Whitefly Densities Research Articles

Enhancing cotton whitefly (Bemisia tabaci) detection and counting with a cost-effective deep learning approach on the Raspberry Pi.

The cotton whitefly (Bemisia tabaci) is a major global pest, causing significant crop damage through viral infestation and feeding. Traditional B. tabaci recognition relies on human eyes, which requires a large amount of work and high labor costs. The pests overlapping generations, high reproductive capacity, small size, and migratory behavior present challenges for the real-time monitoring and early warning systems. This study aims to develop an efficient, high-throughput automated system for detection of the cotton whiteflies. In this work, a novel tool for cotton whitefly fast identification and quantification was developed based on deep learning-based model. This approach enhances the effectiveness of B. tabaci control by facilitating earlier detection of its establishment in cotton, thereby allowing for a quicker implementation of management strategies. We compiled a dataset of 1200 annotated images of whiteflies on cotton leaves, augmented using techniques like flipping and rotation. We modified the YOLO v8s model by replacing the C2f module with the Swin-Transformer and introducing a P2 structure in the Head, achieving a precision of 0.87, mAP50 of 0.92, and F1 score of 0.88 through ablation studies. Additionally, we employed SAHI for image preprocessing and integrated the whitefly detection algorithm on a Raspberry Pi, and developed a GUI-based visual interface. Our preliminary analysis revealed a higher density of whiteflies on cotton leaves in the afternoon and the middle-top, middle, and middle-down plant sections. Utilizing the enhanced YOLO v8s deep learning model, we have achieved precise detection and counting of whiteflies, enabling its application on hardware devices like the Raspberry Pi. This approach is highly suitable for research requiring accurate quantification of cotton whiteflies, including phenotypic analyses. Future work will focus on deploying such equipment in large fields to manage whitefly infestations.

Whiteflies can excrete insecticide-tainted honeydew on tomatoes

Whiteflies are important insect pests in a wide variety of agricultural crops that are targeted with large quantities of insecticides on a global scale. Chemical control is the most common strategy to manage whiteflies, however, recent studies had reported that whiteflies and other hemipterans can excrete insecticides through their honeydew, which could have unanticipated, non-target effects. The objective of this study was to determine the concentration of imidacloprid in honeydew excreted by whiteflies feeding on tomato plants. Imidacloprid was applied at its labeled rate to soil at the base of whitefly-infested plants. Densities of whiteflies were assessed before insecticide treatment and 21 days after treatment (DAT). Honeydew was collected in Petri dishes from 1 to 4 DAT and from 5 to 8 DAT. The volume of the honeydew was calculated using stereo microscopy and then rinsed with ethanol. The rinsates were analyzed to determine imidacloprid concentration using liquid chromatography coupled to mass spectrometry. Honeydew production was further quantified by using water sensitive papers. Imidacloprid reduced densities of nymph and adult whiteflies by 81.5% and 76.0% compared to the control at 21DAT. The non-metabolized parent compound imidacloprid was detected from honeydew samples at both collection dates. At 1–4 DAT, imidacloprid concentrations were 180 ng/30 mL in a volume of 39 mm3 of honeydew. At 5–8 DAT, the imidacloprid concentration was 218 ng/30 mL in a volume of 25 mm3 of honeydew. Though the volume of honeydew decreased, the concentration of imidacloprid numerically increased. Last, whiteflies were still producing honeydew 22 DAT in both treatments. These results revealing significant imidacloprid concentrations in honeydew suggest a strong potential for negative secondary impacts on beneficial insects.

Population dynamics of major insect pests infesting chilly, bottle gourd and cucumber

A set of experiments was carried out to investigate the population dynamics of important insect pests that infest capsicum, bottle gourd and cucumber. Results revealed that aphid (Aphis gossypii Glover), whitefly (Bemisia tabaci Genn.) and leafhopper (Amrasca biguttula), and commenced the activity during the second and third week of October and November. The mean thrips peak population find in the second and third week of October in chilly (6.90) whereas third week for bottle gourd as well as cucumber (8.88 and 9.67 respectively). The average white fly density maximum is seen between the second of October in chilly, bottle gourd and cucumber (6.19, 8.88 and 9.67 respectively). Leaf hopper population also heigh in second week of October (5.02, 5.76 and 5.65) for chilly, bottle gourd and cucumber. Second and third week of October had maximum incidence of thrips and white fly population in bottle gourd as compare to chilly and cucumber.

First Report of African Eggplant Yellowing Virus on Tomato Exhibiting Necrotic Yellowing Symptoms in Northern Côte d’Ivoire

HomePlant DiseaseVol. 107, No. 2First Report of African Eggplant Yellowing Virus on Tomato Exhibiting Necrotic Yellowing Symptoms in Northern Côte d’Ivoire PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of African Eggplant Yellowing Virus on Tomato Exhibiting Necrotic Yellowing Symptoms in Northern Côte d’IvoireA.-J. N’cho, K. Séka, L. Bele, H. Diallo, T. Martin, N. Coulibaly, L. Fondio, M. Hoareau, P. Lefeuvre, and J.-M. LettA.-J. N’choUniversité Nangui Abrogoua, Pôle de Recherche Production Végétale, Abidjan, Côte d’IvoireSearch for more papers by this author, K. SékaUniversité Nangui Abrogoua, Pôle de Recherche Production Végétale, Abidjan, Côte d’IvoireSearch for more papers by this author, L. BeleUniversité Nangui Abrogoua, Pôle de Recherche Production Végétale, Abidjan, Côte d’IvoireSearch for more papers by this author, H. DialloUniversité Nangui Abrogoua, Pôle de Recherche Production Végétale, Abidjan, Côte d’IvoireSearch for more papers by this author, T. MartinUniversité Félix Houphouët Boigny, Centre d’Excellence Wascal, Abidjan, Côte d’IvoireCIRAD, UR Hortsys, Université de Montpellier, Montpellier, FranceSearch for more papers by this author, N. CoulibalyCentre National de Recherche Agronomique, Programme Cultures Maraîchères et Protéagineuses, Bouaké, Côte d’IvoireSearch for more papers by this author, L. FondioCentre National de Recherche Agronomique, Programme Cultures Maraîchères et Protéagineuses, Bouaké, Côte d’IvoireSearch for more papers by this author, M. HoareauCIRAD, UMR PVBMT, F-97410 Saint-Pierre, La Réunion, FranceSearch for more papers by this author, P. LefeuvreCIRAD, UMR PVBMT, F-97410 Saint-Pierre, La Réunion, FranceSearch for more papers by this author, and J.-M. Lett†Corresponding author: J.-M. Lett; E-mail Address: [email protected]https://orcid.org/0000-0003-1585-5338CIRAD, UMR PVBMT, F-97410 Saint-Pierre, La Réunion, FranceSearch for more papers by this authorAffiliationsAuthors and Affiliations A.-J. N’cho1 K. Séka1 L. Bele1 H. Diallo1 T. Martin2 3 N. Coulibaly4 L. Fondio4 M. Hoareau5 P. Lefeuvre5 J.-M. Lett5 † 1Université Nangui Abrogoua, Pôle de Recherche Production Végétale, Abidjan, Côte d’Ivoire 2Université Félix Houphouët Boigny, Centre d’Excellence Wascal, Abidjan, Côte d’Ivoire 3CIRAD, UR Hortsys, Université de Montpellier, Montpellier, France 4Centre National de Recherche Agronomique, Programme Cultures Maraîchères et Protéagineuses, Bouaké, Côte d’Ivoire 5CIRAD, UMR PVBMT, F-97410 Saint-Pierre, La Réunion, France Published Online:30 Jan 2023https://doi.org/10.1094/PDIS-05-22-1016-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleIn February 2019, virus-like symptoms of necrotic yellowing were observed on tomato plants in a field plot in the locality of Odiénné in the Denguélé region of the north of Côte d’Ivoire (8°14.157′N; 6°26.772′W), together with high disease incidence and dense whitefly populations. The observed symptoms were similar to those associated with the poleroviruses (family Solemoviridae) recently described on pepper (Capsicum spp.) in Benin and on African eggplant (Solanum aethiopicum) in Mali (Afouda et al. 2017). To identity the potential agent(s) causing these symptoms, five samples from symptomatic plants and five samples from asymptomatic plants were collected, dehydrated, and subjected to total RNA extraction using the RNeasy Plant Extraction kit (Qiagen, Courtaboeuf, France). The presence of poleroviruses in the samples was tested by RT-PCR using the universal primers PoconF and PococpR (1.4-kb fragment) designed by Xiang et al. (2008) and modified by Knierim et al. (2010) for the detection of poleroviruses. Two symptomatic samples (CI370 and CI371) tested positive. The RT-PCR product amplified from sample CI371 was directly sequenced in a single direction. BLASTn analysis showed that its nucleotide sequence shared 83.2% identity with that of an isolate of African eggplant yellowing virus from Benin (AeYV; KX856975). Based on this reference sequence, specific primers AeYV-F3249 (5′-GTCTAGGTTTCAAAGTCGAGG-3′) and AeYV-RD4339 (5′-CTACCTATTTKGGRTTGTGCAG-3′) were designed for the amplification of a 1,091-bp product covering part of AeYV ORFs 2 and 3 and used in RT-PCR experiments on total RNA extracted from the 10 tomato leaf samples collected in Odiénné. Amplicons of the expected size were obtained from three symptomatic samples (CI367, CI370, and CI371) and subjected to direct sequencing in both directions. BLASTn analysis showed that all three assembled nucleotide sequences (GenBank accession nos. ON228068, ON228069, and ON228070) were identical and shared 98.4 and 93.7% similarity with sequences of the Beninese (KX856975) and Malian (KX856972) isolates of AeYV, respectively. To our knowledge, this is the first report of AeYV both on tomato and in Côte d’Ivoire. The detection of AeYV on pepper, eggplant, and tomato in several West African countries raises the question of whether this virus is emerging elsewhere in West Africa and on other solanaceous crops. Furthermore, while the majority of poleroviruses are transmitted by aphids (Dombrowsky et al. 2010), recent studies have characterized new whitefly-transmitted poleroviruses in Israel (Ghosh et al. 2019) and Brazil (Costa et al. 2020). The high density of whiteflies observed on diseased plants in Côte d’Ivoire raises the question of whether whiteflies also are a vector of AeYV. The distribution, incidence, transmission, and impacts of AeYV on vegetables in West Africa is still unknown and needs to be further investigated to develop accurate control strategies.The author(s) declare no conflict of interest.

Determination of Whitefly Species (Hemiptera: Aleyrodidae) in Southeastern Anatolia Region

Türkiye’nin tüm bölgelerinde tespit edilen Beyazsinek (Hemiptera: Aleyrodidae) türleri üzerinde yapılan taksonomik bir çalışmadır. Güneydoğu Anadolu Projesi (GAP) faliyete başlamasıyla artan bitki türü çeşitliliği ve tüm yıl ürün alınabilmesimesinden kaynaklı olarak tüm yıl varlığını koruyan bir zararlı konumuna gelmiştir. Ayrıca tarımsal sulamadan dolayı artan nem oranı Beyazsinek yoğunluğu artırmış olup bu nedenle tarımsal ürünlerde ciddi zarar verdiği için Güneydoğu Anadolu Bölgesi için önemli bir zararlı olmuştur. 2019-2022 yılları arasında Güneydoğu Anadolu Bölgesi’nde bulunan Şırnak, Siirt, Batman, Diyarbakır, Mardin, Şanlıurfa, Adıyaman, Gaziantep ve Kilis illerindeki farklı konukçulardan toplanan Aleyrodidae familyasına ait türler, pupa ve pupa kabuğunadan morfolojik tanı karakterleri kullanılarak Beyazsinek (Hemiptera: Aleyrodidae) türlerinin belirlenmesi amacıyla yapılmıştır. Çalışmada tarım, orman ve tarım dışı alanlardan örnekler toplanmıştır. Çalışma esnasında örnek toplama yılın tüm dönemlerinde düzensiz çıkışlar yapılarak gerçekleştirilmiştir. Toplanan örneklerden 9 beyazsinek türü tespit edilmiştir. Bu türler; Bemisia afer, B. tabaci, Dialeurodes citri, Dialeurolobus pulcher, D. rhamni, Massileurodes setiger, Siphoninus phillyreae, Trialeurodes vaporariroum ve Tetraleurodes neemani olarak tespit edilmiştir.

The insecticidal potential of neem extracts (Azadirachta indica JUUS) against whiteflies (B. tabaci) in tomato crops

The tomato (Solanum lycopersicum) is one of the main vegetables grown in Sinaloa. This crop is affected by pest insects, such as the white fly (Bemisia tabaci). The objective was to evaluate the effect of different doses of neem-based biorational insecticide on the population density of whiteflies. A completely randomized design was established to evaluate the population density of whitefly adults. The treatments evaluated were different doses of neem leaf extracts (NLE): (T1) control, (T2) 200 g NLE•L-1, (T3) 300 g NLE•L-1, (T4) 400 g NLE•L-1 and (T5) 500 g NLE•L-1. An analysis of covariance was applied to the data obtained and the difference between the means was evaluated using the Tukey test with an α=0.05. Neem extracts had an effect on population density (p≤0.05), by reducing the population as the concentration of the extracts increased. T5 presented the highest reduction with 43.56%±1.6, while T4 presented a reduction of 39.27%±1.7, compared to the control. However, the application of T5 causes damage to the plant, so it can be considered that T4 is more suitable for its application. Therefore, neem extracts had an effect in controlling the whitefly population.

Use of UV-LED light to enhance establishment of Nesidiocoris tenuis for control of Bemisia tabaci infesting greenhouse tomato

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major pest of greenhouse tomato and Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is an effective predator of this whitefly. Previously, we found that 385 nm LED lighting improved the predatory performance of N. tenuis on B. tabaci under laboratory conditions, ostensibly via mutual attraction of bugs and whiteflies to this wavelength, and improved aggregation of both insects around the light sources. Here we verified that LED lighting at 385 nm enhances the establishment of N. tenuis releases on tomato plants infested with B. tabaci under greenhouse conditions. In the first trial, conducted May-July, both whiteflies and predators were released three times; whitefly densities were not affected by LED lighting when predators were absent, but ended the experiment at lower densities when N. tenuis releases were combined with LED lighting than when they were not. In a second trial, conducted September-November under cooler conditions, a single whitefly release established an infestation and was followed by a single release of N. tenuis in two treatments, with and without LED. The LED lighting treatment maintained lower whitefly densities over a two month period in the crop, and higher densities of predators, than the predators-only treatment. Therefore, possible applications of short wavelength LED lighting to enhance N. tenuis augmentation programs in greenhouse settings appear worthy of further evaluation.

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.

Predacious activity of Serangium parcesetosum Sicard (Coleoptera: Coccinellidae) on Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) on caged tomato

Tomatoes are the most familiar and the most common greenhouse vegetable crop in Turkey, as well as worldwide. Main whitefly species problematic in the greenhouses, where tomatoes grown primarily, is Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) in Mediterranean Region of Turkey. Serangium parcesetosum Sicard (Coleoptera: Coccinellidae) is proved as a coccinellid predator of B. tabaci and a voracious feeder by several studies. The hypothesis “the outcome of a biological control program is determined by the initial pest to predator ratio” was examined on caged tomato in greenhouses. The current study showed the influence of initial whitefly density on the whitefly population growth rate, which was independent of the absence or presence of S. parcesetosum (P> 0.05) for the whitefly density × predator release interaction). No significant differences in whitefly suppression from S. parcesetosum predation were monitored between the two initial whitefly densities in both years. The density of the pest was reduced by S. parcesetosum in high and moderate initial whitefly density cages 2-3 weeks after releasing the ladybird beetles. During the experiment, copulating adults, larvae, and pupae of the predatory ladybird beetle were observed in both predator-releasing cages. These results indicated that S. parcesetosum can survive and reproduce on tomato plants in greenhouse production during the spring months in Mediterraenean region of Turkey.

Regulation of dynamics and densities of whitefly Bemisia tabaci by agricultural landscapes in south China

Agricultural landscape patterns can affect the population dynamics of pest insects. We selected four landscapes (flower field, mountain, river and urban) based on principal components analysis in Yunnan Province, south China. Through systematic investigation carried out in tomato fields, we intended to clarify the population dynamics and densities of Bemisia tabaci under different landscape types. During the main activity period of B. tabaci, the population densities of B. tabaci nymphs in tomato fields in the river and the urban landscape types were the highest compared to the other landscape types; the population densities of female adults in tomato fields in the river landscape type were also the highest. While the population densities of B. tabaci nymphs and female adults in the flower landscape type, no more than five individuals (ind.) 100 cm−2 leaf in both years, were the lowest. The density of B. tabaci nymphs in the middle position of tomato plants was higher than those in the other positions, while the density of adults in the upper position of tomato plants was higher, regardless of landscape types. Our findings showed that the population growth of B. tabaci can be easily controlled by the flower landscape type.

A comparison of repetitive releases of single or multiple natural enemy species on the suppression of Bemisia tabaci infesting poinsettias

The repetitive release of Eretmocerus eremicus (Mercet) (Hymenoptera: Aphelinidae) to manage Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a promising strategy on poinsettias in protected culture. Management of B. tabaci, however, may be improved if releases include multiple natural enemy species that attack different B. tabaci life stages. In this study, we investigate whether suppression of B. tabaci on poinsettias is improved by the combination of E. eremicus and Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) compared to either natural enemy alone at release rates 1.2 – 2.7-fold the cost of conventional insecticide inputs. We found that all natural enemy treatments provided significant suppression when starting whitefly populations were below 13.7 ± 1.7 immatures per plant. The combination of E. eremicus and A. swirskii performed equally well compared to either natural enemy alone, in both a substitutive and additive design. These effects, however, were density dependent; neither natural enemy alone nor the combination of natural enemies suppressed whiteflies if initial whitefly density was above 40.8 ± 2.5 immature whiteflies per plant.

Whitefly Abundance on Rooted Poinsettia Cuttings and Finished Poinsettias

In this study, we surveyed the initial whitefly (Aleyrodidae) populations on rooted poinsettia (Euphorbia pulcherrima) cuttings at two commercial greenhouse facilities in both 2017 and 2018 to determine the initial whitefly population at the beginning of poinsettia production and surveyed finished poinsettias at multiple retailers in Tyler, TX, over 2 years to determine whitefly densities considered acceptable by retailers. The initial whitefly population (mean ± se) for all poinsettias was 0.02 ± 0.02 (2017) and 0.33 ± 0.13 (2018) nymphs per plant for grower facility A and 0.05 ± 0.05 (2017) and 0.02 ± 0.01 (2018) nymphs per plant for grower facility B. Of the total 2417 rooted poinsettia cuttings inspected at both locations over 2 years, 29 cuttings had whitefly nymphs (1.2%), 18 had pupae (0.7%), and 23 had exuviae (1.0%). On finished poinsettias sampled at retailers, 4.38 to 40.38 immatures (nymphs + pupae) per plant were found within 60 seconds for any given retailer over the 2 years. We found poinsettias with as many as 220 immatures and 32 adults on a single plant at retailers. This study is the first to quantify densities of whiteflies at retail stores over multiple years.

Computational models to improve surveillance for cassava brown streak disease and minimize yield loss.

Cassava brown streak disease (CBSD) is a rapidly spreading viral disease that affects a major food security crop in sub-Saharan Africa. Currently, there are several proposed management interventions to minimize loss in infected fields. Field-scale data comparing the effectiveness of these interventions individually and in combination are limited and expensive to collect. Using a stochastic epidemiological model for the spread and management of CBSD in individual fields, we simulate the effectiveness of a range of management interventions. Specifically we compare the removal of diseased plants by roguing, preferential selection of planting material, deployment of virus-free 'clean seed' and pesticide on crop yield and disease status of individual fields with varying levels of whitefly density crops under low and high disease pressure. We examine management interventions for sustainable production of planting material in clean seed systems and how to improve survey protocols to identify the presence of CBSD in a field or quantify the within-field prevalence of CBSD. We also propose guidelines for practical, actionable recommendations for the deployment of management strategies in regions of sub-Saharan Africa under different disease and whitefly pressure.

Relationship between Some Environmental and Climatic Factors on Outbreak of Whiteflies, the Human Annoying Insects.

Background:The reports of numerous outbreaks of whiteflies from different parts of the world have increased its medical importance. The aim of this study was to determine relationship between environmental changes and climatic factors with the outbreak of the whitefly population in Tehran, the capital of Iran.Methods:This study was carried out in urban areas of Tehran, where the increasing population of whiteflies was reported frequently during 2018. In order to entrap the whiteflies, 20 yellow sticky cards smeared with white refined grease were installed on the trunks of the trees at twice per month as trapping time intervals. The captured flies were transferred and conserved in cans containing 70% alcohol and were counted accurately under a stereomicroscope. To determine the relationship between air quality index, precipitation, air temperature and air humidity as environmental and climatic factors with the abundance of whiteflies, change point analysis and Generalized Estimating Equations (GEE) was used.Results:The most density of white flies per trap was 256.6 and 155.6 in early October and late September respectively. The number moved closer to zero from November to April. The population of whiteflies was inversely correlated with the level of air quality index (p= 0.99) and precipitation (p= 0.95), and it had a direct correlation with the high temperature. Also, the population of whiteflies had a direct correlation with the level of air humidity in the first half of the yearConclusion:According to these findings, during spring and summer from early May to early October.

Evaluation of cultural control and resistance-breeding strategies for suppression of whitefly infestation of cassava at the landscape scale: a simulation modeling approach.

BACKGROUNDThe whitefly Bemisia tabaci is an important vector of virus diseases, impacting cassava production in East Africa. To date, breeding efforts in this region have focused on disease resistance. Here we use a spatially‐explicit simulation model to explore how breeding strategies for whitefly resistance will influence the population dynamics of whitefly in the context of regional variation in cassava crop management practices.RESULTSSimulations indicated that regions with a short cropping cycle and two cropping seasons per year were associated with high whitefly abundance. Nymph mortality and antixenosis resistance mechanisms were more effective than mechanisms that lead to longer whitefly development times. When spatial variation was introduced in heterogeneous landscapes, however, negative consequences of the antixenosis effect were observed in fields containing whitefly susceptible varieties, unless the proportion of whitefly resistant variety in the landscape was low (~10%) or the amount of matrix in the landscape was high (~75%).CONCLUSIONWe show the importance of considering cropping regime and landscape management context when developing and deploying whitefly‐resistant cassava varieties. Recommendations differ significantly between regions. There may also be unintended negative consequences of higher whitefly densities for whitefly susceptible varieties if uptake of the new variety in a landscape is high, depending on the mechanism of resistance and the landscape context. Furthermore, we show that in some cases, such as where there is substantial fallow combined with a short single‐season crop, the management characteristics of the existing cropping regime alone may be effective at controlling whitefly populations. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Parasitoid Eretmocerus hayati Is Compatible with Barrier Cropping to Decrease Whitefly (Bemisia tabaci MED) Densities on Cotton in China

The whitefly, Bemisia tabaci (Gennadius) cryptic species Mediterranean (MED), is a destructive insect pest worldwide. In order to contribute to controlling B. tabaci by non-chemical methods, we examined the possibility of using a combination of trap/barrier crops and a parasitoid natural enemy in cotton. We performed field experiments using cantaloupe (Cucumis melo) and sunflower (Helianthus annuus) as trap crops and maize (Zea mays) as a barrier crop combined with periodic releases of the parasitoid Eretmocerus hayati in Hebei Province, Northern China. All treatments significantly reduced immature whitefly densities. Parasitism rate was significantly higher in cotton plots intercropped with sunflower and with perimeter-planted cantaloupe. Adult whitefly density was negatively related to parasitoid abundance and was significantly lower in cotton plots intercropped with maize than in the control plots. Intercropping was more effective than perimeter-planting at reducing B. tabaci densities and increasing yield. Parasitoid dispersal was not hampered by barrier crops, indicating that the two methods of control are compatible. These results contribute to the development of integrated pest management methods against this important pest.

Application of phytoseiid mites for whitefly control on roses in the North-West of Russia

Predatory mites Amblyseius swirskii and Neoseiulus cucumeris are considered as effective biocontrol agents against whitefly and thrips in indoors on vegetable crops. Our goal was to assess the effect of these predatory mites on whitefly density on roses indoors in the North-West of Russia. Result showed that the dynamics of the pest population is affected not only by the predator release rate, but also by the time between introductions and their frequency. There was no difference between two species, except one case, when temperatures had risen above 27°C and consequently A. swirskii had a bigger impact on whiteflies than N. cucumeris.

Incidence, severity and distribution of Cassava brown streak disease in northeastern Democratic Republic of Congo.

Cassava fields were prospected from two provinces of the Democratic Republic of Congo (Ituri and Haut Uélé) to evaluate the ampleness of Cassava brown streak disease (CBSD) infection. CBSD pressure was determined by assessing the incidence, severity, whitefly abundance and distribution of the disease viruses in the surveyed provinces. A duplex RT-PCR was performed for the simultaneous detection of Ugandan Cassava brown streak virus (UCBSV) and Cassava brown streak virus (CBSV) on 56 cassava leaves sampled in the study area. Our results show a high field CBSD incidence contrasted to a low severity in both provinces. CBSD severity was similar in both provinces (mean disease severity 2). High densities of whitefly were recorded in Ituri province (10 adult whiteflies plant−1) than in Haut Uélé where density was 5 adults plant−1. However, no relation has been found between whitefly density and CBSD incidence and severity on cassava leaf, root and stems. Molecular analysis showed the incidence of single infections of UCBSV was greater than single infections of CBSV and mixed infections of UCBSV and CBSV. Disease incidence was greater in Ituri than in Haut Uélé; molecular incidence was lower than field incidence. Our results raise the need for appropriate CBSD control strategies in DRC.

Spatial and Temporal Physiognomies of Whitefly and Tomato Yellow Leaf Curl Virus Epidemics in Southwestern Florida Tomato Fields.

Epidemics of tomato yellow leaf curl virus (TYLCV; species Tomato yellow leaf curl begomovirus) have been problematic to tomato production in the southeastern United States since the first detection of the virus in Florida in the late 1990s. Current strategies for management focus on farm-centric tactics that have had limited success for controlling either TYLCV or its whitefly vector. Areawide pest management (AWPM)-loosely defined as a coordinated effort to implement management strategies on a regional scale-may be a viable management alternative. A prerequisite for development of an AWPM program is an understanding of the spatial and temporal dynamics of the target pathogen and pest populations. The objective of this study was to characterize populations of whitefly and TYLCV in commercial tomato production fields in southwestern Florida and utilize this information to develop predictors of whitefly density and TYLCV disease incidence as a function of environmental and geographical factors. Scouting reports were submitted by cooperating growers located across approximately 20,000 acres in southwestern Florida from 2006 to 2012. Daily weather data were obtained from several local weather stations. Moran's I was used to assess spatial relationships and polynomial distributed lag regression was used to determine the relationship between weather variables, whitefly, and TYLCV. Analyses showed that the incidence of TYLCV increased proportionally with mean whitefly density as the season progressed. Nearest-neighbor analyses showed a strong linear relationship between the logarithms of whitefly densities in neighboring fields. A similar relationship was found with TYLCV incidences. Correlograms based on Moran's I showed that these relationships extended beyond neighboring fields and out to approximately 2.5 km for TYLCV and up to 5 km for whitefly, and that values of I were generally higher during the latter half of the production season for TYLCV. Weather was better at predicting whitefly density than at predicting TYLCV incidence. Whitefly density was best predicted by the number of days with an average temperature between 16 and 24°C (T16to24), relative humidity (RH) over the previous 31 days, and vapor pressure deficit over the last 8 days. TYLCV incidence was best predicted by T16to24, RH, and maximum wind speed over the previous 31 days. Results of this study helped to identify the extent to which populations of whitefly and TYLCV exist over the agricultural landscape of southwestern Florida, and the environmental conditions that favor epidemic growth. This information was used to propose an approach to AWPM for timing control measures for managing TYLCV epidemics.

The potential of trap and barrier cropping to decrease densities of the whitefly Bemisia tabaci MED on cotton in China.

The whitefly, Bemisia tabaci (Gennadius) MED, is a destructive insect pest in many countries of the world. Although the use of insecticides for controlling B. tabaci has been effective to a certain extent, pesticides are not an acceptable long-term control method, and alternatives should be sought. This paper focuses on the possibility of controlling B. tabaci on cotton using trap and barrier crops. We performed field experiments using cantaloupe (Cucumis melo) and sunflower (Helianthus annuus) as trap crops, and maize (Zea mays) as a barrier crop in various configurations in Hebei Province, North China. The main activity periods were shortest on cantaloupe and ranged between 16-32 days for immatures and 14-33 days for adults. Adult whitefly densities were not significantly reduced by any treatment. During the main activity period, maize intercropping reduced densities of immature whiteflies from 24.2 individuals (ind.) 100 cm-2 to 4.0 ind.100 cm-2 , but all treatments were successful in significantly reducing immature B. tabaci densities. This resulted in a significant yield premium. Intercropping reduced B. tabaci densities on cotton more than perimeter planting. Maize was more effective to reduce densities of immature whiteflies on cotton than cantaloupe. The results will contribute to the development of more effective and practical approaches for protecting cotton from B. tabaci and lowering chemical pressure on this crop. © 2019 Society of Chemical Industry.