A non-persistently transmitted-virus induces a pull?push strategy inits aphid vector to optimize transmission and spread

Plant viruses are known to modify the behaviour of their insect vectors, both directly and indirectly,generally adapting to each type of virus?vector relationship in a way that enhances transmissionefficiency. Here, we report results of three different studies showing how a virus transmitted in a non-persistent (NP) manner (Cucumber mosaic virus; CMV, Cucumovirus) can induce changes in its host plant,cucumber (Cucumis sativus cv. Marumba) that modifies the behaviour of its aphid vector (Aphis gossypiiGlover; Hemiptera: Aphididae) in a way that enhances virus transmission and spread non-viruliferousaphids changed their alighting, settling and probing behaviour activities over time when exposed toCMV-infected and mock-inoculated cucumber plants. Aphids exhibited no preference to migrate fromCMV-infected to mock-inoculated plants at short time intervals (1, 10 and 30 min after release), butshowed a clear shift in preference to migrate from CMV-infected to mock-inoculated plants 60 min afterrelease. Our free-choice preference assays showed that A. gossypii alates preferred CMV-infected overmock-inoculated plants at an early stage (30 min), but this behaviour was reverted at a later stage andaphids preferred to settle and reproduce on mock-inoculated plants. The electrical penetration graph(EPG) technique revealed a sharp change in aphid probing behaviour over time when exposed to CMV-infected plants. At the beginning (first 15 min) aphid vectors dramatically increased the number of shortsuperficial probes and intracellular punctures when exposed to CMV-infected plants. At a later stage (sec-ond hour of recording) aphids diminished their feeding on CMV-infected plants as indicated by much lesstime spent in phloem salivation and ingestion (E1 and E2). This particular probing behaviour includingan early increase in the number of short superficial probes and intracellular punctures followed by aphloem feeding deterrence is known to enhance the transmission efficiency of viruses transmitted in aNP manner. We conclude that CMV induces specific changes in a plant host that modify the alighting,settling and probing behaviour of its main vector A. gossypii, leading to optimum transmission and spreadof the virus. Our findings should be considered when modelling the spread of viruses transmitted in a NPmanner

Dispersal of aphids, whiteflies and their natural enemies under photoselective nets

Integrated Pest Management of insects includes several control tactics, such as the use of photoselective nets, which may reduce the flight activity of insects. Limiting the dispersal of pests such as aphids and whiteflies is important because of their major role as vectors of plant viruses, while a minor impact on natural enemies is desired. In this study, we examined for the first time the dispersal ability of three vector species, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae) and Myzus persicae (Sulzer) (Hemiptera: Aphididae), in cages covered with photoselective nets. Contrary to the results obtained with aphids, the ability of the whitefly B. tabaci, to reach the target plant was reduced by photoselective nets. In a second set of experiments, the impact of UV-absorbing nets on the visual cues of two important predator species, Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), was evaluated. The anthocorid was caught in higher numbers in traps placed under regular nets, whereas the mites preferably chose environments in which the UV radiation was attenuated. We have observed a wide range of effects that impedes generalization, although photoselective nets have a positive effect on pest management of whiteflies and aphids under protected environments

La transmisión de virus no persistentes estudiada a través del comportamiento de prueba de pulgones

Cinco años de investigación sobre el comportamiento de prueba del pulgón Myzus persicae Sulzer con la ayuda de un monitor electrónico de comportamiento (técnica EPG) han permitido obtener un mejor conocimiento sobre el mecanismo de transmisión no persistente de virus vegetales, empleando como modelo el virus Y de la patata (PVY). Las breves picaduras intracelulares producidas por el pulgón al inicio de la prueba son registradas en el monitor electrónico como breves caídas de potencial (denominadas pds). La presencia y morfología de este patrón de onda pd ha resultado ser clave en el proceso de tranmisión de PVY. Se ha observado que la presencia de al menos una pd es necesaria para la adquisición del virus, y que una mayor frecuencia de pds aumenta la probabilidad de adquisición. Asimismo, se ha comprobado que el proceso de inoculación del virus también tiene lugar durante la pd, más en concreto en su fase inicial III, mientras que la adquisición es un proceso posterior (fase 113). Esta evidencia pone en duda el mecanismo mayoritariamente aceptado de ingestión-egestión, proponiéndose como hipótesis alternativa un mecanismo de ingestión-salivación. Asimismo, la presencia y morfología de la fase 113 de la pd ha proporcionado una explicación satisfactoria al conocido efecto del ayuno previo (que aumenta la eficiencia de transmisión) y a la distinta capacidad vectorial observada en diferentes especies de pulgone

Effects of a bifenthrin-treated net on the natural enemies Aphidius colemani (Haliday) and Adalia bipunctata L. in a cucumber crop in Central Spain. Semi-field experiments

Pest management practices that rely on pesticides are growing increasingly less effective and environmentally inappropriate in many cases and the search of alternatives is under focus nowadays. Exclusion of pests from the crop by means of pesticide-treated screens can be an eco-friendly method to protect crops, especially if pests are vectors of important diseases. The mesh size of nets is crucial to determine if insects can eventually cross the barrier or exclude them because there is a great variation in insect size depending on the species. Long-lasting insecticide-treated (LLITN) nets, factory pre-treated, have been used since years to fight against mosquitoes vector of malaria and are able to retain their biological efficacy under field for 3 years. In agriculture, treated nets with different insecticides have shown efficacy in controlling some insects and mites, so they seem to be a good tool in helping to solve some pest problems. However, treated nets must be carefully evaluated because can diminish air flow, increase temperature and humidity and decrease light transmission, which may affect plant growth, pests and natural enemies. As biological control is considered a key factor in IPM nowadays, the potential negative effects of treated nets on natural enemies need to be studied carefully. In this work, the effects of a bifentrhin-treated net (3 g/Kg) (supplied by the company Intelligent Insect Control, IIC) on natural enemies of aphids were tested on a cucumber crop in Central Spain in autumn 2011. The crop was sown in 8x6.5 m tunnels divided in 2 sealed compartments with control or treated nets, which were simple yellow netting with 25 mesh (10 x 10 threads/cm2; 1 x 1 mm hole size). Pieces of 2 m high of the treated-net were placed along the lateral sides of one of the two tunnel compartments in each of the 3 available tunnels (replicates); the rest was covered by a commercial untreated net of a similar mesh. The pest, Aphis gossypii Glover (Aphidae), the parasitoid Aphidius colemani (Haliday) (Braconidae) and the predator Adalia bipunctata L. (Coccinellidae) were artificially introduced in the crop. Weekly sampling was done determining the presence or absence of the pest and the natural enemies (NE) in the 42 plants/compartment as well as the number of insects in 11 marked plants. Environmental conditions (temperature, relative humidity, UV and PAR radiation) were recorded. Results show that when aphids were artificially released inside the tunnels, neither its number/plant nor their distribution was affected by the treated net. A lack of negative effect of the insecticide-treated net on natural enemies was also observed. Adalia bipunctata did not establish in the crop and only a short term control of aphids was observed one week after release. On the other hand, A. colemani did establish in the crop and a more long-term effect on the numbers of aphids/plant was detected irrespective of the type of net. KEY WORDS: bifenthrin-treated net, Adalia bipunctata, Aphidius colemani, Aphis gossypii, semi-fiel

Flying capacity of Psyttalia concolor and Chrysoperla carnea under a UV-absorbing net (Bionet®) in presence and absence of crop.

Field studies were conducted in walk-in tunnels to determine the flying capacity in the presence and absence of crop, of the parasitoid Psyttalia concolor and the predator Chrysoperla carnea under a UV-absorbent net (Bionet®). Yellow sticky cards were used for insect recovery but neither P. concolor nor C. carnea were very attracted to them, thus captures were too low to permit any meaningful comparisons. Bionet® did not seem to affect the mobility of any natural enemy irrespective of the trap location and monitoring hour. Climatic conditions inside nets were very extreme (average temperatures very high and relative humidity very low) threatening insect survival. New experiments are being developed, trying to find new attractants that permit a significant capture of both natural enemies

Provision of ecological infrastructures to increase pollinators and other beneficial organisms in rainfed crops in Central Spain

In sustainable intensive agriculture, the biodiversity of monoculture fields can be increased by managing the field margins to provide ecological infrastructures that serve as refuges and resources for beneficial organisms (pollinators and natural enemies). In the present work we summarize two years of field trials following the goal to increase biodiversity of beneficial fauna in a barley field in Central Spain by sowing different herbaceous mixtures in the field margins. The presence of arthropods visiting flowers on plots sown with different types of seed mixtures and unsown natural flora (control plot) was compared by visual sampling every week between April and June. The results showed that a combination of herbaceous big-size seeds was the most successful mixture emerging under our experimental conditions and achieved a higher number of visits of beneficial arthropods than the unsown natural vegetation

Situación actual y avances en investigación: vectores de enfermedades emergentes

Peer reviewe

Movement Between Plants: Horizontal Transmission

Peer reviewe

Transmission efficiency of different non-persistent viruses infecting melon by four aphid species

Se realizaron experimentos de transmisión de diferentes aislados de Cucunber mosaic virus (CMV), Watermelon mosaic virus (WMV) y Zucchini yellow mosaic virus (ZYMV) utilizando como vectores colonias establecidas de Aphis gossypii Glover, Myzus persicae (Sulzer), A. fabae Scopoli y A. craccivora Koch. El procedimiento de transmisión utilizado proporciona una estimación de la eficacia de transmisión de virus por cada una de las especies de pulgón. Dos diferentes aislados virales/clones de pulgón fueron evaluados para cada especie de virus utilizando como vector la especie de pulgón más eficiente. A. gossypii fue el vector más eficiente de CMV (100+-0%), mientras que M. persicae mostró la mayor eficiencia para transmitir WMV (67,9+-28,5%) y ZYMV (96,4+-3,6%). Tanto WMV como ZYMV mostraron variabilidad en su eficiencia de transmisión de pulgones. No se encontraron diferencias significativas en la eficiencia de los dos aislados de CMV evaluados. Tampoco se observaron deficiencias en la capacidad de transmisión entre los clones de cada especie de pulgón evaluadas. Los resultados de nuestros estudios de transmisión, junto con la información previa de los patrones temporal y espacial de las epidemias de virus en los cultivos de melón en España, sugieren que una especie de pulgón colonizante como A. gossypii es la que transmite preferentemente CMV. En contraste, WMV es transmitido preferentemente por especies de pulgones no colonizantes tales como M. persicae, que aterrizan en el cultivo de melón a finales de la primavera

Pre-eruptive resorption of dentin in the primary ana permanent dentitions: Case reports and literature review

The emergence of a rapid-spreading olive disease associated with Xylella fastidiosa in southern Italy represents a high risk to susceptible crops in other countries of the Mediterranean basin, if insect vectors occur in the region. The goal of this study was to identify xylem-feeding Auchenorrhyncha that could potentially act as vectors of X. fastidiosa in three regions of Spain (Andalucía, Murcia and Madrid). Samplings with sweep net and stem tap were carried out in October/2004 on grapevines and adjacent crops (olives, nectarine, citrus, Prunus spp.), ornamental trees and herbaceous weeds. Yellow sticky cards were placed in ten vineyards located across 100 km in Andalucía and in three vineyards distant 10-15 km apart in Murcia. Specimens of frequently-trapped species were tested by nested- or multiplex-PCR for the presence of X. fastidiosa. The Typhlocybinae leafhopper, Austroasca (Jacobiasca) lybica (Hemiptera: Cicadellidae) was the most abundant species in vineyards and citrus orchards. Planthoppers (Hemiptera: Fulgoroidea) and psyllids (Hemiptera: Psylloidea) were prevalent on olives. Cicadellinae leafhoppers (known as sharpshooters), which are major vectors of X. fastidiosa in the Americas, were not found in the samples. The only potential vectors were spittlebugs (Hemiptera: Cercopoidea) collected on Populus sp., herbaceous and on conifer trees (Pinus halepense); the spittlebug Neophileanus sp. was common on conifer trees adjacent to a vineyard in Jumilla. None of the insect samples tested positive for X. fastidiosa by PCR assays. However, spittlebugs already associated with susceptible crops in Spain may allow fast spread of X. fastidiosa in case this pathogen is introduce