Host preferences and biotic potential of <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> and <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Hemiptera: Aleyrodidae) in tomato and pepper

Whiteflies Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are important pests in pepper (Capsicum annuum L.) and tomato (Solanum lycopersicum L.) crops in many countries. Contrary to what is observed for all other countries, in Uruguay, B. tabaci is mainly found on pepper and rarely on tomato, while T. vaporariorum is exclusively found on tomato. This study tested the oviposition preferences and biotic potential of these two whiteflies reared on both host plants. The developmental time, survival rates, longevity, fecundity and main population parameters were characterized. Both whitefly species showed different preference patterns regarding their host plants. T. vaporariorum preferred tomato instead of pepper to oviposit. Their developmental time is longer on pepper. B. tabaci preferred pepper, but the difference from tomato was not very strong. Pepper affects the biotic expression of T. vaporariorum negatively, while B. tabaci is able to develop equally on both host plants. These results show that the distribution differences of both whiteflies observed on both host plants could have a biological basis.     

Performance of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> Biotype B on Soybean Genotypes

Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) has been recognized as an important pest of many agricultural systems including soybean [Glycine max (L.) Merrill] crops. As an alternative to chemical control, the use of resistant genotypes represents an important tool for integrated pest management (IPM). This study aimed to evaluate the biological development of Bemisia tabaci biotype B confined on 13 soybean genotypes under greenhouse conditions. Initially, the nymphal period, complete development period (egg–adult), and the viability of the silverleaf whitefly nymphs were evaluated in all genotypes. Then, four genotypes promising for resistance (‘Jackson,’ UX-2569-159, ‘P98Y11,’ and ‘TMG132 RR’) and a susceptible genotype (PI-227687) were selected for further assays, where two insect populations were compared: a first population from the initial rearing (cabbage plants) and another corresponding to insects previously reared out on the selected genotypes. In addition to the parameters evaluated in preliminary tests, we also determined the viability and incubation period of eggs. Moderate levels of resistance (antibiosis/antixenosis) to B. tabaci biotype B were found in three genotypes. ‘P98Y11’ and ‘TMG132 RR’ were less suitable for insect development, extending the development cycle, and UX-2569-159 caused high nymphal mortality. We did not observe a significant increase in the level of plant resistance by the use of previously stressed insects. This suggests that the evaluation of a single whitefly generation may be sufficient to make correct decisions on promising soybean genotypes.     

Resistance of Collard Green Genotypes to <Emphasis Type="Italic">Bemisia tabaci</Emphasis> Biotype B: Characterization of Antixenosis

Bemisia tabaci (Genn.) biotype B (Hemiptera: Aleyrodidae) is an important pest of vegetable crops, including collard greens Brassica oleracea var. acephala (Brassicaceae). The use of resistant genotypes is an interesting option to reduce insect populations and can be used as an important tool for integrated pest management (IPM). This study evaluated 32 genotypes of collard greens against the attack of silver leaf whitefly, with the aim to characterize antixenosis. Initially, a multiple-choice trial was conducted using all genotypes, in which the adult attractiveness was assessed on two leaves per genotype at 24 and 48 h after infestation. After 48 h, one leaf of each genotype was randomly selected for the determination of the number of eggs per square centimeter. From the results of the multiple-choice trial, 13 genotypes were selected for a no-choice oviposition test, following the same method of the previous test. Colorimetric analyses were also performed to establish possible correlations between leaf color and insect colonization. Genotypes HS-20, OE, and VA were less attractive, demonstrating antixenosis. Genotypes LG, VE, J, MG, MOP, HS-20, VA, and MT had less oviposition in the multiple-choice test, which indicated expression of antixenosis. In the no-choice test, genotypes VE, P1C, CCB, RI-919, H, and J had less oviposition, which also characterized antixenosis. Therefore, genotypes VE and J showed the highest resistance stability because both had less oviposition in both test modalities. Thus, the resistance to B. tabaci biotype B indicates the genotypes HS-20, OE, VA, VE, and J are promising for use in breeding programs to develop resistance to whitefly.     

A functional response evaluation of pre-infestation with <Emphasis Type="Italic">Bemisia tabaci</Emphasis> cryptic species MEAM1 on predation by <Emphasis Type="Italic">Propylea japonica</Emphasis> of <Emphasis Type="Italic">Myzus persicae</Emphasis> on host plant tomatoes

Herbivore feeding on host plants may induce defense responses of the plant which influence other herbivores and interacting species in the vicinity, such as natural enemies. The present work evaluated the impact of pre-infestation with the tobacco whitefly Bemisia tabaci cryptic species MEAM 1, on the predation ability of the ladybird Propylea japonica, to the green peach aphid Myzus persicae, on tomato plants. The results show that B. tabaci pre-infestation density, duration, and leaf position, can impact prey consumed by P. japonica under various aphid densities. The aphids consumed by P. japonica in each treatment were fit using the Holling type II functional response equation. The predatory efficiency (a/T _h) of P. japonica was the highest in the treatment with 60 aphids and 48-h infestation directly on damaged leaves. The predatory efficiencies of P. japonica decreased with a reduction of pre-infestation density and duration. We also observed that pre-infestation on young and undamaged leaves increased predation by P. japonica.     

Reduction of sooty mold damage through biocontrol of the greenhouse whitefly <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> (Hemiptera: Aleyrodidae) using selective insecticides in tomato cultivation greenhouses

The proliferation of sooty mold on tomato fruit, Solanum lycopersicum L.—as caused by the secretion of honeydew on the fruit by greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)—has recently become a serious problem in estivo-autumnal greenhouse tomato cultivation in Japan. It is becoming increasingly difficult to control T. vaporariorum using insecticides because whiteflies have developed resistance to a variety of insecticides. As the first step towards integrated pest management, we examined whether the use of selective insecticides could prompt a cascade process in which an increase in parasitoids is followed by a decrease in whitefly occurrence and then a reduction in sooty mold damage. We compared greenhouses in which nonselective insecticides effective against T. vaporariorum and its parasitoids were used (hereafter denoted “nonselective insecticide greenhouses”) with greenhouses in which selective insecticides for T. vaporariorum were used (hereafter denoted “selective insecticide greenhouses”) in terms of the density and level of parasitism of T. vaporariorum as well as the degree of damage from sooty mold. The number of parasitized whiteflies increased with the number of whiteflies in the selective insecticide greenhouses, whereas it remained at low levels regardless of the number of whiteflies in the nonselective insecticide greenhouses. Furthermore, the selective insecticide greenhouses showed significantly higher parasitism levels, fewer whiteflies, and reduced sooty mold damage compared to the nonselective insecticide greenhouses. These results suggest that the use of selective insecticides causes an increase in parasitism, which in turn suppresses the number of greenhouse whiteflies and, eventually, sooty mold.     

Detection of symbionts and virus in the whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Hemiptera: Aleyrodidae), vector of the <Emphasis Type="Italic">Mungbean yellow mosaic India virus</Emphasis> in Central India

Legume crops in Central India, the main soybean production area of the country, may suffer from yellow mosaic disease caused by the Mungbean yellow mosaic India virus (MYMIV). MYMIV is transmitted by the sweet potato whitefly, Bemisia tabaci (Gennadius), which is a species complex composed of various genetic groups. This vector species harbors different endosymbionts among regional strains and among individuals. To elucidate fundamental aspects of this virus vector in the state of Madhya Pradesh, the infection status of the symbionts and the virus in whiteflies was studied. A polymerase chain reaction (PCR) survey of the whiteflies collected in Madhya Pradesh found four secondary endosymbionts, Arsenophonus, Hemipteriphilus, Wolbachia, and Cardinium, in addition to the primary endosymbiont Portiera. Arsenophonus and Hemipteriphilus were highly infected but the infection rates of Wolbachia and Cardinium were low. MYMIV was detected in whitefly populations collected from various host plants in Madhya Pradesh. The whitefly populations belonged to the Asia I and II genetic groups; several different Asia II populations were also distributed. Specific relations were not observed among symbiont infection status, virus infection, and the whitefly genetic groups in the populations of Madhya Pradesh, though Cardinium was highly detected in the Asia II-1 group. New primers, which can be used for PCR template validation and for discriminating two phylogenetically close endosymbionts, were designed.     

Detection of <Emphasis Type="Italic">Diaphorina citri</Emphasis> Kuwayama (Hemiptera: Liviidae) in Kenya and potential implication for the spread of Huanglongbing disease in East Africa

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a damaging pest of citrus globally and has recently been detected in Tanzania. Although direct damage by the pest is seldom of economic importance, the insect is more notorious for its ability to vector the fastidious phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas), the putative causal bacterium of Huanglongbing or Asian citrus greening disease. For many years, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) was known to be the main vector of the African citrus greening disease caused by Candidatus Liberibacter africanus (CLaf), but the recent arrival of D. citri on the continent adds to the dynamics of infection and spread of both diseases on mainland Africa. Following the recent report of the presence of D. citri in Tanzania, an additional delimiting survey was carried out in the region, focusing on Kenya, mainland Tanzania and Zanzibar to detect the presence and ascertain the extent of spread of D. citri. We employed molecular tools based on the use of DNA barcoding to confirm the identity of D. citri. In addition to D. citri, the occurrence of T. erytreae in the same sampling locations is also reported. Adults and nymphs of either D. citri or T. erytreae were collected from citrus at many of the surveyed sites ranging from 19 to 668 m above sea level (masl) in Tanzania, 20–1666 masl in Kenya, and 42–48 masl in Zanzibar. Diaphorina citri was sympatric with T. erytreae at the mid to higher elevations of 1375–1666 masl and no T. erytreae or its open-gall symptoms were detected below 523 masl. Sequences obtained were queried via BLAST and all linked to D. citri of different accession numbers already available on GenBank. This is the first report of the presence of D. citri in Kenya and Zanzibar. The potential implication of the detection and spread of the two pathogens, CLaf and CLas to the citrus industry in East Africa and movement of suitable host plants is discussed.     

Biological activity and specificity of Miridae-induced plant volatiles

The ability of zoophytophagous predators to produce defensive plant responses due to their phytophagous behavior has been recently demonstrated. In the case of tomatoes, the mirids Nesidiocoris tenuis and Macrolophus pygmaeus are able to attract or repel pests and/or natural enemies in different ways. Nevertheless, the herbivore-induced plant volatiles (HIPVs) released by the phytophagy of both mirids, which are responsible for these behaviors, are unknown. In this work, the HIPVs produced by the plant feeding of N. tenuis and M. pygmaeus were characterized. In addition, the role of each HIPV in the repellence or attraction of two tomato pests, Bemisia tabaci and Tuta absoluta, and of the natural enemy Encarsia formosa was evaluated. Six green leaf volatiles (GLVs) plus methyl salicylate and octyl acetate clearly stood out as major differential peaks on the chromatogram in a directed analysis. The six GLV and methyl salicylate were repellent for B. tabaci and attractive to E. formosa, whereas they showed no effect on T. absoluta. Octyl acetate, which was significantly present only in the M. pygmaeus-punctured plants, was significantly attractive to T. absoluta, repellent to E. formosa and indifferent to B. tabaci. Unlike the remaining HIPVs, octyl acetate was emitted directly by M. pygmaeus and not by the plant. Our results showed that mirid herbivory could modulate the pest and natural plant enemy locations, since tomato plants release a blend of volatiles in response to this activity. These results could serve as a basis for future development of plant protection.     

Root nematode infection enhances leaf defense against whitefly in tomato

The foliar response to different herbivores sharing the same hosts is an important topic for the study of plant-insect interactions. Plants evolve local and systemic resistant strategies to cope with herbivores. Many researchers have characterized the mechanisms of leaf responses to insect infestation; however, the fact that roots serve as systemic resistance modulators to leaf herbivores has been widely ignored. Here, we report that tomato (Solanum lycopersicum) plants infected with southern root-knot nematodes (Meloidogyne incognita)—which feed on the roots to form nodules—enhanced leaf defenses against aboveground attackers, specifically, the whitefly (Bemisia tabaci). Our results show that nematode infection reduced the whitefly population abundance because of conferring a stronger SA-dependent defense pathway against whitefly than in tomato plants without nematode infection. Meanwhile, nematode-infected tomato plant also activated the foliar JA-dependent defense pathway at 4 h after whitefly infestation. However, the foliar JA-dependent defense under whitefly infestation alone was suppressed, with the JA content being nearly 30 % lower than that in tomato plants co-infected with nematodes and whiteflies. Furthermore, nematode infection significantly decreased the plant nitrogen concentration in leaves and roots. As a result, nematode infection reduced the number of whiteflies by enhancing foliar SA-dependent defense, activating JA-dependent defense and decreasing nitrogen nutrition. Our results suggest that underground nematode infection significantly enhances the defense ability of tomato plants against whitefly.     

Seasonal and yearly change in adult abundance of a predacious ladybird <Emphasis Type="Italic">Serangium japonicum</Emphasis> (Coleoptera: Coccinellidae) and the citrus whitefly <Emphasis Type="Italic">Dialeurodes citri</Emphasis> (Hemiptera: Aleyrodidae) in citrus groves

Serangium japonicum Chapin (Coleoptera: Coccinellidae) chiefly attacks whiteflies. This study monitored the adult occurrence of the ladybird and the citrus whitefly Dialeurodes citri (Ashmead) (Hemiptera: Aleyrodidae) in citrus groves in central Japan using sticky traps, thereby examining temporal relationships in their abundance. Many S. japonicum adults were captured in a pesticide-free grove where D. citri adults were very abundant, with few adults in neighboring (organic, reduced pesticide, and conventional) groves harboring small numbers of D. citri. The whitefly adults exhibited a large peak in numbers in late May to early June. Two peaks of the ladybird adult numbers were detected in late May to early June and late June to mid-July, ?6 to 7 days, and nearly 1 month after the peak in whitefly adult numbers, respectively. The ladybird adults found during the first peak period would be those that visited citrus trees mainly for oviposition, and the adults caught during the second peak period would be those that newly emerged after consuming immature whiteflies at the larval stage. Based on a yearly change in adult numbers in the pesticide-free grove, i.e., a large increase in S. japonicum numbers followed by a rapid decline in D. citri numbers, the ladybird’s role in controlling the whitefly is discussed.     

Water stress and kaolin spray affect herbivorous insects’ success on cotton

Ecological hypotheses of plant–insect herbivore interactions suggest that insects perform better on weakened plants and plants grown under optimal conditions are less damaged. This study tested the hypothesis that the colonization and oviposition rates by pests with different feeding strategies and levels of specialization are affected in different ways by two conditions commonly faced by commercially grown plants–water deficit and application of kaolin sprays, a reducer of abiotic plant stressors. We used four major pests of cotton as insect herbivore models. Three were chewing Lepidoptera: Alabama argillacea (Hüb.), a monophagous pest on cotton; Heliothis virescens (Fabr.), which is polyphagous, but with cotton as a primary host; and Chrysodeixis includens (Walk.), which is polyphagous, with cotton as secondary host. The fourth pest was a sap-sucking species, the polyphagous whitefly Bemisia tabaci (Gen.). In both choice and no-choice trials, the three chewing pests oviposited significantly less upon water-stressed plants; the greatest effect was observed for C. includens (>90 % reduction in oviposition under choice and >58 % under no-choice conditions). In contrast, the sap-sucking B. tabaci exhibited statistically more colonization and oviposition on water-stressed plants. Application of kaolin sprays reduced colonization and oviposition by all herbivore species tested, irrespective of irrigation regime and feeding strategies.     

Reaping benefits from an invasive species: role of <Emphasis Type="Italic">Harmonia axyridis</Emphasis> in natural biological control of <Emphasis Type="Italic">Aphis glycines</Emphasis> in North America

Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an invasive species present in numerous agroecosystems in North America. Despite adverse impacts as a threat to native biodiversity, a nuisance household invader and a pest in fruit production, H. axyridis also plays a beneficial role as a major component of assemblages of generalist predators in several agricultural crops. Here, we review the role of H. axyridis as a natural enemy of Aphis glycines Matsumura (Hemiptera: Aphididae), an invasive pest of soybean, Glycine max (L.) Merrill (Fabales: Fabaceae), in North America. Harmonia axyridis is often the most abundant predator species attacking A. glycines in soybean agroecosystems. This predator has the potential to both prevent and suppress A. glycines outbreaks. Further studies are needed to fully understand and utilize the potential of H. axyridis as a natural enemy in the management of A. glycines and other agricultural pests in agroecosystems worldwide.     

Virulence of the entomopathogenic fungus <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> using soybean oil formulation for control of the cotton stainer bug, <Emphasis Type="Italic">Dysdercus peruvianus</Emphasis>

The cotton stainer bug Dysdercus peruvianus (Hemiptera: Pyrrhocoridae) is an insect pest that causes heavy losses in cotton plantations. The need to reduce the use of insecticides for control of this pest has increased steadily, and Metarhizium anisopliae (Ascomycota: Clavicipitaceae) could be an important biopesticide candidate to control this pest. The effect of M. anisopliae on D. peruvianus nymphs and adults using formulations with soybean oil and Agral^® was evaluated. Formulation using 10% soybean oil added to 10⁸ conidia mL^?1 (grown on used and reused rice) was the most effective for nymph and adult, causing 100% mortality 6 and 7 days after exposure, respectively. The SEM analysis of infected insects showed that M. anisopliae conidia were able to adhere anywhere on the exoskeleton, but were more abundant between the joints. Using the same rice for two batches of growth may be an option for improving commercial conidial production of M. anisopliae and may reduce overall costs. Its effect on D. peruvianus adults opens a new possibility for using this fungus as an alternative to chemical pesticides and the use of M. anisopliae in association with integrate pest management.     

Flowering banker plants for the delivery of multiple agroecosystem services

Ecosystem services provided by agricultural ecosystems include natural pest control and pollination, and these are important to ensure crop productivity. This study investigates the use of the banker plant Calendula officinalis L. to provide multiple ecosystem services by increasing the abundance of natural enemies for biological control of tomato pests, providing forage resources to wild bees, and improving crop yield. C. officinalis was selected for this experiment as it is used as a banker plant for Dicyphini (Hemiptera: Miridae) predators. Strips of flowering C. officinalis were established in the field edges of tomato fields and arthropod visitation to C. officinalis strips and tomato was measured. Crop damage from multiple pests of tomato was assessed in fields with C. officinalis strips and control sites. The contribution of pollination to crop yield was assessed through a pollinator exclusion experiment. The inclusion of C. officinalis in tomato fields was associated with increased abundance of Dicyphini, parasitoids, bees and other arthropod groups within these strips. A reduction in the total leaf crop damage from Lepidoptera pests was recorded in fields with C. officinalis strips. Increased fruit set and biomass were recorded in open-pollinated tomato but this was not significantly different between control and C. officinalis fields. Results presented here demonstrate that the inclusion of a companion plant can improve the conservation of beneficial arthropods and the delivery of agroecosystem services but efficacy is likely to be improved with the addition of plants, with different functional traits, and with improved attractiveness to crop pollinators.     

Plant and supplementary food sources effect the development of <Emphasis Type="Italic">Dicyphus errans</Emphasis> (Hemiptera: Miridae)

Dicyphus errans (Wolff) (Hemiptera: Miridae) is an omnivorous predator of several pests attacking tomato and other vegetable crops. The nymphal development of D. errans was studied in the presence of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs with or without a water source and in the presence of a leaf of cucumber, eggplant or tomato supplemented with variable food types (E. kuehniella eggs, Artemia sp. cysts, pollen or milk powder) or without the provision of any food. Water provision was found to be essential for the completion of nymphal development even when animal food was offered to predators. When nymphs foraged on leaves in the absence of any food type, development was significantly more favoured on eggplant and cucumber than on tomato. E. kuehniella eggs and Artemia sp. cysts enhanced development of D. errans in comparison to milk powder and pollen. Development and female weight were improved when the food types were offered to the nymphs on a plant leaf than when were provided together with only water. This study contributes to understanding the importance of water vs. plant feeding for the development of D. errans and reveals implications for its mass rearing and application in biological control.     

Phenolic compounds induced by <Emphasis Type="Italic">Bemisia tabaci</Emphasis> and <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> in <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> L. and their relationship with the salicylic acid signaling pathway

Changes in the levels of secondary compounds can trigger plant defenses. To identify phenolic compounds induced by Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) in tobacco (Nicotiana tobacco L.), the content changes of 11 phenolic compounds in plants infested by B. tabaci MEAM1 or Trialeurodes vaporariorum were compared. The chlorogenic acid, catechin, caffeic acid, p-coumaric acid, rutin, and ferulic acid contents in B. tabaci MEAM1-infested tobacco plants increased significantly, having temporal and spatial effects, compared with uninfested control and T. vaporariorum infested plants. The contents were 4.10, 2.84, 2.25, 3.81, 1.46, and 1.91 times higher, respectively, than those in the control. However, a T. vaporariorum nymphal infestation just caused smaller chlorogenic acid, catechin, caffeic acid, and rutin contents increase, which were 2.33, 2.13, 1.59, and 3.19 times higher, respectively, than those in the control. In B. tabaci MEAM1 third-instar nymph-infested plants, chlorogenic acid, catechin, caffeic acid, and rutin increased more significantly in systemic than in local leaves. Salicylate-deficient plants inhibited the induction of the content of 10 phenolic compounds, but not caffeic acid, after a B. tabaci MEAM1 nymphal infestation. Thus, the elevated levels of phenolic compounds induced by B. tabaci MEAM1 were correlated with the salicylic acid signaling pathway and induced the responses of defense-related phenolic compounds.