Lethal and Sublethal Effects of Annona spp. Derivatives on Bemisia tabaci MEAM 1 (Hemiptera: Aleyrodidae) in Tomato

The whitefly Bemisia tabaci(Gennadius) MEAM 1 is one of the main insect species that colonize tomato plants and cause direct and indirect damage. The use of botanical derivatives may be a valuable method of insect control to reduce the inappropriate use of synthetic insecticides on crops. In this study, we evaluated the bioactivity of ethanolic extracts prepared from Annonaceae species compared to that of the commercial insecticides based on acetogenins (Anosom® 1 EC, anonine 10,000 mg L^-1) and thiamethoxam (Actara® 250 WG) on eggs, nymphs, and adults of the whitefly in tomato. Initially, the effects of the ethanolic seed extracts of Annona mucosa (Jacq.), Annona muricata L., and Annona sylvatica A.St.-Hil on adult insect behavior were evaluated. The rates of infestation and oviposition deterrence indicated the inhibitory effects of the extract of A. muricata (500 mg L^-1). Then, the possible systemic effects of the extracts were evaluated; however, no effects on nymphal development or insect viability were observed. The LC₅₀ and LC₉₀ of the ethanolic extract of A. mucosa seeds at 500 mg L^-1 (10.83 and 200.24 mg L^-1, respectively) were estimated and were used in ovicidal tests and compared to positive (Actara® 250 WG and Anosom® 1 EC), and negative controls (water: acetone, 1:1 v/v). At LC₉₀, fewer eggs (35.00%) had hatched at 13 days after application than in the other treatments. The results of this study demonstrate the potential use of botanical derivatives of Annona spp. for the management of B. tabaci MEAM 1 in tomato.

Avocado kernels, an industrial residue: a source of compounds with insecticidal activity against silverleaf whitefly

Fruit processing waste, such as kernels (endocarp + seed) of avocado [Persea americana Mill. (Lauraceae)], could be used as raw material in the preparation of botanical insecticides. In light of this potential, this study assessed the insecticidal action of extracts and fractions from kernels of two avocado cultivars (Breda and Margarida) on Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B, an important pest species in tropical conditions. Ethanolic and aqueous extracts prepared from kernels of P. americana, regardless of the plant cultivar used, caused promising insecticidal activity to whitefly nymphs. Based on yield in crude extracts [10.32 and 9.85% (w/w), respectively, for cultivars Breda and Margarida], on the bioassay results with crude extracts and on the chemical profiles, the ethanolic extract of kernels of P. americana cv. Breda was chose for the continuation of the study. Thus, the ethanolic extract of kernels of cv. Breda (LC₅₀ = 197.84 ppm and LC₉₀ = 567.19 ppm) was selected and subjected to fractionation by the liquid-liquid partition technique. The hexane and dichloromethane fractions of this extract caused significant mortality of nymphs. The analysis using the ultraviolet (UV) and hydrogen nuclear magnetic resonance (¹H NMR) showed the presence of long-chain aliphatic compounds (alkanols or acetogenins of Lauraceae), alkylfurans (or avocadofurans), and unsaturated fatty acids in these fractions, which are possibly related to bioactivity observed in B. tabaci, besides saccharides. The results show that kernels of P. americana are promising sources of compounds with insecticidal action for the control of B. tabaci biotype B, a great opportunity to transform environmental problems into eco-friendly solutions to agriculture.

BIOACTIVITY OF EXTRACTS FROM SOLANACEAE AGAINST Zabrotes subfasciatus

The botanical family Solanaceae has many species producing compounds with insecticidal properties, e.g. nicotine and capsaicin, which are used for pest management in agriculture. This fact provides perspectives to identify insecticidal compounds in Brazilian native species of Solanaceae. In this study, we performed a screening with 25 ethanolic extracts from 17 Solanaceae species in order to evaluate their bioactivity against the Mexican bean weevil, Zabrotes subfasciatus(Coleoptera: Chrysomelidae: Bruchinae). The bioactivity of Solanaceae ethanolic extracts (2500 mg kg-1) was tested with residual contact bioassays. Adults ofZ. subfasciatus were exposed to treated bean grains, and adult mortality, oviposition, F1progeny and damages on grains were quantified. Most of the ethanolic extracts from Solanaceae reduced the number of eggs per sample, the egg-adult viability, the F1progeny and the damages on bean grains promoted byZ. subfasciatus, but none of them interfered on its sex ratio. Ethanolic extract from leaves of Solanum lycocarpumA. St.-Hil promoted the most promissory effects on Z. subfasciatus. This ethanolic extracts can be a suitable alternative to control Z. subfasciatus in stored beans, mainly for small farmers and organic farmers. 

Isolation of Chavibetol and Methyleugenol from Essential Oil of Pimenta pseudocaryophyllus by High Performance Liquid Chromatography

A high performance liquid chromatography (HPLC) method was developed for the simultaneous isolation, on a semi-preparative scale, of chavibetol and methyleugenol from the crude essential oil of P. pseudocaryophyllus leaves. The purity of the isolated compounds and their quantifications were developed using GC/FID. Chavibetol was isolated with high purity (98.7%) and mass recovery (94.6%). The mass recovery (86.4%) and purity (85.3%) of methyleugenol were lower than those of chavibetol. Both compounds were identified on the basis of spectral analysis. The results suggest that the method can provide chavibetol with high purity, mass recovery, and productivity from crude essential, which will be used in bioassays against stored insect pests.

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.

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.

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.

Ação de inseticidas botânicos sobre o curuquerê-da-couve

Resumo: Ascia monuste orseis (Lepidoptera: Pieridae) é uma praga-chave de brassicáceas, cujo controle ainda carece de informações sobre ferramentas alternativas de manejo. Assim, este estudo avaliou, inicialmente em condições de laboratório, a atividade ovicida e larvicida de extratos aquosos de sete espécies vegetais e de um bioinseticida à base de limonoides (DalNeem®) diante dessa praga. Além disso, também foi avaliada a ação antialimentar dos tratamentos em testes com e sem chance de escolha. DalNeem® e extratos aquosos de pó de fumo (Nicotiana tabacum), de eucalipto (Eucalyptus tereticornis) e de timbó (Ateleia glazioveana) reduziram a viabilidade de ovos, sendo o extrato de pó de fumo o tratamento com maior atividade ovicida. Por sua vez, o extrato de pó de fumo e DalNeem® apresentaram a maior ação larvicida via ingestão. Todos os derivados botânicos testados causaram efeito antialimentar para o curuquerê-da-couve. Em teste no campo, o extrato aquoso de pó de fumo apresentou eficácia similar a um inseticida sintético à base de deltametrina (Decis® 25CE). Dessa forma, o extrato aquoso de pó de fumo e o inseticida botânico DalNeem® apresentam potencial para ser utilizados no manejo de A. monuste orseis. 

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.

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.

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.

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.

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.

Comparative toxicity of an acetogenin-based extract and commercial pesticides against citrus red mite

Acetogenins, a class of natural compounds produced by some Annonaceae species, are potent inhibitors of mitochondrial electron transport systems. Although the cellular respiration processes are an important biochemical site for the acaricidal action of compounds, few studies have been performed to assess the bioactivity of acetogenin-based biopesticides on spider mites, mainly against species that occur in orchards. Using residual contact bioassays, this study aimed to evaluate the bioactivity of an ethanolic extract from Annona mucosa seeds (ESAM) (Annonaceae) against the citrus red mite Panonychus citri (McGregor) (Acari: Tetranychidae), an important pest of the Brazilian citriculture. ESAM is a homemade biopesticide which was previously characterized by its high concentration of acetogenins. It caused both high mortality of P. citri females (LC50 = 7,295, 4,662, 3,463, and 2,608 mg l(-1), after 48, 72, 96, and 120 h of exposure, respectively) and significant oviposition deterrence (EC50 = 3.194,80 mg l(-1)). However, there was no effect on P. citri female fertility (hatching rate). In addition, the ESAM efficacy (in terms of its LC90) was compared with commercial acaricides/insecticides (at its recommended rate) of both natural [Anosom(®) 1 EC (annonin), Derisom(®) 2 EC (karanjin), and Azamax(®) 1.2 EC (azadirachtin + 3-tigloylazadirachtol)] and synthetic origin [Envidor(®) 24 SC (spirodiclofen)]. Based on all of the analyzed variables, the ESAM exhibited levels of activity superior to other botanical commercial acaricides and similar to spirodiclofen. Thus, our results indicate that ESAM may constitute a biorational acaricide for citrus red mite integrated pest management in Brazilian citrus orchards, particularly for local use.

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.

Brassinosteroids interact negatively with jasmonates in the formation of anti-herbivory traits in tomato

Given the susceptibility of tomato plants to pests, the aim of the present study was to understand how hormones are involved in the formation of tomato natural defences against insect herbivory. Tomato hormone mutants, previously introgressed into the same genetic background of reference, were screened for alterations in trichome densities and allelochemical content. Ethylene, gibberellin, and auxin mutants indirectly showed alteration in trichome density, through effects on epidermal cell area. However, brassinosteroids (BRs) and jasmonates (JAs) directly affected trichome density and allelochemical content, and in an opposite fashion. The BR-deficient mutant dpy showed enhanced pubescence, zingiberene biosynthesis, and proteinase inhibitor expression; the opposite was observed for the JA-insensitive jai1-1 mutant. The dpy x jai1-1 double mutant showed that jai1-1 is epistatic to dpy, indicating that BR acts upstream of the JA signalling pathway. Herbivory tests with the poliphagous insect Spodoptera frugiperda and the tomato pest Tuta absoluta clearly confirmed the importance of the JA-BR interaction in defence against herbivory. The study underscores the importance of hormonal interactions on relevant agricultural traits and raises a novel biological mechanism in tomato that may differ from the BR and JA interaction already suggested for Arabidopsis.

Bioactivity of neem, Azadirachta indica, against spittlebug Mahanarva fimbriolata (Hemiptera: Cercopidae) on sugarcane

The effect of neem, Azadirachta indica A. Juss, on some biological parameters of Mahanarva fimbriolata (Stil) (Hemiptera: Cercopidae) was studied in the laboratory by using NeemAzal-T/S, Nimkol-LS, and an aqueous neem seed extract. Initially, the LC,, was estimated for nymphs. Later, nymphs fed on sugarcane, Saccharum officinarum L., roots were sprayed with the respective LC,, for each product. The adults were maintained in cages on sugarcane plants sprayed at the base with the maximum rate recommended commercially for the crop (3 liter/ha). Moistened cotton discs surrounding the base of the plant were used as oviposition substrates. The LCso values estimated for NeemAzal, Nimkol, and aqueous extract were 0.014, 0.225, and 0.611%, respectively. There was a reduction in spittlebug longevity, regardless of sex, in relation to the control. Males exposed to the neem products, and aqueous extract showed longevity reductions of approximately 50%, whereas for females the reductions were 55-60%. The neem products and extract reduced fecundity by 75-85%. Morphological and physiological changes were observed in 9% of the eggs from individuals submitted to NeemAzal. Neem-based products, especially NeemAzal, have potential for the control of M. fimbriolata.