Tabaci Biotype Research Articles

Primer reporte de Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae), biotipos B y Q, en soja Glycine max (L.) Merrill (Fabales: Fabaceae) en Paraguay

Whiteflies (Hemiptera: Aleyrodidae) are significant agricultural pests worldwide, primarily because they act as vectors for various plant viruses, including geminiviruses. Additionally, whitefly activity fosters the development of fungal colonies, such as sooty mold (Capnodium spp.), which grows on the sugary secretions (honeydew) produced by these insects. The presence of sooty mold reduces the plant’s photosynthetic capacity, further worsening the negative impact on its growth and development. Together, these factors make whitefly control a challenge for farmers, who must implement integrated pest management strategies to mitigate both the direct damage and the associated diseases that whiteflies can spread. Although approximately 1,200 species of whiteflies have been described, fewer than 40 are considered primary pests, with Bemisia tabaci (Gennadius, 1889) and Trialeurodes vaporariorum (Westwood, 1889) responsible for the greatest agricultural losses worldwide. The emergence of B. tabaci biotypes has prompted significant research, as these biotypes have been linked to economic damage to crops in several nations of the Americas, including Argentina and Brazil. In Paraguay, there is a need to identify local biotypes of B. tabaci led to the collection of whitefly samples from soybean plots in Capitán Miranda and Natalio, Itapúa, Paraguay. DNA was extracted using the Wizard genomic purification kit, followed by PCR amplification of the mitochondrial cytochrome oxidase I (mtCOI) region using specific primers for B. tabaci and T. vaporariorum. Agarose gel electrophoresis confirmed the presence of B and Q biotypes of B. tabaci in both Paraguayan locations, with no detection of T. vaporariorum. Sequencing of the PCR products revealed a 100% match with known sequences for B. tabaci and its biotypes, as confirmed by GenBank BLAST analysis. This research highlights the critical importance of continuously monitoring the population dynamics and geographical distribution of different biotypes. While the expansion of a polyphagous and dynamic pest like the whitefly cannot always be prevented, constant monitoring enables early detection of its spread and allows for the adjustment of management strategies tailored to each region. These measures will not eliminate the pest but will help mitigate damage and manage the problem sustainably and efficiently. The study also emphasizes the need to the effectiveness of insecticides, as resistance has been reported in other countries—an issue not yet explored in Paraguay.

Bioactivity of andiroba oil on whitefly, Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae)

The whitefly, Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae) is a phytophagous insect that is difficult to control and can cause great damage to several crops of economic importance, as it can use more than 600 botanical species as hosts. This study aimed to evaluate the insecticidal and deterrent effect of andiroba (Carapa guianensis Aubl., Meliaceae) fixed oil on B. tabaci biotype B in kale (Brassica oleracea var. acephala). The andiroba oil samples, Manaus and Silves were diluted in acetone P.A. at concentrations of 0.5%, 1%, and 1.5%, and compared with the commercial insecticide Evidence® 700WG (imidacloprid). For the deterrence test, the concentrations were applied on healthy seedlings and placed in a cage with adult insects. Then the oviposition of whiteflies on the leaves was counted. For the mortality test, applications were performed on seedlings with leaves infested with B. tabaci nymphs to evaluate the nymphicidal effect. Analysis of variance was performed using the F test, and comparison of means using the Tukey test (p<0.05), using the statistical program R®. Concentrations of 1% and 1.5% reached a deterrent effect of 82.13% and 88.55%, respectively. All concentrations caused mortality greater than 60%. These results attest to the potential of andiroba oil as an alternative control for the whitefly.

Viral complexity of tomatoes yellow mosaic and leaf curl diseases in lowland and highland areas

AbstractYellow mosaic and leaf curl diseases caused by whitefly‐transmitted begomo virus genera are important problems in tomato (Solanum lycopersicon L.) production in Indonesia, particularly on Java Island. The aims of this survey are to assess the percentages of disease incidence (DI) and disease severity index (DSI), evaluate the spread and complexity of begomovirus and crinivirus infections responsible for yellow mosaic and leaf curl diseases in tomato plants, and identify the species of whitefly insect vectors and their cryptic biotypes in tomato production centers located on Java Island, Indonesia. A total of 43 locations in East, Central, and West Java were surveyed during the dry season from July 2022 to September 2022. Disease incidence and severity were determined by observing 200 samples of tomato plants from five points at each location, with 40 plants per point of land. A total of 116 whitefly samples in microtubes and 215 symptomatic leaf samples were collected. The genus begomovirus and crinivirus infecting tomato were identified by PCR and RT‐PCR using genus‐specific primers. Similarly, whitefly species and their cryptic biotypes were identified by PCR using MCoI gene‐specific primers. Results showed that DI and DSI remarkably differed between the lowlands (66%–89%) and highlands (33%–62%) in the provinces of Central Java and West Java. Furthermore, PCR analysis of 215 infected tomato showing the symptoms of yellow mosaic and curly leaf revealed that three begomoviruses, one crinivirus and their mixed combination both begomoviruses, one crinivirus has been detected in all the samples. Similarly, the whitefly insect vector Bemisia tabaci biotype Q was identified in all areas, whereas Trialeurodes vaporariorum was found only in the East Java and Java highlands, respectively.

Elicitor-Driven Defense Mechanisms: Shielding Cotton Plants against the Onslaught of Cotton Leaf Curl Multan Virus (CLCuMuV) Disease.

Salicylic acid (SA), benzothiadiazole (BTH), and methyl jasmonate (MeJA) are potential elicitors found in plants, playing a crucial role against various biotic and abiotic stresses. The systemic acquired resistance (SAR) mechanism was evaluated in cotton plants for the suppression of Cotton leaf curl Multan Virus (CLCuMuV) by the exogenous application of different elicitors. Seven different treatments of SA, MeJA, and BTH were applied exogenously at different concentrations and combinations. In response to elicitors treatment, enzymatic activities such as SOD, POD, CAT, PPO, PAL, β-1,3 glucanse, and chitinase as biochemical markers for resistance were determined from virus-inoculated and uninoculated cotton plants of susceptible and tolerant varieties, respectively. CLCuMuV was inoculated on cotton plants by whitefly (Bemesia tabaci biotype Asia II-1) and detected by PCR using specific primers for the coat protein region and the Cotton leaf curl betasatellite (CLCuMuBV)-associated component of CLCuMuV. The development of disease symptoms was observed and recorded on treated and control plants. The results revealed that BTH applied at a concentration of 1.1 mM appeared to be the most effective treatment for suppressing CLCuMuV disease in both varieties. The enzymatic activities in both varieties were not significantly different, and the disease was almost equally suppressed in BTH-treated cotton plants following virus inoculation. The beta satellite and coat protein regions of CLCuMuV were not detected by PCR in the cotton plants treated with BTH at either concentration. Among all elicitors, 1.1 mM BTH was proven to be the best option for inducing resistance after the onset of CLCuMuV infection and hence it could be part of the integrated disease management program against Cotton leaf curl virus.

Current Status and Complexity of Three Begomovirus Species in Pepper Plants in Lowlands and Highlands in Java Island, Indonesia.

Three primary species from the Begomovirus genus, Pepper yellow leaf curl Indonesia virus (PepYLCIV), Tomato yellow leaf curl Kanchanaburi virus (TYLCKaV), and Tomato leaf curl New Delhi virus (ToLCNDV), are suspected of spreading throughout pepper production centers, and plants are infected by a single species or a combination of two or three species. This study was conducted to provide complete information about the symptoms, incidence and severity, whitefly biotypes, as well as the dominance status of the three Begomovirus species in pepper-producing areas in Java. A DNA analysis was carried out on leaf samples to identify Begomovirus species and biotypes of B. tabaci collected from 18 areas (16 districts) in lowlands (<400 m asl) and highlands (>700 m asl). The DNA analysis showed that B. tabaci biotype B was the most commonly detected in all locations compared to the A, AN, and Q biotypes. The incidence of begomovirus infection was at a high level, 93% and 88.78% in the lowlands and highlands, respectively. However, the severity of begomovirus infection was significantly higher in the lowlands (54.50%) than in the highlands (38.11%). A single infection of PepYLCIV was most dominant in all locations sampled and caused severe infection, followed by a mixed infection with TYLCKaV. Therefore, the current status of begomovirus infection, especially PepYLCIV, can provide advice to farmers using more tolerant and resistant varieties as well as a breeding strategy for resistant pepper varieties.

Research on Drawing Attention to Overlooked Viruses in Plant Viruses Causing Yellowing-Type Symptoms in Cucurbitaceae

A single-stranded, positive-sense plant RNA virus called the Cucurbit chlorotic yellows virus (CCYV, Crinivirus, Closteroviridae) is comprised of RNA1 and RNA2. It is semipersistently transmitted by the whitefly Bemisia tabaci biotypes MEAM1 and MED. In 2004, CCYV was discovered on melon plants in Japan. Several other cucurbit species, as well as a range of non-species, were subsequently reported from countries such as Saudi Arabia, California, Israel, Taiwan, Sudan, Lebanon, Iran, Greece, Türkiye, Egypt, Spain, and China. Whitefly populations are frequently encountered in cucurbit cultivating areas. Virus plant diseases attributed to whiteflies are common in squash cultivation in the open field and greenhouses in Türkiye, especially in cucumbers and squash. Cucumber vein yellowing virus (CVYV), Cucurbit yellow stunting disorder virus (CYSDV), Tomato leaf curl New Delhi virus (ToLCNDV), Squash vein-yellowing virus (SqVYV) are the leading virus diseases transmitted by Bemisia tabaci. Symptoms caused specifically by these viral diseases are of the yellowing type, although they differ as intervascular yellowing, yellowing of old or young leaves, and upward curling. Besides these viruses, CCYV, a problem in cucurbits, is carried by whitefly like others, causes yellowing type symptoms, and its first record in cucumber was reported in 2017 in Türkiye. However, this virus is ignored in the production of cucurbits, it is a problem in production areas. There are major viruses cause similar symptoms with the presence of the Cucumber chlorotic yellows virus is overlooked in the symptomatological observation. In this study, we tried to reveal the difference of CCYV, which is encountered in cucurbit growing areas in Antalya and whose presence was detected by RT-PCR, from other viruses and emphasized its importance as a virus that should be considered in classical breeding studies.

Insecticide Resistance and Its Management in Two Invasive Cryptic Species of Bemisia tabaci in China.

The sweet potato whitefly Bemisia tabaci is a major agricultural pest with a wide host range throughout the world. The species designation for B. tabaci includes numerous distinct cryptic species or biotypes. Two invasive B. tabaci biotypes, MEAM1 (B) and MED (Q), were found in China at the end of the 20th century and at the beginning of the 21st century. MEAM1 (B) and MED (Q) show higher pesticide resistance levels than native strains, and the levels of resistance vary with changes in insecticide selection pressure. Recent studies have revealed metabolic resistance mechanisms and target site mutations in invasive B. tabaci strains that render them resistant to a range of insecticides and have uncovered the frequency of these resistance-related mutations in B. tabaci populations in China. Novel pest control agents, such as RNA-based pesticides and nano-pesticides, have achieved effective control effects in the laboratory and are expected to be applied for field control of B. tabaci in the future. In this review, we discuss the mechanisms of resistance developed by these invasive B. tabaci populations since their invasion into China. We also provide suggestions for ecologically sound and efficient B. tabaci control.

Synthesis, characterization, and evaluation of derivatives from cardanol as repellents/pesticides agents of Liriomyza sativae (Diptera: Agromyzidae) and Bemisia tabaci (Hemiptera: Aleyrodidae) on melon plants

Hydrogenated cardanol derivatives were evaluated as potentially active insecticides/repellent agents against insect pests such as Liriomyza sativae (Diptera: Agromyzidae) and Bemisia tabaci biotype B (Hemiptera: Aleyrodidae). Benzoylation, acetylation, and methylation were made on the hydrogenated cardanol aromatic ring to synthesize active ingredients with potential insecticide action. Nuclear magnetic resonance spectra (13C and 1H NMR) and infrared (IR) proposed the chemical elucidation of the products. The production of melon seedlings was made and each synthesized products, benzoylated 3-pentadecylphenol, acetylated 3-pentadecylphenol, and methylated 3-pentadecylphenol were applied to seedlings by glass sprayer. Phytotoxicity evaluations were carried out, noting that all the plants showed burnt leaves except for concentration of 1% which the leaves remained healthy look. The insecticidal efficacy as well as the repellent and dissuasive effects were evaluated by a completely randomized design (DIC) and a randomized complete block design (DBCA) with six treatments, five and four replicates respectively. The compounds derived from cardanol did not present insecticidal activity in DBCA for L. sativae; however, they had a noticeable effect on oviposition index (IPO). Ovicidal effect and nymphal mortality only were found for B. tabaci by methylated 3-pentadecylphenol and Mospilan® in terms of dissuasion and oviposition effects in the two bioassays evaluated and, methylated 3-pentadecyl showed a similar behavior as the effect of Abamectin® on the confinement test, with 53.5% - 65.4% repellence of adults, an important data to emphasize that the products synthesized from cardanol are promising in preventing the pests attack such as L. sativae and, B. tabaci.

Development of BC3F2 Tomato Genotypes with Arthropod Resistance Introgressed from Solanum habrochaites var. hirsutum (PI127826)

Arthropod pests are among the biggest problems faced in tomato production worldwide. To overcome the losses caused by these pests, one of the most sustainable and economical strategies is the use of resistance introgressed from wild species. We aimed to develop BC3F2 tomato genotypes with high levels of zingiberene (ZGB) and resistance to whitefly (Bemisia tabaci biotype B), South American tomato pinworm (Tuta absoluta), and the two-spotted spider mite (Tatranychus urticae), from the wild accession of Solanum habrochaites var. hirsutum (accession PI127826). The quantification of ZGB in 520 BC3F2 genotypes and in the parentals yielded the selection of five genotypes with high ZGB content and three with low ZGB content, which were then infested with B. tabaci, T. absolute, and T. urticae. In these eight genotypes and in the parents, the types and amounts of trichomes on the leaves were determined. Additionally, molecular markers were used to identify the genotypes with a higher recurrent genome recovery. The results confirmed the transfer of resistance from S. habrochaites to the BC3F2 genotypes and showed that this resistance seems to be directly related to high concentrations of ZGB and the presence of type IV trichomes.

Loop-mediated isothermal amplification of PBAN gene for molecular diagnosis of Bemisia tabaci biotype Q (Hemiptera: Aleyrodidae)

• LAMP assay for PBAN of the whitefly was developed. • The PBAN-based LAMP primer set showed specific amplification of the target region. • The PBAN-based LAMP assay can be applicable for monitoring B. tabaci biotype Q. The tobacco whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), is a serious pest that transmits tomato yellow leaf curl virus (TYLCV) in tomato. The tobacco whitefly exhibits morphological similarity with the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) which also damages various plants in the greenhouse. Therefore, it is very important to quickly and accurately diagnose whiteflies for applying pest management strategies. In this study, we used a loop-mediated isothermal amplification (LAMP) assay to quickly and effectively detect B. tabaci . Primer sets were investigated for the specificity of B. tabaci by visible detection of the target DNA fragment. Two primer sets for pheromone biosynthesis activating neuropeptide (PBAN) gene were obtained from transcriptomic analysis of B. tabaci biotype Q. The PBAN-based LAMP primer set showed specific amplification of the target region. The optimal conditions for B. tabaci detection were 60 °C for 60 min with four LAMP primers of PBAN. The minimum amount of genomic DNA required for visible detection was 100 ng. These results suggest that the PBAN-based LAMP assay can be applicable for field monitoring of B. tabaci .

Clonostachys rosea: Production by Submerged Culture and Bioactivity Against Sclerotinia sclerotiorum and Bemisia tabaci.

Among the prospective biocontrol agents, the saprophytic filamentous fungus Clonostachys rosea is an excellent necrotrophic mycoparasite of numerous plant pathogenic fungi. However, its commercial development has been hampered by mass production difficulties during solid-state fermentation. Conversely, the submerged liquid fermentation shortens the cultivation time while increasing yields of fungal propagules. However, this method has been overlooked for C. rosea. In this work, we investigated the impact of liquid pre-culture inoculum on the spore production by the two-stage fermentation process using rice grains in comparison to the traditional solid-state fermentation. In parallel, we studied the submerged cultivation of C. rosea by manipulating carbon-to-nitrogen (C:N) ratio and nitrogen source, with the further optimization of spore production in a benchtop bioreactor. Additional bioassays included assessing the bioactivity of water-dispersible microgranules (that contained a submerged conidia) against the whitefly (Bemisia tabaci biotype B) and Sclerotinia sclerotiorum (causal agent of the white mold). Our results showed a maximum concentration of 1.1 × 109 conidia/g-dry-matter after 7 days of cultivation by two-stage fermentation process. The liquid fermentation yielded 1.4 × 109 submerged conidia/ml after 7 days using a medium with a 50:1 C:N ratio, and it also induced the production of microsclerotia (MS) up to 1.35 × 104/ml within 6 days with 10:1 C:N ratio; both media were supplemented with dextrose monohydrate and soybean meal. The fermentation batches carried out in a benchtop bioreactor with medium 50:1 C:N ratio and amended with soybean meal rendered a production peak on the fourth day, corresponding to 1.11 × 109 conidia/ml and 4.35 × 108 colony forming units (CFU)/ml. Following air-drying, the conidia production from air-dried microgranules of C. rosea biomass was estimated at 3.4 × 1010 conidia/g of formulated product upon re-hydration for 7 days. Both submerged conidia and MS of C. rosea inhibited 100% germination of S. sclerotiorum sclerotia by direct parasitism. The air-dried submerged conidia exhibited a suppressive activity on sclerotia (88% mycoparasitism) and early whitefly nymphs (76.2% mortality) that rendered LC50 values of 3.2 × 104 CFU/g soil and 1.5 × 107 CFU/ml, respectively. Therefore, the submerged liquid culture of C. rosea may offer a feasible and cost-effective method for its large-scale production, alleviating critical constraints to their commercial use while providing an additional tool for management of B. tabaci and S. sclerotiorum.

Patterns of the Occurrence of TYLCV and ToCV with Whitefly on Summer-Cultivated Tomato in Greenhouse in Gwangju, Gyeonggi Province

Patterns of occurrence of tomato yellow leaf curl virus (TYLCV) and tomato chlorosis virus (ToCV) with whitefly on summer-cultivated tomato in Gwangju-si, Gyeonggi Province were surveyed using multiplex reverse transcription-polymerase chain reaction in 2020. In addition, distribution of the whiteflies species and their viral transmission rates were investigated throughout the tomato growing season. The infection rates of TYLCV and ToCV increased sharply during harvest, and the single infection rates were 30.9% and 5.0%, respectively, with a mixed infection rate of the two viruses being the highest at 52.2%. Single infection with TYLCV and double infections with TYLCV and ToCV accounted for the majority with 83.1%. Bemisia tabaci were dominant over Trialeurodes vaporariorum in greenhouse grown plants, and all of the investigated B. tabaci biotypes were identified as Mediterranean (MED, formerly known as Q biotype). The transmission rate of TYLCV, detected in every sampled B. tabaci MED population, was 21.4%, and the mixed transmission rate with ToCV was 35.5%. Viruliferous MED whiteflies with ToCV showed a higher rate than that of T. vaporariorum. In the transplant stage, viruliferous rate of both TYLCV and ToCV of B. tabaci was 42.7%; this rate was highest in the harvest stage. In examination of tomato yield, the increase in the mixed infection rate of TYLCV and ToCV led to complete yield loss. When the mixed infection rate increased by 10%, the yield decreased by 405.4 kg/10a.

Infestação de mosca branca (Hemiptera: Aleyrodidae) biótipo B em cultivares de soja no polo Paragominas grãos, Pará

The aim of this study was to evaluate the infestation of whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) biotype B in 19 soybean cultivars in the Paragominas grain pole, 2017/18 crop year. The cultivars selected for planting are based on those normally planted in the Paragominas grain complex and research institutions. The sampling of the incidence of B. tabaci biotype B started on the 7th day after plant emergence (DAE), and the number of eggs, nymphs and adults was recorded weekly, that is, 10 small leaves of the plant evaluated in each plot, until the end of the crop cycle. The number of eggs and nymphs of B. tabaci type B was recorded in the laboratory with the aid of a stereoscopic microscope and adults made in loco. The values obtained were transformed into (x + 0.5)1/2, for normalization of these and submitted to analysis of variance (ANOVA) by the F test (Fisher). Tukey at 5% probability. The cultivar M 8644 IPRO showed the lowest infestation of eggs of B. tabaci and RK 6813RR was the most infested; for nymphs, the highest infestation was observed in cultivar RK 6813RR while in BRS 9383 IPRO there was less infestation; the highest number of whitefly adults was observed in the cultivar P 99R03, and M 8808 had the lowest average of adult insects and the period of highest incidence of whitefly was in the egg stage, in the first seven days after emergence (DAE); the period of 7 DAE was the most infested by adults and whitefly eggs; 35 and 42 DAE more infested by pest nymphs; meteorological factors mean temperature, rainfall and relative humidity do not showed influence on whitefly infestation, and relative humidity explained only 35.59% for incidence of eggs in soybean and the occurrence of adults explained 81% for the same parameter (eggs).

Análise espaço-temporal de mosca-branca Bemisia tabaci (Genn., 1889) biótipo B (Hemiptera: Aleyrodidae) na cultura da soja, no município de Paragominas - Pará

The objective of this study is to evaluate the progress of whitefly Bemisia tabaci biotype B infestation during the crops of 2015, 2016 and 2017, to identify between crops studied in which they increased or decreased infestation and in which month the infestation was more representative, to identify among the cultivars which one or which are most susceptible to the attack and to map the areas of incidence of the whitefly. The research to obtain the data was carried out in the municipality of Paragominas and the data were obtained from Defense Agency of the State of Pará according to the methodology based on a model predefined by the agency. Climatic data on rainfall (mm) for crops were obtained through a database of the Brazilian Agricultural Research Corporation meteorological station. For statistical analysis of data, a database was built into Microsoft Excel spreadsheets. Data were analyzed through regression analysis and compared by the Tukey and Scott &amp; Knott test. For the preparation of the whitefly infestation maps, the Spatial Analyst extension in the ArcGIS 10.1 software was used. In the studied area, the month of April is the one with the highest incidence of the pest, the crop of 2017 presented greater infestation, the cultivar P99R03 RR was the most susceptible to the attack of whitefly, and the cultivars P98Y51 RR and FT PGM, were more resistant to whitefly (B. tabaci) biotype B than the other cultivars.

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.

Resistance of cotton genotypes to silverleaf whitefly (Bemisia tabaci [GENNADIUS] Biotype B)

Silverleaf whitefly (Bemisia tabaci biotype B) has caused significant damage, year after year, and can be considered one of the major pests responsible for the increase in use of insecticides in cotton. This research aimed to evaluate the biology and preference for oviposition and feeding of Bemisia tabaci biotype B in wild cotton genotypes. The experiments were conducted at the Experimental Farm of the Mato Grosso do Sul State University, Cassilândia-MS, from March 24th to May 13th, 2017. The treatments were composed of the following genotypes:, APGO 01 and APGO 02 (Gossypium barbadense),TEX 1116 and TEX 1964 (G. hirsutum) and G. arboreum acquired in EMBRAPA germplasm, BRS 269 (standard cultivar/control) widely grown in Brazil. The infestations were carried out on plants 25 days after emergence in a no-choice test and at 42 days for the free-choice test, the cages they were infested with 100 whitefly adults per plant. The number of eggs per leaf, the density of trichomes, the viability of nymphs and the duration of the juvenile phases, in days, on the youngest leaf in the upper third of the plant were evaluated. The averages for cotton genotypes were grouped by the Scott Knott test at the 5% probability level. Low preference for oviposition of B. tabaci biotype B on genotypes APGO 01 and APGO 02 was observed in the no-choice test. The genotypes APGO 01, APGO 02, and BRS 269 were the least preferred for oviposition and had the lowest density of trichomes at 43 days after emergence in 24 hours after infestation. It was verified that in the genotypes APGO 01 and APGO 02, there was an increase in the density of trichomes, and consequently, there was an increase in the number of eggs per cm² in 48 hours after infestation. After 72 hours of infestation, a positive and significant correlation (r = 0687**) was observed between the number of eggs per cm² and the density of trichomes. A positive correlation was observed between the density of trichomes and the preference of oviposition. A negative effect of glandular trichomes and preference for oviposition was observed for APGO 02.. Resistance by antibiosis and / or non-preference for feeding in the genotypes APGO 01, APGO 02 and G. arboreum were observed for prolonging the development of the insect in the juvenile/nymph phase.

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

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

Insecticidal and inhibitory effects of Meliaceae and Asteraceae extracts to silverleaf whitefly

ABSTRACT Bemisia tabaci (Hemiptera: Aleyrodidae) is a polyphagous insect that causes direct and indirect damage on tomato. Spraying with synthetic insecticides is one of the main control tools for the whitefly; however, the abusive use of this tool can impact the environment and human beings. In this study we evaluated the bioactivity of extracts from plant species from Asteraceae and Meliaceae families on B. tabaci biotype B in tomato. A preliminary bioassay evaluated the effects of the extracts at 2% (w/v) on infestation and oviposition of this whitefly. Then, the nymphicidal and ovicidal effects of the chloroformic extract of Trichilia pallida - TP-Cl at six concentrations were performed. Finally, the TP-Cl LC50 was estimated. All extracts were repellent to the whitefly, except that ones from T. pallida (ethanolic) and Melia azedarach (hexanic), considered neutral at 24 h. All the extracts caused deterrence of oviposition. All concentrations of TP-Cl revealed nymphicidal activity and the highest ones provided the lowest egg viability averages. The estimated LC50 was 0.0955%. These results provide evidence for the potential of the extracts to be used as alternative control agents of B. tabaci biotype B in tomatoes.

Induced Tomato Resistance Against Bemisia tabaci Triggered by Salicylic Acid, β-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 β-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.

First Report of Tomato Chlorosis Virus Infecting Tomato in Pakistan

Tomato chlorosis virus (ToCV) is a bipartite crinivirus (Closteroviridae) consisting of two positive-sense single-stranded RNAs: RNA1 and RNA2 (Fiallo-Olive and Navas-Castillo 2019). It is a phloem-limited virus transmitted by whiteflies (Bemisia tabaci and Trialeurodes vaporariorum) in a semipersistent manner (Fiallo-Olive and Navas-Castillo 2019; Lee et al. 2018). In March 2019, a survey of the tomato crop (cv. Richman) was conducted in the Multan district of Pakistan; 35% of plants in the crop showed virus-like symptoms such as interveinal chlorosis, brittleness, and general yellowing in the older and middle leaves. These symptoms were similar to those caused by ToCV and tomato infectious chlorosis virus (TICV) (Wisler et al. 1998). Tomato plants were infested by dense (20/leaf) whitefly (B. tabaci) populations. Thirty-six samples were collected from different plants (30 symptomatic and six asymptomatic) and were tested for ToCV and TICV. Total RNA was extracted from leaf samples using TRIzol reagent and assayed by RT-PCR, targeting the ToCV movement protein gene with primers ToCV-RNA2-IF and ToCV-RNA2-1R (Lee et al. 2018) and the TICV heat shock protein homolog gene with primers TICV-32 and TICV532 (Vaira et al. 2002). RT-PCR was also performed to target the clathrin adaptor complexes medium subunit (CAC), a reference protein gene of tomato, by using the forward primer 5′-CCTCCGTTGTGATGTAACTGG-3′ and the reverse primer 5′-ATTGGTGGAAAGTAACATCATCG-3′ (amplification size: 173 bp) (Gonzalez-Aguilera et al. 2016). Twenty-seven of 30 samples yielded the 827-bp ToCV product, whereas no amplification was obtained in any of the asymptomatic samples. TICV was not detected in any of the analyzed samples. Whiteflies (B. tabaci biotype B) collected from disease-free cotton plants and reared on cucumber plants (nonhost of ToCV) under greenhouse conditions were used in the transmission assay. One hundred nonviruliferous whiteflies were given an acquisition access period (AAP) of 48 h on an infected ToCV tomato plant and then transferred onto 20 healthy tomato seedlings (hybrid Richman, 5 whiteflies/seedling in one cage) for a 48-h inoculation access period (IAP). To ascertain that the whiteflies were nonviruliferous, 100 whiteflies were transferred onto five healthy tomato plants (20 whiteflies/plant) for an IAP of 48 h. Sixteen of 20 inoculated plants showed typical ToCV symptoms 28 days postinoculation, and ToCV was detected by RT-PCR using the ToCV-specific primers. No symptoms were observed on the negative control plants, confirming the nonviruliferous nature of whiteflies. The ToCV-positive tomato plants were used as a source for back inoculation to an indicator host, Nicotiana benthamiana. About 200 nonviruliferous whiteflies were given a 48-h AAP on the ToCV-infected tomatoes and then transferred to four healthy N. benthamiana plants (50 whiteflies/plant) for a 48-h IAP, and two healthy N. benthamiana plants were controls (fed on by nonviruliferous whiteflies). All ToCV-inoculated N. benthamiana plants showed distinctive symptoms of yellowing, interveinal chlorosis, and leaf brittleness; no symptoms were observed on the control plants. RT-PCR confirmed ToCV in symptomatic indicator plants and its absence in the control plants. The amplicons (movement protein gene) of two selected ToCV isolates from the field plants were sequenced in both directions. The resulting sequences were submitted to NCBI (MN385628 and MN385629). BLASTn analysis of the sequences revealed that the newly identified isolates are 99.88% identical to isolates reported from Turkey (KY419528), China (KJ815045), and Greece (EU284744). To our knowledge, this is the first report of ToCV infecting tomato in Pakistan. The wide occurrence of ToCV and its whitefly vectors in tomato crops in the region indicates that effective integrated management measures are needed to minimize losses caused by the virus in tomato.