Effect of Plant Essential Oil Formulations on Bemisia tabaci MEAM1 (Gennadius) and Its Parasitoid Eretmocerus hayati (Zolnerowich and Rose).

Silverleaf whitefly (SLW), Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), consists of genetically diverse species known to cause significant destruction in many crops around the world. Nowadays, synthetic insecticides are a key component in the management of this pest. However, they also come with disadvantages, such as environmental pollution, pest resistance and recurrence, and toxicity to pollinators and natural enemies. Essential oils from aromatic plants and biocontrol agents may provide a new and safe alternative to synthetic chemicals. In this study, we assessed the lethal impact of three new plant essential oil formulations (referred to as F1, F2, and F3) against the developmental stages of B. tabaci and its parasitoid Eretmocerus hayati (Zolnerowich and Rose) (Hymenoptera: Aphelinidae). The tested formulations consisted of combinations of mustard oil and different surfactants. The formulations were effective against the eggs and nymphal stages of B. tabaci. At the highest concentration assessed (1.23%), F1 was the most effective formulation against the eggs, resulting in 85% mortality, whereas F2 was most effective against the nymphs (92.5% and 88.3% mortality for the young and old nymphs, respectively). However, adult mortality rates were below 40% for all the tested formulations. The range of median lethal concentration (LC50) values was between 0.65 and 1.05% for B. tabaci. The side effects of the three formulations were assessed against E. hayati, treated as parasitized nymphs of B. tabaci. At the highest tested concentration (1.23%), F2 and F3 resulted in 80% and 70% mortality of the parasitoids, respectively (classified as moderately or slightly harmful according to the IOBC), whereas F1 resulted in 17.5% mortality. As F1 was effective against SLW with minimal effects on the parasitoid, it is the most suitable formulation of those tested for use in an integrated pest management (IPM) program targeting the younger life stages of B. tabaci.

Evaluation of the Stability of a 1,8-Cineole Nanoemulsion and Its Fumigant Toxicity Effect against the Pests Tetranychus urticae, Rhopalosiphum maidis and Bemisia tabaci.

Pest control is a main concern in agriculture. Indiscriminate application of synthetic pesticides has caused negative impacts leading to the rapid development of resistance in arthropod pests. Plant secondary metabolites have been proposed as a safer alternative to conventional pesticides. Monoterpenoids have reported bioactivities against important pests; however, due to their high volatility, low water solubility and chemical instability, the application of these compounds has been limited. Nanosystems represent a potential vehicle for the broad application of monoterpenoids. In this study, an 1,8-cineole nanoemulsion was prepared by the low energy method of phase inversion, characterization of droplet size distribution and polydispersity index (PDI) was carried out by dynamic light scattering and stability was evaluated by centrifugation and Turbiscan analysis. Fumigant bioactivity was evaluated against Tetranychus urticae, Rhopalosiphum maidis and Bemisia tabaci. A nanoemulsion with oil:surfactant:water ratio of 0.5:1:8.5 had a droplet size of 14.7 nm and PDI of 0.178. Formulation was stable after centrifugation and the Turbiscan analysis showed no particle migration and a delta backscattering of ±1%. Nanoemulsion exhibited around 50% more bioactivity as a fumigant on arthropods when compared to free monoterpenoid. These results suggest that nanoformulations can provide volatile compounds of protection against volatilization, improving their bioactivity.

Transcriptomic Changes of Bemisia tabaci Asia II 1 Induced by Chilli Leaf Curl Virus Trigger Infection and Circulation in Its Vector.

Bemisia tabaci (Hemiptera: Aleyrodidae) is a highly efficient vector in the spread of chilli leaf curl virus (ChiLCV, Begomovirus) which is a major constraint in the production of chilli in South Asia. Transcriptome analysis of B. tabaci post-6 h acquisition of ChiLCV showed differential expression of 80 (29 upregulated and 51 downregulated) genes. The maximum number of DEGs are categorized under the biological processes category followed by cellular components and molecular functions. KEGG analysis of DEGs showed that the genes are involved in the functions like metabolism, signaling pathways, cellular processes, and organismal systems. The expression of highly expressed 20 genes post-ChiLCV acquisition was validated in RT-qPCR. DEGs such as cytosolic carboxypeptidase 3, dual-specificity protein phosphatase 10, 15, dynein axonemal heavy chain 17, fasciclin 2, inhibin beta chain, replication factor A protein 1, and Tob1 were found enriched and favored the virus infection and circulation in B. tabaci. The present study provides an improved understanding of the networks of molecular interactions between B. tabaci and ChiLCV. The candidate genes of B. tabaci involved in ChiLCV transmission would be novel targets for the management of the B. tabaci-begomovirus complex.

Topical Spray of dsRNA Induces Mortality and Inhibits Chilli Leaf Curl Virus Transmission by Bemisia tabaci Asia II 1.

Chilli leaf curl virus (ChiLCV; genus: Begomovirus), transmitted by Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in a persistent-circulative manner, is a major constraint in chilli production. The present study demonstrates for the first time that a topical spray of naked double-stranded RNA (dsRNA) on chilli plants causes mortality and inability to acquire and transmit ChiLCV in B. tabaci. dsRNA targeting heat shock protein 70 (hsp70) and fasciclin 2 (fas2) of B. tabaci Asia II 1 was first assessed under controlled conditions through oral delivery. Hsp70 and fas2 dsRNA resulted in up to 82.22% and 72% mortality of B. tabaci and around 12.4- and 8.5-fold decreases in mRNA levels, respectively, 24 h post-ingestion. ChiLCV copies in hsp70 dsRNA-fed B. tabaci steadily decreased with an increase in dsRNA concentration and were undetectable at a higher concentration of dsRNA. However, ChiLCV copies significantly increased in fas2 dsRNA-fed B. tabaci. Transmission of ChiLCV by B. tabaci was completely inhibited post-24 h feeding on hsp70 dsRNA at 3 µg/mL. Naked hsp70 dsRNA was topically sprayed on ChiLCV-infected chilli plants like an insecticide. 67.77% mortality of B. tabaci, 4.6-fold downregulation of hsp70 mRNA, and 1.34 × 1015-fold decreased ChiLCV copies in B. tabaci were recorded when adults were exposed to the dsRNA-treated plants under semi-field conditions. Foliar application of naked dsRNA reduced the ChiLCV transmission by 75% without any visible symptoms in the inoculated plants. A total of 2 consecutive sprays of dsRNA provided significant protection to B. tabaci for up to 20 days under semi-field conditions.

Transovarial Transmission of Dolichos Yellow Mosaic Virus by Its Vector, Bemisia tabaci Asia II 1.

The cultivation of dolichos bean [Lablab purpureus (L.) Sweet] has been severely affected by dolichos yellow mosaic virus (DoYMV, Begomovirus) transmitted by whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae). We tested the transovarial transmission of DoYMV in next-generation B. tabaci by PCR, real-time PCR, Southern blot hybridization, and biological transmission. The eggs, laid by DoYMV-exposed B. tabaci, carry the virus in a unique pattern. Only the eggs laid in between 3 and 6 days post virus acquisition by a parent B. tabaci were DoYMV positive. When tested individually in real-time PCR, around 31-53% of the eggs carried the virus. The presence of DoYMV in ovaries and F1 eggs was further substantiated by the hybridization of a Cy3-conjugated nucleic acid probe complementary to the viral strand of DoYMV. Viral DNA was also detected in F1 adults and F2 eggs. B. tabaci progenies carried not only the DoYMV DNA but were also infective. The F1 adults transmitted DoYMV to all tested plants and produced strong yellow mosaic symptoms. An increase in viral copies from egg to nymphal stage indicated propagation of DoYMV in B. tabaci. However, the increase was for a short period and decreased thereafter. The present study provides the first evidence of transovarial transmission and propagation of a bipartite begomovirus in its vector, B. tabaci Asia II 1. The transovarial transmission and replication of DoYMV in B. tabaci have great epidemiological relevance as B. tabaci can serve as a major host of the virus to bridge the gap between the cropping seasons.

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.

Susceptibility of All Nymphal Stages of Bemisia tabaci Biotype B (Hemiptera: Aleyrodidae) to Three Brazilian Isolates of Cordyceps sp. (Hypocreales: Cordycipitaceae) in a Screenhouse Under Variable Temperature and Moisture Conditions.

The susceptibility of 1st to 4th instars of Bemisia tabaci (Gennadius, 1989) (Hemiptera: Aleyrodidae) to three isolates of Cordyceps sp. (Hypocreales: Cordycipitaceae) was evaluated in screenhouse experiments under variable temperatures and moisture conditions. No differences in susceptibility to the Cordyceps sp. isolates were observed among 1st, 2nd, and 3rd instar nymphs with respect to median lethal time (LT50) values. Confirmed mortalities ranged from 63.7 to 87.8% when the isolates were tested at 5 × 107 conidia mL-1. The 4th instar was the least susceptible to the fungal isolates (≤ 36.6% mortality). However, 60.0 to 99.5% of the adults that emerged from 4th instar nymphs previously treated with the fungus succumbed to the infection. Temperature was more detrimental to Cordyceps sp. virulence towards B. tabaci nymphs than relative humidity (RH). At similar RH, median LT50 for 1st instar (9.4 days) was higher than for 3rd instar (5.3 days) when the fungus was tested at 5 × 107 conidia mL-1; minimal temperatures of ≥ 12.6°C compared to ≥ 17.0°C were registered for experiments with 1st and 3rd instars, respectively. However, temperatures ≥ 35°C for 4 to 6 h daily did not affect the efficacy of the fungus against nymphs. Cordyceps sp. showed high virulence to all life stages of B. tabaci at relatively low RH, and an ability to grow extensively over the leaf surface and to produce high amounts of conidia on infected hosts. These attributes certainly boost its potential as an important pest control component of B. tabaci biotype B, especially for management of populations resistant to synthetic insecticides.

Can Generalist Predators Control Bemisia tabaci?

The whitefly, Bemisia tabaci, has developed resistance to many insecticides, renewing interest in the biological control of this global pest. Generalist predators might contribute to whitefly suppression if they commonly occur in infested fields and generally complement rather than interfere with specialized natural enemies. Here, we review literature from the last 20 years, across US cropping systems, which considers the impacts of generalist predators on B. tabaci. Laboratory feeding trials and molecular gut content analysis suggest that at least 30 different generalist predator species willingly and/or regularly feed on these whiteflies. Nine of these predators appear to be particularly impactful, and a higher abundance of a few of these predator species has been shown to correlate with greater B. tabaci predation in the field. Predator species often occupy complementary feeding niches, which would be expected to strengthen biocontrol, although intraguild predation is also common and might be disruptive. Overall, our review suggests that a bio-diverse community of generalist predators commonly attacks B. tabaci, with the potential to exert substantial control in the field. The key challenge will be to develop reduced-spray plans so that generalist predators, and other more specialized natural enemies, are abundant enough that their biocontrol potential is realized.

Induced Tomato Resistance Against Bemisia tabaci Triggered by Salicylic Acid, ß-Aminobutyric Acid, and Trichoderma.

Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biotype B is a key pest of Solanum lycopersicum L. (Solanaceae) throughout the world. In this study, we examined the induction of resistance on tomato plants treated with SA, BABA, and Trichoderma either individually or in combination against B. tabaci biotype B through the assessment of some biological and behavioral aspects of this insect pest. Also, to understand the mode of action of these inducers, we correlated and analyzed the biochemical basis of plant resistance, by measuring levels of polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), and phenolic content in leaves of treated tomato plants. The longest development time of whitefly immature stages was recorded for plants treated with root ß-aminobutyric acid application (RBABA) + root Trichoderma application (RT), root salicylic acid application (RSA) + RT, and RT. In a free-choice assay, B. tabaci adults showed a significantly lower preference for settling and oviposition in RBABA + RT, RSA + RT, and RT in comparison with control. In a no-choice assay, B. tabaci females laid significantly fewer eggs on treatments than those in control, with better results observed in RBABA + RT. Plants responded to different treatments and showed higher induction of PPO, POD, and PAL activities, besides the higher accumulation of phenols in RBABA + RT, RSA + RT, and RT treatments. These results suggest that RBABA + RT, RSA + RT, and RT could be utilized for the induction of effective plant defense against B. tabaci.

Infection by the semi-persistently transmitted Tomato chlorosis virus alters the biology and behaviour of Bemisia tabaci on two potato clones.

Insect-borne plant viruses usually alter the interactions between host plant and insect vector in ways conducive to their transmission ('host manipulation hypothesis'). Most studies have tested this hypothesis with persistently and non-persistently transmitted viruses, while few have examined semi-persistently transmitted viruses. The crinivirus Tomato chlorosis virus (ToCV) is semi-persistently transmitted virus by whiteflies, and has been recently reported infecting potato plants in Brazil, where Bemisia tabaci Middle East Asia Minor 1 (MEAM1) is a competent vector. We investigated how ToCV infection modifies the interaction between potato plants and B. tabaci in ways that increase the likelihood of ToCV transmission, in two clones, one susceptible ('Agata') and the other moderately resistant (Bach-4) to B. tabaci. Whiteflies alighted and laid more eggs on ToCV-infected plants than mock-inoculated plants of Bach-4. When non-viruliferous whiteflies were released on ToCV-infected plants near mock-inoculated plants, adults moved more intensely towards non-infected plants than in the reverse condition for both clones. Feeding on ToCV-infected plants reduced egg-incubation period in both clones, but the egg-adult cycle was similar for whiteflies fed on ToCV-infected and mock-inoculated plants. Our results demonstrated that ToCV infection in potato plants alters B. tabaci behaviour and development in distinct ways depending on the host clone, with potential implications for ToCV spread.

Antibiosis and antixenosis resistance to oviposition by Bemisia tabaci (Gennadius) B biotype (Hemiptera: Aleyrodidae) in soybean genotypes / Antibiose e antixenose para oviposição da Bemisia tabaci (Gennadius) Biótipo B (Hemiptera: Aleyrodidae) em genótipos de soja

This study was aimed at assessing some biological parameters of Bemisia tabaci B biotype at immature stages to examine antibiosis in six soybean genotypes, besides antixenosis resistance to oviposition in choice and non-choice tests, under greenhouse and laboratory conditions. Between April 2016 and August 2016, bioassays were carried out at the Laboratory of Applied Entomology at College of Agricultural Sciences at Federal University of Grande Dourados (UFGD) Dourados (MS), Brazil. The following variables were evaluated: egg incubation period, nymphal and egg-to-adult duration, egg and nymph viability, and egg-to-adult survival on the soybean genotypes 68i70 RSF IPRO, M6210 IPRO, MS 947 IPRO, BMX Potência RR, M6410 IPRO, and ANTA 82 RR. Antixenosis resistance to oviposition by the silverleaf whitefly was found for MS 947 IPRO, while oviposition was highest for ANTA 82 RR, M6210 IPRO, and M6410 IPRO. The genotype MS 947 IPRO adversely affected egg and nymph viability, and egg-to-adult survival rates was the lowest among genotypes (59.75%), suggesting antibiosis resistance to this pest.(AU)

Este trabalho teve por objetivo avaliar a antibiose em seis genótipos de soja da Bemisia tabaci biótipo B mediante alguns parâmetros biológicos das fases imaturas do inseto, assim como analisar a resistência do tipo antixenose para oviposição em testes com e sem chance de escolha, em laboratório e casa de vegetação. Os ensaios foram conduzidos no Laboratório de Entomologia Aplicada da Faculdade de Ciências Agrárias da Universidade Federal da Grande Dourados (UFGD), Dourados (MS), entre os meses de abril e agosto de 2016. As variáveis averiguadas foram: período de incubação dos ovos; período ninfal; duração de ovo a adulto; viabilidade de ovo; viabilidade de ninfa e sobrevivência de ovo a adulto. Os genótipos de soja avaliados foram: 68i70 RSF IPRO, M6210 IPRO, MS 947 IPRO, BMX Potência RR, M6410 IPRO e ANTA 82 RR. O genótipo que apresentou antixenose para oviposição da mosca-branca foi o MS 947 IPRO, e constatou-se que o maior número de postura foi realizado nos genótipos ANTA 82 RR, M6210 IPRO e M6410 IPRO. O genótipo MS 947 IPRO também afetou negativamente a viabilidade de ovos e ninfas, bem como a sobrevivência de ovo a adulto, com as menores porcentagens de sobrevivência (59,75%), indicando possível resistência do tipo antibiose à mosca-branca.(AU)

Feasible sampling plan for Bemisia tabaci control decision-making in watermelon fields.

BACKGROUND: The silverleaf whitefly Bemisia tabaci is one of the most important pests of watermelon fields worldwide. Conventional sampling plans are the starting point for the generation of decision-making systems of integrated pest management programs. The aim of this study was to determine a conventional sampling plan for B. tabaci in watermelon fields. RESULTS: The optimal leaf for B. tabaci adult sampling was the 6th most apical leaf. Direct counting was the best pest sampling technique. Crop pest densities fitted the negative binomial distribution and had a common aggregation parameter (Kcommon ). The sampling plan consisted of evaluating 103 samples per plot. This sampling plan was conducted for 56 min, costing US$ 2.22 per sampling and with a 10% maximum evaluation error. CONCLUSIONS: The sampling plan determined in this study can be adopted by farmers because it enables the adequate evaluation of B. tabaci populations in watermelon fields (10% maximum evaluation error) and is a low-cost (US$ 2.22 per sampling), fast (56 min per sampling) and feasible (because it may be used in a standardized way throughout the crop cycle) technique. © 2017 Society of Chemical Industry.

Performance of Bemisia tabaci Biotype B on Soybean Genotypes.

Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) has been recognized as an important pest of many agricultural systems including soybean [Glycine max (L.) Merrill] crops. As an alternative to chemical control, the use of resistant genotypes represents an important tool for integrated pest management (IPM). This study aimed to evaluate the biological development of Bemisia tabaci biotype B confined on 13 soybean genotypes under greenhouse conditions. Initially, the nymphal period, complete development period (egg-adult), and the viability of the silverleaf whitefly nymphs were evaluated in all genotypes. Then, four genotypes promising for resistance ('Jackson,' UX-2569-159, 'P98Y11,' and 'TMG132 RR') and a susceptible genotype (PI-227687) were selected for further assays, where two insect populations were compared: a first population from the initial rearing (cabbage plants) and another corresponding to insects previously reared out on the selected genotypes. In addition to the parameters evaluated in preliminary tests, we also determined the viability and incubation period of eggs. Moderate levels of resistance (antibiosis/antixenosis) to B. tabaci biotype B were found in three genotypes. 'P98Y11' and 'TMG132 RR' were less suitable for insect development, extending the development cycle, and UX-2569-159 caused high nymphal mortality. We did not observe a significant increase in the level of plant resistance by the use of previously stressed insects. This suggests that the evaluation of a single whitefly generation may be sufficient to make correct decisions on promising soybean genotypes.

Lethal and Inhibitory Activities of Plant-Derived Essential Oils Against Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) Biotype B in Tomato.

The silverleaf whitefly Bemisia tabaci (Genn.) biotype B (Hemiptera: Aleyrodidae) is one of the most severe tomato pests in the world. The damage caused by this insect may compromise up to 100% of crop production, and management of this pest has relied on spraying of synthetic insecticides. However, due to the environmental issues associated with this practice, alternative methods such as the use of botanical pesticides are now used as a strategy of integrated pest management (IPM). We evaluated the effects of essential oils of five plant species on B. tabaci biotype B in tomato and demonstrate that the essential oils (0.5%) of Piper callosum (PC-EO), Adenocalymma alliaceum (AA-EO), Pelargonium graveolens (PG-EO), and Plectranthus neochilus (PN-EO) inhibit the settlement and oviposition of B. tabaci biotype B adults in tomato plants. In fumigation tests, A. alliaceum (AA-EO) at 0.4 µL/L of air after 72 h and 0.1 µL/L of air after 6 h was the most effective against nymphs and adults of B. tabaci biotype B, respectively. The major chemical constituents of PC-EO were identified as being safrole (29.3%), α-pinene (19.2%), and ß-pinene (14.3%), whereas diallyl trisulfide (66.9%) and diallyl disulfide (23.3%) were the major compounds identified in AA-EO. This is the first report on the reduction of oviposition by the use of P. callosum (PC-EO) and A. alliaceum (AA-EO). In addition, the fumigant effect of A. alliaceum (AA-EO) on nymphs and adults has also been reported here for the first time.

Use of lablab (Lablab purpureus (L.) Sweet) for bio-control by native arthropods and its effect on yield of pumpkins.

Silverleaf whitefly (SLW, Bemisia tabaci MEAM1) and aphids are sap-sucking insects, which pose a serious threat to Australian cucurbit crops and the horticulture industry. Traditional chemical control for these insect pests is becoming less effective, and there is a need to search for alternative or supplementary methods. This study aimed to manipulate the habitat of pumpkin crops in a tropical setting (Queensland, Australia), by growing pumpkins (var. Japanese pumpkin) alone and between lablab (Lablab purpureus L. Sweet). It was hypothesized that the presence of lablab will increase the populations of natural enemies, and through their control of insect pests such as SLW and aphids, will affect pumpkin yield. The population of arthropods (natural enemies and pests of pumpkin), with a focus on SLW and aphids, were sampled weekly on both lablab and pumpkin crop for a total of 21 weeks. Results showed that lablab hosted more enemies of SLW per plant than pumpkin in either treatment. In addition, adult SLW numbers were significantly higher in the pumpkin-only crop compared with the pumpkin grown between lablab, while pumpkin in the mixed plantings had significantly more ladybirds and lacewing larvae (P < 0.05). While there was no significant difference in the average fruit weight between treatments, the total weight (kg) and number of marketable pumpkins per hectare was greater (P < 0.05) for the pumpkin/lablab treatment than the pumpkin-only treatment. This study shows that growing lablab alongside a pumpkin crop may enhance natural enemies of SLW and could significantly increase the yield.

Potential of Five Brazilian Populations of Phytoseiidae (Acari) for the Biological Control of Bemisia tabaci (Insecta: Hemiptera).

Biotype B of the whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), causes considerable losses to growers worldwide. Phytoseiid mites have been successfully used for the control of this pest in several countries. The Brazilian phytoseiid fauna is very diverse and potentially useful for this purpose. The aim of this study was to evaluate five Brazilian populations of phytoseiids as candidates for the control of the whitefly, a serious pest of different crops worldwide. Evaluated species were Amblydromalus limonicus (Garman & McGregor), Amblyseius herbicolus (Chant), Amblyseius largoensis (Muma), Amblyseius tamatavensis (Blommers), and Neoseiulus tunus (De Leon), which are found naturally in Brazil and elsewhere. The work was conducted at 28±1°C, 75±10% relative humidity, and a photoperiod of 12:12 (L:D) h. All evaluated phytoseiids preyed on eggs of B. tabaci, with the highest levels of predation recorded for Am. herbicolus and N. tunus, and highest level of oviposition recorded for Am. tamatavensis. The results show the Brazilian populations of those three species to be promising as control agents of B. tabaci. Aleuroglyphus ovatus (Troupeau) (Acari: Acaridae) was found to be a suitable prey for the mass production of those predators. Complementary studies are considered justified, given the positive results of this study.

Potential of two populations of Amblyseius swirskii (Acari: Phytoseiidae) for the control of Bemisia tabaci biotype B (Hemiptera: Aleyrodidae) in Brazil.

Predatory mites of the family Phytoseiidae are commercialized in European and North American countries for the control of whiteflies (Insecta: Aleyrodidae). Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) is one of the predators used for that purpose. This predator is not found in Brazil and in many other countries, but its introduction could promote biological control of Bemisia tabaci (Gennadius) biotype B (silverleaf whitefly) in those countries. The aim of this study was to compare two populations of A. swirskii as predators of eggs of B. tabaci of two different ages, as well as the acceptance of those populations for other food types [eggs of Tetranychus urticae Koch; larvae and protonymphs of Aleuroglyphus ovatus (Troupeau) (Astigmatina: Acaridae) and cattail pollen (Typha domingensis Persoon)]. One of the populations of A. swirskii was collected in the Republic of Benin, in tropical Africa, and the other was commercially available in The Netherlands. The comparison was done to evaluate the population with better potential for practical use, and to determine food types that could be used for mass rearing the predator. Experiments were conducted at 28 ± 1 °C, 80 ± 10 % relative humidity and 12 h photophase. Both populations were able to oviposit when fed eggs of B. tabaci, but the Netherlands population showed higher oviposition rate (2.3 and 1.6 times higher on young and older eggs, respectively). Higher predation rates were observed for eggs up to 24 h of age in comparison with older eggs. Aleuroglyphus ovatus proved to be a promising prey for possible mass rearing of this predator in Brazil, where that astigmatic mite is found naturally when pollen was used as food, no significant difference was observed for oviposition rate between populations. The results suggested a higher potential of the Netherlands population of A. swirskii for the control of B. tabaci biotype B in this country for augmentative biological control, with the possible use of A. ovatus as food for the mass production and pollen of T. domingensis as a food supplement for this predator in practical field releases.

Generating Within-Plant Spatial Distributions of an Insect Herbivore Based on Aggregation Patterns and Per-Node Infestation Probabilities.

Most predator-prey models extrapolate functional responses from small-scale experiments assuming spatially uniform within-plant predator-prey interactions. However, some predators focus their search in certain plant regions, and herbivores tend to select leaves to balance their nutrient uptake and exposure to plant defenses. Individual-based models that account for heterogeneous within-plant predator-prey interactions can be used to scale-up functional responses, but they would require the generation of explicit prey spatial distributions within-plant architecture models. The silverleaf whitefly, Bemisia tabaci biotype B (Gennadius) (Hemiptera: Aleyrodidae), is a significant pest of tomato crops worldwide that exhibits highly aggregated populations at several spatial scales, including within the plant. As part of an analytical framework to understand predator-silverleaf whitefly interactions, the objective of this research was to develop an algorithm to generate explicit spatial counts of silverleaf whitefly nymphs within tomato plants. The algorithm requires the plant size and the number of silverleaf whitefly individuals to distribute as inputs, and includes models that describe infestation probabilities per leaf nodal position and the aggregation pattern of the silverleaf whitefly within tomato plants and leaves. The output is a simulated number of silverleaf whitefly individuals for each leaf and leaflet on one or more plants. Parameter estimation was performed using nymph counts per leaflet censused from 30 artificially infested tomato plants. Validation revealed a substantial agreement between algorithm outputs and independent data that included the distribution of counts of both eggs and nymphs. This algorithm can be used in simulation models that explore the effect of local heterogeneity on whitefly-predator dynamics.

Liquid culture fermentation for rapid production of desiccation tolerant blastospores of Beauveria bassiana and Isaria fumosorosea strains.

A major constraint to the commercial use of fungal biocontrol agents is the availability of low-cost production media and processes. Previous attempts in producing Beauveria blastospores using liquid culture fermentation processes required long fermentation times (6-8days) and produced cells that had poor survival after desiccation and storage. In this study, isolates of Beauveria bassiana and Isaria fumosorosea were evaluated for blastospore yield, desiccation tolerance, storage stability, and biocontrol efficacy using fermentation media containing acid hydrolyzed casein or cottonseed flour as the nitrogen source. Cultures of B. bassiana and I. fumosorosea grown in media containing cottonseed flour produced high blastospore concentrations (>1×10(9)mL(-1)) after 3days which is comparatively less expensive nitrogen source than acid hydrolyzed casein. The resultant air-dried blastospores (<3% moisture) of all fungal isolates survived drying (61-86% viability), irrespective of the nitrogen source tested. Storage stability at 4°C varied with nitrogen source and fungal strain. Air-dried blastospores of B. bassiana strains showed half-lives >14months in contrast to 9.2-13.1months for I. fumosorosea. Blastospores of B. bassiana and I. fumosorosea killed Bemisia tabaci whitefly nymphs faster and required lower concentrations compared with aerial conidia. Our findings support the use of liquid culture fermentation as a cost-effective process to rapidly produce high yields of stable and infective blastospores of either B. bassiana or I. fumosorosea. These results support further evaluation of blastospore sprayable formulations for the control of soft-bodied insects.

Antibiose e não preferência para oviposição de Bemisia tabaci (Genn) biótipo B (Hemiptera: Aleyrodidae) em genótipos de feijoeiro comum / Antibiosis and non preference for the oviposition of Bemisia tabaci (Genn) biotype B (Hemiptera: Aleyrodidae) in common bean genotypes

O feijoeiro comum, Phaseolus vulgaris L., constitui importante fonte de proteína e renda para muitos países, entre eles, o Brasil. Diferentes fatores contribuem para a redução da produção, como os insetos pragas, destacando-se Bemisia tabaci (Genn.) biótipo B. O presente trabalho teve por objetivo identificar genótipos de feijoeiro comum resistentes à B. tabaci biótipo B e os tipos de resistência envolvidos. Para isso, foram realizados dois experimentos desenvolvidos em laboratório e em casa-de-vegetação, avaliando-se 11 genótipos de feijoeiro comum. Para o teste com chance de escolha, o delineamento utilizado foi o de blocos casualizados, e para os testes sem chance de escolha e antibiose, a escolha foi pelo inteiramente casualizado, totalizando seis repetições para cada teste. As variáveis avaliadas foram: período de incubação dos ovos; período ninfal; período de ovo a adulto; viabilidade de ovo a adulto e longevidade de adultos. O genótipo IAC-Harmonia prolongou os períodos ninfal e de ovo a adulto de B. tabaci biótipo B. Os genótipos testados foram igualmente ovipositados pela mosca-branca, em testes com e sem chance de escolha.(AU)

The common bean Phaseolus vulgaris L. constitutes an important source of protein and income for many countries, including Brazil. Different factors contribute with the reduction in production, including pest insects, especially Bemisia tabaci (Genn.) biotype B. This study aimed to identify common bean genotypes resistant to B. tabaci biotype B and the types of resistance involved. Therefore, two experiments were developed in a greenhouse and laboratory, evaluating 11 common bean genotypes. To test the free-choice experimental design, the randomized block design was adopted, and the completely randomized one was selected for the no-choice tests and antibiosis, with six replications for each test. The following variables were evaluated: incubation period of eggs; nymphal; egg to adult; viability of egg to adult and adult longevity. The IAC-Harmony prolonged the nymphal and egg to adult periods of B. tabaci biotype B. The genotypes were also tested by the whitefly oviposition in free and no choice tests.(AU)