Archanara Geminipuncta Research Articles

Host specificity and risk assessment of Archanara geminipuncta and Archanara neurica, two potential biocontrol agents for invasive Phragmites australis in North America

Invasive Phragmites australis is widespread in North America and despite decades of management and large annual expenditures (>5 million US$) using physical and chemical means, local populations and the species range are expanding. Allowing continued expansion does not only threaten native wetland biota but also an endemic North American subspecies Phragmites australis americanus. We used extensive multi-pronged investigations in Europe and North America to evaluate host specificity and impact of two European stem mining noctuid moths, Archanara geminipuncta and A. neurica. Both moth species are specific to the genus Phragmites and both show a very strong, but not absolute, preference for invasive P. australis over endemic P. australis americanus. No-choice tests or tests in small cages provided inconsistent results, but both moths showed consistently high preferences for introduced P. australis. Open field multiple-choice oviposition tests affirmed this; moths laid 6.5% of their eggs on native P. australis americanus. The native subspecies is further safeguarded by increased mortality of eggs and larvae when laid on, or developing in P. australis americanus. Phragmites populations in the southern US, particularly along the Gulf of Mexico, occur outside the climate range of these two temperate moth species. We consider potential threats to P. australis americanus demography due to A. geminipuncta and A. neurica attack to be far smaller than allowing expansion of invasive P. australis to continue. We therefore recommend release of these two biocontrol agents in North America.

Nuove segnalazioni di Nottuidi (Lepidoptera) per l’Italia meridionale

NEW RECORDS OF NOCTUID MOTHS IN SOUTHERN ITALY (LEPIDOPTERA) (Contribution to the knowledge of Lepidoptera in southern Italy. XIX) 75 species are reported in the present paper, 11 of wich are new for southern Italy. Among them, one (Aletia (Aletia) languida) is new for Italian fauna, two (Parascotia nisseni, Metachrostis velocior) are new for continental Italy, two (Paradrina fuscicornis, Gortina borelii lunata) are new for central-southern Italy and six (Tathorhynchus exsiccata, Luperina samnii, Archanara geminipuncta, Hecatera corsica weissi, Leucania comma, Tholera cespitis) are new for southern Italy. Moreover 11 species were collected for the first time in Campania, 12 in Apulia, 15 in Basilicata and 45 in Calabria. Key words: Macrolepidoptera, new reports, faunistic.

Comparison of Biology and Host Plant Use of <I>Archanara geminipuncta</I>, <I>Archanara dissoluta</I>, <I>Archanara neurica</I>, and <I>Arenostola phragmitidis</I> (Lepidoptera: Noctuidae), Potential Biological Control Agents of <I>Phragmites australis</I> (Arundineae: Poaceae)

Abstract Phragmites australis (Cavanilles) Trinius ex Steudel (Arundineae: Poaceae) is an invasive plant in freshwater and brackish North American wetlands. Inability to control this grass with chemical, mechanical, or physical means resulted in initiation of a biological weed control program. As part of investigations of potential biocontrol agents attacking P. australis in Europe, we compared distribution, life history, and host plant use of four sympatric stem-boring noctuid moths in the field and in common gardens. Archanara geminipuncta (Haworth) is the most widespread and abundant species followed by Archanara dissoluta (Treitschke), Archanara neurica (Hubner), and Arenostola phragmitidis (Hubner). The two early species, Aren. phragmitidis and Arch. neurica, hatch from overwintering eggs ≈2 wk before the later species, and shorter larval development causes adults of early species to emerge 2–4 wk before Arch. geminipuncta and Arch. dissoluta. Early Aren. phragmitidis and Arch. geminipuncta instars a...

Impact of Archanara geminipuncta (Lepidoptera: Noctuidae) on aboveground biomass production of Phragmites australis

Abstract Management of invasive plants with biological control rests on the assumption of herbivores as structuring forces of plant community composition, but only 30% of programs achieve substantial plant suppression. Control is often caused by a few successful agents, and improvements in the ability to select the most promising species would greatly improve weed biocontrol programs. We evaluated impact of different larval stages and larval densities of the stem boring noctuid Archanara geminipuncta on height and biomass production of Phragmites australis in the field and in a common garden in the native European range. In the field, stem biomass was reduced 21.5–64.5% by A. geminipuncta attack with the largest reduction due to early larval feeding. In the common garden, P. australis performance declined linearly (stem height 40%, biomass 50%; and percentage of flowering stems 90%) as attack rates increased. Significant field and common garden impact and the large Eurasian distribution indicate great potential of A. geminipuncta for biocontrol of introduced P. australis in North America if host specificity tests produce favorable results. If approved for release, we anticipate that A. geminipuncta could establish throughout the range of introduced P. australis in North America. We also anticipate that this moth will build high populations with significant impact on height, aboveground biomass, and clonal expansion of P. australis . This attack is expected to reduce competitive ability of P. australis , favoring native wetland species and preventing further negative ecological impacts associated with the current spread of introduced P. australis in North America.

Do competition and selective herbivory cause replacement of Phragmites australis by tall forbs?

We investigated the role of biotic factors in determining abundance of the low marsh species Phragmites australis and the high marsh species Epilobium hirsutum. In a 2-year field experiment, at a position where Phragmites and Epilobium co-occurred, responses of both species to each other’s removal were measured. In the second year, we also tested if larvae of Archanara geminipuncta, which feed exclusively on Phragmites shoots, affect the competitive ability of Phragmites relative to Epilobium. For both species, removal of aboveground material by clipping did not enhance shoot size or decrease variability in shoot size of the removed species itself. Surprisingly however, shoot numbers of both species increased after removal of the other, which demonstrates that there was a mutual inhibition of each other’s abundance. Comparing the responses of Archanara-infested and non-infested Phragmites shoots revealed no increased competitive suppression by Epilobium due to selective herbivory. Instead, we found that herbivore activity was lower in plots with Epilobium, which demonstrates that Archanara population size is reduced by the presence of non-host plant species. These results contradict the common assumption that biotic factors constrain a species upper limit along flooding gradients. Instead, our result suggest that different biotic interactions may counteract each other and thus slow down replacement by successive species.

Insects on common reed ( Phragmites australis): community structure and the impact of herbivory on shoot growth

In this paper, community structure of endophagous insects attacking common reed ( Phragmites australis (Cav.) Trin ex Steud.) and impact of herbivory on shoot growth was analyzed in south west Germany. All the 26 phytophagous insects were monophagous, i.e. restricted to their host plant P. australis, which appeared to be due to the predictability and apparency of the large and ancient Phragmites stands. Habitat types were clearly separated due to the mean shoot diameter (‘dry’ and ‘wet’ reed) and the mean level of shoot damage (high and low abundance of Archanara shoots). The stem-boring moth Archanara geminipuncta greatly influenced structure of the insect community, due to heavy shoot damage, and could be classified to be the key species of the reed ecosystem. In contrast to common expectations of negative effects, Archanara shoot damage enhanced populations of many insect species, so insect guilds of ‘primary attackers’ (on the main shoot) and ‘secondary attackers’ (on damaged shoots) could be separated. Primary attackers either killed the growing point or attacked the apical, medium or basal internodes, while secondary attackers were facilitated by shoot damage and could also be subdivided in four guilds: Inquilinous species living between the wilting leaves of damaged shoots, attackers of the side shoot growing in response to the destruction of apical meristems, saprophagous species feeding on Archanara droppings, and the successor community of bees and wasps nesting in empty galls or broken shoots. There is a continuum from evident plant damage, e.g. by stem-boring moths and leaf-sucking aphids, to enhanced shoot growth due to the parasitic influence of gall makers, e.g. the significant shoot elongation by the gall midge Giraudiella inclusa. In Europe, conservationists are concerned about the die-back of P. australis, while in North America and Australia, P. australis is considered to be an invasive weed. Classical biological control with the introduction of European insects (like the moth A. geminipuncta) is discussed.

Fragmentation of Phragmites Habitats, Minimum Viable Population Size, Habitat Suitability, and Local Extinction of Moths, Midges, Flies, Aphids, and Birds

Results from populations of insects and birds inhabiting Phragmites habitats were used to analyze effects of fragmentation. Flush‐crash cycles of the stem‐boring moth Archanara geminipuncta (Lepidoptera, Noctuidae) showed regionally concurrent, local extinctions despite an originally enormous population size (more than 180,000 adults), emphasizing the importance of metapopulation dynamics. Further, A. geminipuncta could be considered a keystone species, since shoot damage facilitated more than twenty species of herbivores, saprovores (of the caterpillars’ feces), and their parasitoids. The gall midge Lasioptera arundinis could survive only in side shoots induced by shoot damage of A. geminipuncta.Small Phragmites stands had thinner shoots (due to a water or nutrient deficiency) and shoots with more leaves (due to a better light supply) than large stands, thereby influencing species‐specific demands for habitat suitability and nutritiousness of reed tissue. In other words significance of habitat fragmentation could not be assessed by area alone. For example, two chloropid flies depending on thin, yellowish shoots survived only in small habitats or in the unmown edges of large habitats.Local persistence of Phragmites herbivores depended on much larger population sizes than could be expected from a population size sufficient to maintain genetic variation. At least 11,000 adults of the gall midge Giraudiella inclusa (or more than 84,000 galls) were necessary to avoid local extinction.With regard to conservation management of reed habitats, nature reserves should consist of old and unmown reeds, have fewer disturbed (particularly, fewer mown) habitat edges, measure more than two hectares (priority should go to the largest remaining fragments), and be surrounded by nearby reed habitats providing reservoir populations and diverse shoot types.

Coexistence, Tritrophic Interactions and Density Dependence in a Species-Rich Parasitoid Community

1. Data from parasitoids attacking galls of Giraudiella inclusa Fr. (Diptera: Cecidomyiidae) from Phragmites australis Trin. were used to assess the factors dictating species richness and coexistence in a community. 2. Species richness of the 14 parasitoids could be related to the high frequency and apparency of both the galls and the Phragmites monocultures. Four non-galling species of Cecidomyiidae attacking P. australis had only 2-3 parasitoid species, presumably due to the less visible and less heterogeneous microhabitat offered to the parasitoids. 3. Distribution of midge galls was due to several plant characteristics with percentage parasitism and parasitoid coexistence determined by the site of gall induction. The stem-boring moth Archanara geminipuncta Haw. (Lepidoptera: Noctuidae) was a key factor for the heterogeneous gall distribution and thereby favoured coexistence of the galls' parasitoid species: Giraudiella-galls induced on side shoots, grown from Archanara-damaged shoots, increased percentage parasitism of two parasitoid species and reduced parasitism of one species. 4. Parasitoid foraging was concentrated on temporally and spatially separated subpopulations with the microscale of host density (gall cluster size per reed internode) influencing percentage parasitism only in two out of eight species, and with the macroscale (gall abundance per habitat) having no effect at all. These findings do not meet expectations for density-dependent host regulation, but support a resource heterogeneity hypothesis. Both midge and parasitoid populations appeared to be 'limited from below' rather than 'controlled from above'. 5. The prediction that host density is negatively correlated with parasitoid diversity was not supported.

Fluctuations in Abundance of a Stem-Boring Moth Damaging Shoots of Phragmites australis: Causes and Effects of Overexploitation of Food in a Late-Successional Grass Monoculture

Flush-crash cycles of the monophagous and univoltine moth Archanara geminipuncta, which greatly damages the silicate-rich shoots of common reed P. australis, showed a non-equilibrium nature of population fluctuations in this late-successional, apparent, and undistrubed grass monoculture. The striking similarities to pest outbreaks in crops (early successional plants in man-made pure stands) are discussed (...)

Attack by a Stem-Boring Moth Increases Susceptibility of Phragmites Australis to Gall-Making by a Midge: Mechanisms and Effects on Midge Population Dynamics

The role of plant stress and shoot damage in the population dynamics of a grassinhabiting gall maker was assessed in the field. Four generations of Giraudiella inclusa (Diptera, Cecidomyiidae), developing in grain-like galls inside the internodes of common reed Phragmites australis, were sampled from nine habitats in northern West Germany from 1981 to 1984. Thin shoots of dry reed, stressed by water and nutrient deficiency, contained less silicate, caused less mortality of gall-inducing first instar larvae and had higher gall abundance than thick and intact shoots of wet reed. Thick shoots damaged by the stem-boring moth Archanara geminipuncta (Lepidoptera, Noctuidae) developed narrow side shoots that were highly susceptible to attack of the 2nd to 4th midge generation, thereby causing an increase of egg survival and gall abundance. Such facilitation among herbivores is a poorly known type of food web interaction. Differentiation between dry and wet reed and number of side shoots m-2 explained 92% of the variation of midge gall abundance between habitats and years. Availability of susceptible food, easily measurable by shoot characters, was the key factor in midge population dynamics.

Variability of the grass Phragmites australis in relation to the behaviour and mortality of the gall-inducing midge Giraudiella inclusa (Diptera, Cecidomyiidae)

Variability within and between shoots of the grass Phragmites australis proved to be important for both survival (successful gall induction) and reproduction (larval weight) of the gall-inducing midge Giraudiella inclusa. The ovipositing females and the migrating first instar larvae chose a predictable microhabitat within shoots and within internodes characterized by a high nutritional quality (nitrogen, mineral content, sugar, water) and reduced palnt defense properties (silicate). Clutch size increased with the shoot diameter, larval scramble competition could not be detected. Female shoot selection was random, although the chances of successful gall induction greatly differed between shoots. Thick and intact shoots (≥6 mm) led to a high larval mortality. But thick shoots destroyed apically by stem-mining caterpillars (of the noctuid moth Archanara geminipuncta) had on average large gall clusters. Accordingly, the adjustment of the clutch size to the shoot diameter resulted in an advantage for the gall midge females only when shoots were thin and short (i.e. stressed by water and nutrient deficiency) or heavily damage (i.e. stressed) by caterpillars. Thus, the monophagous gall maker G. inclusa did not compensate for all features of intershoot variation of P. australis, although grasses are well-known for their simple plant architecture and their low diversity and low concentration of secondary compounds.

Bioecology ofLydella thompsoni Herting, [Dip. Tachinidae] within the Rhone Delta in Southern France

Lydella thompsoni Hertin,Tachinidae, is an endoparasitoid frequently associated in southern France with larvae ofOstrinia nubilalis, Pyralidae, Sesamia nonagrioides, Noctuidae, Archanara geminipuncta andA. dissoluta, Noctuidae. The tachinid was reared successfully at 21°C in the laboratory by providing the adult flies with a high humidity, a light intensity of 8,000–10,000 lux for mating and a mixture of casein proteolysate and honey as food. Under such conditions, the flies lived for about 30 days and about half of them mated successfully. Hosts were infested by dissecting mature tachinid females and placing 1–2 of the extracted planidia onto each moth larva. Half of the planidia successfully entered their larval hosts.

Delayed Response of Common Reed Phragmites australis to Herbivory as a Cause of Cyclic Fluctuations in the Density of the Moth Archanara geminipuncta

The moth Archanara geminipuncta (Haworth) is an important herbivore of common reed. The moth has one generation per year. The stem-boring larvae may kill up to 80% of the apical parts of reed shoots. In an experimental reed field in the Netherlands a fluctuation was found in the infestation of the reed during which the survival of the larvae became zero every three years. The aim of this study was to search for the factors responsible for this fluctuation. For survival the larvae of Archanara need reed shoots with a diameter of more than 5 mm. Reed is a rhizomatous plant and the reed shoots have an annual growth habit. The reaction of the plant to damage in a certain year is the formation of thinner shoots in the next year. It appeared that apart from the important influence of competition between the larvae at high densities, the delayed response of the plant to damage was very significant in causing the periodic (local) extinction. The possible adaptive nature of the variation in shoot diameter is discussed.

Étude Expérimentale du Rôle de la Température Dans la Diapause Embryonnaire d'Archanara Geminipunct [Lep. Noctuidae

SummaryThe Noctuid moth Archanara geminipuncta is an alternate host for the Tachinid fly Lydella thompsoni, parasite of the European corn borer. The annual synchronization of host and parasite cycles partially depends on host development. The latter has been studied. The host species goes through an embryonic diapause from July to next April. The eggs are not reactivated unless they undergo a period of low temperatures (+ 2 °C for 3 months). In the south of France this stage is terminated at the end of the year. Then, the development goes slowly on throughout the winter months. At this time, the temperature threshold is about + 8 °C. Hatching usually occurs in April; consistent with local meteorological data, half of the eggs are most likely to hatch between March 26 and May 5 (probability 95 p. 100).