Intraguild predation and interference by the mealybug predator Cryptolaemus montrouzieri on the parasitoid Leptomastix dactylopii

The compatibility of the encyrtid parasitoid Leptomastix dactylopii with the coccinellid beetle Cryptolaemus montrouzieri against the citrus mealybug, Planococcus citri, is determined by the extent of intraguild predation and interference by the predator. We tested the preference of the adults and fourth-instar larvae of C. montrouzieri for healthy mealybugs and parasitized mealybugs harboring 1-, 4-, 7- and 14-day-old parasitoid larvae. The experiments were conducted in no-choice (only unparasitized mealybugs or parasitized mealybugs of one parasitoid age were offered at one time) and choice (unparasitized and parasitized mealybugs of a specific age were offered simultaneously) tests. Both the adults and larvae of C. montrouzieri fed on unparasitized and parasitized mealybugs but strongly discriminated against the hardened mummies (14 days old). We also investigated the influence of the presence of C. montrouzieri to the foraging effectiveness of L. dactylopii. The level of parasitism by L. dactylopii was reduced from about 13 to 6% when the number of the C. montrouzieri was increased from zero to four. We recommended that the releases of C. montrouzieri should be conducted 14 days after the releases of L. dactylopii to reduce intraguild predation on the parasitized mealybugs and to avoid interference with the foraging parasitoids.     

Analysis of population dynamics of diamondback moth, (Plutella xylostella (Lepidoptera: Plutellidae)) at two sites in central Ethiopia, with particular reference to parasitism

Change in diamondback moth (DBM) (Plutella xylostella L.) numbers and level of parasitism on head cabbage (Brassica oleracea var. capitata) was monitored for two seasons in two different agroecological zones representing the highland and lowland brassica-producing areas of central Ethiopia in 2001 and 2002. Two to three generations in the highland site and three to five generations in the lowland site per cabbage growing season were observed. Three parasitoids were recorded at both locations. These were Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae), Diadegma sp. (Hymenoptera: Ichneumonidae), and Apanteles sp. (Hymenoptera: Braconidae). Diadegma sp. was the dominant parasitoid at the highland site and O. sokolowskii was dominant at the lowland site. Rainfall and maximum temperature significantly influenced DBM numbers and parasitoid activity at the highland experimental site.     

Structure of a herbivore–parasitoid community: Are parasitoids shared by different herbivore guilds?

Plant–herbivore–parasitoid interactions are a common occurrence in terrestrial food webs. Few parasitoids are thought to be shared by host insects of different feeding guilds because different parasitism strategies are required to use hosts of different feeding types. However, this assumption has rarely been tested using data from nature. To clarify whether parasitoids are shared among host guilds, I examined the structure of parasitoid communities on herbivore guilds associated with two Rhododendron species (Ericaceae) in a temperate secondary forest in central Japan. Leaf- and flower-feeding insects were collected from Rhododendron reticulatum and Rhododendron macrosepalum shrubs and reared in the laboratory for 3 years from April 1999 to March 2002. In total, 79 species of holometabolous herbivores (Lepidoptera, Diptera, Coleoptera, and Hymenoptera) were recorded, with 62 species on R. reticulatum and 51 species on R. macrosepalum. A total of 81 parasitoid species (Hymenoptera and Diptera) was recorded from the sampled herbivores, with 48 species from those on R. reticulatum and 50 species from those on R. macrosepalum. In total, 36 herbivore species were parasitised by 1–18 parasitoid species per host species, although the number of parasitoid species was strongly affected by sample size. Parasitoids that had two or more host species frequently attacked herbivore species from different families or on different host plants, whereas they did not attack species from different herbivore guilds; no parasitoids were shared between external feeders and rollers. Therefore, my results support the hypothesis that few parasitoids are shared among herbivores of different feeding guilds.     

Adult parasitoids of the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), feed on artificial diet on pine boles, pine canopy foliage and understory hardwood foliage

This study examined adult parasitoids of Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae) utilizing an artificial parasitoid food on locations with and without hosts. Eliminade™ was applied to bark on boles of infested pines, to pine canopy foliage and to understory hardwood foliage. Adult parasitoids were collected, identified and dissected to determine the presence of Eliminade™ within their guts. Individuals from eight parasitoid species were collected on pine boles within D. frontalis infestations in the Talladega National Forest (Alabama) in the summer of 1999 and 2000. Mean percentage of parasitoids feeding on Eliminade™ was 62±10% during both summers. Percentage of parasitoids feeding was the same 24 h after Eliminade™ application, regardless of food location or parasitoid species. Seven days later, level of parasitoid feeding on Eliminade™ was insignificant in the pine canopy and hardwood understory. In contrast, percent of parasitoid feeding on Eliminade™ applied to pine boles remained the same between 1 and 7 days of the application. Therefore, not only will adult parasitoids visit and feed on artificial food on pine boles with hosts, but also non-host locations such as pine canopy and understory hardwood foliage. These results have implications for potential sources of adult nutrition for parasitoids of D. frontalis.     

Dendrosoter protuberans (Hymenoptera: Braconidae), An Important Elm Bark Beetle Parasitoid

The most favourable period for Dendrosoter protuberans development occurred when wasps were introduced 16 days after the beginning of Scolytus multistriatus development (the greatest number of emerged wasps per a single parasitoid female with a very positive sexual index and high percentage of parasitised elm bark beetle larvae). No significant differences were observed in parasitoid efficiency between the 11^th and the 21^st day. The most unfavourable period for elm bark beetle parasitisation was six days after the beginning of S. multistriatus development (a low reproduction of D. protuberans, a negative sexual index and a low number of destroyed S. multistriatus larvae). The reproduction of both the elm bark beetle and D. protuberans was greater in the first, than in the second generation. The developmental period of D. protuberans in the first generation was approximately two days longer than in the second generation. Furthermore, the development of females was 1-2 days longer than the development of males. D. protuberans developed most successfully on S. multistriatus (the most abundant parasitoid reproduction with the longest developmental period and a very positive sexual index that resulted in a high percentage of parasitised larvae) and then on S. ensifer, S. pygmaeus and Pteleobius kraatzi. On the other hand, S. scolytus larvae were the poorest host of all elm species - the reproduction of D. protuberans in this species was the scarcest with the shortest period of development and a negative sexual index, hence larval parasitisation was the lowest.     

Prey selection by Dicyphus hesperus of infected or parasitized greenhouse whitefly

The development of effective biological control programs in which predators are integrated with other natural enemies such as parasitoids and entomopathogens requires an understanding of their interactions. In this study we examined the extent to which the omnivorous mirid bug Dicyphus hesperus, an effective biological control agent of greenhouse whiteflies, accepts prey that are either parasitized by the specialist whitefly parasitoid, Encarsia formosa or infected by the generalist fungal entomopathogen, Beauveria bassiana. In non-choice laboratory experiments, we measured how parasitism and infection of greenhouse whitefly, Trialeurodes vaporariorum, as related to parasitoid age and course of fungal infection, might alter the probability of feeding by second instar or adult female predators. Predation by D. hesperus was similar for parasitized and unparasitized whiteflies, regardless of parasitoid age. However, predators generally avoided feeding on infected whiteflies, particularly when infection was manifested through the presence of oosporein or hyphae on the surface of prey.     

Suppression of Anthonomus eugenii (Coleoptera: Curculionidae) pepper fruit infestation with releases of Catolaccus hunteri (Hymenoptera: Pteromalidae)

The pepper weevil, Anthonomus eugenii Cano, is an important pest of Capsicum spp. pepper in Florida, Puerto Rico, and Central America. Catolaccus hunteri Crawford is the most abundant parasitoid attacking pepper weevil larvae in Florida. Weekly releases of C. hunteri at a rate of 1600 adults per 0.2-ha plot in organically-grown bell pepper, C. annuum L., beginning at first bloom resulted in fewer weevil infested fruit compared to 0.2-ha plots where no parasitoids were released. Weekly releases of C. hunteri adults on nightshade, Solanum americanum Mill, during the fall/winter off-season followed by weekly releases of the same parasitoid in adjacent bell pepper during the spring in-season resulted in fewer infested pepper fruit compared to off-season nightshade and in-season pepper where no parasitoids were released. The results of these experiments demonstrate the potential of augmentative releases of C. hunteri for suppressing infestations of pepper fruit by pepper weevil larvae.     

Increasing vineyard floral resources may not enhance localised biological control of the leafroller Epiphyas postvittana (Lepidoptera: Tortricidae) by Dolichogenidea spp. (Hymenoptera: Braconidae) parasitoids

In agroecosystems, the efficacy of biological control exerted by many parasitoids is predicted to be enhanced where the availability of floral resources is increased. Such resources may attract parasitoids and enhance their longevity and fecundity. In Hawke's Bay, New Zealand, this prediction was tested by adding varying quantities of potted flowering alyssum (Lobularia maritima) (Brassicaceae) to plots containing apple plants (Malus domestica) inoculated with larvae of the leafroller, Epiphyas postvittana (Lepidoptera: Tortricidae). In two replicated trials, over 90% of the parasitoids from recovered larvae were Dolichogenidea spp. (Hymenoptera: Braconidae). In both trials increasing the percentage of alyssum did not result in a corresponding increase in the leafroller parasitism rate. Instead, the primary influence on parasitism rates was due to Dolichogenidea spp. dispersing from a nearby orchard. A significant negative correlation was observed in leafroller parasitism as a function of distance from this orchard. A vineyard to the north of the study site also influenced parasitism rates. Our results suggest the orchard was a regional source population for this parasitoid, and the abundance of local resources such as alyssum did not influence parasitoid foraging. At the level of our entire study block, our effective area of resource provision was 0.1%. A level of resource provision higher than that used in this study may be necessary to test for a positive influence on local parasitism rates. From our results, it appears that for parasitoids with relatively high dispersal rates, the availability of local resources may not be as important as a regional source population.     

Changes in Biological Characteristics of Trichogramma pretiosum (Hym.: Trichogrammatidae) Reared on Eggs of Anagasta kuehniella (Lep.: Pyralidae) for 23 Generations

Possible changes in biological characteristics of Trichogramma pretiosum (Riley) (Hymenoptera: Trichogrammatidae) were monitored during 23 generations reared on eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae), to determine quality control parameters in rearing procedures of this parasitoid. Parasitism rates (percent of eggs parasitized) of T. pretiosum varied from 10 to 76%, with lower values for the first four generations. From the 17th generation, the variability in the parasitism rate was lower. Viability (percent adult emergence rate) of T. pretiosum in eggs of A. kuehniella varied from 22 to 100%, again with lower values in earlier generations. Adult longevity of T. pretiosum varied from 5.3 to 15.9 days, and showed a reduced longevity with increasing number of generations. Sex ratio of the offspring of this parasitoid was not affected by the timing of parasitism on eggs of A. kuehniella.     

Parasitism activity of Peristenus spp. (Hymenoptera: Braconidae) on Lygus lineolaris (Hemiptera: Miridae) nymphs prior to the establishment of P. digoneutis in southwestern Quebec

Parasitism of tarnished plant bug nymphs, Lygus lineolaris (Palisot de Beauvois) was investigated on different weeds and on lettuce, celery and alfalfa-clover, in a muck soil area of southwestern Quebec. The phenology of parasitism, defined as the time during which female parasitoids are active in the field, was evaluated. Two nymphal parasitoid species were found: Peristenus pallipes (Curtis) and P. pseudopallipes (Loan). Lygus lineolaris was most abundant on stinging-nettle with levels of parasitism of 17% (P. pallipes) and 27% (P. pseudopallipes) and on alfalfa-clover with levels of parasitism of 25% (P. pallipes) and 8% (P. pseudopallipes). On lettuce, parasitism by P. pseudopallipes was below 4% while no parasitism was observed on celery. The dissection and rearing methods were used to estimate parasitism, and dissection usually yielded parasitism levels higher than rearing. Degree-days requirements of both host and parasitoids were used to calculate the period of activity of parasitoid adults. The estimates of adult activity were 47 days from late May to early July for P. pallipes, and 42 days from mid-July to late August for P. pseudopallipes.     

Multiparasitism by the pupal parasitoids, Xanthopimpla stemmator (Hymenoptera: Ichneumonidae) and Pediobius furvus (Hymenoptera: Eulophidae) on two African cereal stemborers, Chilo partellus (Lepidoptera: Crambidae) and Busseola fusca (Lepidoptera: Noctuidae)

The outcome of multiparasitism by two pupal parasitoids, the exotic solitary ichneumonid Xanthopimpla stemmator and the indigenous gregarious eulophid Pediobius furvus, was studied using the invasive crambid stem borer Chilo partellus and the indigenous noctuid Busseola fusca as hosts. Two parasitism sequences were observed, where X. stemmator oviposited before P. furvus, and vice versa. In addition, the effect of time between first and second parasitism on parasitoid emergence, development, sex ratio, and number of offspring was assessed. For most treatments, time interval between parasitism had no significant effect on the percentage if pupae producing either P. furvus or X. stemmator. In general, X. stemmator outcompeted P. furvus irrespective of the order of oviposition, time interval between ovipositions and host species. Further studies, especially on host finding capacity of the two parasitoid species are required to determine the competitiveness of the two species under field conditions.     

Effect of host egg viability on reproduction and development of Trichogramma cacoeciae and T. principium (Hymenoptera: Trichogrammatidae)

A combination of a sterile insect technique, resulting in infertile eggs, and of an egg parasitoid, should provide better control of codling moth than either alone. Non-choice laboratory experiments were conducted with infertile and fertile codling moth eggs to evaluate the potential parasitism and reproduction of Trichogramma cacoeciae Marchal and T. principium Sug. et Sor. The tendency of T. cacoeciae females to attack infertile eggs was similar to that for fertile eggs, whereas T. principium showed a greater preference for infertile eggs than fertile eggs. The fertility status of the host did not affect the number of eggs that were parasitized but fewer F₁ progeny emerged from infertile eggs when parasitized than from fertile eggs. When T. cacoeciae and T. principium parasitized infertile host eggs their mean developmental time was prolonged but the viability and quality of parasitoid progeny was not influenced by the fertility status of the host eggs. The study demonstrates the compatibility of use of T. cacoeciae and T. principium in an integrated program employing the sterile insect technique for codling moth management.     

An Immunoassay Method for Detecting Microctonus aethiopoides (Hymenoptera: Braconidae: Euphorinae) Parasitism in the Alfalfa Weevil, Hypera postica (Coleoptera: Curculionidae)

A simple immunological assay was developed as an alternative to the dissection/visualization method for detecting the presence of the parasitoid, Microctonus aethiopoides Loan, in the alfalfa weevil, Hypera postica (Gyllenhal). The dot-blot assay was validated using laboratory-reared and field-collected adult weevils of known parasitization status. The dot-blot assay was also used to estimate the developmental stage of the parasitoid within parasitized adult hosts. The assay results can be used to forecast parasitoid emergence dates and estimate the parasitism rate of M. aethiopoides in alfalfa weevil populations.     

Reproductive compatibility of several East and West African Cotesia sesamiae (Hymenoptera: Braconidae) populations and their crosses and backcrosses using Sesamia calamistis (Lepidoptera: Noctuidae) as the host

The relative importance of the braconid Cotesia sesamiae, a gregarious larval parasitoid of lepidopteran stemborers, varies greatly with region in Africa; while the most common parasitoid of noctuid stemborers in eastern Africa, it is rare in western Africa. Thus, several strains of C. sesamiae from Kenya are envisaged for introduction into western Africa. The present study investigates the reproductive compatibility between four populations of C. sesamiae from West Africa and Kenya with the noctuid Sesamia calamistis as the host using reciprocal crosses as well as backcrosses of hybrid females with males of the parental populations. Searching time of the male for the female and mating period varied significantly with couple and ranged between 0.78-1.9 min and 3.4-12.8 s, respectively. Crosses that involved females from inland Kenya (KI) did not yield any female offspring. However, backcrosses of hybrid female bearing a KI male genome with a KI male yielded both female and male offspring. Thus, there was a partial reproductive incompatibility between KI and West African populations which suggested that the latter were infected with Wolbachia sp. However, this should not affect the efficacy of a population introduced from East into West Africa, as there is a high degree of sib-mating in this gregarious parasitoid species. It was concluded that the regional differences in the relative importance of C. sesamiae was due to differences in the insect and plant host range of the different populations.     

不同启动子调控外源基因在斑玉蕈中的表达分析

启动子是控制基因转录的重要顺式元件,也是遗传转化实验中驱动外源基因表达的重要工具。在同一真菌中,不同启动子驱动外源基因表达水平可能存在明显差异。因此,选择合适的启动子是提高外源基因表达水平的关键。本研究分别应用花椰菜病毒35S RNA（cauliflower mosaic virus 35S RNA,CaMV35S）和斑玉蕈甘油醛-3-磷酸脱氢酶（Hypsizygus marmoreus glyceraldehyde-3-phosphate dehydrogenase,HmGPD）基因的启动子构建了两个遗传转化质粒,在斑玉蕈中分别驱动外源的植物花青素合成基因表达,并利用来自刺芹侧耳的萎锈灵抗性基因进行转基因筛选。两个质粒通过农杆菌介导转化斑玉蕈单核菌株后,对具有萎锈灵抗性的转化子经PCR方法进行转基因验证,并运用实时荧光定量PCR对阳性转化子中外源基因的表达水平进行比较分析。结果表明,CaMV35S和HmGPD基因的启动子均成功驱动了植物花青素合成基因在斑玉蕈中转录,为增强基因表达而引入的内含子在转录过程中均被正确切割。其中,HmGPD启动子驱动外源基因表达水平比CaMV35S启动子驱动外源基因表达水平强22-36倍。     

A biological assessment of Apophua simplicipes (Hymenoptera: Ichneumonidae) as a parasitoid of the oblique banded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae)

Apophua simplicipes (Cresson) (Hymenoptera: Ichneumonidae) is a common parasitoid of the oblique banded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) in organically managed apple orchards in the southern interior of British Columbia, Canada. The biological characteristics of a laboratory colony of A. simplicipes were studied. When held at 15 and 25°C and provided with honey water, individual females survived an average of 60.6±6.1 and 29.8±4.7 days, oviposited 196.7±50.7 and 326.6±51.3 eggs and parasitized a total of 163.4±40.4 and 229.4±35.8 hosts, respectively. Females oviposited into first through fourth instar oblique banded leafrollers, with significantly more parasitism occurring in the first two instars compared to the third and fourth instars. No parasitoid larvae survived past the first larval stage in parasitized fourth instar hosts. Apophua simplicipes did not parasitize larvae of three-lined leafroller, Pandemis limitata (Robinson) (Lepidoptera: Tortricidae) which is sympatric with oblique banded leafrollers in orchards in the southern interior of British Columbia. Female predation and host feeding from wounds on early instars of both leafroller species was observed under laboratory conditions. In addition, early instar hosts exited diet feeding sites in response to the probing activity of the ovipositing wasps. A similar escape reaction in the orchard may cause a leafroller larva to move away from its feeding site, making it more vulnerable to predation or movement off the tree. Apophua simplicipes larvae emerged from fifth and sixth instar hosts. Parasitized oblique banded leafroller hosts consumed significantly less meridic diet than unparasitized female larvae from fifth instar through to parasitoid emergence or leafroller pupation. Our laboratory results suggest that A. simplicipes may reduce field populations of oblique banded leafroller and decrease pest feeding damage.     

Parasitism-induced effects of Glyptapanteles liparidis (Hym., Braconidae) on the juvenile hormone titer of its host, Lymantria dispar: the role of the parasitoid larvae

Parasitization by the gregarious larval endoparasitoid Glyptapantles liparidis induces a dramatic increase in the hemolymph juvenile hormone (JH) titer (especially JH III) of its host larva, Lymantria dispar. Here, we investigated the role of the parasitoid larvae in JH synthesis and release by in vitro and in vivo experiments. GC-MS analyses confirmed that the rising hemolymph JH titer coincided with the time at which the parasitoids molt to the second larval instar. Peak values in host hemolymph titers were observed prior to parasitoid emergence, and titers dropped to negligible levels within 24 h after parasitoid emergence. Whole body extracts from excised second instar parasitoids yielded JH III and trace amounts of JH II. The in vitro secretory activity of the corpora allata (CA) of L. dispar larvae was not enhanced by parasitization. When the host's CA were separated by neck ligation, we found elevated JH III titers, but no JH II in the hemolymph of the posterior section, which contained the parasitoids. Parasitoids that were kept in in vitro culture produced and released only JH III. The parasitoids’ ability to secrete JH and to molt independently from their host's molting cycles indicates that at least second instar parasitoids are hormonally self-reliant.     

Comparative studies on the influence of relative humidity and temperature on life table parameters of two populations of Cotesia flavipes (Hymenoptera: Braconidae)

Cotesia flavipes Cameron (Hymenoptera: Braconidae) is a gregarious larval koinobiont parasitoid of gramineous stemborers from the Indo-Australian region. More recently, it has been introduced into several countries in East and southern Africa for regulation of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). Establishment has varied from country to country and within country, suggesting that abiotic factors, such as temperature and relative humidity, may influence parasitoid performance. In this work, the effect of temperature and relative humidity on life table parameters of two populations of C. flavipes were measured. The results indicated that the factors and their interactions significantly affected the population growth of C. flavipes. The intrinsic rate of increase of the North Pakistan population of Cotesia flavipes was higher than that of the Indian population at all humidities at 28°C, but there were no differences at other temperatures or humidities.     

An IC-PCR method for detection of Cryptosporidium and Giardia in natural surface waters in Finland

We developed an immunocapture-based polymerase chain reaction (PCR) assay for simultaneous detection of Cryptosporidium parvum oocysts and Giardia intestinalis cysts in surface water. Using primer pairs Cry9/Cry15 and LaxA/LaxB for Cryptosporidium and Gdh1/Gdh4 for Giardia, the sensitivity of the entire detection procedure (dealing with concentration, separation, DNA purification and PCR amplification) was at the level of 50–100 oocysts and cysts. Of 54 surface water samples, 4 were positive for Cryptosporidium and 1 for Giardia. Cryptosporidium and Giardia were detected for the first time in surface water in Finland.