Stages Of Whitefly Research Articles

Knockout of ecdysis triggering hormone receptor (ETHr) gene adversely affects the nymphal molting and adult reproduction in Bemisia tabaci

Bemisia tabaci (Gennadius) is one of the most dangerous polyphagous pests in the world causing damage to various crops by sucking sap during the nymphal and adult stages. Chemical management of whiteflies is challenging because of the emergence of pesticide resistance. RNA interference has been well established in whitefly to study the functions of various genes. G-protein coupled receptors (GPCRs) are important targets for development of new generation insecticides. In this study, Ecdysis triggering hormone receptor (ETHr) gene expression was recorded in different stages of whitefly and its function has been studied through RNAi. The expression of ETHr is highest in third-instar nymphs followed by other nymphal instars, pupae and newly emerged adults. Silencing of ETHr resulted in significantly higher adult mortality (68.88%), reduced fecundity (4.46 eggs /female), reduced longevity of male and female (1.05 and 1.40 days, respectively) when adults were fed with dsETHr @ 1.0 μg/μl. Silencing of ETHr in nymphs lead to significantly higher mortality (81.35%) as compared to control. This study confirms that ETHr gene is essential for growth and development of whitefly nymphs and adults. Hence, it can be future target for developing dsRNA based insecticides for management of whitefly.

Effect of some insecticides, depletion and risk assessment against whitefly stages, Bemisia tabaci (Gennadius) on cucumber cultivation

Effect of some insecticides, depletion and risk assessment against whitefly stages, Bemisia tabaci (Gennadius) on cucumber cultivation

Precision and Accuracy of Field Versus Laboratory Bioassay Insecticide Efficacy for the Control of Immature Bemisia tabaci.

Ecotoxicological studies often result in reports on the limitation and sometime failures of biological assay data to predict field response to similar treatments. Nevertheless, it is widely accepted that controlled bioassays can better quantify the specific mortality response of a target pest species to a specific toxin. To quantify the relationship between whitefly bioassay and field response data, we evaluated a controlled laboratory bioassay and a concurrent cucurbit field trial method to assess insecticide efficacy for controlling the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). This was based on oviposition and nymphal development. We specifically tested the assumptions that a maximum dose bioassay would more precisely measure insecticide efficacy as compared with a comparable field spray test evaluation, and the response would be equal between the bioassay and the field as a measure of control accuracy for both adult oviposition and development of nymphal stages. To make a direct comparison, we tested the same whitefly population subsamples from 352 plots in eight cucurbit field experiments in Georgia, USA, in 2021 and 2022. The bioassays provide significantly precision for estimating proportional whitefly response. As expected, treatment-specific nonequivalence in immature whitefly counts between the bioassay and field, i.e., a lack of accuracy, only occurred with insecticides that were not highly toxic to all growth stages of whiteflies.

Technique to deliver dsRNA in Bemisia tabaci nymphs and its validation through silencing of juvenile hormone esterase gene

AbstractRNA interference (RNAi) is a technique employed to investigate the functions of various genes in whitefly and other insects. The effectiveness of the RNAi technique depends upon the delivery of dsRNA into the insects and it has been achieved through microinjection, oral feeding, egg soaking, transfection, topical application, spraying with nanoparticles, leaf‐mediated dsRNA feeding or plant‐mediated/ transgenic plants. In Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), most of the studies on RNAi were conducted on the adult through either injection or oral feeding. There is a need to develop a system to deliver dsRNA in whitefly nymphs because the first instar nymphs after hatching find a suitable place on the leaf and feed on the same place till adult emergence. So, we evaluated nine different techniques using different sponges, tubes, and, Petri plates for feeding nymphs. The detached leaf survived for maximum number of days (8.25 days) with minimum nymphal mortality (12.01%) in the Whitefly Nymphal Feeding System‐1 (WNFS‐1) treatment; therefore, WNFS‐1 was selected for the delivery of dsRNA to B. tabaci nymphs. In WNFS‐1, blue food dye was used to confirm that nymphs were being fed, and the results were evidenced by blue‐coloured bodies. The juvenile hormone esterase (jhe) gene was silenced in order to successfully deliver dsRNA to nymphs using WNFS‐1 and resulting in much higher nymphal mortality (68.36%). Therefore, WNFS‐1 is a reliable method of delivering dsRNA for the purpose of silencing the genes in the nymphal stages of whiteflies. The WNFS system may also be used extensively to evaluate any chemistry (insecticides, hormones, biopesticides, etc.) in nymphs of whitefly.

Dissipation and Residues of Imidacloprid and Its Efficacy against Whitefly, Bemisia tabaci, in Tomato Plants under Field Conditions.

The whitefly, Bemisia tabaci, is the main pest for many field and horticultural crops, causing main and significant problems. The efficiency of imidacloprid insecticide as seed treatment and foliar spray at three rates against the whitefly, B. tabaci, was evaluated in tomato plants under field conditions; in addition, insecticide residues were determined in tomato leaves and fruits. The obtained results revealed that the seedlings produced from treated seeds with imidacloprid were the most effective treatment in decreasing whitefly stages. Reduction percentages of whitefly stages in seedlings produced from treated seeds and sprayed with ½, ¾ and 1 field rates of imidacloprid were more than that produced from untreated seeds. Tomato fruit yield in seedlings produced from treated seeds and sprayed with one recommended rate of imidacloprid was more than that of untreated seeds. The residues of imidacloprid in leaves and fruits in seedlings produced from treated seeds and sprayed with field rate were more than that of untreated seeds; additionally, the residues were higher in leaves than in fruits. The residual level in fruits was less than the maximum residual level (MRL = 1 mg kg-1) of the Codex Alimentarius Commission. The half-life (t ½) was 6.99 and 6.48 days for leaves and fruits of seedlings produced from treated seeds and 5.59 and 4.59 days for untreated seeds. Residues in tomato fruits were less than the MRL, therefore, imidacloprid is considered an unconventional insecticide appropriate for B. tabaci control that could be safe for the environment.

First record of Delphastus argentinicus Nunenmacher (Coccinellidae: Serangiini) as a predator to whitefly in cassava crops

Cassava crops hold high agricultural importance in Paraná State, Brazil. However, cassava root production is adversely impacted by pests. Aleyrodids, in particular, cause great damage to cassava fields, necessitating better knowledge of predators found in these agroecosystems and novel biological control strategies for integrated pest management. This study reports the first occurrence of the predatory lady beetle Delphastus argentinicus Nunenmacher, preying on all life stages of whiteflies in cassava fields. Given the economic and social importance of cassava crops in Brazil and the deleterious potential of aleyrodid species, it is recommended to conduct behavioral and bioecological studies assessing the application of D. argentinicus as a biocontrol agent in integrated pest management programs.

Study of the Efficacy of Moringa Leaf Extract as an Insecticide against White Fly and Aphids Insects

In this study, we demonstrate the effect of plant extracts on whitefly and aphid’s insects that are economically harmful to crops and plants in greenhouse. A laboratory experiment was carried out to study the effect of four concentrations (0.5, 1.0, 2.0 and 3.0 g/l) of the alcoholic extract of the Moringa plant on whitefly and aphid’s insects. The results showed that the concentration of 3 g/l was significantly superior to the other concentrations used in the experiment, achieving percentage mortality rates of 95% in the nymph’s stage, where the account of insects decreased from 100 live insects before spraying to 5 live insects only after 72 hours of treatment with this concentration. In addition, the percentage mortality rate at the adult stage reached 91%, in which the counts of live insects decreased from 100 live insects before spraying to 9 insects after spraying with this concentration, where the rates of increase in the mortality efficiency rates reached at a concentration of 3 g/l compared to the other concentrations and at the nymph stage (13.09, 35.71, 50.79%), respectively, while the increase rates were at the nymph stage of aphids (16.25, 34.78, 47.61%), respectively. Whereas, the concentration of 0.5 g/l was the least effective in average efficiency of the concentrations used in the experiment in controlling the target insect, where it achieved a lower value of mortality rate, recording remarkable decrease, which reached at the nymphs and adults stages of whitefly and aphids insects (63, 60, 63, 61%), respectively. The chemical examinations for the detection of the plant extract content from the active compounds showed that it contains tannins, glycosides, phenols, resins, carbohydrates, saponins, alkaloids and terpenes.

First record of the genus Acletoxenus (Diptera: Drosophilidae) and its predaceous species A. formosus (Leow, 1864) in Egypt, with some field observations and biological remarks

BackgroundThe genus Acletoxenus (tribe Gitonini, subfamily Steganinae, family Drosophilidae) is a small widespread genus, comprising only four species worldwide, namely: Acletoxenus indicus Malloch, 1929, A. quadristriatus Duda, 1936, A. meijerei Duda, 1924 in addition to A. formosus (Leow, 1864), the species of the present study. The larvae of Acletoxenus spp. are known as predators of whiteflies.ResultsThe genus Acletoxenus and its predaceous species A. formosus (Leow, 1864) are recorded in the present study for the first time from Egypt. This species was found associated with the immature stages of the glasshouse whitefly, Trialeurodes vaporariorum Westwood, 1856 (Hemiptera: Aleyrodidae) feeding on the castor bean plant, Ricinus communis L. which has been grown at the Plant Protection Institute, Agricultural Research Center, Giza, Egypt. The morphological diagnoses, in situ predatory behavior in the field and ex situ biological remarks in the laboratory were discussed.ConclusionThe predaceous drosophilid fly, Acletoxenus formosus (Leow, 1864), is recorded herein with its genus for the first time from Egypt as the second representative of the tribe Gitonini (subfamilies Steganinae, family Drosophilidae) in the country. The recording of this species in Egypt is of a great interest as it will encourage and lead to further research on different biological aspects. This drosophilid is a beneficial fly as its larvae are predators of immature stages of whiteflies (family Aleyrodidae) and it could be used as a potential biological control agent.

Effect of Feeding Stage and Density of Whiteflies on Subsequent Aphid Performance on Tobacco Plants

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) is a cosmopolitan, highly polyphagous agricultural pest, which has the capacity to displace other native insect herbivores. Here, equipped with an integrated approach, the effect of developmental stages and feeding density of whiteflies on Myzus persicae performance in tobacco plants are investigated. Bioassay results showed that B. tabaci nymphs, but not adult, pre-infestation significantly reduced survival and fecundity of M. persicae, and the strongest resistance to M. persicae was detected at the medium density (9–10 nymphs/cm2). Neither low nor high feeding density of B. tabaci nymphs triggered visible resistance to aphids. However, no significant results were detected in salicylate-deficient NahG plants after B. tabaci nymph infestation. In addition to performance distinctions, hormone quantification and qPCR results revealed very different effects for nymph and adult whitefly stages on the defense responses in tobacco. B. tabaci nymph infestation significantly increased SA accumulation and SA-responsive genes (PR-1a, PR-2a) expression but suppressed JA-regulated responses. In contrast, tobacco plants responded to adult infestation by slightly increasing in both SA- and JA-regulated defenses. Furthermore, higher transcription level of Bt56, coding gene of a secretory salivary effector, was recorded in nymphs vs. adults, while silencing of Bt56 by virus-induced gene silencing (VIGS) partly impaired the aphid resistance induced by B. tabaci nymphs. These results proved that the induction of tobacco defense responses varied with the feeding stages of whiteflies: nymphs of B. tabaci, but not adults, induced a defense response against aphids, with a density threshold for this induced resistance.

Validation of a sampling method: using one square centimeter for sampling the immature stages of Bemisia tabaci in soybean

AbstractRecently, a sampling method was proposed to estimate the population of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in soybean, Glycine max (L.) Merr. (Fabaceae), by counting its immature stages on 1 cm² leaf surface as a sampling unit to reduce the effort required. However, no study has verified whether this sampling unit could accurately estimate the immature stages similar to counting individuals in the total area of a soybean leaflet. Thus, we studied the correlation between the counts performed in 1 cm² and those in the total area of a leaflet to validate the ‘squared centimeter’ method as a sampling unit for immature stages of the whitefly. The research was carried out in two commercial soybean crops during the 2018/2019 harvest in Brazil. Each sampling was conducted by four individuals at 12 random collection points in the field. A plant was divided into three parts: apical, middle, and lower thirds, where a trifoliate leaf was removed from each of these plant thirds. For the evaluation, the trifoliate leaf was divided into left, central, and right leaflets. The immature whitefly population on its abaxial face was evaluated using two methods: counting in 1 cm² and counting in the total area of the leaflet. The four stages of immature B. tabaci quantified and identified were egg, crawler, nymphal stage 1–4 (N1–N4), and pseudo‐pupa. Significant positive correlations were detected between the mean counts in 1 cm² and in the total area of the soybean leaflet for the four whitefly stages. However, the correlation was weak for the crawler stage. Therefore, this study elucidates that 1 cm2 as sampling unit is suitable for estimating the population densities of eggs, N1–N4, and pseudo‐pupa stages of B. tabaci in soybean plants.

Using Multiple Natural Enemies to Manage Sweetpotato Whiteflies (Hemiptera: Aleyrodidae) in Commercial Poinsettia (Malpighiales: Euphorbiaceae) Production

Abstract In this case study, we investigate the efficacy and economics of using two natural enemies in an integrated pest management (IPM) program to manage sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), in commercial poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) production. Two similar greenhouses at each of three different grower locations were designated as either the IPM or the conventional insecticide greenhouses in southeastern United States. In the IPM greenhouses, we released Eretmocerus eremicus (Rose & Zolnerowich) (Hymenoptera: Aphelinidae) weekly and Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) every 4 wk, and selective insecticides were used to treat high whitefly densities as needed. In the conventional greenhouses, growers were autonomous in their insecticide application decisions. All whitefly stages were counted weekly on a maximum of 20 leaves per 50 randomly sampled poinsettias and 50 flagged (i.e., revisited) poinsettias in every greenhouse. Whitefly densities were consistently similar or higher in the IPM greenhouses compared to their conventionally managed counterparts for the duration of the trial. The cost of inputs and labor for whitefly management in the IPM greenhouses was between 0.57- and 3.0-fold the cost of conventional management. Our study supports that releasing E. eremicus and A. swirskii can reduce insecticide applications by 25–78% and may be considered a feasible strategy to manage B. tabaci in commercial poinsettia production in place of conventional insecticidal control in southeastern United States.

Activity of novel insecticides against different life stages of whitefly (Bemisia tabaci)

Whitefly, Bemisia tabaci (Gennadius), in North Cotton Growing Zone of India adversely affect cotton yield. Both the nymphal and adult stages of whitefly cause damage by sucking the sap from leaf tissue and honey dew secretion. In this study, the efficacy of new generation insecticides, viz. pyriproxyfen 10EC@1250 ml/ha, spiromesifen 22.9SC @500 ml/ha, flonicamid 50WG @200g/ha, and diafenthiuron 50WP @ 500g/ha were evaluated against different stages of whitefly under confined as well as field conditions in Bt cotton.The experiment conducted in screen house revealed significantly higher per cent reduction of whitefly nymphs in spiromesifen 22.9SC (49.36, 75.17) followed by pyriproxyfen 10EC (33.26, 75.07) in comparison to all other treatments after 5 and 7 days of spray, respectively. Under field conditions, pooled analysis of six experiments showed that flonicamid 50WP was more effective, being at par with pyriproxyfen 10EC, diafenthiuron 50WP, spiromesifen 22.9SC after 10 days of spray as compared to standard check, ethion 50EC and control against whitefly adults. It is concluded that pyriproxyfen10EC and spiromesifen 22.9SC have good nymphicidal action while flonicamid 50WP and diafenthiuron 50WP have adulticidal action.Therefore, for its effective management, these novel insecticides can be rotated alternatively depending upon the stage of pest dominating in the cotton field.

How Spiromesifen affects some biological parameters and switching behavior of predatory mite Amblyseius swirskii (Acari: Phytoseiidae) when feeding on different ratios of mixed preys

Two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and silverleaf whitefly, Bemisia tabaci (Gennadius) (Hem.: Aleyrodidae) are among the most destructive pests under greenhouse conditions which is primirarily countered using chemical pesticides. Due to insecticidal and acaricidal effectiveness of Spiromesifen (Oberon®), agricultural producers extensively used this chemical to control both whitefly and spider mite populations. In the present study, effects of recommended concentration of Spiromesifen on some biological and behavioral attributes of predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) feeding on different ratios of two-spotted spider mite and silverleaf whitefly were investigated. Different treatments were defined as 1 (150 immature stages of mite + 0 immature stages of whitefly), 2 (120 mite + 30 whitefly), 3 (90 mite + 60 whitefly), 4 (75 mite + 75 whitefly), 5 (60 mite + 90 whitefly), 6 (30 mite + 120 whitefly) and 7 (0 mite + 150 whitefly). According to the results, mortality percentage of adult individuals was not significantly affected by different ratios of prey. With increasing ratio of preys tested in experimental arena, feeding activity of predatory mite on both preys was increased. However, in the case of T. urtice, linear relation observed between the initial number of mite offered and number of mite eaten was more significant. Reproductive responses of female predators to different ratios of mixed preys had no specified trend. Furthermore, switching behavior was not detected in female predators. Our results have considerable role for increasing biological efficacy of A. swirskii in integrated management programs of different pests.

Bacterial endosymbionts in life stages of Asia II-1 genetic group of Bemisia tabaci

Bacterial endosymbionts are present in majority of the agricultural pests and provide various physiological and ecological traits to its host. The beneficial traits are responsible for the success of these host insects in utilization of their plant hosts, in developing resistance to insecticides and in transmitting viruses as vectors. This study reveals the identification and localization of various bacterial endosymbionts, both primary (Portiera) and secondary (Wolbachia, Rickettsia and Arsenophonus) in the life stages of Asia II genetic group of whitefly Bemisia tabaci (Gennadius) deploying diagnostic polymerase chain reaction and technique of fluorescence in situ hybridization (FISH). The observation on the localization of bacterial endosymbionts was prominent in specialized cells called bacteriocytes in all the life stages of whitefly among the nymphs and adults.

Field Performance of Insecticides Treatments against the Immature and Adult Stages of Whitefly on Tomato Plant

Field experiments were carried out during 2015 and 2016 seasons at the experimental farm, Faculty of Agriculture, Saba-Basha, Alexandria University to evaluate the efficacy Prev-AM®, Planta® and Mospilan® against B. tabaci on tomato plants. prev-AM® achieved the highest initial and residual reduction% of whitefly adults giving (84.8%, 69.7%), respectively. Planta® achieved the highest initial and residual reduction% of whitefly immature giving (78.7%, 81.2%), respectively. On the other hand Mospilan® achieved the least initial effect. Sequence 4 (prev-AM®, Planta®) recorded the highest initial and residual reduction% of whitefly adult giving (86.3%, 83.1%), respectively. Sequence 5 (Planta®, Mospilan®) gave the highest initial and residual reduction% of whitefly immature giving (89.2%, 88.8%), respectively. Natural pesticides based on plant-essential oils may represent alternative crop protectants. From this study, orange oil and pyriproxyfen may introduce an effective control agents against whitefly in tomato field.

BIOLOGICAL CONTROL OF SOME PIERCING-SUCKING INSECT PESTS OF THE BEAN (PHASEOLUS VULGARIS L.) UNDER OPEN FIELD AND GREENHOUSE CONDITIONS

Sep. 19, 2016 Accepted: Sep. 24 , 2016 ABSTRACT: This work was conducted to study the biological impact of releasing the eleven-spotted ladybeetle, Coccinella undecimpunctata , Linnaeus (Coleoptera: Coccinellidae) in the control of the cotton whitefly, Bemisia tabaci , Gennadius, the cotton aphid, Aphis gosspyii , Glover infesting common bean, Phaseolus vulgaris, Linnaeus. Experiments were carried out during the period of 15 February, till 15 May 2014 at a private farm and a greenhouse located at El-Menoufia Governorate, Egypt. Biweekly leaf samples were examined for the different stages of insects under study to determine the efficacy and the optimum time for releasing the predator. The obtained results indicated that the highest reduction percentages of preys (83.1%) at the level of 15 larvae/ plant under greenhouse conditions, were recorded four weeks after releasing. The grand mean reduction percentages of aphid and whitefly stages under greenhouse conditions along ten weeks of releasing were 38.24, 45.86, and 49.68 % for the treatments of 5, 10 and 15 newly hatched larvae/plant, respectively. Under open field conditions, the results revealed that the highest reduction percentages of preys were recorded at the eighth and tenth week after releasing. The grand mean reduction percentages of aphid and whitefly stages under open field conditions along ten weeks of releasing were 38.0, 39.9, and 40.9 % for the treatments of 5, 10 and 15 freshly hatched larvae/plant, respectively.

Side Effects of Some Cotton Pesticides on the Dominant Spider Families in Cotton Fields

Survey was carried out at Elgemmeza Agricultural Research Station in a Colton field for Piacing sucking pests and associated predators along two successive seasons (2013 & 2014) during May-August months by using examination of leaves and plants shaking methods, during vegetative and flowering stages. The toxic eilect o fthrec pesticides on piercing sucking pests (whitetly and jassids) and its side effect on true spiders were also studied. Moreover, the toxic effect of three pesticides on cotton leafworm, Spodoptera littoralis and its side effect on true spiders. Results showed that, the highest numbers of spiders in cotton fields were recorded in August, in addition, the highest families occurrence were Linyphiidae and Philodromidae representing 39.02 and 21.8 %, respectively. As for the average numbers of collected predators, there were significant differences in the total numbers of true spiders & aphid lion and other predators (Ladybirds, Rove beetle, Flower bugs). As for pesticides, Applud gave the highest average numbers of reduction percentages of white fly stages infested cotton plants followed by Acetamprid and KZ oils. The decrease percentages of true spiders as side effects of applied pesticides were 29.35 and 21.05 % for Lufenuron and Difluhenzuron and 43.77 % for Profenofos in cotton fields. It could be concluded that true spiders played an important role in suppressing pest populations and in delaying pest outbreaks in the cotton growing season.

Culturable bacteria in Asia I and Asia II genetic groups of whiteflyBemisia tabaci(Gennadius) species complex

This study enumerats the cultivable gut bacteria in the developmental stages of whitefly (Bemisia tabaci species complex) populations belonging to the Asia II-1 and Asia I genetic groups. The gut bacterial density was assessed by growing them in growth media for all the developmental stages viz., egg, four nymphal instars and adult. The highest bacterial density was observed with adults in both Asia II-1 (2.09×106± 0.19 cfu/ml) and Asia I (6.4×105±0.146 cfu/ml genetic groups). Analysis of morphological and biochemical characteristics revealed the presence of Pseudomonas and Sphingomonas. Specific association of Proteus spp., and Acinetobacter respectively, with Asia II-1 and Asia I genetic group was also noticed. The use of diverse growth media and biochemical kits for isolation and identification of culturable gut bacteria are also discussed.

Efficacy and Dose Response of Soil-Applied Neem Formulations in Substrates With Different Amounts of Organic Matter, in the Control of Whiteflies, Aleyrodes proletella and Trialeurodes vaporariorum (Hemiptera: Aleyrodidae).

Neem products have been used frequently as an alternative to synthetic pesticides, because of their insecticidal, insect antifeedant, and growth-regulating effects. Moreover, new formulations are continually being developed and therefore, they have to be evaluated for their efficacy and persistence. In this regard, two soil-applied products-a liquid-based drenching solution NeemAzal-T and NeemAzal granules-were evaluated against two whitefly species, Aleyrodes proletella L. and Trialeurodes vaporariorum (West) on Brussels sprout and tomatoes, respectively. The plants were grown in two substrates: one was a commercial substrate (CS) composed of 15% humus, 35% clay, and 50% peat, and the other was a commercial substrate and sand mixture in 1:1 ratio. The main objective of the study was to evaluate the efficacy, persistence, and dose response of the two soil-applied NeemAzal formulations in substrates with different amount of organic matter. The results show that the efficacy of neem formulations was dose dependent, with the highest doses of NeemAzal granules (300 mg/kg=21 mg azadirachtin [AZA]/kg of substrate) and NeemAzal T (2 ml/kg=20 mg AZA/kg of substrate) achieving up to 100% mortality of immature stages of whiteflies. NeemAzal caused significantly higher mortality in immature stages of both whitefly species with CS + sand mixture than with pure CS. Persistence of the NeemAzal formulations was not influenced by the substrate type but rather by time span between treatment application and infestation, with significant decrease in efficacy when whiteflies were exposed 10 d after treatments.

English

Ecology of whitefly Bemisia tabaci Genn., has been studied extensively in the recent past and a varying response was observed on different host plants. The degree of this variation is because of type of host plant combination. The present investigation was conducted to find out the comparative age specific survival, mortality and life table parameters in presence of four major fruit bearing vegetables that is brinjal (Solanum melongena L.), chili (Capsicum annuum L.), tomato (Lycopersicon esculentum Mill.) and okra (Abelmoschus esculentus (L.) Moench), under laboratory conditions (26±3°C, RH: 75±5% and photophase: 14 h). The maximum survival and minimum mortality was observed on brinjal, while chili has been documented with reciprocity. Among the host plants, on which whitefly was reared, brinjal has shown superiority, documenting least mortality and shorter development of immature stages of whitefly. Least generation time (23.67±0.97 days) was observed on brinjal and maximum time was consumed on chili (33.57±1.10 days). Similarly, the highest intrinsic rate of increase (rm) was recorded on brinjal followed by tomato and the smallest rm was observed on chili. A significant difference in net reproductive rate (Ro) was perceptible, being highest on tomato (89.50±2.13 females/female). However; corresponding potential fecundity and maximum mean egg laying was received on brinjal. Fastest doubling time was also recorded on brinjal (8.41±0.02 days) followed by tomato (10.87±0.03 days) while maximum doubling time was witnessed on chili (14.01±0.05 days). The highest annual rate of increase (ARI), 1.27±0.02x1010 of individuals per year was found on brinjal and lowest on chili. The host preference of whitefly on the basis of present investigations, can be arranged in the following order brinjal>tomato>okra>chili. Key words: Bemisia tabaci, life table, fruit bearing vegetables, life parameters, female fertility