Mealybug Planococcus Citri Research Articles

The amount of heterochromatic proteins in the egg is correlated with sex determination in Planococcus citri (Homoptera, Coccoidea)

In the mealybug Planococcus citri, there are no identifiable sex chromosomes. Early in the development of embryos destined to become males, the genome contributed by the sperm undergoes heterochromatization and, following an inverted type of meiosis, will be eliminated. Only two vital sperms are therefore produced, both carrying the same maternally derived genome. A differential distribution observed on the two spermatids during male germline cyst formation of chromatin remodeling factors such as HP1 and methylated K9 histone H3 prompted us to propose an imprinting/sex determination model in which the imprinted sperm is the one to undergo heterochromatization at syngamy. The sex ratio is normally 1:1, but aged females are known to produce almost exclusively male progeny, suggesting that the imprinting pattern of the male gamete in P. citri, though necessary, is apparently not sufficient for sex determination. We report here that egg cells of aged females show larger amounts of HP1 and Su(Var)3-9 than egg cells of young females. These data suggest that a determinant of sex may be the amount of maternally derived heterochromatic proteins.

Epigenetic marks for chromosome imprinting during spermatogenesis in coccids

The establishment of sex-specific epigenetic marks during gametogenesis is one of the key feature of genomic imprinting. By immunocytological analysis, we thoroughly characterized the chromatin remodeling events that take place during gametogenesis in the mealybug Planococcus citri, in which an entire haploid set of (imprinted) chromosomes undergoes facultative heterochromatinization in male embryos. Building on our previous work, we have investigated the interplay of several epigenetic marks in the regulation of this genome-wide phenomenon. We characterized the germline patterns of histone modifications, Me(3)K9H3, Me(2)K9H3, and Me(3)K20H4, and of heterochromatic proteins, PCHET2 (HP1-like) and HP2-like during male and female gametogenesis. We found that at all stages in oogenesis chromatin is devoid of any detectable epigenetic marks. On the other hand, spermatogenesis is accompanied by a complex pattern of redistribution of epigenetic marks from euchromatin to heterochromatin, and vice versa. At the end of spermatogenesis, sperm heads are decorated by all the molecules we tested, except for PCHET2. However, only Me(3)K9H3 and Me(2)K9H3 are still detectable in the male pronucleus. We suggest that the histone H3 lysine 9 methylation is the signal used to establish the male-specific imprinting on the paternal genome, thus allowing it to be distinguished from the maternal genome in the developing embryo.

Inhibition Studies of Cellulolytic Activities Isolated from Planococcus Citri

The study was performed to isolate the cellulolytic activities from a mealy bug Planococcus citri and to check their enzyme inhibition against leaf extract of Azdirachta indica and Buxus Sempervirens. Enzyme assay confirmed the presence of endoglucanase activity. Aqueous and non-aqueous fractions showed the maximum inhibition. Proteins containing fraction also reflected inhibition of activity that might lead to identification of some active peptides against cellulolytic activity.

Desenvolvimento de <em>Planococcus citri</em> (Risso, 1813) (Hemiptera: Pseudococcidae) em cafeeiros

The citrus mealybug Planococcus citri (Risso, 1813) feeds mainly on flowers and fruits of coffee plants from blooming until harvest. Little is known about its development in coffee although its occurrence is already known for several years. This work aims to study the nymph development of this mealybug in coffee plants. Eggs were isolated from a stock culture kept in laboratory and placed inside Petri dishes containing leaf sections in agar. The tested cultivars were Acaia Cerrado, Mundo Novo, Catuai Vermelho ( Coffea arabica ) and Apoata ( C. canephora ). Insects were kept in a climatized chamber at 25oC, 70 ± 10% humidity and 12-hour photophase. The longest development period in females was obtained in cultivar Catuai Vermelho. No differences in mortality were found among cultivars. Mealybugs developed in all cultivars and the results did not show clear differences in susceptibility.

Aspectos biológicos de Chrysoperla externa (Hagen) predando Oligonychus ilicis (McGregor) e Planococcus citri (Risso)

The red mite Oligonychus ilicis (McGregor, 1917) and the mealybug Planococcus citri (Risso, 1813) are considered important pests of the coffee plant ( Coffea arabica L.), causing yield losses. The predator Chrysoperla externa (Hagen, 1861) is associated with those pests. The objective of this work was to evaluate the development of the immature and adult phases of the predator fed, in the immature phase, on those coffee plant pests and their effects on both fecundity and survival rate of larvae, pupae and eggs in laboratory. The bioassays were carried out in the laboratory of the EcoCentro/CTSM-EPAMIG, Lavras, MG, at 25 ± 1oC, 70 ± 10% of relative humidity and 12 hours´ photophase. The experimental design was completely randomized with 10 treatments representing the possible combinations of the diets: Anagasta kuehniella (Zeller, 1879) eggs as the standard food, mites and mealybugs, with 30 replicates. The preys were supplied either singly or associated between each other in each instar or alternated in the instars with eggs of A. kuehniella . Significant alterations occurred in weight, larval and pupal survival, when the larvae were fed with only one prey type or with the combination of mites plus mealybugs, compared to eggs of A . kuehniella. It was demonstrated that O. ilicis e P. citri singly supplied to larvae of C. externa , is not the food adequate for the development of larvae. Only the red mite as a food caused 100% of death of the lacewing’s larvae in the second instar.

Feeding behavior ofCryptolaemus montrouzieri on mealybugs parasitized byAnagyrus pseudococci

The citrus mealybugPlanococcus citri (Risso) and the vine mealybugPlanococcus ficus (Signoret) (Hemiptera: Pseudococcidae) are two worldwide polyphagous pests of citrus, vineyards and ornamental plants in greenhouses. Biological control of these pests may rely on the combined release of parasites and predators, which can be affected by intraguild predation (IGP). This study investigated the feeding behavior of different stages ofCryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) on mealybugs parasitized byAnagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae) 2, 4, 6, 8 and 10 days. The study was conducted in a climate-controlled room at 28±1° C, 16L:8D, and 65±10% r.h. The highest consumption values for all stages ofC. montrouzieri occurred with 2- and 4-day parasitized mealybugs, whereas the predator did not feed on either species of mealybug parasitized for longer periods, due to the onset of mummification.

Indexação biológica de genótipos de bananeira para o Banana streak virus

O Banco Ativo de Germoplasma (BAG) de bananeira é a base do programa de melhoramento genético da Embrapa Mandioca e Fruticultura Tropical. O objetivo deste trabalho foi indexar os acessos do BAG para o vírus das estrias da bananeira (Banana streak virus, BSV). Cada amostra foliar, coletada dos 220 acessos do BAG foi utilizada na inoculação de três plantas de bananeira 'Caipira' produzidas por micropropagação. As plantas foram inoculadas, através da cochonilha vetora Planococcus citri Risso, fornecendo-se um acesso de aquisição de 24 horas e de transmissão de 48 horas. Como controle positivo e negativo foram utilizadas plantas previamente analisadas por PCR, quanto a presença de BSV. Entre 15 e 70 dias após a inoculação, as plantas indicadoras apresentaram os primeiros sintomas. Desta forma, verificou-se que 44 dos 220 acessos estavam infectados com BSV.

Spatial analysis of epidemics of Grapevine leafroll associated virus-3

Several vineyards in Rias Baixas and one in the Ribeira Sacra (Spain) were monitored and the spatial pattern of leafroll-diseased grapevine was analysed at several dates. Unidimensional aggregation analysis (ordinary runs), bidimensional analysis, and disease gradients analysis were used as methods of study of spatial aspects of epidemics of GLRaV. At very low insect populations the mealybug Planococcus citri transmitted the GLRaV-3 from infected plants to healthy ones planted between them in an experimental plot at Beluso; an initial focus of leafroll-infected grapevines was detected 2 years after planting at the area where the vectors had been located infesting the old plants. Within 8 years some new foci appeared and coalesced, and the incidence reached >80%. In three commercial plots where no vectors were observed, the spatial analysis of the diseased plants showed three different situations. In Meano, the study of the evolution of the spatial patterns of diseased plants between 1992 and 2005 suggested slow vectorial field transmission of GLRaV-3. In Goian the analysis for only 2 years suggested random distribution; therefore the viruses were arriving with the planting material, but the runs analysis of some lines suggested incipient spread of GLRaV-3. In Portomarin the incidence of both GLRaV-2 and 3 was low and their distribution was random, without any evidence of field spread. These examples of the study of the spatial analysis of leafroll-infected plants may be helpful to determine whether or not spread of the viruses is occurring, and the best control measures to take.

Epigenetic regulation of facultative heterochromatinisation inPlanococcus citrivia the Me(3)K9H3-HP1-Me(3)K20H4 pathway

Using RNA interference (RNAi) we have conducted a functional analysis of the HP1-like chromobox gene pchet2 during embryogenesis of the mealybug Planococcus citri. Knocking down pchet2 expression results in decondensation of the male-specific chromocenter that normally arises from the developmentally-regulated facultative heterochromatinisation of the paternal chromosome complement. Together with the disappearance of the chromocenter the staining levels of two associated histone modifications, tri-methylated lysine 9 of histone H3 [Me(3)K9H3] and tri-methylated lysine 20 of histone H4 [Me(3)K20H4], are reduced to undetectable levels. Embryos treated with double-stranded RNA (dsRNA) targeting pchet2 also exhibit chromosome abnormalities, such as aberrant chromosome condensation, and also the presence of metaphases that contain 'lagging' chromosomes. We conclude that PCHET2 regulates chromosome behavior during metaphase and is a crucial component of a Me(3)K9H3-HP1-Me(3)K20H4 pathway involved in the facultative heterochromatinisation of the (imprinted) paternal chromosome set.

Wrap attack of the spider Achaearanea tepidariorum (Araneae: Theridiidae) by preying on mealybugs Planococcus citri (Homoptera: Pseudococcidae)

Predation by Achaearanea tepidariorum (Koch 1841) on mealybugs Planococcus citri (Risso 1813) is facilitated by the design of its web, which features a tangle of sticky gumfooted lines, and wrap attacks as well as the ability to handle the prey, whose body is covered with a waxy secretion, via silk. Crawling, i.e., wingless, mealybugs (in particular those in the nymphal stages and adult females and, to a lesser extent, winged males) are caught by means of the gumfooted lines, covered with globules of an adhesive secretion. The process of wrap attack and subsequent handling of the captured prey is a series of the following consecutive events: (1) confining and immobilising the mealybugs with sticky silk; (2) biting with chelicerae and paralyzing the prey with a toxin; (3) detaching the confined prey, attached to the tense threads, from the plant surface and catapulting it toward the central section of the web; (4) wrapping the catapulted prey in viscid silk emitted by the spinning apparatus; (5) transporting the wrapped prey to the central section of the web; (6) wrapping the prey in the central section of the web in nonsticky silk, whose tufts are present in this part of the web even before the attack; (7) filling the prey with digestive fluid; (8) sucking the prey empty; and (9) cleaning the chelicerae and mouth parts. The process of silk tuft wrapping was described for the first time. The described ability to hunt mealybugs implies the possibility of using A. tepidariorum spiders for biological control of these pests.

Characterisation of Banana streak Mysore virus and evidence that its DNA is integrated in the B genome of cultivated Musa

We have sequenced the complete genome of an isolate of Banana streak virus from banana cv. 'Mysore' and show that it is sufficiently different from a previously characterised isolate from cv. 'Obino l'Ewai' to warrant recognition as a distinct species, for which the name Banana streak Mysore virus (BSMysV) is proposed. The structure of the BSMysV genome was typical of badnaviruses in general, although ORF I had a non-conventional start codon. Evidence that at least part of the BSMysV genome is integrated in the B genome of cultivated Musa is presented and transmissibility by the mealybug Planococcus citri also demonstrated.

Germline cyst development and imprinting in male mealybug Planococcus citri

In the epigenetic modifications involved in the phenomenon of imprinting, which is thought to take place during gametogenesis, one of the primary roles is exerted by histone tail modifications acting on chromatin structure. What is more, in insects like mealybugs, with a lecanoid chromosome system, imprinting is strictly related to sex determination. In many diverse species gametes originate in specific, highly evolutionarily conserved structures called germline cysts. The use of staining techniques specific for fusomal components like F-actin has allowed us to describe for the first time the morphogenesis of male germline cysts in the mealybug Planococcus citri. Antibodies to anti-methylated lysine 9 of histone H3 (MeLy9-H3) and anti-heterochromatin protein 1 (HP1) were used during cyst formation to investigate the involvement of these epigenetic modifications in the phenomenon of imprinting and their possible concerted action in sex determination in P. citri. These observations indicate: (i) a specific role for F-actin in the segregation, typical of the lecanoid chromosome system, of genomes of paternal origin; (ii) that the two vital gametes originating from a given meiosis, although carrying the same genome, differ in the levels of both MeLy9-H3 and HP1, one of them being more heavily labelled by both antibodies.

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.

DNA methylation in insects.

Cytosine DNA methylation has been demonstrated in numerous eukaryotic organisms and has been shown to play an important role in human disease. The function of DNA methylation has been studied extensively in vertebrates, but establishing its primary role has proved difficult and controversial. Analysing methylation in insects has indicated an apparent functional diversity that seems to argue against a strict functional conservation. To investigate this hypothesis, we here assess the data reported in four different insect species in which DNA methylation has been analysed more thoroughly: the fruit fly Drosophila melanogaster, the cabbage moth Mamestra brassicae, the peach-potato aphid Myzus persicae and the mealybug Planococcus citri.

Whitefly wax as a cue for phoresy in the broad mite, Polyphagotarsonemus latus (Acari: Tarsonemidae)

Broad mite, Polyphagotarsonemus latus (Acari: Tarsonemidae) exhibits a specific phoretic relationship with whiteflies. Under field conditions most broad mites, caught in sticky traps, are attached to whiteflies. Under laboratory conditions, attachment occurs equally well in the dark and light. Mites do not differentiate between the sexes of their phoretic host Bemisia tabaci. However, mite attachment to B. tabaci is greatly diminished by washing the host with various organic solvents, chloroform in particular. The effect of whitefly waxy particles on broad mite behavior was studied using wax from the whitefly Aleyrodes singularis and from the mealybug Planococcus citri. Broad mites were not only attracted specifically to the A. singularis waxy particles-treated leaf areas but were also attached to leaf trichomes in this area. The results of this study suggests the importance of olfactory cues from the whitefly waxy particles in the recognition process of the phoretic host and/or the induction of the attachment behavior to whitefly legs or leaf trichomes.

Facultative heterochromatization in parahaploid male mealybugs: involvement of a heterochromatin-associated protein.

The behavior of chromosomes during development of the mealybug Planococcus citri provides one of the most dramatic examples of facultative heterochromatization. In male embryos, the entire haploid paternal chromosome set becomes heterochromatic at mid-cleavage. Male mealybugs are thus functionally haploid, owing to heterochromatization (parahaploidy). To understand the mechanisms underlying facultative heterochromatization in male mealybugs, we have investigated the possible involvement of an HP-1-like protein in this process. HP-1 is a conserved, nonhistone chromosomal protein with a proposed role in heterochromatinization in other species. It was first identified in Drosophila melanogaster as a protein enriched in the constitutive heterochromatin of polytene chromosome. Using a monoclonal antibody raised against the Drosophila HP-1 in immunoblot and immunocytological experiments, we provide evidence for the presence of an HP-1-like in Planococcus citri males and females. In males, the HP-1-like protein is preferentially associated with the male-specific heterochromatin. In the developing male embryos, its appearance precedes the onset of heterochromatization. In females, the HP-1-like protein displays a scattered but reproducible localization pattern along chromosomes. The results indicate a role for an HP-1-like protein in the facultative heterochromatization process.

Encapsulation Rates of Three Encyrtid Parasitoids by Three Mealybug Species (Homoptera: Pseudococcidae) Found Commonly as Pests in Commercial Greenhouses

Encapsulation rates of the parasitoids Leptomastix dactylopii Howard, Leptomastix epona (Walker), and Anagyrus fusciventris (Girault) (Hymenoptera: Encyrtidae) by the mealybugs Planococcus citri Risso, Pseudococcus viburni (Signoret), and Pseudococcus longispinus (Targioni-Tozzeti) (Homoptera: Pseudococcidae) were studied under controlled laboratory conditions. At 23°C, of the nine host–parasitoid combinations studied, encapsulation was absent only in the combination of L. dactylopii with P. citri. Complete encapsulation (100% of all parasitoid eggs) occurred with L. dactylopii on P. viburni and L. epona on P. citri. In all other combinations studied (six at 23°C and three at 28°C), various degrees of encapsulation were observed. At 23°C, rates of effective encapsulation (the percentage mealybugs in which encapsulation of all parasitoid eggs occurred) were 53.4% (L. dactylopii in P. longispinus), 33.4% (L. epona in P. viburni), 11.2% (L. epona in P. longispinus), 86.4% (A. fusciventris in P. citri), 69.6% (A. fusciventris in P. viburni), and 3.3% (A. fusciventris in P. longispinus). At 28°C, encapsulation of L. dactylopii in P. longispinus was significantly higher than that at 23°C (68.4% vs 53.8%, respectively). However, in A. fusciventris, encapsulation in P. viburni at 28°C was significantly lower than that at 23°C (36.5% vs 69.6%, respectively). Encapsulation rates of A. fusciventris in P. longispinus were not affected by the rearing temperature. Numbers of parasitoid eggs laid per host were similar for all host–parasitoid combinations (1.0–2.2); only L. epona in P. citri was significantly higher (2.2) than the other host–parasitoid combinations (1.0–1.5). Percentage parasitism of hosts was lowest for A. fusciventris in P. citri (16.3% vs 51.7–66.4%, for all other host–parasitoid combinations). Parasitoid larvae that emerged from encapsulated egg capsules were detected in some host–parasitoid combinations at 23 and 28°C. Such larval escape from encapsulation significantly increased mealybug mortality only for A. fusciventris on P. viburni (up 14.8%) as compared to all other combinations studied (0.7 to 2.6%). Differences in levels of encapsulation observed in these host–parasitoid combinations have practical implications for choice of appropriate parasitoids for biological control.

Involvement of histone H4 acetylation in the epigenetic inheritance of different activity states of maternally and paternally derived genomes in the mealybug Planococcus citri.

Modification of histones by acetylation is a well-known mechanism for the establishment and maintenance of specific chromatin structures with different activity states. In Planococcus citri males the paternal genome, early in development, becomes mostly inactive and heterochromatic. As we had not found methylation in the genome of P. citri, we analyzed the acetylation state of histone H4. We report here that, in males, differences in the level of histone H4 acetylation are indeed present in the two genomes of different parental origin; these differences were confirmed by treatment with the histone deacetylase inhibitor Trichostatin A. There is also evidence of acetylation of histone H4 on metaphase chromosomes. Our data therefore suggest a role of histone H4 acetylation in the imprinting of the paternal genome in P. citri males, thus supporting a role of modification of chromatin-related structural proteins in the epigenetic transmission of imprinting.

Oviposition behavior of Coccidoxenoides peregrinus, a parasitoid of Planococcus ficus

AbstractThe encyrtid parasitoid, Coccidoxenoides peregrinus has been used as a biological control agent against the mealybugs Planococcus citri and Planococcus ficus. This study examined the behavior and host selection of C. peregrinus attacking P. ficus. Adult parasitoids were fed a 0.1% solution of acridine orange, a DNA binding dye used to label C. peregrinus eggs. In a choice test, adult parasitoids were offered equal numbers of first through fourth instars of P. ficus and behavior of C. peregrinus was filmed and analyzed. Acridine orange labeled ova of the parasitoids found within mealybug hosts fluoresced green under fluorescence microscopy and presence of fluorescing eggs in hosts was used to determine oviposition events. A time budget prepared for C. peregrinus indicated that this parasitoid spent the majority of its time searching (71.64%) and grooming (15.06%). The average probing duration over all instars which led to oviposition from single visits was 4.93±0.62 s. A total of 35.51% of probes from all attacks led to ovipositions, whereas 33.72% of single visits to hosts resulted in ovipositions. Detection of fluorescing acridine orange labeled eggs showed all instars of P. ficus were acceptable for oviposition by C. peregrinus. There was a significant preference to probe second, third, and fourth instars rather than first instars of P. ficus. Host feeding was not observed for this parasitoid.

Identification of the immature instars of mealybugs (Hemiptera: Pseudococcidae) found on citrus in Australia

AbstractAn identification guide is provided to most of the immature stages of six mealybug species (Hemiptera: Coccoidea: Pseudococcidae) that might be collected from citrus (Rutaceae) in Australia. This information is important for foreign quarantine inspections because mealybugs intercepted on Australian citrus exports are often nymphs. A key and a table, based on microscopic features, allow separation of the first‐, second‐ and third‐instar nymphs and identification to species for second‐ and third‐instar females. Selected diagnostic features of second‐instar females are illustrated. Second‐instar male nymphs also can be identified as they resemble the second‐instar females of their species except for the possession of dorsal ducts that secrete the wax of the male cocoon. Immatures stages are diagnosed for the pink hibiscus mealybug Maconellicoccus hirsutus (Green), the spherical mealybug Nipaecoccus viridis (Newstead), the citrus mealybug Planococcus citri (Risso), the citrophilous mealybug Pseudococcus calceolariae (Maskell), the longtailed mealybug Pseudococcus longispinus (Targioni Tozzetti), and the tuber mealybug Pseudococcus viburni (Signoret) [formerly Pseudococcus affinis (Maskell)].