Antonia Soto

Molecular and morphological characterisation of Pseudococcidae surveyed on crops and ornamental plants in Spain.

Mealybugs (Hemiptera: Pseudococcidae) are common invasive pests in Europe, causing major problems on crops and ornamental plants. However, very few data are available concerning the mealybug fauna of southern Europe. This lack of data and the difficulty of identifying mealybugs morphologically by traditional techniques currently limit the perspectives for efficient specific pest management. The aim of this study was to provide multi-criterion characterization of mealybugs surveyed in eastern Spain in order to facilitate their routine identification through DNA sequencing or the use of derived species-specific molecular tools. We characterised 33 mealybug populations infesting crops and ornamental plants in eastern Spain, using a combination of molecular and morphological techniques, including the sequencing of the universal barcode DNA region cytochrome c oxidase subunit I (COI). This characterisation has led to the identification of ten species and provides sequence data for three previously unsequenced species, contributing to the phylogenetic knowledge of the family Pseudococcidae. In addition, the intraspecific variations found in the populations of five mealybug species provide insight into their invasion history.

Study of the flying ability of Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae) adults using a computer-monitored flight mill.

The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae), native to tropical Asian regions, has become a serious threat to palm trees all over the world. Knowledge of its flight potential is vital to improving the preventive and curative measures currently used to manage this pest. As R. ferrugineus is a quarantine pest, it is difficult to study its flight potential in the field. A computer-monitored flight mill was adapted to analyse the flying ability of R. ferrugineus through the study of different flight parameters (number of flights, total distance flown, longest single flight, flight duration, and average and maximum speed) and the influence of the weevils sex, age, and body size on these flight parameters. Despite significant differences in the adult body size (body weight and length) of males and females, the sex of R. ferrugineus adults did not have an influence on their flight potential. Neither adult body size nor age was found to affect the weevils flying abilities, although there was a significantly higher percentage of individuals flying that were 8-23 days old than 1-7 days old. Compared to the longest single flight, 54% of the insects were classified as short-distance flyers (covering <100 m) and 36 and 10% were classified as medium- (100-5000 m) and long-distance (>5000 m), respectively. The results are compared with similar studies on different insect species under laboratory and field conditions.

Guiding Classical Biological Control of an Invasive Mealybug Using Integrative Taxonomy

Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae) is a mealybug of Southern African origin that has recently been introduced into Eastern Spain. It causes severe distortions on young citrus fruits and represents a growing threat to Mediterranean citrus production. So far, biological control has proven unsatisfactory due to the absence of efficient natural enemies in Spain. Hence, the management of this pest currently relies only on chemical control. The introduction of natural enemies of D. aberiae from the native area of the pest represents a sustainable and economically viable alternative to reduce the risks linked to pesticide applications. Since biological control of mealybugs has been traditionally challenged by taxonomic misidentification, an intensive survey of Delottococcus spp. and their associated parasitoids in South Africa was required as a first step towards a classical biological control programme. Combining morphological and molecular characterization (integrative taxonomy) a total of nine mealybug species were identified in this study, including three species of Delottococcus. Different populations of D. aberiae were found on wild olive trees, in citrus orchards and on plants of Chrysanthemoides monilifera, showing intra-specific divergences according to their host plants. Interestingly, the invasive mealybug populations from Spanish orchards clustered together with the population on citrus from Limpopo Province (South Africa), sharing COI haplotypes. This result pointed to an optimum location to collect natural enemies against the invasive mealybug. A total of 14 parasitoid species were recovered from Delottococcus spp. and identified to genus and species level, by integrating morphological and molecular data. A parasitoid belonging to the genus Anagyrus, collected from D. aberiae in citrus orchards in Limpopo, is proposed here as a good biological control agent to be introduced into Spain.

New records of mealybugs (Hemiptera: Pseudococcidae) from Spain

Five mealybug (Hemiptera: Pseudococcidae) species were identified as new records for Spain: Phenacoccus madeirensis (Green), Phenacoccus solani Ferris, Dysmicoccus boninsis (Kuwana), Hypogeococcus pungens Granara de Willink and Ferrisia malvastra (McDaniel).

Density and Structure of Saissetia oleae (Hemiptera: Coccidae) Populations on Citrus and Olives: Relative Importance of the Two Annual Generations

Abstract Saissetia oleae (Olivier) (Hemiptera: Coccidae) populations were studied and compared in citrus (Citrus spp.) and olive (Olea europaea L.) groves to determine the number of generations, crawler emergence periods and changes in population density during the year. Ten citrus and four olive groves were sampled regularly between March 2003 and December 2005 in eastern Spain, covering an area of 10,000 km2. Each sample consisted of 16 branches and 64 leaves. Saissetia oleae populations presented a similar trend in both crops during the three years of study. Populations peaked in July, when crawlers emerged after the egg-laying period, and decreased during several months due to mortality of first instars in summer. A second crawler emergence period, with lower numbers and more variability from year to year, occurred between October and March. Populations did not increase during this period, probably because most eggs and crawlers perished during the winter and also because females that gave rise to this fall-winter generation were half as big and fecund as spring females. No differences were found between the size of mature females that had developed on citrus and on olives during the spring. Considering this population pattern, the best seasonal period to apply pesticides to control S. oleae would be at the end of July, when populations are synchronous, all crawlers have already emerged, and first instars predominate.

Distribution and Sampling of the whiteflies Aleurothrixus floccosus, Dialeurodes citri, and Parabemisia myricae (Homoptera: Aleyrodidae) in Citrus in Spain

Abstract From 1993 to 1995 data sets were collected from four citrus groves in Valencia, Spain, to determine the distribution patterns of eggs and nymphs of Aleurothrixus floccosus (Maskell), Dialeurodes citri (Ashmead), and Parabemisia myricae (Kuwana) on leaves, and to develop reliable sampling plans for estimating densities of immature whiteflies. A. floccosus showed higher aggregation than the other two species. The dispersion index b from the Taylor power law did not vary between different developing stages for A. floccosus and D. citri, reaching overall values of 1.70 and 1.53, respectively. In P. myricae, b was 1.60 for eggs and N1, and 1.46 for the remaining nymphs. The minimum number of leaves to estimate the population density with a coefficient of variation of 0.25 for densities above 10 immature whiteflies per leaf was 40 for D. citri and P. myricae, and 250 for A. floccosus. Binomial sampling programs for the three species were rejected for pest management purposes due to the high sample sizes required. The enumerative procedure of counting the number of insects per leaf appears to be the most suitable method for D. citri and P. myricae. For A. floccosus an index of occupation (from 0 to 10) linearly related to the proportion of the leaf undersurface occupied by this insect was found to be reliable and time-saving. Examining 150 leaves with this index achieves the desired relative variation level of 0.25 for most population densities usually found in commercial groves.

Fortuitous biological control of the invasive mealybug Phenacoccus peruvianus in Southern Europe

Phenacoccus peruvianus Granara de Willink (Hemiptera: Pseudococcidae) is a Neotropical invasive mealybug that has rapidly spread throughout Mediterranean Basin. It has established itself as the principal pest of several ornamental plants, causing considerable problems in nurseries and urban landscapes. The aim of this study was to determine the natural enemy complex of this pest and report the feasibility of its biological control. Six urban green spaces were surveyed in eastern Spain from 2008 to 2010. The most abundant natural enemies of P. peruvianus were found to be the primary parasitoids Acerophagus n. sp. near coccois and Leptomastix epona Walker (Hymenoptera: Encyrtidae). Phenacoccus peruvianus populations were lower during the second and third year of the survey, coinciding with an increase of the parasitoid Acerophagus sp., which displaced the native L. epona. Differential female offspring and resource preemption are discussed as the main reasons for this displacement.

Seasonal Phenology, Spatial Distribution, and Sampling Plan for the Invasive Mealybug Phenacoccus peruvianus (Hemiptera: Pseudococcidae)

ABSTRACT Phenacoccus peruvianus Granara de Willink (Hemiptera: Pseudococcidae) is an invasive mealybug of Neotropical origin. In recent years it has invaded the Mediterranean Basin causing significant damages in bougainvillea and other ornamental plants. This article examines its phenology, location on the plant and spatial distribution, and presents a sampling plan to determine P. peruvianus population density for the management of this mealybug in southern Europe. Six urban green spaces with bougainvillea plants were periodically surveyed between March 2008 and September 2010 in eastern Spain, sampling bracts, leaves, and twigs. Our results show that P. peruvianus abundance was high in spring and summer, declining to almost undetectable levels in autumn and winter. The mealybugs showed a preference for settling on bracts and there were no significant migrations between plant organs. P. peruvianus showed a highly aggregated distribution on bracts, leaves, and twigs. We recommend a binomial sampling of 200 leaves and an action threshold of 55% infested leaves for integrated pest management purposes on urban landscapes and enumerative sampling for ornamental nursery management and additional biological studies.

Factors influencing adult female oviposition in the citrus leafminer Phyllocnistis citrella

1 The citrus leafminer (CLM) Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) is a serious pest in most citrus‐growing regions of the world. The influence of leaf length, citrus species or variety, leaf colour tone and temperature on CLM oviposition was studied from field observations and laboratory experiments. The spatial distribution of eggs on leaves was also examined. Field data were obtained from 1100 samples collected in eastern Spain for 7 years.

Molecular evidence for ongoing complementarity and horizontal gene transfer in endosymbiotic systems of mealybugs

Intracellular bacterial supply of essential amino acids is common among sap-feeding insects, thus complementing the scarcity of nitrogenous compounds in plant phloem. This is also the role of the two mealybug endosymbiotic systems whose genomes have been sequenced. In the nested endosymbiotic system from Planococcus citri (Pseudococcinae), “Candidatus Tremblaya princeps” and “Candidatus Moranella endobia” cooperate to synthesize essential amino acids, while in Phenacoccus avenae (Phenacoccinae) this function is performed by its single endosymbiont “Candidatus Tremblaya phenacola.” However, little is known regarding the evolution of essential amino acid supplementation strategies in other mealybug systems. To address this knowledge gap, we screened for the presence of six selected loci involved in essential amino acid biosynthesis in five additional mealybug species. We found evidence of ongoing complementarity among endosymbionts from insects of subfamily Pseudococcinae, as well as horizontal gene transfer affecting endosymbionts from insects of family Phenacoccinae, providing a more comprehensive picture of the evolutionary history of these endosymbiotic systems. Additionally, we report two diagnostic motifs to help identify invasive mealybug species.