ABSTRACT Since its introduction during the late 1980s, tomato yellow leaf curl disease (TYLCD) ha... more ABSTRACT Since its introduction during the late 1980s, tomato yellow leaf curl disease (TYLCD) has become one of the most serious threats of greenhouse tomatoes in the south of Sardinia (Italy). To gain information about the epidemiology of the disease, we monitored for four years the seasonal variations in viral inoculum and the dynamics of vector populations outside greenhouses, in one of the main tomato production areas of the island. Our results indicate that in this district the risk of disease transmission to tomato crops is high for at least five months, from May to September. Both the spread of the disease and the trends of whitefly population, consisting mainly of the greenhouse whitefly Trialeurodes vaporariorum, generally showed a major peak in June, with an environmental inoculum capable in most cases of infecting 80-100% of tomato bait plants. During summer, when the vector of the disease Bemisia tabaci became prevalent, the patterns of TYLCD incidence and whitefly population diverged, with the former remaining high and the latter decreasing to lower levels. By early autumn the incidence of virus infection finally dropped drastically. These results confirm the reports of field observations, which indicate greenhouse tomatoes grown in summer as the most exposed to TYLCD.
Tomato yellow leaf curl disease (TYLCD) has been known for more than 40 years, but only since the... more Tomato yellow leaf curl disease (TYLCD) has been known for more than 40 years, but only since the end of the 1980s it became widespread in all important tomato growing areas of the Mediter- ranean basin. Two virus species have been recorded in Italy, Tomato yellow leaf curl virus (TYLCV), and, Tomato yellow leaf curl Sardinia virus (TYLCSV), both in the genus Begomovirus , family Geminiviridae . TYLCSV is present in Sicily and Sardinia since 1989, while TYLCV was first reported in Sicily in 2002 and in Sardinia in 2004. Today the two viral species coexist in tomato crops of the most relevant Italian tomato growing areas. This nat- ural coexistence in the field may favour possible genetic ex- change: the DNAs of the two viruses share about 70% sequence identity, with some short regions nearly identical. This prompted us to search for interspecific hybrids in field samples collected in Sicily and Sardinia. PCR assays were designed for detecting pos- sible recombination within the IR r...
Communications in agricultural and applied biological sciences, 2009
The whiteflies Bemisia tabaci and Trialeurodes vaporariorum and their associated viruses constitu... more The whiteflies Bemisia tabaci and Trialeurodes vaporariorum and their associated viruses constitute a major threat to tomato crops in the Mediterranean region. Continuous host availability and mild climate are thought to be among the factors contributing to the outbreaks of whitefly-related problems in this area. We carried out a year-long survey to investigate the relative contribution of different plants, agricultural and not, and indoor/outdoor crops as hosts of the two whiteflies and the tomato yellow leaf curl disease (TYLCD) in a multi-crop system typical of tomato growing areas in southern Sardinia (S. Margherita di Pula, Cagliari, Italy). For this purpose, during 2005 we monitored whitefly population trends in different plots of a horticulture farm, evaluated seasonal changes in the infestation density of the two pests on the most represented host species and assessed the incidence of TYLCD on tomato crops and susceptible weeds. Whitefly catches on yellow sticky traps were f...
Communications in agricultural and applied biological sciences, 2009
Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV) are amo... more Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV) are among the most virulent pathogens of greenhouse tomatoes in Sardinia (Italy). To investigate the relationship between seasonal population trends of the vector Bemisia tabaci and the dynamics of TYLCD spread to susceptible crops, between May and October 2007 we carried out a survey in a tomato growing area located in the south of the island. On three farms specialized in the production of fresh market tomatoes we monitored, outside commercial greenhouses, the following parameters related to TYLCD epidemiology: mean weekly catches of the whiteflies B. tabaci and Trialeurodes voporariorum on yellow sticky traps, ratio between the two whitefly species and proportion of B. tabaci adults carrying TYLCSV/TYLCV in adult samples collected on hosts not susceptible to the disease, proportion of tomato plants infected by TYLCSV/TYLCV after a two-week exposure to open field conditions. Generally speakin...
Communications in agricultural and applied biological sciences, 2009
In Sardinia (Italy) Tomato yellow leaf curl disease (TYLCD) re-emerged in 2003, after a period of... more In Sardinia (Italy) Tomato yellow leaf curl disease (TYLCD) re-emerged in 2003, after a period of decline, producing severe yield losses in protected tomato crops. This epidemic outbreak highlighted the inadequacy of the approach to TYLCD management based chiefly on the chemical control of its vector, the whitefly Bemisia tabaci, and the use of 40-mesh nets for greenhouse screening. To evaluate the reliability of alternative practices for implementation within IP&DM programmes, in 2007 and 2008 we carried out two field experiments on greenhouse tomato crops planted in summer. In both trials we tested the use of UV-reflective mulches (UVRM) or floating row covers (NWRC), against an uncovered control on clear mulch. Furthermore, we assessed the effectiveness of acibenzolar-S-methyl, a SAR elicitor, as subplot factor in a split plot design. In 2007 because of the low incidence of the disease it was not possible to assess differences among the treatments. However a significant increase ...
Evaluating the structure of enemy biodiversity effects on prey in agroecosystems can provide insi... more Evaluating the structure of enemy biodiversity effects on prey in agroecosystems can provide insights into biological pest control functioning. With this aim, theoretical models that describe biological mechanisms underlying prey suppression can be developed and confronted with experimental data by means of model selection. Here, we confront multiplicative risk models to evaluate the structure of multiple predator effects on the whitefly Trialeurodes vaporariorum provided in tomatoes by two spiders (Oxyopes lineatus and Pityohyphantes phrygianus) and two mirids (Nesidiocoris tenuis and Macrolophus melanotoma). Biologically meaningful parameters retained in the best models showed that several predator traits differently affected pest control: species-specific per capita predation rates, prey use extent, different type of interactions between predators, and the response of predator species to prey density and environmental temperature. Even from a limited perspective of single-pest control and short term experiment, this study suggests that assembly of the four predator species results in predator complementarity across prey life stages and density, interactions of prey and predators with environmental conditions, and interactions between predators that do not result in whitefly control disruption. Such information about enemy biodiversity and whitefly control functioning can drive hypotheses about sustainable pest management options in local agroecosystems.
Background The predatory mirids of the genus Macrolophus are key natural enemies of various econo... more Background The predatory mirids of the genus Macrolophus are key natural enemies of various economically important agricultural pests. Both M. caliginosus and M. pygmaeus are commercially available for the augmentative biological control of arthropod pests in European greenhouses. The latter species is known to be infected with Wolbachia -inducing cytoplasmic incompatibility in its host- but the presence of other endosymbionts has not been demonstrated. In the present study, the microbial diversity was examined in various populations of M. caliginosus and M. pygmaeus by 16S rRNA sequencing and denaturing gradient gel electrophoresis. Results Besides Wolbachia, a co-infection of 2 Rickettsia species was detected in all M. pygmaeus populations. Based on a concatenated alignment of the 16S rRNA gene, the gltA gene and the coxA gene, the first is phylogenetically related to Rickettsia bellii, whereas the other is closely related to Rickettsia limoniae. All M. caliginosus populations wer...
A cura di A. Sirigu e M. Nannini 2 La pubblicazione di questo opuscolo è stata finanziata dalla R... more A cura di A. Sirigu e M. Nannini 2 La pubblicazione di questo opuscolo è stata finanziata dalla Regione Autonoma della Sardegna nell'ambito dei progetti di ricerca "Difesa del pomodoro da mensa in coltura protetta dall'accartocciamento fogliare giallo" e "Indagini epidemiologiche sul TSWV e prove di difesa del carciofo dai tripidi vettori del virus" (Deliberazione Giunta Regionale N. 44/8 del 25.10.2006).
ABSTRACT Since its introduction during the late 1980s, tomato yellow leaf curl disease (TYLCD) ha... more ABSTRACT Since its introduction during the late 1980s, tomato yellow leaf curl disease (TYLCD) has become one of the most serious threats of greenhouse tomatoes in the south of Sardinia (Italy). To gain information about the epidemiology of the disease, we monitored for four years the seasonal variations in viral inoculum and the dynamics of vector populations outside greenhouses, in one of the main tomato production areas of the island. Our results indicate that in this district the risk of disease transmission to tomato crops is high for at least five months, from May to September. Both the spread of the disease and the trends of whitefly population, consisting mainly of the greenhouse whitefly Trialeurodes vaporariorum, generally showed a major peak in June, with an environmental inoculum capable in most cases of infecting 80-100% of tomato bait plants. During summer, when the vector of the disease Bemisia tabaci became prevalent, the patterns of TYLCD incidence and whitefly population diverged, with the former remaining high and the latter decreasing to lower levels. By early autumn the incidence of virus infection finally dropped drastically. These results confirm the reports of field observations, which indicate greenhouse tomatoes grown in summer as the most exposed to TYLCD.
Tomato yellow leaf curl disease (TYLCD) has been known for more than 40 years, but only since the... more Tomato yellow leaf curl disease (TYLCD) has been known for more than 40 years, but only since the end of the 1980s it became widespread in all important tomato growing areas of the Mediter- ranean basin. Two virus species have been recorded in Italy, Tomato yellow leaf curl virus (TYLCV), and, Tomato yellow leaf curl Sardinia virus (TYLCSV), both in the genus Begomovirus , family Geminiviridae . TYLCSV is present in Sicily and Sardinia since 1989, while TYLCV was first reported in Sicily in 2002 and in Sardinia in 2004. Today the two viral species coexist in tomato crops of the most relevant Italian tomato growing areas. This nat- ural coexistence in the field may favour possible genetic ex- change: the DNAs of the two viruses share about 70% sequence identity, with some short regions nearly identical. This prompted us to search for interspecific hybrids in field samples collected in Sicily and Sardinia. PCR assays were designed for detecting pos- sible recombination within the IR r...
Communications in agricultural and applied biological sciences, 2009
The whiteflies Bemisia tabaci and Trialeurodes vaporariorum and their associated viruses constitu... more The whiteflies Bemisia tabaci and Trialeurodes vaporariorum and their associated viruses constitute a major threat to tomato crops in the Mediterranean region. Continuous host availability and mild climate are thought to be among the factors contributing to the outbreaks of whitefly-related problems in this area. We carried out a year-long survey to investigate the relative contribution of different plants, agricultural and not, and indoor/outdoor crops as hosts of the two whiteflies and the tomato yellow leaf curl disease (TYLCD) in a multi-crop system typical of tomato growing areas in southern Sardinia (S. Margherita di Pula, Cagliari, Italy). For this purpose, during 2005 we monitored whitefly population trends in different plots of a horticulture farm, evaluated seasonal changes in the infestation density of the two pests on the most represented host species and assessed the incidence of TYLCD on tomato crops and susceptible weeds. Whitefly catches on yellow sticky traps were f...
Communications in agricultural and applied biological sciences, 2009
Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV) are amo... more Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV) are among the most virulent pathogens of greenhouse tomatoes in Sardinia (Italy). To investigate the relationship between seasonal population trends of the vector Bemisia tabaci and the dynamics of TYLCD spread to susceptible crops, between May and October 2007 we carried out a survey in a tomato growing area located in the south of the island. On three farms specialized in the production of fresh market tomatoes we monitored, outside commercial greenhouses, the following parameters related to TYLCD epidemiology: mean weekly catches of the whiteflies B. tabaci and Trialeurodes voporariorum on yellow sticky traps, ratio between the two whitefly species and proportion of B. tabaci adults carrying TYLCSV/TYLCV in adult samples collected on hosts not susceptible to the disease, proportion of tomato plants infected by TYLCSV/TYLCV after a two-week exposure to open field conditions. Generally speakin...
Communications in agricultural and applied biological sciences, 2009
In Sardinia (Italy) Tomato yellow leaf curl disease (TYLCD) re-emerged in 2003, after a period of... more In Sardinia (Italy) Tomato yellow leaf curl disease (TYLCD) re-emerged in 2003, after a period of decline, producing severe yield losses in protected tomato crops. This epidemic outbreak highlighted the inadequacy of the approach to TYLCD management based chiefly on the chemical control of its vector, the whitefly Bemisia tabaci, and the use of 40-mesh nets for greenhouse screening. To evaluate the reliability of alternative practices for implementation within IP&DM programmes, in 2007 and 2008 we carried out two field experiments on greenhouse tomato crops planted in summer. In both trials we tested the use of UV-reflective mulches (UVRM) or floating row covers (NWRC), against an uncovered control on clear mulch. Furthermore, we assessed the effectiveness of acibenzolar-S-methyl, a SAR elicitor, as subplot factor in a split plot design. In 2007 because of the low incidence of the disease it was not possible to assess differences among the treatments. However a significant increase ...
Evaluating the structure of enemy biodiversity effects on prey in agroecosystems can provide insi... more Evaluating the structure of enemy biodiversity effects on prey in agroecosystems can provide insights into biological pest control functioning. With this aim, theoretical models that describe biological mechanisms underlying prey suppression can be developed and confronted with experimental data by means of model selection. Here, we confront multiplicative risk models to evaluate the structure of multiple predator effects on the whitefly Trialeurodes vaporariorum provided in tomatoes by two spiders (Oxyopes lineatus and Pityohyphantes phrygianus) and two mirids (Nesidiocoris tenuis and Macrolophus melanotoma). Biologically meaningful parameters retained in the best models showed that several predator traits differently affected pest control: species-specific per capita predation rates, prey use extent, different type of interactions between predators, and the response of predator species to prey density and environmental temperature. Even from a limited perspective of single-pest control and short term experiment, this study suggests that assembly of the four predator species results in predator complementarity across prey life stages and density, interactions of prey and predators with environmental conditions, and interactions between predators that do not result in whitefly control disruption. Such information about enemy biodiversity and whitefly control functioning can drive hypotheses about sustainable pest management options in local agroecosystems.
Background The predatory mirids of the genus Macrolophus are key natural enemies of various econo... more Background The predatory mirids of the genus Macrolophus are key natural enemies of various economically important agricultural pests. Both M. caliginosus and M. pygmaeus are commercially available for the augmentative biological control of arthropod pests in European greenhouses. The latter species is known to be infected with Wolbachia -inducing cytoplasmic incompatibility in its host- but the presence of other endosymbionts has not been demonstrated. In the present study, the microbial diversity was examined in various populations of M. caliginosus and M. pygmaeus by 16S rRNA sequencing and denaturing gradient gel electrophoresis. Results Besides Wolbachia, a co-infection of 2 Rickettsia species was detected in all M. pygmaeus populations. Based on a concatenated alignment of the 16S rRNA gene, the gltA gene and the coxA gene, the first is phylogenetically related to Rickettsia bellii, whereas the other is closely related to Rickettsia limoniae. All M. caliginosus populations wer...
A cura di A. Sirigu e M. Nannini 2 La pubblicazione di questo opuscolo è stata finanziata dalla R... more A cura di A. Sirigu e M. Nannini 2 La pubblicazione di questo opuscolo è stata finanziata dalla Regione Autonoma della Sardegna nell'ambito dei progetti di ricerca "Difesa del pomodoro da mensa in coltura protetta dall'accartocciamento fogliare giallo" e "Indagini epidemiologiche sul TSWV e prove di difesa del carciofo dai tripidi vettori del virus" (Deliberazione Giunta Regionale N. 44/8 del 25.10.2006).
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