyllocnitis citrella Stainton (Lepidoptera: Gracillariidae).

The development and reproduction of the citrus leafminer (CLM), Phyllocnistis citrella Stainton, were evaluated in six citrus genotypes in order to identify genotypes with resistance traits that could be applied in a program for the development of citrus varieties resistant to the citrus leafminer. Tests were conducted under controlled laboratory conditions (25 ± 1ºC, 70 ± 10% RH, and 14h photophase). Seedlings of each genotype tested were infested with eggs obtained from a stock colony of CLM maintained on 'Cravo' lemon (Citrus limonia L. Osbeck), and the duration and survival of the eggs, larval and pupal stages, pupal size and weight, fecundity and longevity of adults, and sex ratio were evaluated. No influence was observed on the duration and survival of eggs, larvae and pupae of P. citrella. However, pupae obtained in the hybrid C x R(4) were significantly smaller and lighter than pupae from the remaining treatments. Adult females from the hybrids C x R(4) and C x R(315) were the least fecund. However, the lowest value for the corrected reproductive potential (CRP) was recorded in the hybrid C x R(315), suggesting that this genotype is the least favorable for the development and reproduction of CLM. On the other hand, the highest CRP value obtained in the 'Rugoso' lemon confirms the susceptibility of this genotype, indicating it as the most suitable for CLM.

Induction of insect plant resistance to the spittlebug Mahanarva fimbriolata Stål (Hemiptera: Cercopidae) in sugarcane by silicon application.

Changes in the agroecosystem with the increase of green cane harvesting in Brazil affected the insect populations associated to this crop, and secondary pests like the spittlebug Mahanarva fimbriolata Stål, became much more important. Many studies have demonstrated the active role played by silicon in plant defense against herbivory. The objective of this study was to evaluate the effects of silicon applications on the biology of the spittlebug reared on two resistant (SP79-1011 and SP80-1816) and one susceptible (SP81-3250) sugarcane cultivars. Sugarcane plants were grown under greenhouse conditions and submitted to different treatments: with and without silicon fertilizer in two different soil type (sandy and clay soil). The newly hatched nymphs were transferred to sugarcane roots and placed into boxes with lids, to keep a moistened and dark environment favoring their growth and maintenance of the root system, providing food access to the developing nymphs. After emergence, adult males and females were placed in cages for mating and oviposition. The silicon absorbed and accumulated in the plant caused an increase in nymphal mortality, and depending on the sugarcane cultivar tested this element also provided an increase in the duration of the nymphal stage and a decrease in the longevity of males and females. 'SP79-1011' presented the highest silicon content in leaves, and M. fimbriolata had the highest nymph mortality and the shortest female longevity. The pre-oviposition period, fecundity and egg viability were not affected by the silicon content in plants or the cultivar used.

Efeito de extratos orgânicos de Meliaceae sobre Bemisia tabaci (Gennadius) biótipo B em tomateiro / Effect of organic extracts from Meliaceae on Bemisia tabaci (Gennadius) B biotype in tomato plants

Avaliou-se o efeito de extratos orgânicos de Azadirachta indica. Melia azedarach. Toona ciliata e Trichilia pallida (Rutales: Meliaceae) sobre ovos e ninfas de Bemisia tabaci (Hemiptera: Aleyrodidae) biótipo B. Folhas e ramos foram secos, moídos e submetidos à extração (Soxhlet) em diclorometano e em etanol. Visando estabelecer uma concentração adequada para os estudos subsequentes, foram utilizados ovos oriundos de 40 adultos que foram mantidos por 24h em folíolos de tomateiro em gaiolas de voil. Após 9 dias, contou-se o número de ninfas e pulverizou-se o extrato de folhas de .. pallida em diclorometano em diferentes concentrações (0,32; 0,56; 1,0; 1,8 e 3,2%), além de água e acetona (controles). A mortalidade ninfal foi avaliada após sete dias. O experimento foi conduzido em delineamento inteiramente aleatorizado, com sete tratamentos e quatro repetições. Posteriormente, extratos em diclorometano e em etanol foram pulverizados sobre ovos na concentração selecionada (0,56%), em experimentos distintos para cada solvente. Após nove dias, avaliou-se a mortalidade dos ovos e fez-se nova pulverização, avaliando-se, após sete dias, a mortalidade ninfal. Os experimentos foram conduzidos em delineamento com blocos aleatorizados (10 tratamentos e quatro repetições). Os dados foram submetidos à análise de regressão, análise de variância e comparados pelo teste de Tukey. Observou-se maior rendimento dos extratos em etanol em relação aos extratos em diclorometano. Os extratos em diclorometano de folhas e de ramos das meliáceas afetaram significativamente a sobrevivência de ovos e ninfas da mosca-branca. Os extratos em etanol afetaram a fase de ninfa, mas não apresentaram atividade ovicida.

The effect of organic extracts from Azadirachta indica. Melia azedarach. Toona ciliata and Trichilia pallida (Rutales: Meliaceae) on eggs and nymphs of Bemisia tabaci (Hemiptera: Aleyrodidae) B biotype was assessed. Leaves and branches were dried, ground and submitted to extraction (Soxhlet) with dichloromethane and ethanol. To establish an adequate concentration for the subsequent tests, eggs were used originating from 40 adults maintained for 24h on tomato leaves in voile cages. After 9 days, the number of nymphs was determined and the dichloromethane extract from T. pallida leaves was sprayed at different concentrations (0.32, 0.56, 1.0, 1.8 and 3.2%); water and acetone were also used (controls). The nymphal mortality was evaluated after 7 days. An entirely randomized design was used, with 7 treatments and 4 replications. Afterwards, dichloromethane and ethanol extracts were sprayed on eggs at the selected concentration (0.56%), in different experiments. After 9 days, the egg mortality was evaluated and a new spraying was conducted to assess the nymphal mortality after 7 days. These experiments were conducted in a randomized block designed (10 treatments and 4 replications). The data was submitted to regression analysis, analysis of variance and compared by the Tukey test. A higher yield was observed for the ethanol extracts in relation to the dichloromethane extracts. The dichloromethane extracts from leaves and branches from meliaceas significantly affected the survival of the whitefly eggs and nymphs. The ethanol extracts affected the nymphal phase, but did not present ovicidal activity.