First record of the nesting whitefly, Paraleyrodes minei Iaccarino, 1990 (Hemiptera, Aleyrodidae) in Malta

The nesting whitefly, Paraleyrodes minei is the latest exotic whitefly species to be found breeding in Malta and was originally described from specimens collected from Citrus crops in Syria by Iaccario (1990). It is the only member of the subfamily Aleurodicinae that has been found in Malta, all the other species belong to the subfamily Aleyrodinae. Its arrival had been anticipated since it was spreading rapidly in Sicily (Italy), an island only 50 nautical miles to the Northpeer-reviewe

Resistance status of the carmine spider mite, Tetranychus cinnabarinus and the twospotted spider mite, Tetranychus urticae to selected acaricides on strawberries.

The carmine spider mite, Tetranychus cinnabarinus (Boisduval) and the twospotted spider mite, Tetranychus urticae Koch, are serious pests of strawberries and many other horticultural crops. Control of these pests has been heavily dependent upon chemical acaricides. Objectives of this study were to determine the resistance status of these two pest species to commonly used acaricides on strawberries in a year-round intensive horticultural production region. LC90 of abamectin for adult carmine spider mites was 4% whereas that for adult twospotted spider mites was 24% of the top label rate. LC90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 0.5%, 0.5%, 1.4% and 83% of their respective highest label rates for carmine spider mite eggs, 0.7%, 2.7%, 12.1% and 347% of their respective highest label rates for the nymphs. LC90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 4.6%, 11.1%, 310% and 62% of their respective highest label rates for twospotted spider mite eggs, 3%, 13%, 432,214% and 15% of their respective highest label rates for the nymphs. Our results suggest that T. cinnabarinus have developed resistance to bifenazate and that the T. urticae have developed resistance to hexythiazox. These results strongly emphasize the need to develop resistance management strategies in the region

Effect of photoperiod and host distribution on the horizontal transmission of Isaria fumosorosea (Hypocreales: Cordycipitaceae) in greenhouse whitefly assessed using a novel model bioassay

A model bioassay was used to evaluate the epizootic potential and determine the horizontal transmission efficiency of Isaria fumosorosea Trinidadian strains against Trialeurodes vaporariorum pharate adults under optimum conditions (25±0.5°C, ~100% RH) at two different photoperiods. Untreated pharate adults were arranged on laminated graph paper at different distributions to simulate varying infestation levels on a leaf surface. Four potential hosts were located 7, 14 and 21 mm away from a central sporulating cadaver simulating high, medium and low infestation levels, respectively. Percent hosts colonized were recorded 7, 12, 14 and 21 days post-treatment during a 16- and 24-h photophase. After 21 days, mean percent hosts colonized at the highest, middle and lowest infestation levels were 93 and 100%, 22 and 58%, 25 and 39% under a 16- and 24-h photophase, respectively. From the results, it was concluded that the longer the photophase, the greater the percentage of hosts colonized, and as host distance increased from the central sporulating cadaver, colonization decreased. The use of this novel model bioassay technique is the first attempt to evaluate the epizootic potential and determine the horizontal transmission efficiency of I. fumosorosea Trinidadian strains under optimal environmental conditions at different photoperiods. This bioassay can be used to assess horizontal transmission efficiency for the selection of fungi being considered for commercial biopesticide development

Impact of host plant species and whitefly species on feeding behavior of Bemisia tabaci

Whiteflies of the Bemisia tabaci species complex are economically important pests of cassava. In Africa, they cause greatest damage through vectoring viruses responsible for cassava mosaic disease and cassava brown streak disease. Several cryptic species from the B. tabaci complex colonize cassava and neighboring crops, but the feeding interactions between the different crops and B. tabaci species are unknown. The electrical penetration graph (EPG) technique makes it possible to conduct detailed feeding studies of sap-sucking insects by creating an electric circuit through the insect and the plant. The apparatus measures the voltage fluctuations while the wired-up insect feeds and produces graphs that describe feeding behavior. We utilized EPG to explore the feeding behavior of cassava-colonizing whiteflies (SSA1-SG3) on cassava, sweet potato, tomato, and cotton; and sweet potato-colonizing whiteflies (MED and IO) on cassava and sweet potato. Results show that: (1) feeding of SSA1-SG3 is not restricted to cassava. The least preferred host for SSA1-SG3 was tomato, where probing was delayed by 99 min compared to 10 min on other hosts, furthermore mean duration of phloem ingestion events was 36 min compared to 260 min on cassava. (2) Feeding of MED on cassava appeared to be non-functional, as it was characterized by short total phloem ingestion periods (5 h). (3) Wire diameter affects the feeding in a statistically and practically significant manner. Implications for whitefly control and studies of host whitefly resistance are discussed.</p

Impact of some crop management practices on tomato infestation/infection by the whitefly-begomovirus complex in Cuba

Introduction. In the framework of the INCO-BETOCARIB Project titled "Begomovirus disease management for sustainable production of tomato in the Caribbean" which operated from 2003- 2006, we conducted a survey aiming at assessing the impact of cultural practices on the infestation/infection of tomato plots by whitefly (Bemisia tabaci)/begomovirus (TYLCV). Materials &amp; Methods. The survey was conducted in the West and Central regions of Cuba in respectively 100 and 96 tomato plots in open fields (71% of the plots) and under shelter (29%). Results and Conclusion. Analysis of data showed that both TYLC resistant (e.g. Vyta and ARO 8479F1) and susceptible (e.g. Amalia and HC 3880) cultivars were cultivated in open fields whereas only resistant cultivars were cultivated in sheltered plots. In open fields, TYLC disease incidence and severity were found to be significantly higher on susceptible, compared to resistant cultivars. Whitefly infestation and TYLCV incidence were higher in the West region as compared to the Central region, while the reverse was observed for severity of the disease. Whitefly infestation in open fields was high when no chemical protection measure was applied in the nursery and low under high chemical protection. The reverse tended to be observed when considering chemical application in the field, which might be an indirect indication that chemical protection negatively affects natural regulation processes. Implications of the results of this survey for agroecological management of the vector/disease complex in Cuba are discussed. (Résumé d'auteur

Efficient Protein Expression and Virus-Induced Gene Silencing in Plants Using a Crinivirus-Derived Vector.

Plant virus-based vectors are valuable tools for recombinant gene expression and functional genomics for both basic and applied research. In this study, Lettuce infectious yellows virus (LIYV) of the genus Crinivirus was engineered into a virus vector that is applicable for efficient protein expression and virus-induced gene silencing (VIGS) in plants. We examined gene replacement and “add a gene” strategies to develop LIYV-derived vectors for transient expression of the green fluorescent protein (GFP) reporter in Nicotiana benthamiana plants. The latter yielded higher GFP expression and was further examined by testing the effects of heterologous controller elements (CEs). A series of five vector constructs with progressively extended LIYV CP sgRNA CEs were tested, the longest CE gave the highest GFP expression but lower virus accumulation. The whitefly transmissibility of the optimized vector construct to other host plants, and the capability to accommodate and express a larger gene, a 1.8 kb β-glucuronidase (GUS) gene, were confirmed. Furthermore, the LIYV vector was also validated VIGS by silencing the endogenous gene, phytoene desaturase (PDS) in N. benthamiana plants, and the transgene GFP in N. benthamiana line 16c plants. Therefore, LIYV-derived vectors could provide a technical reference for developing vectors of other economically important criniviruses

Lebensdauer des räuberischen Marienkäfers Serangium parcesetosum Sicard (Col., Coccinellidae) mit natürlicher und künstlicher Nahrung

The little known ladybird, Serangium parcesetosum SICARD (Col., Coccinellidae) seems to be an important predator of whiteflies. It has found attacking Bemisia tabaci (GENN.) (Hom., Aleyrodidae) (KAPADIA & PURI 1992), Aleurolobus barodensis MASK (PATEL et al. 1996), Aleurothrixus floccosus MASKELL (ABBOUD & AHMAD 1998), Bemisia argentifolii BELLOWS and PERRING (LEGASPI et al. 2001) as well as Dialeurodes citri (ASHMEAD) (YIGIT et al. 2003). However, in Germany the laboratory studies demonstrated that S. parcesetosum is a promising predator of B. tabaci (AL-ZYOUD & SENGONCA 2004; SENGONCA et al. 2004; AL-ZYOUD et al. 2005a, b; SENGONCA et al. 2005). One of the important features for a successful predator is to live for a long period on the prey species and also not feed on the plant in the prey absence. Long longevity accomplished by voraciously feeding of S. parcesetosum adults resulted in a successful control of B. argentifolii (ELLIS et al. 2001). To use this predator successfully in controlling the whiteflies, especially B. tabaci and Trialeurodes vaporariorum WESTWOOD (Hom., Aleyrodidae), it was important to investigate its natural and artificial nutritional sources. However, such knowledge of S. parcesetosum is still insufficient or completely lacking in the literature. Therefore, the present work was directed to study the longevity of S. parcesetosum on natural nutritional sources such as B. tabaci and T. vaporariorum as well as on certain artificial nutritional sources at two different temperatures in the laboratory.Der in der Literatur nur wenig bekannte Marienkäfer Serangium parcesetosum SICARD (Col., Coccinellidae) scheint, ein spezialisierter Prädator der Weißen Fliegen zu sein. Untersuchungen über die Lebensdauer eines Prädators sind eine der wichtigsten Parameter für seine erfolgreiche Verwendung in der biologischen Bekämpfung. Solche Informationen über S. parcesetosum sind bisher in der Literatur allerdings nur unzulänglich bekannt bzw. fehlen vollständig. Folglich war das Ziel dieser Arbeit, bei zwei unterschiedlichen Temperaturen im Labor zu untersuchen, wie lang S. parcesetosum mit Bemisia tabaci (GENN.) bzw. Trialeurodes vaporariorum WESTWOOD (Hom., Aleyrodidae) als Beute sowie mit bestimmten künstlichen Nahrungen überleben kann. Die Ergebnisse zeigten, dass beide Geschlechter von S. parcesetosum auf Baumwolle mit B. tabaci als Beute, mit Ausnahme der Männchen bei 30°C, signifikant länger mit allen anderen Nahrungen lebten. Bei beiden Temperaturen war die Lebensdauer der Weibchen, mit allen untersuchten Nahrungen, signifikant länger als die der Männchen. Sie schwankte bei beiden Geschlechtern von durchschnittlich 94,3 (&#9794;&#9794;) bis 175,4 (&#9792;&#9792;) Tagen bei 18°C bzw. 50,3 (&#9794;&#9794;) bis 92,4 (&#9792;&#9792;) Tage bei 30°C mit den getesteten Nahrungen. Die adulten Weibchen und Männchen von S. parcesetosum konnten für eine beträchtliche Zeit mit künstlichen Nahrungen überleben. Bei beiden Temperaturen war die durchschnittliche Überlebensdauer beider Geschlechter bei einem Angebot von 10%iger Honig-Emulsion als Nahrung signifikant länger als nur mit Baumwollblättern bzw. ohne ein Angebot an Nahrung

Defining Hierarchical Decision Trees for Encarsia Formosa Strategies from Greenhouse Tomato Consultants' Perspectives

Market pressure is forcing New Zealand greenhouse tomato growers to shift from conventional to more environmentally-friendly pest control methods such as IPM (Integrated Pest Management). Growers can access IPM manuals, but these tend to provide generalized advice, which they find difficult to apply to their own situations. Alternatively, growers can use consultants to tailor IPM strategies to their own situations. One method of providing growers with better advice is to capture the knowledge of "expert" consultants and translate this into a form that can be used by growers. To this end, two consultants with expertise in IPM strategy were studied and their knowledge documented. This paper focuses on the strategies the expert consultants used to tailor Encarsia formosa, a natural enemy of greenhouse whitefly, to individual greenhouse's specific needs. Both consultants used an IPM template and seven to eight decision criteria to tailor their advice to individual grower's situations. These decisions were represented as hierarchical decision trees. One consultant started with low Encarsia rates for a short time before increasing them while the other consultant started with high Encarsia rates for a longer period before decreasing them later. Growers' risk perceptions and acceptance of the consultants' pest threshold levels influenced the success of the IPM strategy.decision trees, consultants, Encarsia, greenhouse tomato, Farm Management,

Identification of a mutation in the para-sodium channel gene of the cattle tick Rhipicephalus (Boophilus) microplus associated with resistance to synthetic pyrethroid acaricides

Resistance against synthetic pyrethroid (SP) products for the control of cattle ticks in Australia was detected in the field in 1984, within a very short time of commercial introduction. We have identified a mutation in the domain II S4-5 linker of the para-sodium channel that is associated with resistance to SPs in the cattle tick Rhipicephalus (Boophilus) microplus from Australia. The cytosine to adenine mutation at position 190 in the R. microplus sequence AF134216, results in an amino acid substitution from leucine in the susceptible strain to isoleucine in the resistant strain. A similar mutation has been shown to confer SP resistance in the whitefly, Bemisia tabaci, but has not been described previously in ticks. A diagnostic quantitative PCR assay has been developed using allele-specific Taqman® minor groove-binding (MGB) probes. Using the assay to screen field and laboratory populations of ticks showed that homozygote allelic frequencies correlated highly with the survival percentage at the discriminating concentration of cypermethrin