Sean T. Murphy

Impacts of an Invasive Non-Native Annual Weed, Impatiens glandulifera, on Above- and Below-Ground Invertebrate Communities in the United Kingdom

Vegetation community composition and the above- and below-ground invertebrate communities are linked intrinsically, though few studies have assessed the impact of non-native plants on both these parts of the community together. We evaluated the differences in the above- (foliage- and ground-dwelling) and below-ground invertebrate communities in nine uninvaded plots and nine plots invaded by the annual invasive species Impatiens glandulifera, in the UK during 2007 and 2008. Over 139,000 invertebrates were identified into distinct taxa and categorised into functional feeding groups. The impact of I. glandulifera on the vegetation and invertebrate community composition was evaluated using multivariate statistics including principal response curves (PRC) and redundancy analysis (RDA). In the foliage-dwelling community, all functional feeding groups were less abundant in the invaded plots, and the species richness of Coleoptera and Heteroptera was significantly reduced. In the ground-dwelling community, herbivores, detritivores, and predators were all significantly less abundant in the invaded plots. In contrast, these functional groups in the below-ground community appeared to be largely unaffected, and even positively associated with the presence of I. glandulifera. Although the cover of I. glandulifera decreased in the invaded plots in the second year of the study, only the below-ground invertebrate community showed a significant response. These results indicate that the above- and below-ground invertebrate communities respond differently to the presence of I. glandulifera, and these community shifts can potentially lead to a habitat less biologically diverse than surrounding native communities; which could have negative impacts on higher trophic levels and ecosystem functioning.

Reproductive Biology of Two Nontarget Insect Species, Aphis gossypii (Homoptera: Aphididae) and Orius sauteri (Hemiptera: Anthocoridae), on Bt and non-Bt Cotton Cultivars

Abstract Transgenic Bt cotton, engineered to continuously produce activated Δ-endotoxins of the soil bacteria Bacillus thuringiensis, holds great promise in controlling Helicoverpa armigera and other lepidopteran pests. However, it also may impact the invertebrate community, which needs to be clarified. The effects of Bt cotton on two nontarget insects, Aphis gossypii and Orius sauteri, were assessed under semifield and laboratory conditions. Mean total duration of nymphal stages of A. gossypii was shorter (5.9 versus 6.3 d), and rm was higher (0.418 versus 0.394) on conventional Simian 3 (the most frequently planted non-Bt cotton in northern China) than on Bt transgenic NuCOTN 33B (the first Bt cotton commercially planted in China). Mean duration of fourth-instar O. sauteri was significantly longer on transgenic GK-12 (3.7 d) than on NuCOTN 33B (3.2 d), but no different from Simian 3. Mean total mortality was significantly lower on Simian 3 (3.7%) than on GK-12 (14.8%). During the fourth instar, the predator consumed a significantly higher number of prey on Simian 3 (202.3 prey) than on NuCOTN 33B (159.0), whereas the mean total number of A. gossypii prey consumed during the nymphal stage was significantly higher on Simian 3 (336.8 prey) and GK-12 (330.3 prey) than on NuCOTN 33B (275.7). No detrimental effects were detected on development (nymphs, adults, and progeny eggs), fecundity, longevity, and egg viability of O. sauteri on Bt cotton aphids compared with non-Bt cotton aphids. These results suggest that Bt cotton cultivars GK-12 and NuCOTN 33B have no direct effect on nontargets A. gossypii and O. sauteri. Germplasm divergence may account for the negative effects observed on A. gossypii and O. sauteri when reared on NuCOTN 33B or NuCOTN 33B-fed aphids. The biological meanings of the small difference observed between GK-12 and Simian 3 on survival of O. sauteri will require close monitoring over longer time periods.

Within-season dynamics of red palm mite (Raoiella indica) and phytoseiid predators on two host palm species in south-west India.

Field surveys were conducted monthly between December 2008 and July 2009 in Kerala, south-west India to compare the population dynamics of the red palm mite Raoiella indica (RPM) on two host plants Areca catechu and Cocos nucifera during one non-monsoon season when, in general, RPM populations increase. The aim was to examine the effects of host plant, host plant locality and the impact of climatic factors on RPM and related phytoseiid predators. There were significantly higher RPM densities on areca in peak season (May/June) compared to coconut; although significantly more coconut sites were infested with RPM than areca. Although no one climatic factor was significantly related to RPM numbers, interactions were found between temperature, humidity and rainfall and the partitioning of host plant locality showed that where conditions were warmer and drier, RPM densities were significantly higher. Specifically on coconut, there was a significant relation between RPM densities and the combined interaction between site temperature, site humidity and phytoseiid densities. There was a marked difference in the density of phytoseiids collected between areca and coconut palms, with significantly more on the latter, in several months. Amblyseius largoensis was the most commonly collected phytoseiid in association with RPM, although Amblyseius tamatavensis species group and Amblyseius largoensis species group were collected in association with RPM also. There was also evidence of a weak numerical response of the combined phytoseiid complex in relation to RPM density the previous month on coconut but this was not observed on areca.

Temperature and plant nutrient effects on the development, survival and reproduction of Cinara sp. nov., an invasive pest of cypress trees in Africa

Cinara sp. nov., previously identified as Cinara cupressi (Buckton) (Homoptera: Aphididae), is an important alien aphid pest of cypresses and junipers, and invaded Africa in the late 1980s. The work reported here was carried out as part of a larger programme aimed at the classical biological control of the aphid in Africa. Basic life history attributes including life table statistics of the aphid were quantified in order to facilitate the development of efficient aphid culturing methods and essential baseline information necessary for the culturing of potential parasitoid biological agents prior to selection for introduction to Africa. Developmental rates and fecundity were studied under four constant temperatures (10 °C, 15 °C, 20 °C, and 25 °C). The effects of several plant nutrients (nitrogen, potassium and phosphorus) supplied at different dose levels on life history attributes of Cinara sp. nov. were also studied.

Invasive mikania in Chitwan National Park, Nepal: the threat to the greater one-horned rhinoceros Rhinoceros unicornis and factors driving the invasion

As part of a census of the Indian rhinoceros Rhinoceros unicornis a survey was conducted to measure the extent of invasion by the neotropical plant mikania Mikania micrantha across major habitats of Chitwan National Park important for the conservation of the rhinoceros. Previous work has demonstrated that this fire-adapted plant can smother and kill native flora such as grasses and sapling trees, several of which are important fodder plants of the rhinoceros. Here, additional studies were conducted on the risks of anthropogenic factors (natural resource collection and grassland burning) contributing to the spread and growth of the plant. Mikania is currently found across 44% of habitats sampled and almost 15% of these have a high infestation (> 50% coverage). Highest densities were recorded from riverine forest, tall grass and wetland habitats and this is where the highest numbers of rhinoceroses were recorded in the habitats surveyed during the census. Local community dependence on natural resources in the core area of the Park is high. The range and volume of resources (e.g. fodder) collected and the distances travelled all pose a high risk of the spread of mikania. Of greater significance is the annual burning of the grasslands in the Park by local communities, estimated at 25–50% of the total area. It is imperative, therefore, that core elements of a management plan for mikania incorporate actions to control burning, reduce spread and raise awareness about best practice for local resource management by local communities.

An ecological comparison of Impatiens glandulifera Royle in the native and introduced range

Understanding the ecology of plant species in their whole range (native and introduced) can provide insights into those that become problematic weeds in the introduced range despite being benign components of the vegetative community in the native range. We studied the morphological traits of Impatiens glandulifera in the native (Indian Himalayas) and introduced (UK) range and evaluated what influences natural enemies and arbuscular mycorrhizal fungi (AMF) have on plant performance. We compared height, total leaf area, root: shoot ratio, natural enemy damage and the colonisation of AMF from individual plants within and between ranges twice in 2010 during the months of June and August. In addition, in August 2010, we estimated the number of reproductive units (expressed as the sum of flowers, seed capsule and seeds) at each site. We found that all morphological traits varied between populations and countries, though in general introduced populations, and the semi-natural population in India, showed higher performance compared to natural native populations. There was only an indication that natural enemy damage, which was significantly higher in the native range, negatively affected reproductive units. Within the introduced range, the percentage colonisation of AMF was negatively associated with plant performance indicating that I. glandulifera may associate with an incompatible AMF species incurring a cost to invasive populations. We conclude that species which are heavily regulated in the native range, though still show high levels of performance, should be considered undesirable introductions into similar ecoclimatic ranges due to the potential that these species will become highly invasive species.

Host Age Choice for Oviposition in Pauesia juniperorum (Hymenoptera: Braconidae: Aphidiinae) and its Effect on the Parasitoid's Biology and Host Population Growth

Pauesia juniperorum has been selected as a potential agent for the biological control of Cinara cupressivora, an important introduced pest of conifers in Africa. As part of the pre-introductory assessment studies, selection of different host age categories for oviposition was studied in choice and no choice experiments. The duration of development and adult size of parasitoid progeny developing in different host age categories were compared. The effects of parasitism on survival and reproduction of five categories of the apterous morph of the host ranging in age from 3-15 days was also studied. The age of hosts had a significant influence on the degree with which different categories were parasitized. Host defensive behaviour, which increased with age, influenced the outcome of attempts by the parasitoid to oviposit. The effect was greater in older hosts, but in young hosts their small size was more important in enabling aphids to escape parasitism. The duration of development decreased while adult size i...

The Invasive Liriomyza huidobrensis (Diptera: Agromyzidae): Understanding Its Pest Status and Management Globally

Liriomyza huidobrensis (Blanchard) is native to South America but has expanded its range and invaded many regions of the world, primarily on flowers and to a lesser extent on horticultural product shipments. As a result of initial invasion into an area, damage caused is usually significant but not necessarily sustained. Currently, it is an economic pest in selected native and invaded regions of the world. Adults cause damage by puncturing abaxial and adaxial leaf surfaces for feeding and egg laying sites. Larvae mine the leaf parenchyma tissues which can lead to leaves drying and wilting. We have recorded 365 host plant species from 49 families and more than 106 parasitoid species. In a subset of the Argentinian data, we found that parasitoid community composition attacking L. huidobrensis differs significantly in cultivated and uncultivated plants. No such effect was found at the world level, probably due to differences in collection methods in the different references. We review the existing knowledge as a means of setting the context for new and unpublished data. The main objective is to provide an update of widely dispersed and until now unpublished data, evaluate dispersion of the leafminer and management strategies in different regions of the world, and highlight the need to consider the possible effects of climate change on further regional invasions or expansions.

Would the control of invasive alien plants reduce malaria transmission? A review

Vector control has been the most effective preventive measure against malaria and other vector-borne diseases. However, due to concerns such as insecticide resistance and budget shortfalls, an integrated control approach will be required to ensure sustainable, long-term effectiveness. An integrated management strategy should entail some aspects of environmental management, relying on coordination between various scientific disciplines. Here, we review one such environmental control tactic: invasive alien plant management. This covers salient plant-mosquito interactions for both terrestrial and aquatic invasive plants and how these affect a vector’s ability to transmit malaria. Invasive plants tend to have longer flowering durations, more vigorous growth, and their spread can result in an increase in biomass, particularly in areas where previously little vegetation existed. Some invasive alien plants provide shelter or resting sites for adult mosquitoes and are also attractive nectar-producing hosts, enhancing their vectorial capacity. We conclude that these plants may increase malaria transmission rates in certain environments, though many questions still need to be answered, to determine how often this conclusion holds. However, in the case of aquatic invasive plants, available evidence suggests that the management of these plants would contribute to malaria control. We also examine and review the opportunities for large-scale invasive alien plant management, including options for biological control. Finally, we highlight the research priorities that must be addressed in order to ensure that integrated vector and invasive alien plant management operate in a synergistic fashion.

Forecasting the global extent of invasion of the cereal pest Spodoptera frugiperda, the fall armyworm

Fall armyworm, Spodoptera frugiperda, is a crop pest native to the Americas, which has invaded and spread throughout sub-Saharan Africa within two years. Recent estimates of 20-50% maize yield loss in Africa suggest severe damage to livelihoods. Fall armyworm is still infilling its potential range in Africa, and could spread to other continents. In order to understand fall armyworm’s year-round, global, potential distribution, we used evidence of the effects of temperature and precipitation on fall armyworm life-history, combined with data on native and African distributions to construct Species Distribution Models (SDMs). Fall armyworm has only invaded areas that have a climate similar to the native distribution, validating the use of climatic SDMs. The strongest climatic limits on fall armyworm’s year-round distribution are the coldest annual temperature and the amount of rain in the wet season. Much of sub-Saharan Africa can host year-round fall armyworm populations, but the likelihoods of colonising North Africa and seasonal migrations into Europe are hard to predict. South and Southeast Asia and Australia have climate that would permit fall armyworm to invade. Current trade and transportation routes reveal Australia, China, India, Indonesia, Malaysia, Philippines, and Thailand face high threat of fall armyworm invasions originating from Africa.