Elsa Borges da Silva

Management strategies of mealybug pests of citrus in mediterranean countries

Six mealybug species have been reported as citrus pests in the Mediterranean Basin: the citrus mealybugPlanococcus citri (Risso), the citriculus mealybugPseudococcus cryptus Hempel, the longtailed mealybugPseudococcus longispinus (Targioni-Tozzetti), the citrophilus mealybugPseudococcus calceolariae (Maskell), the obscure mealybugPseudococcus viburni (Signoret) and the spherical mealybugNipaecoccus viridis (Newstead). Some of these species,e.g. N. viridis, have recently been introduced into the region and are still spreading. Mealybugs are usually occasional or minor pests of citrus, but some species can reach key pest status. Mealybug management strategies in citrus have been based mostly on classical biological control and, to a lesser extent, on augmentative releases. However, chemical control is widely used, mainly because of the poor adaptation of the principal natural enemies to the climatic conditions of the Mediterranean. The application of pheromones is still restricted to monitoring the citrus mealybug, whose sex pheromone is commercially available. Mass trapping and mating disruption should be considered for possible use in IPM programs as an alternative method to supplementary chemical treatments. Enhancement of biological control through management of ant populations is another promising tactic for control of mealybugs. Strategies for managing mealybug pests of citrus, and possible levels of integration of different tactics according to the pest status, are discussed.

Effect of ground cover vegetation on the abundance and diversity of beneficial arthropods in citrus orchards

The effect of ground cover upon the communities of beneficial arthropods established in the canopy of lemon trees was investigated, by comparing three ground-cover management treatments applied: RV, resident vegetation; S, sowed selected species; and BS, bare soil by controlling weeds with herbicide. Over two consecutive years, arthropod communities in the tree canopy were sampled periodically by beating and suction techniques. Significantly higher numbers of beneficial arthropods were found in the RV and S treatments in comparison with bare soil. Spiders and parasitoid wasps were the two most common groups, representing, respectively, 70% and 19% of all catches in beating samples and 33% and 53% in suction samples. For the RV and S treatments, significant seasonal deviations from the bare soil treatment were observed using principal response curves. Similar seasonal patterns were observed over the two years. The RV and S treatments showed significant positive deviations from the BS treatment in late spring and summer, accounted for the higher numbers of parasitoid wasps, coccinelids and lacewings present. By contrast, the seasonal deviations observed for the spider community differed from those of the remaining arthropods. During late winter and early spring, the RV and S treatments presented a higher abundance of spiders in the tree canopy, in comparison with bare soil, whereas in the summer significantly more spiders were found in the bare soil treatment. Spider movements between tree canopy and ground vegetation layers may justify this result.

Kairomonal response of the parasitoid Anagyrus spec. nov. near pseudococci to the sex pheromone of the vine mealybug

The occurrence of a kairomonal response of the parasitoid Anagyrus spec. nov. near pseudococci (Hymenoptera: Encyrtidae) to (+)‐(1R,3R)‐cis‐2,2‐dimethyl‐3‐isopropenyl‐cyclobutanemethanol acetate (PcA, namely, planococcyl acetate) and (S)‐(+)‐lavandulyl senecioate (LS), the respective female sex pheromones of its hosts, the citrus mealybug, Planococcus citri (Risso) and the vine mealybug, Planococcus ficus (Signoret) (Homoptera: Pseudococcidae) was investigated. Attraction to the pheromones was tested by employing pheromone traps in field trials and by static air olfactometer bioassays in the laboratory. Female wasps showed a significant response to LS, in both field and olfactometer experiments. No significant response was registered to the sex pheromone of P. citri. Despite the similarity between the structures of LS and its analogue (S)‐(+)‐lavandulyl isovalerate (LI), no significant response to the latter compound was observed. It seems that differences between the structures of the carboxylate moiety of the respective molecules (LS and LI) markedly affect the kairomonal attractiveness to the parasitoid. The kairomonal response of Anagyrus spec. nov. near pseudococci was neither influenced by the host habitat nor by the host species on which it developed. This suggested innate behaviour of Anagyrus spec. nov. near pseudococci, possibly derived from evolutionary relationships between the parasitoid and P. ficus. The practical implications of the results are discussed.

Can facultative parthenogenesis occur in biparental mealybug species

The existence of facultative parthenogenesis in mealybugs has been reported by different authors and questioned by others in relation to certain species. We tested the hypothesis of facultative parthenogenesis in relation to three mealybug species, Planococcus citri (Risso), Pseudococcus calceolariae (Maskell) and Pseudococcus viburni (Signoret). The results suggest that these mealybug species are obligate amphimictic.

Defense Response of Native and Alien Mealybugs (Hemiptera: Pseudococcidae) Against the Solitary Parasitoid Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera: Encyrtidae)

The host behavioral and immune (encapsulation) defenses against the parasitoid Anagyrus sp. nr. pseudococci were compared for five mealybug species with different phylogenetic relationships and geographical origins: i) a Mediterranean native mealybug species, Planococcus ficus, with a long co-evolutionary history with the parasitoid; ii) three alien mealybugs species, Planococcus citri, Pseudococcus calceolariae and Pseudococcus viburni, with a more recent co-evolutionary history; and iii) a fourth alien mealybug species, Phenacoccus peruvianus, with no previous common history with the parasitoid. Three host defense behaviors were registered: abdominal flipping, reflex bleeding and walking away. The native host Pl. ficus and its congener Pl. citri exhibited the lowest probability of defense behavior (0.11 ± 0.01 and 0.09 ± 0.01 respectively), whereas the highest value was observed in P. viburni (0.31 ± 0.02). Intermediate levels of defense behavior were registered for Ps. calceolariae, and Ph. peruvianus. The probability of parasitoid encapsulation was lowest and highest for two alien host species, Ph. peruvianus (0.20 ± 0.07) and Ps. viburni (0.86 ± 0.05), respectively. The native host Pl. ficus, its congener Pl. citri and Ps. calceolariae showed intermediate values (0.43 ± 0.07, 0.52 ± 0.06, and 0.45 ± 0.09, respectively). The results are relevant with respect to biological control and to understand possible evolutionary processes involved in host range of A. sp. nr. pseudococci.

Host selection behaviour and specificity of the solitary parasitoid of mealybugs Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera, Encyrtidae)

The host selection behaviour of Anagyrus sp. nr. pseudococci was compared in no-choice tests among five mealybug species of different geographical and phylogenetic origin, including the Mediterranean native host, Planococcus ficus and four exotic mealybug species, one of the same genus, Pl. citri, two Pseudococcus species, Ps. calceolariae and Ps. viburni and a more distant one, Phenacoccus peruvianus. All five studied mealybug species were recognised by the parasitoid as potential hosts and parasitised, but the behavioural pattern of host recognition, host handling and the level of host acceptance of Anagyrus sp. nr. pseudococci significantly varied among the five studied species, indicating a clear preference for the two Planococcus species, Pl. ficus in particular. The results suggest that A. sp. nr. pseudococci has a broader host range and a more generalist behaviour in comparison with other Anagyrus species. Practical implications of the findings are discussed.

Mating Behavior and Performance in the Two Cosmopolitan Mealybug Species Planococcus citri and Pseudococcus calceolariae (Hemiptera: Pseudococcidae)

Mating strategies of mealybugs were investigated using two heterogeneric cosmopolitan species as case study: Planococcus citri (Risso) and Pseudococcus calceolariae (Maskell). Male mating behavior of the studied species differed in respect to mate selection, and frequency and duration of copulation. Females played an active role in mate selection, by either facilitating or resisting copulation. This is a first evidence of female sexual active behavior in scale insects. In both species, male predisposition to mate was affected by previous exposition to light. The frequency of courtship and copulation decreased with the age of females for Pl. citri but not for Ps. calceolariae. Mating frequency increased with female colony density in both species.

Suitability of five mealybug species (Hemiptera, Pseudococcidae) as hosts for the solitary parasitoid Anagyrus sp. nr. pseudococci (Girault) (Hymenoptera: Encyrtidae)

Anagyrus sp. nr. pseudococci is an endoparasitoid which has been used as a biological control agent of mealybug pests. In this study, we compared the suitability of five mealybugs species with different phylogenetic relationships and geographical origins as hosts of this parasitoid. The selected mealybugs were: (1) a Mediterranean-native species, Planococcus ficus, sharing a long co-evolutionary history with the parasitoid; (2) three exotic species, the Afrotropical Planococcus citri, the Australasian Pseudococcus calceolariae and the Neotropical Pseudococcus viburni, with a recent history; and (3) the Neotropical Phenacoccus peruvianus, with no previous common history with the parasitoid. Host suitability was assessed based on different fitness parameters, such as body size, developmental time, emergence rate and sex ratio. The parasitoid was able to complete development in all mealybug species. Nevertheless, its emergence rate significantly varied among mealybug species, with the highest values observed in Pl. ficus and Pl. citri, intermediate values in Ps. calceolariae and the lowest ones in Ps. viburni and Ph. peruvianus. The body size of adult wasp females varied with host suitability and was positively correlated with other measures of parasitoid fitness, including the emergence rate and the sex ratio. The parasitoid developmental time differed among mealybug species but did not correlate with any other measure of fitness. A female biased sex ratio was found in the parasitoid progeny emerged from all mealybug species, except in Ps. viburni and Ph. peruvianus. There was a direct relationship between the proportion of females in the parasitoid progeny and the emergence rate.

Isolation and characterization of fifteen polymorphic microsatellite loci for the citrus mealybug, Planococcus citri (Hemiptera: Pseudococcidae), and cross-amplification in two other mealybug species

1Computational Biology and Population Genomics Group, Centro de Biologia Ambiental, Departamento de Biologia Animal, Faculdade de Ciencias da Universidade de Lisboa, 1749-016 Lisboa, Portugal 2Centro de Estudos Florestais, Instituto Superior de Agronomia, 1349-017 Lisboa, Portugal 3Centro de Estudos do Ambiente e do Mar (CESAM), Departamento de Biologia Animal, Faculdade de Ciencias da Universidade de Lisboa, 1749-016 Lisboa, Portugal 4Centro de Engenharia dos Biossistemas, Instituto Superior de Agronomia, 1349-017 Lisboa, Portugal 5Department of Entomology, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel

First record of the pepper tree psyllid, Calophya schini Tuthill (Hemiptera, Calophyidae), in the Palaearctic region

The presence of the psyllid Calophya schini infesting the Peruvian pepper tree, Schinus molle, was detected in several localities in the region of Lisbon, in Portugal. This is the first record of this jumping plant-louse in Europe and the Palaearctic region.