Total Parasitism Rate Research Articles

How rapidly do invasive birch forest geometrids recruit larval parasitoids? Insights from comparison with a sympatric native geometrid

Two related issues in studies of biological invasions are how quickly the enemy complexes of invasive species become as species-rich and efficient as those of native species and how important enemy release is for the establishment and spread of invaders. We addressed these issues for the geometrid moths Operophtera brumata and Agriopis aurantiaria, who invaded the coastal mountain birch forest of northern Norway by range expansion approximately a century and 15 years ago, respectively. This was done by comparing larval parasitoid species richness and prevalence among the invaders and the native geometrid Epirrita autumnata. We found that E. autumnata and O. brumata both hosted seven parasitoid species groups, whereas A. aurantiaria hosted only one. Several parasitoid groups were shared between two or more of the geometrids. Total larval parasitism rates were similar in all three geometrid species, and comparison with published studies on larval parasitism in Western Europe suggested that O. brumata and A. aurantiaria do not suffer lower parasitism rates in our study region than in their native ranges. Our results indicate that accumulation of larval parasitoids on invasive geometrids in coastal mountain birch forest may reach completion within a few decades to at least a century after the invasion, and that establishment and spread of such invaders is unlikely to be facilitated by release from larval parasitism. Our investigations also uncovered a high degree of spatiotemporal synchrony between the total larval parasitism rates of O. brumata and A. aurantiaria, suggesting that larval parasitism of different geometrid species in the study system is governed by some common external factor.

Dispersal and competitive impacts of a third fire ant decapitating fly (Pseudacteon obtusus) established in North Central Florida

Self-sustaining classical biological control agents offer hope for permanent wide-area control of imported Solenopsis fire ants in the United States because escape from abundant natural enemies left behind in Argentina is a likely reason for unusually high fire ant densities in the United States. The fire ant decapitating fly Pseudacteon obtusus Borgmeier (Diptera: Phoridae) was released as a biocontrol agent of the red imported fire ant (Solenopsis invicta Buren) in Gainesville, FL because it is a common parasitoid of this ant in Argentina and because it has a higher propensity of attacking fire ants along foraging trails than the two Pseudacteon species previously released. Field surveys of a rapidly expanding P. obtusus population (8–12km/yr) proved that this fly was capable of thriving and successfully competing with the much more abundant Pseudacteon curvatus Borgmeier. However, Pseudacteon tricuspis Borgmeier, the first decapitating fly released, was effectively excluded from most sample sites when faced with competition from both P. curvatus and the similar-sized P. obtusus. Despite clear evidence for competitive exclusion, P. tricuspis abundance at sample sites was positively correlated with the abundance of its two competitors—probably because of moderate to strong covariability in the suitability of sample sites for all three congeners. The addition of P. curvatus, the second parasitoid released, increased total parasitism pressure on fire ant populations by about 10-fold. The addition of P. obtusus, the third species, did not measurably improve total guild parasitism rates on imported fire ants in North Central Florida (as assessed by roadside trap counts), but the performance of this species will likely vary with habitat, region, and climate.

Larval parasitoids and larval diseases of Malacosoma neustria L. (Lepidoptera: Lasiocampidae) detected in Erzurum Province, Turkey

The larval parasitoids and larval diseases of Malacosoma neustria (L.) (Lepidoptera: Lasiocampidae) in various host plants were investigated in Erzurum Province, Turkey, during 2004 and 2005. The larval parasitoids were reared in a laboratory, and a total of 29 parasitoid species were established in association with the larvae of M. neustria in the families Tachinidae (Diptera), Braconidae, Ichneumonidae, and Chalcidoidea (Hymenoptera). Of the 6 tachinid parasitoids, Pales pavida (Meigen) was the most prevalent species and accounted for 25% of the tachinid records. Among the tachinids, there were 2 new records for the Turkish fauna: Exorista amoena Mesnil and Palesisa nudioculata Villeneuve. Exorista amoena was reared from M. neustria for the first time. The braconid species Meteorus lionotus Thomson and Cotesia vanessa (Reinhard) were also reared from M. neustria for the first time. Among the 10 chalcidoid species reared, Monodontomerus aereus Walker and Brachymeria secundaria (Rusc.) were the most prevalent species. Five chalcidoid species, Asaphes suspensus (Nees), A. vulgaris Walker (Pteromalidae), Brachymeria secundaria (Ruschka) (Chalcididae), Eupelmus urozonus Dalman (Eupelmidae), and Eurytoma verticillata (F.) (Eurytomidae), were reared from M. neustria for the first time. Of the 10 species of ichneumonids reared, Exeristes roborator F. was the most abundant and accounted for 35% of the total ichneumonid records. The total parasitism rate of all parasitoids was 33.7%. As disease agents of M. neustria, the nuclear polyhedrosis virus and 4 pathogenic bacteria, Brevibacillus agri, Alcaligenes xylosoxydans xylosoxydans (Achromobacter xylosoxidans), Bacillus lentimorbus, and Serratia fonticola, were diagnosed. All of the bacteria from M. neustria were recorded for the first time. The percentage of diseased larvae was low, about 3%.

Effect of intercropping pepper with sugarcane on populations of Liriomyza huidobrensis (Diptera: Agromyzidae) and its parasitoids

The effect of intercropping pepper with sugarcane on populations of the leafminer Liriomyza huidobrensis Becker was investigated over two seasons (2007, 2008) in Yunnan, China. Populations of adults, the female:male sex ratios and the densities of larval mines were significantly higher in pepper monoculture than in intercropping in a 2:2 pattern (2 rows of pepper to 2 rows of sugarcane), which in turn were significantly higher than intercropping in a 1:2 pattern (1 row of pepper to 2 rows of sugarcane). The densities of the parasitoids of the leafminer were significantly higher in intercropping than in the pepper monoculture. The total parasitism rates were 71.6%, 22.5% and 5.9% in 2007, and 69.5%, 20.6% and 5.9% in 2008, in the 1:2, 2:2 and pepper monoculture, respectively. The lower densities of leafminer adults, the lower female:male sex ratio, and smaller numbers of larval mines in the intercropping systems were attributed to the intercropping pattern and the growth of pepper. These results indicate that intercropping is suitable for the control of L. huidobrensis on pepper plants. These results demonstrate the utility of intercropping of pepper with sugarcane in the management of L. huidobrensis.

Extrafloral Nectar in an Apple Ecosystem to Enhance Biological Control

A common goal of conservation biological control is to enhance biodiversity and increase abundance and effectiveness of predators and parasitoids. Although many studies report an increase in abundance of natural enemies, it has been difficult to document increases in rates of biological control. To enhance parasitism of the tufted apple bud moth, Platynota idaeusalis (Walker) (Lepidoptera: Tortricidae), alternate food was provided by interplanting peaches bearing extrafloral nectaries into apple (Malus spp.) orchards. Laboratory studies showed that the presence of nectar increased longevity and parasitism rates by Goniozus floridanus (Bethylidae), the dominant parasitoid of tufted apple bud moth in West Virginia. In orchard studies, we found the total number of hymenopteran parasitoids was higher on peach (Prunus spp.) trees than on adjacent apple trees. Abundance of parasitic Hymenoptera also was significantly higher on the side of traps facing away from rather than toward peach trees, indicating attraction to peach trees. However, total parasitism rates of tufted apple bud moth were not affected by the presence of peach extrafloral nectar in any field studies. Insect injury to fruit at harvest showed that fruit from orchards with interplanted peach trees had less injury from San Jose scale, Quadraspidiotus perniciosus (Comstock) and stink bugs (Pentatomidae) than fruit from an apple monoculture. Although interplanting with peach trees did not produce the hypothesized result of increased biological control, the experiment did have beneficial results for pest management. These results demonstrate the importance of collecting data on variables beyond the targeted species when evaluating habitat manipulation experiments to fully assess the impact on the ecosystem.

Pupal Parasitoids ofYponomeuta malinellus(Lepidoptera: Yponomeutidae) in Northeast Asia

Pupal parasitism of the apple ermine moth, Yponomeuta malinellus Zeller (Lepidoptera: Yponomeutidae), was investigated in northeast Asia with the goal of identifying potential biological controls of the moth, which threatened the apple industry in Washington State, USA during the 1980s. Seven primary and 2 secondary parasitoids were recorded from 27, 472 pupae collected and reared from a total of 20 collections at 16 sites in Korea, northern Honshu and Hokkaido Islands in Japan, and Shanxi Province in China during a 4-year period from 1988 to 1991. The mean total parasitism rate was highest in Korea (38.5%), while the lowest rate of 2.1% was recorded from Shanxi, China. The mean total parasitism rate detected from Hokkaido and Honshu Islands in Japan was 17.2 and 10.1%, respectively. The ichnueumonid wasp Herpestomus brunnicornis Gravenhorst dominated the parasitism in Korea and Japan, while Coccygomimus disparis (Viereck) was responsible for most mortality of the moth pupae in Shanxi, China. Diadegma armillatum (Gravenhorst) caused very low mortality in this study, although it is known as an important parasitoid from Europe and Eurasia. There were significantly different levels of parasitism rates of apple ermine moth pupae among geographical locations sampled, likely due to the habitat type and host plant of the apple ermine moth. Herpestomus brunnicornis collected from Korea and Japan was established in Washington State, USA as a biocontrol agent of the apple ermine moth.

Parasitos em alfaces (Lactuca sativa) de mercados e feiras livres de Lages - Santa Catarina

Objective: To evaluate the contamination of lettuces (Lactuca saliva) with parasites of Public Health peculiar interest sold in Lages, Santa Catarina. Materials and Methods: A nonprobabilitic intentional sampling method was used, in which eight supermarkets and two public markets were selected according to their scope of activity and sales volume for the town. The 122 samples obtained from eight supermarkets and from two open-air markets were analyzed by the techniques of spontaneous sedimentation (Lutz), centrifugation and fluctuation in zinc sulphate (Faust), centrifugation and fluctuation in sucrose solution (Sheather) and modified Ziehl Neelsen coloration. Results: The total parasitism rate was 88.5% (108/122), 77% (94/122) in the supermarkets samples and 11.5% (14/122) in the open-air markets samples. The Lutz technique has detected 46.7% (57/122) infected lettuces; Sheather and Faust technique identified 31.1% (38/122) and 10.6% (13/122) of lettuces infected with eggs and/or oocysts of parasites, respectively. The Eimeria, Giardia e Entamoeba were the most prevalent genders. Conclusions: The analyzed samples presented low hygienic standards, showing that more intense sanitary inspection is needed during all stages of vegetable productive process.

Effects of urbanisation on the parasitoid community of a leafminer

Urbanisation may have detrimental effects on communities of parasitoids, affecting their species richness, abundance, and species dominance. Here we investigated the influence of the degree of urbanisation on parasitoid communities of Liriomyza commelinae (Frost) (Diptera: Agromyzidae), a leafminer of Commelina erecta L. (Commelinaceae), in the city of Córdoba, Argentina. To study changes in species richness, the specific composition of parasitic complexes and their degree of impact on the leafminer, 18 sampling sites from the centre to the outskirts of the city were selected and different variables indicative of urbanisation were quantified in each site. During January and February of 2005 and 2006, all mined leaves found in each plant patch were collected and the following variables were estimated: proportion of mined patches, abundance of the leafminer, total parasitoid species richness, total parasitism rates and parasitism due to the most abundant parasitoid species. The percentage of mined patches and leafminer abundance increased with urbanisation degree. Estimates of parasitoid species richness were not influenced by urbanisation degree but increased with species richness of mined plants. Changes in the specific composition of species along the urbanisation gradient were observed. Although parasitism by one of the species studied was higher in more urbanised sites of the city, the total parasitism rate of L. commelinae was not affected by urbanisation degree, species richness of mined plants or leafminer abundance. It appears that urbanisation benefits the herbivore species here studied but not through altering parasitoid activity. Changes in parasitoid community composition reflex dissimilar tolerance to environmental conditions displayed by different parasitoid species.

Host specialization in habitat specialists and generalists

Generalists and specialists use different cues to find their habitat and essential resources. While generalists have the advantage of exploiting a wider range of resources, they are predicted to be less efficient in using one particular resource compared to specialists. The level of specialization of parasitoids can be either at the habitat or at the host level; strategies used by either type are expected to differ. We examined interactions between three aphid parasitoid species that are a habitat specialist Aphidius rhopalosiphi, a habitat generalist Aphidius ervi, and a host generalist Praon volucre on three cereal aphids, Sitobion avenae, Metopolophium dirhodum and Rhopalosiphum padi. We compared total parasitism rate across behavioral and physiological variation in a non-choice test. Next, we addressed total parasitism in two phases to examine: (1) the response of parasitoids to different hosts through the behavioral sequence from antennation through oviposition, and (2) the physiological suitability of different hosts for oviposition and larval development. Parasitization typically involved the following behavioral steps: (1) antennal contact, (2) abdominal bending, and (3) ovipositor insertion (acceptance). A. rhopalosiphi had the same number of antennal contacts with the three aphids but showed fewer instances of abdominal bending towards R. padi. Pre-contact host preference was found for A. ervi but it did not correspond to the level of acceptance. The number of antennal contacts by P. volucre corresponded to the parasitization level of the aphid species but more mummies were produced on M. dirhodum than on R. padi. These results suggest that parasitoid species that are habitat specialists react similarly to the different host species present in the same habitat, whereas generalist species exhibit clear preferences during host selection. Preferences were, however, not always related to host suitability.

Parasitoid complex and parasitism rates of the horse chestnut leafminer, Cameraria ohridella (Lepidoptera: Gracillariidae) in the Czech Republic, Slovakia and Slovenia

The horse chestnut leaf miner, Cameraria ohridella Deschka & Dimi¸ , is a species of unknown origin that recently invaded most of Europe, causing serious damage to horse chestnut trees, Aesculus hippocastanum. Parasitism was studied over a period of three years in the region of Plze�� in the Czech Republic. Additional collections were made in Slovakia and Slovenia. The parasitoid complex, dominated by polyphagous idiobiont parasitoids of the family Eulophidae, is similar to that found in other studies in Europe. Minotetrastichus frontalis (Nees) was the most abundant parasitoid found, except in Slovakia where Pediobius saulius (Walker) dominated. One parasitoid species, the eulophid Cirrospilus diallus (Walker) was recorded for the first time from C. ohridella. A new method is proposed to calculate stage-specific and total parasitism rates. Parasitism rates of spinning larvae and pupae were higher than of feeding larvae; however, total parasitism was low. We estimated that between 1% and 17% of moths died from parasitism during the larval and pupal stages whereas the rate of mortality caused by other factors varied from 7% to 62%, depending on the locality, year and generation. The proposed method for calculating total parasitism, based on the integration of stage-specific parasitism rates, which takes into account the mortality not directly attributed to parasitism, is discussed and compared with other methods commonly used in studies on C. ohridella.

Trap-nest occupation by solitary wasps and bees (Hymenoptera: Aculeata) in a forest urban remanent

Temporal variation of solitary wasps and bees, nesting frequency, mortality, and parasitism were recorded from a remanent forest in Belo Horizonte, MG, Brazil. Wasps and bees were collected in trap-nests placed in areas with 25, 100, and 400 m2, from February to November 2004. The 137 trap-nests collected contained 11 species of wasps and bees. Wasps occupied most nests (75%). Occupation peaks occurred in March (25%) and September (26%); in June, the lowest occupation (2%) was observed. Except for Trypoxylon (Trypargilum) lactitarse Saussure, no significant correlation was found between number of occupied nests, and temperature and rainfall means. In the nests, 48% of the immature specimens died; 13% of the nests were parasitized. Total death and parasitism rates of wasps and bees differed significantly.

Natural occurrence of Wolbachia-infected and uninfected Trichogramma species in tomato fields in Portugal

Minute egg parasitoids of the genus Trichogramma (Hymenoptera; Trichogrammatidae) are promising candidates for biological control of lepidopteran pests in tomato in Portugal. This certainly applies to native Trichogramma strains that have thelytokous reproduction, i.e., produce only daughters. In Trichogramma wasps, thelytoky is mostly induced by the intracellular bacterium Wolbachia. In this study, we carried out a field survey of native Trichogramma species in four locations in Ribatejo, the main processing tomato region of Portugal, and determined the prevalence of Wolbachia in those species. Five Trichogramma species were found to emerge from lepidopteran eggs collected in the field, namely Trichogramma bourarache, Trichogramma cordubensis, Trichogramma evanescens, Trichogramma pintoi, and Trichogramma turkestanica. T. evanescens and T. pintoi were by far the dominating species representing, respectively, 64.9 and 26.4% of the trichogrammatids collected. Total natural parasitism rates of the collected lepidopteran eggs by Trichogramma wasps ranged from 28.2 to 64.6%. Three Trichogramma species were found to be infected with Wolbachia, namely T. cordubensis, T. evanescens, and T. turkestanica. All the wasp broods belonging to T. cordubensis were infected, whereas low infection rates were found in T. evanescens (0.9% of the broods) and T. turkestanica (4.5% of the broods). The latter represents the first record of a Wolbachia infection in T. turkestanica. Sequencing of the Wolbachia surface protein, wsp, revealed this Wolbachia infection to be related to other Wolbachia infections in Trichogramma wasps. As Wolbachia-infected thelytokous strains exist for T. evanescens, the most abundant Trichogramma species naturally occurring in the tomato fields of the Ribatejo region, this species offers interesting and powerful options for biological control of lepidopteran pests in processing tomato in this region.

Diversity, function and stability in parasitoid communities

The parasitoid assemblages associated with grass‐feeding chalcid wasps in Great Britain were used to examine the relationships between diversity (species richness), community function (total parasitism rate) and stability (variability in parasitism rate over time). Species‐rich communities did not generate higher parasitism rates than species‐poor communities, nor was temporal variation of parasitism rates related to parasitoid community richness. The mechanisms underlying hypotheses linking species richness and community function and stability are discussed in the light of these results. Because all parasitoid species represent a single functional group, a lack of complementarity in the ways they use their resources may explain why diversity is not linked to function or community stability. A second likely reason is that these parasitoid communities are under bottom‐up control, thus exerting little or no influence on total system function and variability. This is likely to be common in parasitoid communities.

Determinants of assemblage size for the parasitoids of Cecidomyiidae (Diptera).

The parasitoids known to attack 191 phytophagous species of gall midges (Cecidomyiidae) were used to examine factors influencing parasitoid assemblage size. The number of parasitoid species a midge species supports was tested against nine variables describing geographical, biological and ecological attributes of hosts. The apparency of midge larvae was found to have the greatest influence on parasitoid assemblage size; highly visible species support more parasitoids than less visible ones. Pupation site and midge voltinism also significantly affect associated parasitoids, at least for highly apparent hosts. Biogeographic region, host-plant architecture and the plant parts infested were found to be of secondary importance. The surface texture of infested plant parts, the number of midge larvae occupying galls and the diversity of plant tissues infested have minimal apparent effects on parasitoid richness. Parasitoid assemblage size and total parasitism rates were also found to be positively correlated for 73 galling and nongalling midge species, and gallers typically suffer higher levels of parasitism than non-gallers. Using these data to test the "enemy hypothesis", which proposes that the galling habit has evolved to escape attack from parasitoids, we conclude that parasitoid pressure cannot account for the presence of galls in the Cecidomyiidae.

Reduction in Variegated Cutworm (Lepidoptera: Noctuidae) Injury to Peppermint by Larval Parasitoids

Variegated cutworm (VC), Peridroma saucia (Hubner), parasitism rates in western Oregon and peppermint leaf consumption rates of parasitized and unparasitized larvae were measured for use in a VC economic threshold model. Instars 4–6 consumed an average of 184 cm2, equivalent to 888 mg (dry weight) of peppermint foliage. Total consumption by larvae parasitized by Meteorus communis (Cresson) was reduced by 93%. Total parasitism rates averaged 35.1% for instars 2–4 and 5.4% for instar 5. Parasitism rates were related to time of season and inversely related to the log of larval instar 2–4 host density. M. communis contributed 11% to total parasitism, while Meloboris sp. and Campoletis sp. composed 84% of larval parasitoids reared from field-collected larvae. Based on final VC head capsule measurements, only 2% of all larval parasitoids reared allowed hosts to reach a size sufficient to cause significant damage that occurs during the final two instars. Accounting for natural biological control by these early instar larval parasitoids will permit a 34% increase in economic thresholds for VC in peppermint.