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. http://www.phytoparasitica.org posting August 4, 2008.     

Encapsulation rates of the parasitoid <Emphasis Type="BoldItalic">Anagyrus</Emphasis> sp. nr. <Emphasis Type="BoldItalic">pseudococci</Emphasis>, by three mealybug species (Hemiptera: Pseudococcidae)

Laboratory studies assessing the degree of suitability of the mealybugs Planococcus ficus (Signoret), Planococcus citri (Risso) and Pseudococcus calceolariae (Maskell), towards the Sicilian ecotype of the encyrtid parasitoid Anagyrus sp. nr. pseudococci were carried out. All three species of mealybugs were shown to encapsulate the eggs of the encyrtid; however, significant differences were revealed among them in rates of encapsulation and/or superparasitism. The level of aggregate encapsulation and effective encapsulation of the parasitoid eggs by P. citri (74.95 ± 0.87 and 60.19 ± 1.70, respectively) was significantly higher than that recorded for P. ficus (aggregate encapsulation = 58.43 ± 0.83 and effective encapsulation = 31.31 ± 1.55) and significantly lower than the values found in Ps. calceolariae (93.99 ± 0.97 and 88.61 ± 2.03, respectively). As such, rates of parasitism were significantly lower for P. ficus compared with both P. citri and Ps. calceolariae. The two latter species of mealybugs showed similar rates of parasitism by A. sp. nr. pseudococci. Moreover, a significantly higher rate of superparasitism was found for Ps. calceolariae compared with both P. citri and P. ficus, whereas no significant differences were found between the two species of Planococcus for this parameter.     

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.     

Response by encapsulation of four mealybug species (homoptera: pseudococcidae) to parasitization byAnagyrus pseudococci

The frequency of encapsulation of eggs ofAnagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae) by four mealybug species:Planococcus citri (Risso),PL vovae (Nasonov),Pl. ficus (Signoret) andPseudococcus cryptus Hempel (=citriculus Green), was studied under controlled laboratory conditions. The aggregate percentage of encapsulated eggs (AE) and the percentage of efficient encapsulation (EE) (= percent parasitized mealybugs wherein encapsulation prevented the development of all parasitoid larvae) byPl. citri andPl. vovae did not differ significantly (39.0%vs 38.2% AE and 15.4%vs 17.6% EE, respectively), but was significantly higher than inPs. cryptus (16.2% AE and 5.4% EE). Encapsulation byPl. vovae was significantly higher than byPl. ficus (38.2%vs 20.1% AE and 17.6% vs 7.7% EE, respectively). Neither the host plant nor the rearing temperature significantly affected the incidence of parasitoid encapsulation. It is suggested thatA. pseudococci displays a relatively low physiological adaptation toPl. citri; thus, in a citrus grove, for example,ca 40% of the parasitoid eggs might be lost due to encapsulation. The question of a possible association between encapsulation and host—parasitoid relationships among the mealybugs studied andA. pseudococci, is discussed.     

Effect of Buprofezin onIcerya Purchasi andPlanococcus Citri

The effectiveness of buprofezin (aqueous suspensions from 25% wettable powder) on cumulative nymph mortality and reproduction of two homopterous pests,Icerya purchasi Maskell (Margarodidae) andPlanococcus citri (Risso) (Pseudococcidae), was investigated under laboratory conditions. Buprofezin was very effective against crawlers of both species. Dipping in concentrations of 0.002%, 0.01% and 0.05% (a. i.) resulted in 91–99% nymph mortality ofP. citri, whereas 100% mortality was recorded whenI. purchasi was treated at 0.05% (a. i.); the 3rd-instar nymphs ofI. purchasi were less susceptible to the chemical. Death of the larval stages occurred mainly during the molting process to the 2nd-instar nymphs. At 0.05%, buprofezin sprayed on adults slightly reduced fecundity and decreased egg hatch to 31% forI. purchasi and, depending on the exposure period of the females, to 49-7% forP. citri. Buprofezin at 0.05% exhibited strong ovicidal activity onP. citri, resulting in inhibition of over 80% egg hatch.     

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. http://www.phytoparasitica.org posting Oct. 3, 2004.     

Laboratory assay of the effectiveness of the entomopathogenic fungus Isaria farinosa (Holmsk.) Fries (Sordariomycetes: Hypocreales) against the vine mealybug Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), even under the use of fungicides

The vine mealybug, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), is one of the main pests in vineyards. At present biological control of the pest is based on the release of hymenopterous parasitoids and coccinellid predators. The effectiveness of an entomopathogenic fungus, Isaria farinosa, as an alternative biological control agent on vine mealybug P. ficus was investigated by using different inoculum densities and different relative humidity levels. The fungus caused more than 80% mortality at 95% relative humidity and at 1 × 10⁸ conidia ml^?1 inoculum density. The mortality effects of the fungus decreased in lower humidity levels and lower spore densities. The inhibitory effects of common fungicides, used in vineyards, on I. farinosa were also investigated. Sulphur, copper oxychloride, fosetyl-Al and chlorothalonil did not decrease the effectiveness of I. farinosa as a pathogen of vine mealybug. With the application of tebuconazole, penconazole and mancozeb, the most inhibitory fungicides on the entomopathogen, the mortality rates of mealybugs, inoculated with I. farinosa, decreased from 86% to 42%, 34% and 45%, respectively, in the adult females; from 94% to 51%, 45% and 45%, respectively, in the first nymphal stages; and from 86% to 56%, 49% and 63%, respectively, in ovisacs.     

Parasitoid complex of <Emphasis Type="Italic">Planococcus ficus</Emphasis> (Signoret) (Hemiptera: Pseudococcidae) in Turkey

In this study a survey for determining the parasitoid complex of Planococcus ficus (Signoret) (Hemiptera: Coccomorpha: Pseudococcidae) was conducted in Adana and Mersin Provinces, Turkey. Five primary, two primary/secondary, two secondary parasitoid species associated with P. ficus, were found. Clausenia josefi Rosen and Chartocerus kurdjumovi (Nikol’skaya) are new records for Turkish fauna.     

大洋臀纹粉蚧和南洋臀纹粉蚧TaqMan实时荧光PCR检测方法

臀纹粉蚧属有多个种类是重要的农业害虫,大洋臀纹粉蚧(Planococcus minor(Maskell))和南洋臀纹粉蚧(Planococcus lilacius Cockerell)是我国有重要检疫意义的有害生物.这两种臀纹粉蚧经常从进口泰国和东南亚水果口岸检疫中截获,但形态学方法很难进行准确鉴定.本研究首次利用mtDNA COI基因设计了两条特异性探针,应用TaqMan实时荧光PCR方法对大洋臀纹粉蚧和南洋臀纹粉蚧进行了快速准确鉴定.     

龟纹瓢虫对柑橘木虱的捕食功能反应及猎物偏好性

为评估龟纹瓢虫Propylea japonica对柑橘木虱Diaphorina citri的生物防治潜能，在实验室条件下测定龟纹瓢虫1~4龄幼虫和成虫对柑橘木虱5龄若虫的捕食功能反应、搜寻效应、自身密度干扰反应以及捕食偏好性。结果表明，龟纹瓢虫1~4龄幼虫和成虫对柑橘木虱5龄若虫的捕食功能反应均符合Holling II型功能反应类型，其各虫态龟纹瓢虫的瞬时攻击率分别为0.313、0.610、0.234、0.585和0.675，处理时间分别为0.088、0.077、0.013、0.008和0.016 d，龟纹瓢虫4龄幼虫对柑橘木虱5龄若虫的捕食能力最大，为73.125，龟纹瓢虫成虫、3龄幼虫、2龄幼虫、1龄幼虫次之，捕食能力分别为42.188、18.000、7.922和3.557。各虫态龟纹瓢虫对柑橘木虱5龄若虫的搜寻效应随柑橘木虱5龄若虫密度升高而下降；在柑橘木虱5龄若虫密度一定的条件下，各虫态龟纹瓢虫对柑橘木虱5龄若虫的捕食率随自身密度升高而下降，其自身密度干扰方程为E=0.421P^-0.52；当柑橘木虱5龄若虫和豆蚜Aphis craccivora 4龄若虫2种猎物共存时，龟纹瓢虫成虫对其食物选择性指数均小于1，表明龟纹瓢虫成虫对这2种猎物无捕食偏好性。表明龟纹瓢虫对柑橘木虱5龄若虫有较强的防控潜能。     

Susceptibility of the obscure mealybug,Pseudococcus viburni (Signoret) (Pseudococcidae), to South African isolates of entomopathogenic nematodes

Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), the obscure mealybug, is a serious pest of apples and pears in South Africa. The potential use of entomopathogenic nematodes (EPNs) against P. viburni was assessed in laboratory bioassays. The results showed Heterorhabditis zealandica (J34) to be most effective, causing 80% mortality of P. viburni 48-h post inoculation at 25 ºC. After 48 h, the LD₅₀ and LD₉₀ values were 54 and 336 nematodes, respectively. H. zealandica (J34) and Steinernema yirgalemense successfully reproduced in P. viburni, with H. zealandica (J34) attaining greater penetration ability than did the S. yirgalemense. Mealybug size affected infectivity, with the crawlers being less susceptible (22%) than were the adults and intermediates, with mortalities of 78% and 76%, respectively. H. zealandica (J34) were able to enter the apple core of infested apples, where they infected the P. viburni. This work represents the first report on using EPNs to control P. viburni.     

Differentiation of Phoma foveata from P. exigua using a RAPD Generated PCR-RFLP Marker

Phoma foveata and P. exigua variety exigua both infect potatoes and are morphologically very similar. P. foveata produces a pigment which allows differentiation from P. exigua in culture. Discrimination of the two species based on the production of a secondary metabolite, which is dependent on the growth conditions, is not reliable. Therefore, there is a need to develop nucleic acid based identification markers. A 482bp random amplified polymorphic DNA (RAPD) fragment from P. foveata was isolated and sequenced. Polymerase chain reaction (PCR) primers, developed from the sequence of the RAPD product, amplified a 474bp fragment for P. foveata and P. exigua varieties exigua, diversispora, inoxydibilis and sambuci-nigrae. The similarity of the PCR fragments was demonstrated by sequence analysis and by using the restriction enzymes DdeI and DpnII. P. foveata was distinguished from the four varieties of P. exigua on the basis of the RFLP patterns of the PCR fragment. Ten isolates of P. foveata and nine of P. exigua var. exigua from different geographic locations were tested and all isolates but one showed the restriction digest pattern of the PCR fragment (PCR-RFLP) specific to each species. One isolate of P. foveata demonstrated a PCR-RFLP pattern similar to P. exigua var. exigua leading to the conclusion that the isolate had been previously misidentified as a strain of P. foveata lacking the ability to produce pigment.     

Development of Strain-specific Primers for a Strain of Gliocladium catenulatum Used in Biological Control

The randomly amplified polymorphic DNA (RAPD) technique was used to develop strain-specific primers for Gliocladium catenulatum strain J1446, which is promising in biological control. One of the primer pairs developed proved to be strain-specific; strain J1446 was differentiated from 16 G. catenulatum strains and six other strains of two Gliocladium species, as well as from Trichoderma virens, and isolates of Nectria spp. and Fusarium spp. Specific primers were also tested with DNA isolated from cucumber leaves, treated or untreated with a solution made from Gliocladium powder. The expected amplification product was produced only from treated leaves. DNA isolated from Gliocladium-treated potato tubers and fungi grown in peat was also used in amplification reactions. Strain-specific primers detected strain J1446 when the amount of DNA was 5pg or more. Some variation between the Gliocladium strains was found by the random amplified microsatellites method (RAMS) and the universally primed polymerase chain reaction method (UP-PCR), but no clear fragments specific to strain J1446 were produced. Cross-blot hybridisation of UP-PCR products differentiated strain J1446 from T. virens, but not from the Gliocladium isolates. The 28S rDNA sequences and -tubulin sequences were identical or very similar in all Gliocladium strains. Thus, it is possible that the Gliocladium strains of the present study are conspecific, which means that a revision in the taxonomy of Gliocladium species may be necessary.     

Pathogenicity and RAPD analysis of Phytophthora nicotianae pathogenic to pepper in Tunisia

Nine isolates of Phtophthora nicotianae were isolated from infected pepper plants. Their pathogenicity was studied in Capsicum annuum in comparison with P. nicotianae isolates from tomato and tobacco. The pathogenicity test showed that pepper isolates of P. nicotianae are adapted to their host. Banding patterns obtained by RAPD analysis with six oligonucleotide primers revealed polymorphism that grouped the isolates independently of the plant host. The polygenic dendrogram showed that pepper isolates were more similar to tomato isolates than to tobacco isolates. The RAPD bands of 1300 and 1500 bp, detected with primers OPD-01 and OPD-10, respectively, appeared specific to the most pathogenic pepper isolates. The OPK-08-1950 seems specific to the isolates of P. nicotianae from tomato. These results suggest that host specified might occur in P. nicotianae and that may be due to interspecific hybridization events resulting in novel pathogenic behavior.     

Differentiation of Cotton-defoliating and Nondefoliating Pathotypes of Verticillium dahliae by RAPD and Specific PCR Analyses

Severe Verticillium wilt of cotton in southern Spain is associated with the spread of a highly virulent, defoliating (D) pathotype of Verticillium dahliae. Eleven of the D and 15 of a mildly virulent, nondefoliating (ND) pathotype were analyzed by random amplified polymorphic DNA (RAPD) using the polymerase chain reaction (PCR). Six of 21 primers tested generated pathotype-associated RAPD bands. Another 21 V. dahliae isolates were compared in blind trials both by RAPD-PCR using the six selected primers and pathogenicity tests on cotton cultivars. There was a 100% correlation between pathotype characterization by each method. Unweighted paired group method with arithmetic averages cluster analysis was used to divide the 47 V. dahliae isolates into two clusters that correlated with the D or ND pathotypes. There was more diversity among ND isolates than among D isolates, these latter isolates being almost identical. ND- and D-associated RAPD bands of 2.0 and 1.0kb, respectively, were cloned, sequenced, and used to design specific primers for the D and ND pathotypes. These pathotype-associated RAPD bands were present only in the genome of the pathotype from which they were amplified, as shown by Southern hybridization. The specific primers amplified only one DNA band of the expected size, and in the correct pathotype, when used for PCR with high annealing temperature. These specific primers successfully characterized V. dahliae cotton isolates from China and California as to D or ND pathotypes, thus demonstrating the validity and wide applicability of the results.     

基于两性生命表评价取食柑橘木虱对六斑月瓢虫和龟纹瓢虫生长发育及种群的影响

为有效防控重要害虫柑橘木虱Diaphorina citri,在实验室条件下测定取食柑橘木虱后六斑月瓢虫Cheilomenes sexmaculata和龟纹瓢虫Propylea japonica各虫态的发育历期,利用构建的年龄-阶段两性生命表对取食柑橘木虱后六斑月瓢虫、龟纹瓢虫生长发育及其种群参数进行研究。结果显示,取食柑橘木虱后六斑月瓢虫羽化前的发育历期为14.80 d,显著长于取食柑橘木虱后龟纹瓢虫的14.41 d;取食柑橘木虱后六斑月瓢虫和龟纹瓢虫产卵期分别为15.88 d和10.23 d,前者显著长于后者;取食柑橘木虱后六斑月瓢虫净增殖率、内禀增长率和周限增长率分别为25.48、0.10 d-1和1.10 d-1,取食柑橘木虱后龟纹瓢虫净增殖率、内禀增长率和周限增长率分别为14.13、0.06 d-1和1.06 d-1,均低于取食柑橘木虱后六斑月瓢虫;取食柑橘木虱后六斑月瓢虫和龟纹瓢虫的平均世代周期分别为33.87 d和44.95 d,前者显著短于后者。表明取食柑橘木虱后六斑月瓢虫和龟纹瓢虫均能完成整个世代,且六斑月瓢虫种群增长优于龟纹瓢虫,可大规模繁殖六斑月瓢虫,可用于柑橘木虱...     

Intraspecific diversity within avocado field isolates of <Emphasis Type="Italic">Rosellinia necatrix</Emphasis> from south-east Spain

Fifty-five isolates of Rosellinia necatrix, the cause of common avocado white root rot disease, were collected from south-east Spain and characterised according to their virulence behaviour and their molecular patterns to assess broader levels of genetic diversity. Virulence properties were revealed by in vitro inoculation on avocado plants. Differences in reaction types showed variability among these isolates. No sequence differences were observed when the internal transcribed spacer 1 (ITS1) and ITS2 regions and DNA fragments of the β-tubulin, adenosine triphosphatase and translation elongation factor 1 genes were explored in representive isolates from five virulence groups. Random amplified polymorphic DNA (RAPD) amplifications were also performed for each isolate using 19 random primers. Four of these primers revealed polymorphism among isolates and repetitive and discriminative bands were used to build an unweighted pair group with arithmetic mean tree. However, RAPD clustering showed low stability, and no correlation between RAPD and virulence groups was observed, possibly indicating high levels of sexual recombination.     

Characterization and differentiation of <Emphasis Type="Italic">Erwinia carotovora</Emphasis> strains from mulberry trees

We recently reported that two diverse types (types 1 and 2) were identified among strains of Erwinia carotovora from mulberry trees. Type 1 strains were similar to E. carotovora subsp. carotovora (Ecc), whereas type 2 strains were distinct from Ecc and other E. carotovora strains. In this study, seven more mulberry strains of type 2 and reference strains were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and randomly amplified of polymorphic DNA (RAPD). On the basis of SDS-PAGE profiles of whole-cell proteins, type 2 strains had high similarity with one another. In addition, they had an unique peptide band with a molecular mass of approximately 28kDa. RAPD analysis showed that they were also effectively differentiated by a strong, specific RAPD fragment for type 2 strains. Based on these two approaches, we have confirmed that the present type 2 strains from mulberry can be discriminated clearly from other soft rot Erwinia species.     

Relation between pathogenicity and genetic variation within <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis>

The relation between diversity of pathogenicity on clubroot-resistant (CR) cultivars of Chinese cabbage (Brassica rapa subsp. pekinensis) bred in Japan and DNA polymorphisms in 17 populations of Plasmodiophora brassicae from cruciferous plants was examined by inoculation tests and random amplified polymorphic DNA (RAPD) analysis using 18 arbitrary primers. Four pathotypes (A–D) were identified after inoculation of six CR cultivars of Chinese cabbage in the 17 populations from cruciferous crops. A relatively high level of genetic diversity was also detected among these populations in the RAPD analysis. Although the four pathotypes could not be clearly differentiated using the RAPD data, most populations of three pathotypes had a consistent location on the dendrogram. All pathotype B (virulent on five cultivars except Utage 70) and D (avirulent on all cultivars) populations, which were common in incompatible interactions with cv. Utage 70, were located in a single subcluster. All five pathotype C populations (virulent only on cv. Utage 70) except for one population grouped in another single subcluster. Because four pathotype A populations (virulent on all six cultivars, races 4 and 9) fell in different subclusters, the populations may be genetically polyphyletic. Populations from cruciferous weed Cardamine flexuosa differed remarkably from those from cruciferous crops in pathogenicity on common cultivars of Chinese cabbage and turnip and C. flexuosa, but they grouped in a single cluster with all race 9 populations from crops. Race 9 populations from crops may thus be closely related to populations from the weed rather than to races 1 and 4 from crops.