Tomato Whiteflies Research Articles

Fate and dietary risk assessment of pyriproxyfen, dinotefuran, and its metabolites residues in tomato across different regions in China.

Registration of a new formulation called 30% suspension concentrate (30% SC, pyriproxyfen 10% + dinotefuran 20%) to inhibit the occurrence of whitefly in tomato is currently under review in China, so it is necessary to research the residue behavior and dietary risk of pyriproxyfen and dinotefuran in tomato under field conditions. According to Good Agricultural Practices (GAP), the formulation was sprayed once at the dosage of 112.5g a.i./ha (active ingredient/hectare) at the initial stage of the occurrence of tomato whitefly and the recommended pre-harvest interval (PHI) for sampling was 5days. Meanwhile, the residues of pyriproxyfen, dinotefuran, and the metabolites of dinotefuran in tomato samples were determined using QuEChERS (quick, easy, cheap, effective, rugged, and safe) and high-performance liquid chromatography-tandem mass spectrometry. The results showed that the terminal residue levels of the analytes detected in tomato samples were below 0.19mg/kg for pyriproxyfen and 0.25mg/kg for dinotefuran at the recommended PHI (5days), which were lower than the maximum residue limits of China. The dietary risk assessment was also carried out based on field trial results, toxicological data, and Chinese dietary pattern. Both the chronic risk quotients (≤ 26.59%) and acute risk quotients (≤ 1.14%, general population, > 1year) of pyriproxyfen and dinotefuran were far below 100%, indicating a low risk to consumers' health. The paper will be conducive to provide guidance for the rational application of these insecticides on tomato.

Endophytic fungi for biological control of whitefly and tomato leaf miner in Tanzania

Tomato whiteflies (Bemisia tabaci) and leaf miners (Tuta absoluta) are devastating pests of tomato (Lycopersicon esculentum). Pest management using broad spectrum synthetic pesticides is discouraged due to harmful effects on human health and the environment. The objective of this study was to assess the potential of endophytic fungi as bioextracts against tomato whiteflies and leaf miners, as an alternative to synthetic insecticides in Tanzania. The study was done using morphological and molecular techniques, during January 2019 to February 2020 in Arusha region in Tanzania. Three endophyte isolates from pyrethrum (Chrysanthemum cinerariifolium) and lemon grass (Cymbopogon citratus) were identified with resemblance to members of Fusarium sp and Altenaria sp, by 90 and 82 % similarity, respectively; based on phylogenetic clustering patterns and macro- and micro-morphological characteristics. Bioextracts from endophytes of lemon grass leaves (Elg1); and pyrethrum flowers (Epf1) and leaves (Epl1), showed significant repellency properties (F0.05 (df, 15) = 27.052, P = 0.0001) on whiteflies by 54, 76 and 36%, respectively. They also caused significant lethality (F0.05 (df, 11) = 59.559, P = 0.0001) of tomato leaf miner larvae and whiteflies (F0.05 (df, 11) = 53.600, P = 0.0001). The underlying effect was attributed to possession of flavonoid and total phenolics as active ingredients in the bioextracts. This was commensurate to the levels flavonoid and total phenolic contents, which were considerably more in bioextracts of lemon grass and pyrethrum flower (F0.05 (df, 8) = 10.35, P = 0.0114) and (F0.05 (df, 8) = 40.84, P = 0.0003, respectively), than in pyrethrum leaves.

Evaluation of some Organophosphorous Insecticides against the Tomato Whitefly, Bemisia tabaci (GENN.) Collected from some Upper Egypt Governorates with Relation to Esterases Enzyme Activities

The tomato whitefly, Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) is a worldwide pest of many crops. Organophosphorous (OP) insecticides have been used to control this insect for many years and are still being used despite the development of resistance. In this work’ evaluation of the biological activity of three organophosphorous insecticides, profenofos 72% E.C. (Selecron); chlorpyrifos 48% E.C.(Dursban) and fenitrothion 50% E.C. (Sumithion) on the felid strain of tomato whitefly was carried out on tomato plants. Whitefly adults were collected from four different Egyptian Governorates throughout three successive years (2016-2018). The LC50 value of each compound in each Governorate was used to determine the biochemical responses of this insect pest.The colorimetric test of esterase activity is a useful tool to detect the level of resistance against this group of insecticides. The obtained results showed that profenofos insecticide was more toxic on the tested insects followed by chlorpyrifos, while fenitrothion showed a low toxic effect on the tested insects in all years. The activities of α and β esterases have fluctuated up and down in some Governorates.

Integrated Management of Tomato Whitefly Under Greenhouse Conditions

The whitefly Bemisia tabaci (Gennadius, 1889) is a major pest species in many agricultural crops worldwide. Growers from the Vale do Caí region, in Southern Brazil (Rio Grande do Sul state) have been facing severe economic losses due to the increasing damages caused by this sucking insect in their horticultural crops. Small-scale farming in the Vale do Caí region relies heavily on horticulture, with many families involved in the activity and a consumer market spread throughout the whole state. Virus transmission and other damages inflicted by B. tabaci are especially harmful to tomato plants, and the managing of the pest currently demands two thirds of all chemical insecticides used in the region. While chemical control remains the main strategy for whitefly management on tomato crops, control failures and lack of updated information have led tomato growers to raise the number of sprays per crop cycle, with selection of resistant populations and harmful effects on the environment as consequent risks. The aim of this work was to evaluate chemical compounds and bioinsecticides in the control of B. tabaci nymphs and adults on tomato plants grown in two different greenhouses and under natural infestation conditions. The most efficient treatment for the control of B. tabaci adults was cyantraniliprole + lambda-cyhalothrin (50+30 g a.i. ha-1) with 64% of average control efficiency. As for nymph control, the most efficient treatment was the Embrapa formula, a bioinsecticide composed of 0.5% flaxseed oil + 0.5% neutral detergent + 0.3% sodium bicarbonate, which resulted in 72% of whitefly control in average.

Tomato Farmers Knowledge of Integrated Pest Management Technique for White fly in Two Villages in Abo Homos Province of in Beheira Governorate

The present research aimed at analyzing the knowledge of whitefly comprehensive control method among tomato growers in two villages of Abu Homus district at Behira governorate. Abu homus was selected as one of the major areas for tomato plantations, and the villages of Botoros and Jawad Hosney were chosen for they have concentrated tomato plantations that witness large outspreads of whitefly infestation. The data were collected through questionnaire during interview of a random sample of 124 growers according to Crigssy and Morgan equation. The statistical methods applied in the study were; mean, repeated charts, percentage, Pearson's correlation, and multiple regression. The results show that: 82.26% of the respondents have low and medium knowledge of the tomato whitefly comprehensive control method and they suggest a significant positive relation between the respondents' knowledge degree of the tomato whitefly comprehensive control method and the following; total area planted with vegetables, total area planted with tomato, level of knowledge of the damages resulting from using pesticides in vegetables pests control and the level of participation in extension activities (p 0.01). There was a significant positive relation between the dependent variable and the number of education years (p0.05). The following variables had positive impact; number of years of education, total area planted with vegetables, total area planted with tomato, level of participation in extension activities (p0.01) based on the calculated t values (-3.167, 2.619, 2.424 and 5.224) respectively. Also these variables account for 58% of the changes in respondents' degree of knowledge of the tomato whitefly comprehensive control method based on R2 value, that is, 0.576. Cucumber growers had several problems upon applying the tomato white fly comprehensive control method including; high process of control pesticides, lack of pesticides alternatives, not applying farming circulations systems for tomato, growing whitefly hosting plants next to tomato such as cucurbits, applying pesticides in not suitable times and lack of good application equipment, small number of extension fields applying tomato whitefly comprehensive control method.

Rearing tomato whitefly and field evaluation of modified and unmodified conidia of Beauveria bassiana, Isaria farinosa, Metarhizium anisopliae and low rates of chlorpyrifos under tropical conditions.

The whitefly ( Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a serious pest of a wide range of economically important agricultural and ornamental crops in all agro-ecological regions in the world. This study evaluated the efficacy of conidia of entomopathogenic Beauveria bassiana (BB 315), Isaria farinosa (ARSEF 5081) and Metarhizium anisopliae (Ma 275.86DC), against whitefly ( Bemisia tabaci ) under tropical climate. Two forms of conidia: (a) modified conidia (conidia with improved ecological competence), and (b) unmodified conidia of the three isolates were subjected to heat treatment (45°C) for 5 days. Germination rates of these conidia before and after their exposure to heat were compared at 25 °C on Sabouraud Dextrose Agar (SDA, aw= 0.995) to assess resilience to heat stress. Further, assessment of germination potentials of conidia was conducted at three aw levels (0.995, 0.98 and 0.96: corresponding to different levels of water availability). Thereafter, they were tested against B. tabaci infestation on tomato plants and insect densities after the treatments were compared with the effect of low rate chlorpyrifos. The conidia germinated differently on SDA at the three a w levels and the rate of germination of modified conidia of each isolate was significantly higher at 0.98 a w (F 2, 16 =0.31, P=0.001). Modified conidia of B. bassiana appeared more tolerant to temperature stress. All the isolates significantly reduced pest incidencerelative to control after 14 days and there was no significant difference (P>0.05) between the effect of modified and unmodified conidia against B. tabaci in the field. The level of control achieved using the conidia of the three fungal isolates was comparable with the chlorpyrifos treatment. Key Words : Bemisia tabaci, entomopathogen, water activity

Control of tomato whiteflies using the confusion effect of plant odours

Glasshouse tomato production is reduced by the whitefly Trialeurodes vaporariorum, a major worldwide pest of glasshouse crops. Whitefly control is achieved using pesticides or parasitoids, which have drawbacks. There is thus a need for other control methods. For instance, the use of volatile compounds from plant odours could profoundly change the behaviour of plant-eating insects. This practice should be safe because plant odours are usually harmless to humans. Therefore, we have studied the effect of plant volatiles on whiteflies feeding on tomato plants. The rationale was to use the confusion effect by supplying whiteflies with a super-abundance of volatiles. We removed plant headspace volatiles from multiple whitefly host plants. Then, we presented these volatiles to whiteflies feeding on tomato plants. At the same time, whitefly stylet penetration is monitored using electrical penetration graphs (EPG). Plant colonisation, egg laying and honeydew production are analysed in separate experiments. Data are compared to controls in which extracted volatiles from tomato and air alone are presented to the whiteflies. The only significant effect produced by exposure to multiple-host volatiles is a pronounced reduction in the incidence of phloem-related waveforms during the 15-h EPG recording. This represents a delay in, rather than a cessation of, phloem-related activities as there is no related reduction in long-term performance. The confusion effect thus does not appear to exert strong effects on whitefly behaviour here.

Screening of Some Foliar Chemical Insecticides against White Fly (<i>Bemisia tabaci</i>) on Tomato at Metema District, North Gondar, Ethiopia

Tomato is one of the vegetable crops growing in Ethiopia and important cash crops for small scale growers with a potential for increasing incomes in rural areas, improving the living standards and creating employment opportunities for women and youth. Vegetables in tropical countries are the crops which are often attacked most seriously by arthropod pests. Among the major insect pests, white flies, one of a serious leaf-sucking pest, cause direct damage to plants by sucking plant sap. The experiment was conducted in farmer’s field with supplementary irrigation at Aftete-Kumer locality in Metema District since 2011/12 to select effective foliar insecticide for white fly control. The experiment was initiated with 5 treatments such as 4 foliar insecticides and control. Foliar chemical insecticides such as Ethiosulfan 35% EC, Ethiothoate 40% EC, Ethiolathion 50% EC and Metasystox 250% EC were used with rate of 2, 1.5, 1.5 and 0.9 milliliter per plot respectively and arranged by using RCBD with three replications. Melka shola tomato variety was used in this study. Post spray count was carried out three times at 2, 5 and 7 days after applying the insecticides. All data were analyzed by using SAS computer software. Plots sprayed with Ethiothoate and Ethiolathion showed less significant difference on stand counting at harvesting with mean number of plants of 48.3 and 41.6 per plot respectively as compared to plots sprayed with Ethiosulfan (39.60), Metasystox (37.6) and Control (37). All treatments were not shown significant difference on pre-spraying count of adult white flies. In case of post-spray count of adult white flies, Ethiothoate showed highly significant difference (p < 0.05) with least number of white flies population (1.6 per leaf) followed by Ethiolathion (2 per leaf). The highest number of adult white flies was recorded from control (25) and Metasystox (16.6) followed by Ethiosulfan (14.3). Regarding yield, there was significant difference (p < 0.05) between treatments. The highest yield was obtained from Ethiothoate (401.6 grams per plot) and Ethiolathion (356.67 grams per plot) followed by Metasystox (119.6 grams per plot) and Ethiosulfan (113.3 grams per plot). The lower yield was obtained from control (81.6 grams per plot). Ethiothoate and Ethiolathion have shown highest efficacy in controlling tomato white fly through reducing the population.

Reaction of some tomato cultivars to tomato leaf curl virus and evaluation of the endophytic colonisation with Beauveria bassiana on the disease incidence and its vector, Bemisia tabaci

Tomato line LA1478 and Pusa Ruby were resistant to tomato leaf curl virus (TLCV) disease. They registered higher plant height, number of branches, total phenol content and yield per plant than the other cultivars. Variety Peto 86 was tolerant to the disease while the other popular tomato cultivars, i.e. Ace, Early Pack, Money Maker, Prichard and Strain B were highly susceptible to the disease. Plant height and number of branches per plant revealed significantly positive association with fruit yield per plant. The disease index of TLCV exhibited significant negative correlations with plant height, total phenol content and fruit yield per plant – 0–4 and 5–25 adult whiteflies were observed on resistant susceptible cultivars. In the case of epiphytically colonisation by Beauveria bassiana conidia, not all developing hyphae on the leaf surface penetrated the whitefly cuticle. Many of the germ tubes elongated to a short distance before terminating its growth. On the other hand, the rapid staining of tomato tissues injected with B. bassiana conidial suspension indicates that the entomopathogenic fungus was established inside tomato tissues until the end time of the trial. The direct injection with the spore suspension yielded high post-colonisation, where the fungus was recovered from sites distant from the point of inoculation. This indicates that the fungus has the potential to move throughout the plant tissues. Laboratory bioassay of tomato whitefly feeding on tomato tissues containing B. bassiana conidial spores indicates that plant endophytic colonisation with entomopathogenic fungi may reduce insect survival on these plants. LT50 values of the test diet were between three and four days. The mortality of Bemisia tabaci was high in the case of endophytically colonisation compared to epiphytically one (90.0% compared to 10.0% during three days) for whiteflies fed tomato tissues containing 1.5 × 107 B. bassiana spores/ml. Application of B. bassiana as an artificial endophyte inside tomato plants can be an important component in the integrated control of tomato whiteflies. The endophytic colonising can achieve biocontrol effect based on induced disease resistance in plant tissues. According the available references, this is the first report on B. tabaci controlling by plant endophytic treatment.