The effect of the armored scale,Rhizaspidiotus donacis (Hemiptera: Diaspididae), on shoot growth of the invasive plant Arundo donax (Poaceae: Arundinoideae)

The effect of feeding by the armored scale, Rhizaspidiotus donacis (Leonardi, 1920) (Hemiptera: Diaspididae) on the growth of the plant Arundo donax L. (Poaceae) was evaluated under field conditions in its native range. The study was designed to evaluate the impact of R. donacis, a candidate agent for biological control of A. donax which is invasive in arid riparian ecosystems of the Southwestern USA and Mexico. The study was carried out at five A. donax sites in the Province of Alicante, Spain, differing in altitude and climate. At each site, 30 infested lateral shoots were selected and 15 were randomly treated monthly with imidacloprid insecticide. Shoot lengths were measured monthly over a 1-year period in a comparative growth analysis. Shoots infested with R. donacis had an over 2-fold reduced growth rate as compared to treated shoots. Growth of shoots varied by site, and the effect of R. donacis on growth was most pronounced in the late spring, when mature females produced first instar scale crawlers. The impact of R. donacis on A. donax growth under field conditions in the native range, combined with its narrow host specificity, indicate that R. donacis is a promising candidate for biological control of A. donax in North America and other areas invaded by this weed.     

Evaluation of Spanish Arundo scale Rhizaspidiotus donacis (Hemiptera; Diaspididae) survival and fecundity on three new world genotypes of Arundo donax (Poaceae; Arundinoideae)

A pre-release evaluation of survival and fecundity of the arundo scale, Rhizaspidiotus donacis, was conducted on three invasive genotypes of the riparian weed, Arundo donax. The three A. donax genotypes were collected from Laredo, Austin and Balmorhea, TX, which represented the majority of the genotypic diversity found in Texas watersheds. Although R. donacis developed on all three genotypes of the plant, the Austin A. donax genotype, followed by the Laredo genotype, were the most suitable in terms of the size of first-generation immature and adult scale populations that developed after crawler release. Both the Laredo and Austin genotypes of A. donax are likely to be of Spanish origin and are close genetic matches with scale's original host plant genotype in Alicante, Spain. In comparison, survival was lowest on the phylogenetically distant genotype of A. donax from Balmorhea, TX. Although the population size of settled, immature second-generation scales varied in a manner similar to that of the first generation, the fecundity of isolated first-generation females was not significantly different across the three plant genotypes, suggesting that R. donacis is not a genotype specialist in terms of nutrient assimilation for reproduction. Rather, differences in genotype suitability affect rates of success of crawler settling. These results indicate that selection of scale genotype from the native range may have a moderate influence on the success of R. donacis and ultimately the biological control programme.     

Evaluation of biogeographical factors in the native range to improve the success of biological control agents in the introduced range

Biogeographical factors associated with the invasive weed Arundo donax were evaluated at 22 different locations in four countries in its native range in reference to its key herbivore, an armoured scale insect, Rhizaspidiotus donacis. Data on climate, plant health and quality, soil conditions and anthropogenic influences were analysed for each site and compared to populations of R. donacis. Climate modelling from location data in Spain and France accurately predicted the native range of the scale in the warmer, drier parts of Italy and Greece and was used to predict its distribution in North America. Presence of the scale was not associated with specific soil type or characteristics. However, it was positively associated with a higher percentage of dead stems and significantly lower biomass of A. donax. Micronutrient sampling using leaf material found that sulphur was negatively correlated with aluminium and positively correlated with boron for scale density. Disturbance of field sites by cutting and/or addition of supplemental irrigation during summer appeared to disrupt the synchronised seasonal phenology of A. donax and R. donacis, leading to more robust stands. These biogeographical factors from the native range indicate that R. donacis should have the greatest impact in warm, dry climates in the introduced range where A. donax is undisturbed.     

Host range of the European,rhizome-stem feeding scale Rhizaspidiotus donacis (Hemiptera: Diaspididae), a candidate biological control agent for giant reed,Arundo donax (Poales: Poaceae) in North America

The armored scale Rhizaspidiotus donacis (Leornardi) was evaluated as a potential biological control agent of the invasive reed grass Arundo donax in North America. No-choice tests, native range field surveys and non-target host exposures were used to determine the fundamental host range of the scale collected from Caloma, Spain and Perpignan, France. Thirty-five species, including two genotypes of A. donax and seven ecotypes of Phragmites australis, along with closely related grasses, economic grasses and habitat associates were tested. In quarantine no-choice testing using releases of 200 crawlers per plant, normal development of R. donacis was observed on A. donax and A. formosana, with very limited survival to the adult stage on Spartina alterniflora and Leptochloa spp. In follow-up studies using 1000 crawlers per plant, 10 live adult females were found on Leptochloa virgata, and one adult female on Spartina alterniflora, but average adult female abundance per plant was (2580%) 26-times lower on L. virgata and over (39,090%) 100-times lower on S. alterniflora than on A. donax. Field surveys were conducted at five locations in Spain and France at which A. donax infested with R. donacis, co-occurred with two non-target species of concern and R. donacis was only found on A. donax. Six-month field host exposures in Spain using potted Leptochloa plants entwined with heavily infested A. donax confirmed that R. donacis is specific to Arundo under field conditions. Based on our results, the scale R. donacis appears to be specific to the genus Arundo and is unlikely to harm native or cultivated plants in the Americas.     

Impact of the biological control agent Tetramesa romana (Hymenoptera: Eurytomidae) on Arundo donax (Poaceae: Arundinoideae) along the Rio Grande River in Texas

Five years post-release of the arundo gall wasp, Tetramesa romana, into the riparian habitats of the lower Rio Grande River, changes in the health of the invasive weed, Arundo donax, or giant reed, have been documented. These changes in plant attributes are fairly consistent along the study area of 558 river miles between Del Rio and Brownsville, TX, and support the hypothesis that the arundo wasp has had a significant impact as a biological control agent. Plant attributes were measured prior to release in 10 quadrats at each of 10 field sites in 2007, and measured again at the same undisturbed sites, 5 years after the release of T. romana, in 2014. Above ground biomass of A. donax decreased on average by 22% across the 10 sites. This decline in biomass was negatively correlated to increased total numbers of T. romana exit holes in main and lateral shoots per site in 2014 compared to 2007. Changes in biomass, live shoot density and shoot lengths, especially the positive effect of galling on main and lateral shoot mortality, appear to be leading to a consistent decline of A. donax. Economically, this reduction in A. donax biomass is estimated to be saving 4.4 million dollars per year in agricultural water. Additional impacts are expected as populations of the wasp increase and as other biological control agents such as the arundo scale, Rhizaspidiotus donacis, become more widespread.     

Tripius gyraloura n. sp. (Aphelenchoidea: Sphaerulariidae) parasitic in the gall midge Lasioptera donacis Coutin (Diptera: Cecidomyiidae)

A new nematode, Tripius gyraloura n. sp., is described from the arundo gall midge, Lasioptera donacis Coutin (Diptera: Cecidomyiidae). This gall midge is being considered as a biological control agent for use in North America against the introduced giant reed Arundo donax (L.) (Poaceae: Cyperales). Thus the present study was initiated to investigate a nematode parasite that was unknown at the time studies with L. donacis were initiated. The new species has a rapid development in the fly host and the mature parasitic female nematodes evert their uterine cells in the hosts’ hemolymph. Because large numbers of nematodes sterilise the host, eradication of the parasite from laboratory colonies of the midge may be necessary before populations of the fly are released.     

Impact of the Arundo scale Rhizaspidiotus donacis (Hemiptera: Diaspididae) on the weight of Arundo donax (Poaceae: Arundinoideae) rhizomes in Languedoc southern France and Mediterranean Spain

Arundo donax L. (Poaceae) is native to Mediterranean Europe and invasive in the Rio Grande Basin of North America. Rhizomes from nine sites in France and Spain infested with a candidate control agent, the armoured scale Rhizaspidiotus donacis (Hemiptera: Diaspididae) weighed 50% less than those from nine sites without scale.     

Impact of the arundo wasp,Tetramesa romana (Hymenoptera: Eurytomidae), on biomass of the invasive weed,Arundo donax (Poaceae: Arundinoideae), and on revegetation of riparian habitat along the Rio Grande in Texas

An invasive grass, Arundo donax, occupies thousands of hectares of arid riparian habitat along the Rio Grande in Texas and Mexico, and has negative impacts on national security, water resources, and riparian ecosystems. The shoot-tip-galling wasp Tetramesa romana was released in 2009 between Brownsville and Del Rio, Texas, and has dispersed over 800?km along the river channel. Plots along the river were surveyed for shoot counts of arundo and all other plant species in 2016 at seven sites in regions in which prior studies had documented a 22% decline in arundo biomass (estimated from live shoot length) from 2007 to 2014. Estimated live biomass declined a further 32% between 2014 and 2016. Native plants accounted for 86% of the 44 species encountered in plots. Individual plots averaged five plant species, and arundo was most abundant in only 9 of 21 plots. Arundo live biomass and shoot density were negatively associated with plant diversity, indicating that live arundo interferes with germination and/or survival of other plant species. The proportion of dead shoots in plots, proportion of wasp-galled shoots, and density of exit holes made by emerging adult wasps per metre live main shoot length were positively associated with plant diversity in a combined model. Regressions indicated that the effects of wasp damage measures on diversity were mediated through their effects on main shoot mortality. By reducing live arundo biomass, the arundo wasp is fostering recovery of native plant communities at riparian sites along the Rio Grande.     

Wildfire promotes dominance of invasive giant reed (Arundo donax) in riparian ecosystems

Widespread invasion of riparian ecosystems by the large bamboo-like grass Arundo donax L. has altered community structure and ecological function of streams in California. This study evaluated the influence of wildfire on A. donax invasion by investigating its relative rate of reestablishment versus native riparian species after wildfire burned 300 ha of riparian woodlands along the Santa Clara River in southern California in October 2003. Post-fire A. donax growth rates and productivity were compared to those of native woody riparian species in plots established before and after the fire. Arundo donax resprouted within days after the fire and exhibited higher growth rates and productivity compared to native riparian plants. Arundo donax grew 3–4 times faster than native woody riparian plants—up to a mean of 2.62 cm day⁻¹—and reached up to 2.3 m in height less than 3 months after the fire. One year post-fire, A. donax density was nearly 20 times higher and productivity was 14–24 times higher than for native woody species. Three mechanisms—fire-adapted phenology, high growth rate, and growth response to nutrient enrichment—appear to promote the preemption of native woody riparian species by A. donax after fire. This greater dominance of A. donax after wildfire increased the susceptibility of riparian woodlands along the Santa Clara River to subsequent fire, potentially creating an invasive plant-fire regime cycle. Moreover, A. donax infestations appear to have allowed the wildfire to cross the broad bed of the Santa Clara River from the north, allowing thousands of acres of shrubland to the south to burn.     

Densities of the arundo wasp,Tetramesa romana (Hymenoptera: Eurytomidae) across its native range in Mediterranean Europe and introduced ranges in North America and Africa

Tetramesa romana is a biological control agent of the giant reed, Arundo donax (Poaceae: Arundinoideae), which is an invasive weed in the riparian habitats of the Rio Grande Basin of Texas, the southwestern U.S.A. and northern Mexico. Field evaluations were conducted in the native range of T. romana in Mediterranean Europe and in the introduced ranges of Texas, California, and South Africa to compare densities of the wasp. Population densities and percentage parasitism levels for the 2017 year are compared to meteorological variables (average temperature, precipitation, and heat units). In the introduced ranges of Texas (intentional) and South Africa (adventive) T. romana population densities were 39 and 10-fold higher than in the native range, respectively. Percentage parasitism of T. romana in Texas and in the native range of Thessaloniki, Greece were 2.0% and 34.3%, respectively. Annual heat unit accumulation was 1.3–2.7-fold higher at Texas sites than at other introduced or native sites, and heat units were positively associated with exit hole counts at introduced sites. Annual precipitation was 2-fold higher at Texas and South African sites than in California and the native range sites. Favourable weather conditions and reduced parasitism in Texas along the Rio Grande, as compared to the native range, allows T. romana to reach higher population levels and cause considerable damage to A. donax.     

Laboratory host range testing of Neomusotima conspurcatalis (Lepidoptera: Crambidae) – a potential biological control agent of the invasive weed,Old World climbing fern,Lygodium microphyllum (Lygodiaceae)

Old World climbing fern, Lygodium microphyllum, is a serious invasive weed in south Florida. Development of biological control is vital for sustainable management of L. microphyllum. Neomusotima conspurcatalis was discovered in Hong Kong in 1997 and was subsequently found causing feeding damage on L. microphyllum in much of its native range in Asia. Quarantine testing of N. conspurcatalis used 37 non-Lygodium fern species representative of New World genera of cultivated ferns and fern allies, one gymnosperm, three crop species, six Lygodium species, and the primary host L. microphyllum. No significant oviposition or feeding was observed on any of the 41 non-Lygodium species evaluated. Oviposition and feeding occurred on all Lygodium species, but amounts were low and usually significantly less than observed on L. microphyllum. The exception was L. japonicum, which was preferred as an oviposition host. Neomusotima conspurcatalis was only able to complete development on L. japonicum and L. palmatum, but survival on these species was only half that occurring on L. microphyllum. Neomusotima conspurcatalis is a Lygodium specialist. Lygodium japonicum is an invasive weed in the United States. Lygodium palmatum is restricted to areas of the United States where freezing winter temperatures would be lethal to N. conspurcatalis. It was concluded that N. conspurcatalis would pose no threat to native or cultivated plants in North America or the Caribbean and should be considered for biocontrol of L. microphyllum. A release petition was submitted in 2005. An USDA-APHIS release permit for N. conspurcatalis was issued in 2007.     

Life history and host range of Sauris nr. purpurotincta,an unsuitable biological control agent for Chinese tallowtree

Foreign surveys in China discovered a defoliating insect species feeding on the leaves of Chinese tallowtree (Triadica sebifera), an invasive weed of the southeastern U.S.A. The life history of this species, Sauris nr. purpurotincta (Lepidoptera: Geometridae), was examined and larval no-choice and adult multiple-choice host range tests were conducted in quarantine to evaluate their suitability for biological control of Chinese tallowtree. The results indicated that the larvae have five instars and require approximately 22 days to complete development to the adult stage. Host range tests indicated that the larvae could not feed and complete development on most species tested. However, 40% of the larvae survived when fed leaves of Hippomane mancinella, a state-listed endangered species in Florida, and all larvae survived when fed Morella cerifera, a common native species of the southeastern U.S.A. Multiple-choice oviposition tests indicated eggs were laid on leaves of both a south Florida native plant Gymnanthes lucida and Chinese tallowtree. Considering this broad host range, this species will not be considered further for biological control of Chinese tallowtree in the U.S.A.     

Biogeographical comparison of the arthropod herbivore communities associated with Lepidium draba in its native, expanded and introduced ranges

Aim To examine the composition and structure of the arthropod community on the invasive weed Lepidium draba in its native, expanded and introduced ranges, in order to elucidate the lack of a biotic constraint that may facilitate invasion. Location Europe and western North America. Methods Identical sampling protocols were used to collect data from a total of 35 populations of L. draba in its native (Eastern European), expanded (Western European) and introduced (western US) ranges. A bootstrapping analysis was used to compare herbivore richness, diversity and evenness among the regions. Core species groups (monophages, oligophages and polyphages) on the plant were defined and their abundances and host utilization patterns described. Results Species richness was greatest in the native range, while species diversity and evenness were similar in the native and expanded range, but significantly greater than in the introduced range of L. draba. Specialist herbivore abundance was greater in the native and expanded compared with the introduced range. Oligophagous Brassicaceae‐feeders were equally abundant in all three ranges, and polyphagous herbivore abundance was significantly greater in the introduced range. Overall herbivore abundance was greater in the introduced range. Host utilization was more complete in the two European ranges due to monophagous herbivores that do not exist in the introduced range. Root feeders and gall formers were completely absent from the introduced range, which was dominated by generalist sap‐sucking herbivores. However, one indigenous stem‐mining weevil, Ceutorhynchus americanus, occurred on L. draba in the introduced range. Main conclusions This is, to our knowledge, the first study documenting greater herbivore abundance on an invasive weed in its introduced, compared with its native, range. However, greater abundance does not necessarily translate to greater impact. We argue that, despite the greater total herbivore abundance in the introduced range, differences in the herbivore community structure (specialist vs. generalist herbivory) may contribute to the invasion success of L. draba in the western USA.     

Molecular evidence for a single genetic clone of invasive Arundo donax in the United States

Arundo donax (giant reed) is an aggressive invasive weed of riparian habitats throughout the southern half of the United States from California to Maryland. Native to Asia, the species is believed to have been initially introduced into North America from the Mediterranean region although subsequent introductions were from multiple regions. To provide insight into the potential for biological control of A. donax, genetic variation in plants sampled from a wide geographical area in the United States was analyzed using Sequence Related Amplification Polymorphism (SRAP) and transposable element (TE)-based molecular markers. Invasive individuals from 15 states as well as four populations in southern France were genetically fingerprinted using 10 SRAP and 12 TE-based primer combinations. With the exception of simple mutations detected in four plants, A. donax exhibited a single multilocus DNA fingerprint indicating a single genetic clone. The genetic uniformity of invasive A. donax suggests that classical biological control of the species could be successful. A lack of genetic diversity in the invaded range simplifies identification of native source populations to search for natural enemies that could be used as biocontrol agents.     

Host range evaluation of the leaf-feeding beetle,Zygogramma bicolorata and the stem-boring weevil,Listronotus setosipennis demonstrates their suitability for biological control of the invasive weed,Parthenium hysterophorus in Ethiopia

The invasive weed, parthenium (Parthenium hysterophorus L.) (Asteraceae: tribe Heliantheae), damages agriculture, adversely impacts biodiversity and is hazardous to human and animal health in Ethiopia. The host range of two natural enemies, a leaf-feeding beetle, Zygogramma bicolorata (Coleoptera: Chrysomelidae) and a stem-boring weevil, Listronotus setosipennis (Coleoptera: Curculionidae) was evaluated for biological control of the weed in Ethiopia. The specificity of Z. bicolorata and L. setosipennis was assessed against 29 and 31 non-target plant species, respectively. The host range of Z. bicolorata and L. setosipennis was first assessed using no-choice tests to examine their oviposition and feeding response on non-target plants. Although oviposition by Z. bicolorata occurred on six non-target species in four Asteraceae species in no-choice tests, it was significantly lower than on parthenium and no larvae developed. Zygogramma bicolorata nibbled the leaves of one of the five niger seed (Guizotia abyssinica L. – an oil seed crop closely related to parthenium) cultivars tested, but feeding and oviposition were significantly less than on parthenium. Furthermore, choice tests indicated that Z. bicolorata did not oviposit nor feed on G. abyssinica when parthenium was present. In no-choice tests, L. setosipennis did not oviposit on any of the non-target species assessed. Mean oviposition on parthenium was 39.0?±?3.4 eggs per plant whereas no eggs were laid on any of the 31 species tested. Based on these and other host range tests, permission was obtained to field release Z. bicolorata and L. setosipennis in Ethiopia.     

原产地和入侵地紫茎泽兰对泽兰实蝇的选择性、卵巢蛋白质含量与解毒酶活性的影响

[目的] 紫茎泽兰是我国危害严重的恶性入侵杂草。比较专一性天敌泽兰实蝇对该杂草入侵前后植株的适应性,是揭示外来植物入侵后适应性机制的重要科学问题之一。[方法] 比较泽兰实蝇对原产地和入侵地紫茎泽兰植株的寄主选择性,并测定寄生于2类植株的上泽兰实蝇卵巢蛋白质含量及乙酰胆碱酯酶、羧酸酯酶、谷胱甘肽S-转移酶活性。[结果] 泽兰实蝇对原产地和入侵地紫茎泽兰的选择无显著性差异;寄生在紫茎泽兰入侵地植株上的卵巢蛋白质含量较原产地植株上更高。解毒酶活力比较表明,入侵地紫茎泽兰上泽兰实蝇的羧酸酯酶活性低于原产地上的,但谷胱甘肽S-转移酶（雌虫）活性比较则相反,乙酰胆碱酯酶活性比较均无显著性差异。[结论] 紫茎泽兰入侵后,专一性天敌泽兰实蝇的适应性有所下降,丰富了外来植物入侵机制中天敌逃逸假说的内涵。     

Laboratory host range of Austromusotima camptozonale (Lepidoptera: Crambidae), a potential biological control agent of Old World climbing fern,Lygodium microphyllum (Lygodiaceae)

Old World climbing fern, Lygodium microphyllum, is one of the most serious invasive weeds impacting south Florida and development of biological control is crucial for sustainable management. Larvae of a small moth, Austromusotima camptozonale, were discovered defoliating L. microphyllum in Australia. Preliminary testing suggested this moth was a Lygodium specialist. Laboratory host range testing was conducted on 65 species of test plants, from 31 families, comprising seven Lygodium species, four close relatives, 45 other species of ferns and fern allies, eight agricultural crops and one gymnosperm species plus the primary host L. microphyllum. Significant oviposition occurred only on other species of Lygodium. No eggs were laid on the agricultural crops, or about half the species of non-Lygodium ferns and fern allies tested. Oviposition on the other non-Lygodium ferns was very low, except on Anemia adiantifolia and Blechnum serrulatum, which received modest egg loads, but did not support development to adult. Larval feeding was low to non-existent on all the non-Lygodium species. Larvae developed to adult only on the native, American climbing fern L. palmatum, and to a lesser extent on L. japonicum. Lygodium japonicum is a naturalized invasive weed in the United States. Colonies of A. camptozonale were unable to persist on L. palmatum and died out in two to seven generations. Freezing winter temperatures in states where L. palmatum occurs would be lethal to A. camptozonale. It was concluded that A. camptozonale would pose no threat to native or cultivated plants in North America or the Caribbean and should be considered as a weed biological control agent against L. microphyllum.     

Insect herbivores associated with the introduced weed Bidens frondosa L. (Asteraceae) in Korea,and their potential role as augmentative biological control agents

The annual herb Bidens frondosa L., native to North America, is an invasive weed. Currently no information is available on the insect herbivores associated with this weed in Korea. A survey was carried out at two‐weekly intervals from May to October 2008 at two sites, and the incidence and abundance of various insect herbivores studied. A total nine species of insects was recorded and among them the defoliating caterpillar Hadjina chinensis (Wallengren) (Lepidoptera) was the only species known to have host plants restricted to genus Bidens. Further host specificity studies are required to evaluate the potential of this insect as a candidate for augmentative biological control agent for B. frondosa in Korea. All other insect species are either polyphagous or known crop pests.     

Host range of the defoliator Strepsicrates sp. is too broad for biological control of the invasive weed Rhodomyrtus tomentosa

In its native range the invasive weed, Rhodomyrtus tomentosa is host to a suite of herbivores. One, Strepsicrates sp. (Lepidoptera: Tortricidae), was collected in China in 2014, introduced under quarantine in Florida, USA, and tested against related species to determine its host range and suitability for biological control. In no-choice tests, neonates fed and completed development to the pupal stage on several species of Myrtaceae, including the target weed R. tomentosa, the exotics Melaleuca quinquenervia, and Eucalyptus camaldulensis, and three native species, Eugenia axillaris, Mosiera longipes and Morella cerifera (Myricaceae). Due to the broad host range exhibited in quarantine testing, this species will not be pursued as a biological control agent of R. tomentosa.     

Ecological correlates of invasion by <Emphasis Type="Italic">Arundo donax</Emphasis> in three southern California riparian habitats

Arundo donax L. (Poaceae) is an aggressive invader in California’s riparian habitats. Field experiments were conducted to examine invader and site attributes important in early invasion. One hundred A. donax rhizomes were planted along five transects into each of three southern California riparian habitats. Pre-planting rhizome weight was recorded, along with site variables including percent bare ground, litter depth, PAR, soil moisture, soil temperature, incidence of herbivory, native canopy cover, and plant community richness and diversity. A. donax shoot emergence, survival time, and shoot height were recorded for approximately 10 months. The experiment was repeated over three years in different locations within each site. When years and sites were pooled to reveal large-scale patterns, A. donax performance was explained by rhizome weight, soil moisture, bare ground, soil temperature, and herbivory. When each site was considered singly, A. donax was positively correlated with different variables in each location. Species richness was correlated with A. donax performance in only one site. Our results indicate that A. donax establishment in riparian habitats is promoted by both vegetative reproduction and favorable abiotic environmental factors and relatively unaffected by the composition of the native community. The positive response of A. donax to disturbance (bare ground) and high resource availability (soil moisture), combined with a competitive perennial habit suggest that this species takes advantage of a competitive-ruderal life history. The ability of A. donax to respond to different conditions in each site combined with low genetic and phenotypic variation seen in other studies also suggests that a high degree of environmental tolerance contributes to invasion success.