Copidosoma Koehleri Research Articles

Increasing floral diversity for selective enhancement of biological control agents: A double-edged sward?

Summary Floral resource subsidies can have differential effects on insect herbivores compared with the herbivores’ natural enemies. While the nectar of many plant species enhances parasitoid fitness, it may also increase damage by herbivores. This may occur as a result of enhanced herbivore fitness or by enhancing fourth-trophic-level processes, possibly disrupting a trophic cascade as a result. The responses of different arthropod guilds to different floral resource subsidies were compared using Plutella xylostella (Hyponomeutidae), its parasitoid Diadegma semiclausum (Ichneumonidae) and data from two other published herbivore–parasitoid systems. These were Dolichogenidea tasmanica (Braconidae) and its host Epiphyas postvittana, and Copidosoma koehleri (Encyrtidae) and its host Phthorimaea operculella. The parasitoids and hosts in the three systems exhibited differential responses to the nectar sources. The differential response was not explained by morphology, demonstrating that physical access to nectaries alone does not determine the potential of flowers as a food source. For some flowering plants, enhancement of herbivore and parasitoid fitness occurred. Other flowering plants, such as buckwheat and phacelia, conferred a selective enhancement on parasitoids by increasing only their fitness. More effective conservation biocontrol may be achieved by the provision of selective floral resources. Attempts to ‘engineer’ agroecosystems to enhance biological control require an extensive knowledge of the ecology of the herbivore, its enemies and their interactions with potential resource subsidies.

Biological Suppression of Potato Tubermoth, Phthorimaea operculella (Zeller) with Exotic Parasitoids and Microbial Agents under Field and Storage Conditions

Investigations on bioefficacy of parasitoids and microbial agents against potato tubermoth (PTM), Phthorimaea operculella (Zeller) (Lepidoptcra: Gelechiidae) were carried out under field and storage conditions of potato during 1996-1997. The results showed that three sprays of endosulfan 0.05 per cent at 10 days interval proved to be the most effective and on par with four releases of Chelonus blackburni Cameron @ 15000 adults/ha/release at weekly interval, Copidosoma koehleri Blanchard @ 50000 adults/ha/lrelcase and Trichogramma chilonis Ishii @ 50000 adults/ha/releasc at weekly interval, and three sprays of Bacillus Thuringiensis Berliner @ 1 kg/ha at 10 days interval. Amongst the parasitoids, maximum parasitism was recovered through retrieval with C. blackburni (71.78 %), followed bye C. koehleri (69.39%) and T. chilonis (61.33%). Under storage conditions ( Arnies ), initial release of C. blackburni @ 2 adults/kg tubers recorded minimum tuber infestation (7.21 %) after 60 days.

Flowers in tri‐trophic systems: mechanisms allowing selective exploitation by insect natural enemies for conservation biological control

AbstractMany insects have coevolved with certain angiosperm taxa to act as pollinators. However, the nectar and pollen from such flowers is also widely fed upon by other insects, including entomophagous species. Conservation biological control seeks to maximise the impact of these natural enemies on crop pests by enhancing availability of nectar and pollen‐rich plants in agroecosystems. A risk with this approach is that pests may also benefit from the food resource. We show that the flowers of some plants (viz., buckwheat, Fagopyron esculentum Moench and dill, Anethum graveolens L.), and the extrafloral nectaries of faba bean (Vicia faba L.) benefit both Copidosoma koehleri Blanchard (Hymenoptera: Encyrtidae) and its host, the potato pest, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae). In contrast, phacelia (Phacelia tanacetifolia Benth) and nasturtium (Tropaeoleum majus L.) benefited only the parasitoid. When adult moths of P. operculella were caged with flowers of phacelia or nasturtium, longevity of males and females, egg laying life, fecundity, average oviposition rate, and number of eggs in ovaries at death were no greater than in the control treatment with access to shoots without flowers plus water. All the foregoing measures were increased compared to the control when the moths were allowed access to dill, buckwheat or faba bean extrafloral nectaries. Such ‘selectivity’ has the potential to make the use of floral resources in conservation biological control more strategic. We present morphometric and observational evidence to illustrate how such mechanisms may operate.

Sub‐lethal effects of foliar pubescence on the egg parasitoid Copidosoma koehleri and influence on parasitism of potato moth, Phthorimaea operculella

Entomologia Experimentalis et ApplicataVolume 87, Issue 1 p. 115-118 Sub-lethal effects of foliar pubescence on the egg parasitoid Copidosoma koehleri and influence on parasitism of potato moth, Phthorimaea operculella J. Gooderham, J. Gooderham Department of Ecology and Evolutionary Biology, Monash University, Clayton, Victoria, AustraliaSearch for more papers by this authorP. C. E. Bailey, Corresponding Author P. C. E. Bailey Department of Ecology and Evolutionary Biology, Monash University, Clayton, Victoria, Australia*Author for correspondenceSearch for more papers by this authorG. M. Gurr, G. M. Gurr Orange Agricultural College, The University of Sydney, Orange, New South Wales, AustraliaSearch for more papers by this authorL. R. Baggen, L. R. Baggen Orange Agricultural College, The University of Sydney, Orange, New South Wales, AustraliaSearch for more papers by this author J. Gooderham, J. Gooderham Department of Ecology and Evolutionary Biology, Monash University, Clayton, Victoria, AustraliaSearch for more papers by this authorP. C. E. Bailey, Corresponding Author P. C. E. Bailey Department of Ecology and Evolutionary Biology, Monash University, Clayton, Victoria, Australia*Author for correspondenceSearch for more papers by this authorG. M. Gurr, G. M. Gurr Orange Agricultural College, The University of Sydney, Orange, New South Wales, AustraliaSearch for more papers by this authorL. R. Baggen, L. R. Baggen Orange Agricultural College, The University of Sydney, Orange, New South Wales, AustraliaSearch for more papers by this author First published: 17 October 2003 https://doi.org/10.1046/j.1570-7458.1998.00312.xCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume87, Issue1April 1998Pages 115-118 RelatedInformation

The Influence of Food onCopidosoma koehleri(Hymenoptera: Encyrtidae), and the Use of Flowering Plants as a Habitat Management Tool to Enhance Biological Control of Potato Moth,Phthorimaea operculella(Lepidoptera: Gelechiidae)

The effects of flowering plants on the longevity and fecundity of the proovigenic egg parasitoid Copidosoma koehleri Blanchard, an important parasite of potato moth, Phthorimaea operculella (Zeller), were studied in the laboratory and in the field. Laboratory experimentation showed that fecundity was increased in the presence of honey. When C. koehleri females were deprived of hosts for the first 5 days of their adult lives, neither the total number of eggs laid nor longevity were significantly affected. Longevity was significantly increased when adults were caged on flowering plants of dill, borage, or coriander. Field cage experiments supported these observations with rates of parasitism in P. operculella being significantly higher in fed treatments. A second field trial found that rates of parasitism were greater among P. operculella larvae recovered from potato plants growing close to a strip of flowers than in larvae 20 m distant. Pest populations and levels of crop damage were, however, increased by proximity of flowering plants. Laboratory studies subsequently quantified the effect of some flowers on P. operculella, finding that buckwheat and coriander were at least equivalent to honey in increasing fecundity and adult longevity. Findings are discussed in relation to the use of flowering plants as a tool in habitat management for pest control. The use of “selective food plants,” which allow only beneficial insects access to nectaries, is proposed as a new strategy.

The effects of temperature and host density on the development and survival of Copidosoma koehleri

AbstractDevelopmental rates for Copidosoma koehleri Blanchard (Hymenoptera: Encyrtidae) and its host, Phthorimaea operculella (Zeller), were determined at 10, 15, 23, 27, 29, 32, 34 and 35 °C from host egg to adult. The developmental rates determined for both species showed good fit to mathematical models of insect development. At 15 °C mean emergence of adult C. koehleri was 15 days after P. operculella adults emerged. At 29 °C mean emergence of C. koehleri was only 5 days after that of P. operculella. P. operculella developed at 35 °C, but parasitized larvae, and therefore C. koehleri, did not tolerate temperatures above 32 °C. In the presence of C. koehleri, host survival was low (3%) at low host egg densities, but greater (20%) at higher host densities. Parasitized larvae of P. operculella were less able to compete for food resources, as measured by adult emergence.

The influence of introduced parasitoids on the potato moth, Phthorimaea operculella (Lepidoptera: Gelechiidae) in Victoria, Australia

The distribution of introduced parasitoids of Phthorimaea operculella (Zeller) in Victoria is described. Apanteles subandinus Blanchard and Orgilus lepidus Muesebeck were most abundant, but Copidosoma koehleri Blanchard was also recorded from several sites. Detailed analysis of data obtained through regular monitoring revealed that, in an area free from insecticides, parasitoids were a major factor in controlling P. operculella. This result differs from previously published opinions on the effect of parasitoids, and is attributed to the analysis of data, in this study, on a generational basis. The effect of insectide applications on P. operculella and its parasitoids is discussed.

Fertility of the polyembryonic parasite Copidosoma koehleri, effect of humidities on life length and relative abundance as compared with that of Apanteles subandinus in potato tuber moth

SUMMARYMales and females of Copidosoma koehleri were kept separately in desiccators producing relative humidities of 20, 40 and 70% at 24 and 28°C and found to be very susceptible to low relative humidity. They lived less than 1 day at 20%, about 2 and 4 days at 40% and about six times longer than these respectively at 70% r.h. When kept at 26°C and 70% r.h. females of C. koehleri parasitised 98.8 hosts. The number of parasites that emerged from a male brood was 21.2 and from a female brood 33.2. Mated females produced 3026 progeny and unmated 2289. The sex ratio of broods produced by mated females was 1:1 and the female percentage among progeny was 59. It is known that C. koehleri is rare at the beginning of the potato‐growing season and becomes the predominant parasite later on. It is known also that in potato crops when the plants are small at the beginning of the season the air within the crop is less humid but as the canopy of foliage develops, relative humidity rises and becomes higher than at 1.2 m above ground. It is suggested that relative humidity in the potato crop is the major factor affecting the relative abundance of C. koehleri and Apanteles subandinus in South Africa.

Techniques for Culturing and Mass Producing Parasites of the Potato Tuberworm1

Techniques for the culture and mass production of parasites of Phthorimaea operculella (Zeller) are described. The ovipositional requirements of 11 larval and 3 egg-larval parasites are given. Their developmental period ranged from 15 days for Apanteles dignus Muesebeck and Orgilus lepidus Mueseheck to 28 days for Chelonus blackburni Cameron; male:female sex ratio of their progeny from 1:1 for A. dignus and Copidosoma koehleri (Blanchard) to 5:1 for Diadegma stellenbochense (Cameron) and Temelucha sp.

Some gamma radiation effects on host-parasitoid relationships.

The encyrtid Copidosoma koehleri Blanchard, when reared in previously irradiated potato tuberworm (Gnorimoschema operculella (Zeller)) hosts, showed symptoms of nutritional deficiency which included lessened polyembryony, slower development, and higher mortality in the various stages of the life cycle. The host larvae, irradiated before hatching from the egg, were smaller than normal, weighed less, and stored much less of the suprastomodaeal fat tissue on which C. koehleri subsists during its polygerm stage. The larval period of the braconid Macrocentrus ancylivorus Rohwer was lengthened in such hosts, and there was greatly increased mortality of the adults within their cocoons. However, previous irradiation of the host eggs had no effect on the development of the trichogrammatid egg parasite Trichogramma semifumatum (Perkins). Dosages of 0.5-2 kilorads applied directly to polygerms of C. koehleri in previously unirradiated hosts induced pathological conditions. Embryos grew abnormally large and many failed to complete their embryonic development, and the embryonic period generally was lengthened. Though irradiation damage was thus evident at a very early stage in C. koehleri, its expression in M. ancylivorus was generally delayed until the adult stage. The percentage of emergence of adults from cocoons was reduced by low dosages given to eggs or larvae, and when such dosages were given to second-stage larvae the females that survived to adulthood were crippled, with short wings and curled ovipositors and antennae.

Polyembryony in Copidosoma koehleri Blanchard

Polyembryonic development in Copidosoma koehleri Blanchard is traced from the ovarian egg to the adult stage. Polyembryony apparently results from the change in cytoplasmic-nuclear balance when the formation of the polar region removes about half the cytoplasm of the egg. Furthermore, the extent of polyembryonic division is increased when the amount of nuclear material is increased by the addition of a sperm nucleus, more individuals being produced from fertilized than from unfertilized eggs. The mean number of adult parasites constituting an exclusively male brood was 21, while the mean number of individuals found in female broods was 31.4. This sexual differential in the amount of polyembryonic division is explained on the basis of a sperm-influence hypothesis. This theory is further substantiated by the androgenetic development of eggs inactivated by heavy dosages of x-rays. The polygerminal mass is invariably found to be associated with the fat body of the larval host in the region dorsal to the stomodaeum, and a remarkable ingrowth of host tracheae occurs to supply the respiratory demands of the developing parasite embryos. The extraordinary, precocious larval forms known as "asexual" are found to be present at a very early stage in the embryonic development of Copidosoma koehleri. The origin of broods of mixed sexes is explained upon the basis of superparasitism. The quantitative and experimental studies included in this paper are offered as a new approach to the investigation of insect polyembryony.