Tabaci Nymphs Research Articles

Effect of entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, on Thrips tabaci Lindeman (Thysanoptera: Thripidae) populations in different onion cultivars

BackgroundThrips tabaci Lindeman (Thysanoptera: Thripidae) is the key pest of onions that causes economic yield losses in commercial onion production in Pakistan. In this study, potential of the entomopathogenic fungi (EPF), Beauveria bassiana and Metarhizium anisopliae, as a bio agent was evaluated to manage buildup of thrips population on onion crop.ResultsEfficacy tests for EPF were conducted against T. tabaci infesting 3 different onion varieties (Phulkara, Swat 1, and Virio 7). Commercial formulations of B. bassiana strain GHA and M. anisopilae strain ESC-1, were evaluated at 4 different concentrations (108, 109, 1010, and 1011 conidia/ml) under field conditions for 2 years. The efficacy was assessed 3, 5, 7, and 10 days after spray application of the whole onion plant. Efficacy expressed as T. tabaci (nymphs and adults) percent population reduction in comparison to controls. Maximum corrected percent population reduction was observed in onion plants treated with B. bassiana 1011 conidia/ml, i.e., 86.62, 84.59, and 86% in Phulkara, Swat 1, and Virio 7 onion varieties respectively, after 10 days of spray application. While onion plants treated with M. anisopliae 108 conidia/ml showed minimum corrected percent population reduction, i.e., 69.42, 68.45, and 69.11% in Phulkara, Swat 1, and Virio 7 onion varieties respectively, after 10 days of spray.ConclusionsBeauveria bassiana could significantly reduce thrips population and could provide a better long-term management of T. tabaci on onion. B. bassiana had a high toxic effect against offspring production of the T. tabaci under field conditions than M. anisopliae.

Functional Response and Predation Rate of Dicyphus cerastii Wagner (Hemiptera: Miridae).

Simple SummaryBiological control (BC) is an effective way to regulate pest populations in horticultural crops, allowing the decrease of pesticide usage. On tomato, predatory insects like plant bugs or mirids provide BC services against several insect pests. Native predators are adapted to local conditions of climate and ecology and therefore may be well suited to provide BC services. Dicyphus cerastii is a predatory mirid that is present in the Mediterranean region and occurs in tomato greenhouses in Portugal. However, little is known about its contribution to BC in this crop. In this study, we evaluated how prey consumption is affected by increasing prey abundance on four different prey, in laboratory conditions. We found that the predator can increase its predation rate until a maximum is reached and that prey characteristics like size and mobility can affect predation. Dicyphus cerastii showed high predation rates for all prey species tested, allowing us to conclude that this species is an interesting predator for BC in tomato crops.Dicyphine mirids are important biological control agents (BCAs) in horticultural crops. Dicyphus cerastii Wagner can be found in protected tomato crops in Portugal, and has been observed feeding on several tomato pests. However, the predation capacity of this species is poorly studied. In order to investigate the predation capacity of D. cerastii, and how it is affected by prey size and mobility, we evaluated the functional response (FR) and predation rate of female predators on different densities of four prey species: Myzus persicae 1st instar nymphs (large mobile prey), Bemisia tabaci 4th instar nymphs, Ephestia kuehniella eggs (large immobile prey) and Tuta absoluta eggs (small immobile prey). Experiments were performed on tomato leaflets in Petri dish arenas for 24 h. Dicyphus cerastii exhibited type II FR for all prey tested. The predator effectively preyed upon all prey, consuming an average of 88.8 B. tabaci nymphs, 134.4 E. kuehniella eggs, 37.3 M. persicae nymphs and 172.3 T. absoluta eggs. Differences in the FR parameters, attack rate and handling time, suggested that prey size and mobility affected predation capacity. Considering the very high predation rates found for all prey species, D. cerastii proved to be an interesting candidate BCA for tomato crops.

Virulence of Five Isolates of Indigenous Beauveria Bassiana Against Eggs and Nymphs of Bemisia Tabaci Gennadius (Hemiptera: Aleyrodidae)

This research aims to study the virulence of five isolates of Beauveria bassiana to eggs and nymphs of Bemisia tabaci on tomato. In the experiment eggs and second instar nymphs of B. Tabaci were used. Five isolates of the fungus, i.e., WS, TD312, PD114, PA221, PB211, were tested. Conidial concentration of B. bassiana used were 108 conidia/ml. Experimental parameters included mortality of eggs and nymph and percentage of adult emergence. The results showed that all B. bassiana isolates tested were able to kill B. tabaci eggs but with very low mortality (2-19%). Mortality of second instar B. tabaci nymphs was dependent on the fungal isolates. Isolate WS had the highest virulence, which caused 70% mortality of 2nd instar nymphs, with a LT50 of 4.87 days. Nymphs of B. tabaci were highly susceptible to B. bassiana infection compared with eggs. B. bassiana applicated to nymphs of B. tabaci can decrease the percentage of adult emergence.

Predacious Effect of Some Predatory Mites on Thrips tabaci Lindeman (Thysanoptera: Thripidae) Infesting Rogina Tomato Hybrid

Thrips is a harmful cosmopolitan polyphagous pest with marked serious and adverse effects on over 200 host plants, it infests tomatoes, sucking and destroying its seedlings. This study was carried out in a Rogina tomato hybrid field in three governorates, El-Beheira, El-Faiyum and El-Sharqia, in Egypt. In order to evaluate the efficacy of five predatory mites (Mesostigmata: Phytoseiidae) namely; Typhlodrompis swirskii, Phytoseiulus persimilis, Neoseiulus cucumeris, Typhlodromus nigavi and Neoseiulus californicus as well as the recommended combination (abamectin + Egyxide oil) as standard insecticide (1 ml + 2.5 ml/l) separately or combined with each other against Thrips tabaci nymphs and adults. The current study indicated that the single treatment with T. swirskii and N. cucumeris as well as the recommended combination (abamectin + Egyxide oil) were the most efficient as a bioagent control against T. tabaci in tomato plants in all three governorates, followed by T. nigavi, whereas P. persimilis and N. californicus has no role as a biocontrol agent for T. tabaci in single treatment compared with control. Moreover, alternately using predatory T. swirskii in combination with other predators (N. cucumeris, T. nigavi and N. californicus) showed significant reductions (95.8–99.95 %) in T. tabaci populations without any incompatibility or competition between each other compared with control in all three governorates (LSD: 3.46, indicated that there is no significant difference between treatments in all governorates). In general, the reduction effect of all treatments in El-Faiyum was decreased more than the other two governorates. This study demonstrated that T. tabaci in tomato can be reduced by using T. swirskii and N. cucumeris singly or alternately mixing with other predators mentioned above. In the light of these results, the T. swirskii and N. cucumeris singly or alternately should be considered when deciding on the timing of abamectin applications within IPM strategies.

Genome-Wide Identification and Analysis of Chitinase-Like Gene Family in Bemisia tabaci (Hemiptera: Aleyrodidae).

Simple SummaryFor the sake of growth and development, old exuviums of Bemisia tabaci nymphs should be periodically substituted by new ones until a final emergence turns them into adults. During ecdysis, chitinases are of great importance in chitin degradation and turnover of cuticles, which provides us potential targets for RNA interference-based B. tabaci management. Therefore, we annotated 14 chitinase and chitinase-like genes in B. tabaci based on data of genome and transcriptomes. With the help of a nanomaterial-promoted RNAi method, we found that silencing of BtCht10, BtCht5, and BtCht7 resulted in significant increase of death rate on B. tabaci nymphs and the developmental duration was noticeably postponed for BtCht2-silenced nymphs.Chitinases are of great importance in chitin degradation and remodeling in insects. However, the genome-wide distribution of chitinase-like gene family in Bemsia tabaci, a destructive pest worldwide, is still elusive. With the help of bioinformatics, we annotated 14 genes that encode putative chitinase-like proteins, including ten chitinases (Cht), three imaginal disk growth factors (IDGF), and one endo-β-N-acetylglucosaminidase (ENGase) in the genome of the whitefly, B. tabaci. These genes were phylogenetically grouped into eight clades, among which 13 genes were classified in the glycoside hydrolase family 18 groups and one in the ENGase group. Afterwards, developmental expression analysis suggested that BtCht10, BtCht5, and BtCht7 were highly expressed in nymphal stages and exhibit similar expression patterns, implying their underlying role in nymph ecdysis. Notably, nymphs exhibited a lower rate of survival when challenged by dsRNA targeting these three genes via a nanomaterial-promoted RNAi method. In addition, silencing of BtCht10 significantly resulted in a longer duration of development compared to control nymphs. These results indicate a key role of BtCht10, BtCht5, and BtCht7 in B. tabaci nymph molting. Our research depicts the differences of chitinase-like family genes in structure and function and identified potential targets for RNAi-based whitefly management.

Isolation, characterization, and bio-insecticidal efficiency of Ethiopian isolates of Bacillus thuringiensis against Galleria mellonella L. (Lepidoptera: Pyralidae) and tomato whitefly, Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae)

BackgroundBacillus thuringiensis is a Gram-positive, rod-shaped, and spore-forming microbial entomopathogen. The silverleaf whitefly, Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae), is a worldwide important cryptic species causing serious economic damage to several vegetable crops including tomato. The aim of this study was to characterize and evaluate the bio-insecticidal effects of locally isolated Bacillus thuringiensis (Bt) against Galleria mellonella and Bemisia tabaci.ResultsThirty-one isolates of Bt were obtained from 70 soil samples based on cultural characterization coupled with insecticidal crystal protein detection. All of the 31 bacterial isolates were pre-screened for their bio-insecticidal property against the greater wax moth, Galleria mellonella L. larvae. Only 20 (64.5%) isolates were virulent to G. mellonella with a percentage mortality that ranged from 2.50 to 95%. The groEL gene sequences of all 20 entomopathogenic indigenous isolates displayed 99–100% similarity with Bt isolates. Bioassay evaluation of 12 selected isolates against 3rd to 4th nymphal instars of B. tabaci with spore-crystal suspensions of 1 × 109 spores/ml caused 0 to 31.25%, 0 to 57%, and 0 to 82.5% percentage mortality within 48, 96, and 144 h accordingly. Among isolates of Bt, isolate AAUDS-16 had the highest virulence, followed by the isolate AAUES-69D with LC50 values of 9.67 × 106 spores/ml and 1.16 × 107 spores/ml, respectively. The virulent isolates were tested for their growth response to a different temperature range between 15 and 40 °C. All isolates showed a maximum growth rate around 30 °C.ConclusionsBt isolates of AAUES-69D and AAUDS-16 displayed high insecticidal potential against B. tabaci nymphs and G. mellonella larvae, and showed a maximum growth rate in a wide range of temperature. High virulence and temperature-tolerant isolates should be important candidates for diverse insecticidal toxin studies.

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 (9.4days) was higher than for 3rd instar (5.3days) 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 6h 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.

Simplified insecticide toxicity determination method for Nesidiocoris tenuis using contaminated diet

Nesidiocoris tenuis is a zoophytophagous mirid bug widely studied for its role in preying on major greenhouse pests. Since N. tenuis has now been known for its vigorous predation potential on pests such as Bemisia tabaci, many applied entomologists are now recommending that N. tenuis be merged into the Integrated Pest management (IPM) systems. However, successful integration of N. tenuis into any IPM system depends on thorough evaluation with compatible pesticides, as incompatible pesticides can offset the whole idea of IPM. Here, we simulate the field situation where N. tenuis feeds directly on a contaminated B. tabaci nymph or leaves. However, instead of using live B. tabaci nymphs, we used brine shrimp eggs, Artemia salina (Linnaeus, 1758). Brine shrimp eggs have been reported to be an excellent factitious supplementary diet in augmenting N. tenuis populations. Thus, we use brine shrimp eggs to determine the toxicity of pesticides, to which the calculated mortality rates can be used to determine which pesticides can be used together with N. tenuis in an IPM system against any related pest.•We developed a customized containment system that promotes aeration and minimize contamination.•Pesticide contaminated hatched brine shrimp eggs is delivered to N. tenuis in the aerated containment system.•In addition to established methods such as leaf dipping or insect dipping, this method shows to mimic N. tenuis feeding on contaminated B. tabaci nymphs in field conditions thus, predicts how a pesticide may be of toxic or compatible with N. tenuis when both are integrated together.

Evidence for coabundance of leafminer flies and whiteflies in melon crops

ABSTRACT Interspecific competitions are important mechanisms in structuring ecological communities, including agroecosystems, in which different species may share the same food resource. In melons, two major pests coexist in time and space, Liriomyza sativae Blanchard (Diptera: Agromyzidae) and Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). The former feeds on the leaf mesophyll, while the latter on the phloem sap. Therefore, the same niche exploitation can trigger interactive processes between both populations. The present research aimed to determine if there are positive or negative interactions between whiteflies and leafminers under field conditions. The experiment was conducted in four commercial melon fields in northeast Brazil in two planting seasons. Thirty random plants were weekly selected for detection of whitefly nymphs and leafminer larvae throughout the entire crop cycle. The data was organized and analyzed considering the species abundance of L. sativae (larvae) and B. tabaci (nymphs and adults) in the same plant. Thus, the coabundance of species was investigated by using regressions with Poisson errors. The results suggest different fractions of negative, positive and neutral (not significant relationships) coabundance between the two species. Among 34 significant interactions, 56% were negative, suggesting that more than half of significant interactions are due to interspecific competition with negative coabundance.

Substrate-borne vibrations reduced the density of tobacco whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) infestations on tomato, Solanum lycopersicum: an experimental assessment

Managing pests with insecticides is probably the most conventional available control method. However, insecticide overuse often results in resistance and subsequent pest resurgence, and often adversely affects the ecosystem. The physical management of insect pests by utilizing substrate-borne vibrations, sounds, or both is increasingly attracting attention as an alternative, as it has modest ecosystem impacts. This method exploits vibroacoustic insect communication used for mating and the perception of approaching enemies, provoking behavioral responses in an ingenious manner. We aimed to examine whether substrate-borne vibrations effectively drive away tobacco whiteflies [Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae)], which are serious agricultural pests. To do so, B. tabaci individuals were artificially introduced into greenhouses where tomato (Solanum lycopersicum L.) plants were reared. A substantial reduction in the average density of B. tabaci nymphs and adults was achieved by transmitting vibrational stimuli to the plants. At the same time, no obvious reduction was found in the number of tomato plant flowers. Although the performance of the vibrational device and transmission procedures requires further improvement, the present results shed light on the potential of substrate-borne vibrations as a promising alternative for pest management.

Larvas de Delphastus davidsoni Gordon (Coleoptera: Coccinellidae) predando ninfas de mosca branca

RESUMO: A couve-manteiga, Brassica oleracea L. var. acephala, Brassicaceae destaca-se por ser susceptível a diversos insetos-praga, dentre esses a ‘mosca-branca’, Bemisia tabaci Genn. (Hemiptera: Aleyrodidae). A família Coccinellidae abriga insetos com hábito predatório, contribuído no controle biológico de diversas pragas, o que permite a otimização de métodos sustentáveis ao meio ambiente. Deste modo, objetivou-se avaliar a predação das larvas de joaninha Delphastus davidsoni Gordon (Coleoptera: Coccinellidae) sobre ninfas de B. tabaci. O experimento foi conduzido em casa de vegetação e no laboratório da Universidade Estadual de Alagoas – UNEAL, Campus I, em Arapiraca- AL, durante os meses de outubro a novembro/2017. Para implantação do experimento em laboratório, foi utilizado papel filtro, algodão umedecido e um quadrante da folha da couve manteiga 3 cm2. A população de ninfas de B. tabaci foi reduzida em 82% pelas larvas de D. davidsoni. A ação dos coccinelídeos possibilitou também um declínio na população adulta em 38% da presa. Assim, as larvas de joaninhas apresentaram alto potencial significativo para o controle das ninfas do hemíptero-praga., posteriormente reduzindo o número de insetos adultos. A espécie D. davidsoni é um inseto predador promissor de B. tabaci, podendo ser indicada ao controle biológico na cultura da couve.
 PALAVRAS-CHAVE: Controle biológico. Horticultura. Monitoramento.

Studies on the within-plant distribution of whitefly, Bemisia tabaci (Gennadius) in potato and development of a sequential sampling plan

Whitefly, Bemisia tabaci (Gennadius), is a major constraint for seed potato production in India. For its efficient management, the within-plant distribution of B. tabaci was explored, and a sequential sampling plan was developed for potato crops. The highest proportion of B. tabaci adults, nymphs, and eggs was found on leaf numbers 3–7, 6–9, and 2–6, respectively (with leaf numbers beginning at the apical meristem). The count of adults from three leaves (nodes 4, 5, and 6) from the top stratum in a plant is proposed as a sample unit. Green's and Kuno's methods were used to develop fixed precision sequential sampling plans which yielded a similar average required sample size, except at lower densities (≤1 whitefly per plant). This information will enable efficient monitoring of B. tabaci.

Efficiency of certain insecticides & bio-products against Bemisia tabaci (Genn.) and Tetranychus urticae koch on potato plants under field conditions AT QALUBIA GOVERNRAT, EGYPT.

A field experiment was conducted during autumn plantation in season 2017 at Qaha, Qalubiya Governorate to evaluate the efficiency of ten different control agents; four of them are biorational components (garlic extract, rosemary oil + sunflower oil, sesame oil and chili oil), three of them are natural pesticide (Techno Oil, Top9 and Berna Star), one agent of them is bio-pesticide (bio-fly) and two chemical pesticide (Blanch 48% SC, Mospilan 20% SP) in reducing the population densities of Bemisia tabaci and Tetranychus urticae on Hatma potato cultivar. The results indicated that there were significant differences between the ten tested compounds in reducing the population density of B. tabaci nymphs; Mospilan 20% SP was the most potent compounds in reducing the population density of B. tabaci nymphs causing the highest reduction percentage (83.58 %), while Top9 gave a low effect with reduction percentage (49.32%) and Bio-fly gave moderate reduction percentage (63.92%). These compounds could be divided into two groups according to the reduction percentage: 1st group contains Mospilan 20% SP, Blanch 48% SC (chemical pesticides), Berna Star and Techno Oil (natural pesticides), respectively. 2nd group contains on Bio-fly (bio-pesticide), sesame oil, garlic extract, chili oil, rosemary oil + sunflower oil (biorational components), and Top9 (natural pesticide) on B. tabaci nymphs. Results also revealed that there were significant differences between the mean of general reduction percentage of the ten tested compounds on T. urticae population. Mospilan 20% SP recorded the highest reduction percentage (73.1 %), (rosemary oil + sunflower oil) treatment recorded the lowest reduction percentage 41.97% and Top9 gave moderate reduction percentage (60.03%). These compounds could be divided into two groups: 1st group contains on Mospilan 20% SP, Techno Oil, Blanch 48% SC, garlic extract, Top9, chili oil, sesame oil and Berna Star respectively. 2nd group contains on Bio-fly and (rosemary oil + sunflower oil) respectively

Whitefly-induced tomato volatiles mediate host habitat location of the parasitic wasp Encarsia formosa, and enhance its efficacy as a bio-control agent.

Whitefly Bemisia tabaci is a phloem-feeding insect and causes extensive agricultural damage around the world. Although the parasitic wasp Encarsia formosa is widely used to control B. tabaci on glasshouse tomatoes, low efficiency and discontinuity are frequently recorded. It has been well-documented that herbivore-induced plant volatiles (HIPVs) are important cues in the foraging behavior of the natural enemies of herbivores. However, the volatiles emitted from tomatoes infested by different developmental stages of B. tabaci (nymphs versus adults) have not been compared in terms of their effects on E. formosa attraction. Olfactometer assays with four tomato cultivars revealed that the E. formosa wasps showed a significant attraction to the volatiles from adult-infested plants (except for cv. Castlemart), but not to those from nymph-infested plants. In a close-range habitat, however, the wasps appeared to use visual or tactile cues derived from nymphs for host location. Volatile analyses and behavioral assays showed that wasp attraction was correlated with enhanced β-myrcene and β-caryophyllene emissions from adult-infested plants. Furthermore, the use of B. tabaci adult-induced plant cues under glasshouse conditions resulted in a higher parasitism rate by this parasitoid. Our findings confirm that E. formosa uses the HIPVs resulting from feeding of B. tabaci adults to locate host habitat. Release of β-myrcene and β-caryophyllene from dispensers may enhance the efficacy of E. formosa as a biological control agent against B. tabaci in glasshouse production systems.

Antagonistic interaction between male-killing and cytoplasmic incompatibility induced by Cardinium and Wolbachia in the whitefly, Bemisia tabaci.

Cardinium and Wolbachia are maternally inherited bacterial symbionts of arthropods that can manipulate host reproduction by increasing the fitness of infected females. Here, we report that Cardinium and Wolbachia coinfection induced male-killing and cytoplasmic incompatibility (CI) when they coexisted in a cryptic species of whitefly, Bemisia tabaci Asia II7. Cardinium and Wolbachia symbionts were either singly or simultaneously localized in the bacteriocytes placed in the abdomen of B. tabaci nymphs and adults. Cardinium-Wolbachia coinfection induced male-killing and resulted in a higher female sex ratio in the intraspecific amphigenetic progeny of Asia II7 ICWH and ICWL lines; interestingly, male-killing induction was enhanced with increased Cardinium titer. Moreover, single infection of Wolbachia induced partial CI in the Asia II7 IW line and resulted in reduced fecundity, higher embryonic mortality, and lower female sex ratio. The uninfected Asia II7 IU line had significantly higher fecundity, lower embryonic and nymphal mortalities, and a lower level of CI than both the Wolbachia-infected Asia II7 IW line and the Cardinium-Wolbachia-coinfected Asia II7 ICWH line. Our findings indicate that Cardinium-Wolbachia coinfection induced male-killing, which may have had antagonistic effects on Wolbachia-induced CI in the Asia II7 whiteflies. For the first time, our study revealed that B. tabaci Asia II7 reproduction is co-manipulated by Cardinium and Wolbachia endosymbionts.

The data set on vertical distribution pattern of Bemisia tabaci genn. (Homoptera: Aleyrodidae) in several vegetable crops.

Bemisia tabaci is one of the main pests of vegetable crops in the tropics, including in Indonesia. The vertical distribution pattern of B. tabaci on investigated vegetable plants can be used to establish a sample observation unit in monitoring activities of pest control management. This data showed the vertical distribution pattern of B. tabaci on vegetable plants gathered from two different locations, namely from the high land of Ciwidey District, Bandung City (string bean, kidney bean, and tomato) and the low land of Sliyeg District, Indramayu City (eggplant, towel gourd, cucumber, and long beans). The data of B. tabaci nymph population were then analyzed to determine vertical distribution patterns.

Predatory functional response and fitness parameters of Orius strigicollis Poppius when fed Bemisia tabaci and Trialeurodes vaporariorum as determined by age-stage, two-sex life table.

BackgroundThe polyphagous predatory bug O. strigicollis is an active predator used to control thrips and aphids. The whitefly species Bemisia tabaci and Trialeurodes vaporariorum are voracious pests of different economic agricultural crops and vegetables.MethodIn this study, the Holling disc equation and the age-stage, two-sex life table technique were used to investigate the functional response and biological traits of third instar nymphs and adult female O. strigicollis when presented third instar nymphs of both whitefly species as prey.ResultsThe results showed a type II functional response for each life stage of O. strigicollis when fed each whitefly species. The calculated prey handling time for different O. strigicollis life stages were shorter when fed T. vaporariorum than when fed B. tabaci nymphs. In contrast, the nymphal development of O. strigicollis was significantly shorter when fed B. tabaci than T. vaporariorum nymphs. Additionally, the total pre-oviposition period of adult females was statistically shorter when fed B. tabaci nymphs than T. vaporariorum nymphs. Furthermore, the survival rates and total fecundity of O. strigicollis were higher when fed B. tabaci than T. vaporariorum. There were no significant differences in any population parameters of O. strigicollis when fed either whitefly species. These results show that O. strigicollis could survive and maintain its populations on both species of whitefly and could therefore serve as a biological control agent in integrated pest management (IPM).

Augmentation and compatibility of Beauveria bassiana with pesticides against different growth stages of Bemisia tabaci (Gennadius); an in vitro and field approach.

Bemisia tabaci is a notorious agricultural pest that causes serious damage to many crops via herbivory and spread of viral diseases. Effective control measures are, therefore, required. Integrating entomopathogenic fungi into the chemical control system offers promise for B. tabaci management. In-vitro assays on the augmentative effect of Beauveria bassiana GHA strain with insecticides, and its compatibility with fungicides were tested. Varying egg mortality was observed for most insecticides except for milbemectin. Pyrifluquinazon was less effective against the nymphs. Flonicamid showed no insecticidal effect on either nymphs or adults. However, increased mortality in nymphs and adults was observed when flonicamid was mixed with Beauveria bassiana GHA strain. Furthermore, no significant synergistic effect of mixing pesticides with B. bassiana GHA strain was observed. Most insecticides (when not mixed with B. bassiana) showed high (>80%) mortality against B. tabaci nymphs and adults. Most fungicides tested showed no inhibitory effects on B. bassiana GHA strain against B. tabaci nymphs and adults. Fungistatic effect was observed in the mycelial and spore germination inhibition studies. Weekly rotation of some pesticides with B. bassiana GHA strain in greenhouse conditions yielded significant reduction in different growth stages of B. tabaci. However, no significant difference in viral incidence was observed. Laboratory and field tests showed positive effects of augmenting pesticides and B. bassiana GHA strain against B. tabaci nymphs and adults. Therefore, augmentation of pesticides and B. bassiana GHA strain is one prospect towards developing an effective B. tabaci IPM system. © 2020 Society of Chemical Industry.

Direct and Indirect Impact of Artemisia judaica Extract on Euseius scutalis

The potential of extract of Artemisia Judaica L. against the predator Euseius scutalis (Athias-Henriot) and two kinds of prey that fed on them, first-instar nymphs of whitefly and second instar larvae of onion thrips, The results showed that, the effect of extract on B. tabaci nymphs recorded great decline in the rate of mortality to 26.8% compared to 81.6% respectively; The same results on T. tabaci larvae were increased from 23.95% to 77% respectively, by increasing the applied concentration from 125 to 2000 ppm., while when newly emerged E. scutalis adult treated with the same concentration of extract increased total percent mortality such increase was concentration dependent. Indirect exposure technique of is more effective than the direct exposure technique. Therefore, when using the plant extract and the predator in one control program is recommended to spray the extract first and then release the predator about 48 hours later.

Preferences of Bemisia tabaci Gennadius (Homoptera : Aleyrodidae) towards host plants

Bemisia tabaci is one of the main pests in vegetable crops, which is a poliphagus and has more than 600 species of host plant. This study purposed to determine B. tabaci preference on some host plants, which were tomatoes, peppers, eggplant, beanstalk, red beans, soya, Ageratum, knob grass and prickly amaranth. Research carried in the screen house, Department of Plant Pests and Diseases, Faculty of Agriculture, Universitas Padjadjaran, from August 2011 to January 2012. The experiments used randomized block design with nine treatments and three replications. Observation variables were population density of B. tabaci nymphs and imago and trichome form of host plant that was used in the experiment. The results showed the highest population density of B. tabaci nymphs which were 1318.6 nymphs at eggplant and 588.33 nymphs at red beans, meanwhile no nymph was found at paper plants. Population density observations of B. tabaci imago on eggplant and red beans for each were 76.33 and 114.33 imago. On trichome observation, visually B. tabaci preferred leaves with a high density trichome.