Herbicide evaluation for the control of wild taro

Wild taro (Colocasia esculenta (L.) Schott), is an exotic, emergent perennial that has established in many shallow-water wetlands throughout the southern United States. Although wild taro is a cultivated crop in many tropical and subtropical areas of the world, its invasion in riverine and lacustrine wetlands in the U.S. has resulted in the loss of habitat for native plant species. Once established, wild taro forms dense, monotypic stands that reduce the diversity of native vegetation, as has occurred in Louisiana, Florida, and Texas (Akridge and Fonteyn 1981, Simberloff et al. 1997). Akridge and Fonteyn (1981) reported that although wild taro is considered naturalized in south-central Texas, its present dominance along the San Marcos River has altered the native vegetational structure and dynamics of this river system. The objective of this study was to evaluate the efficacy of four aquatic herbicides for control of wild taro.

The weevil-watermilfoil interaction at different spatial scales: what we know and what we need to know

The North American weevil ( Euhrychiopsis lecontei (Dietz)) is being considered as a biological control agent for Eurasian watermilfoil ( Myriophyllum spicatum L.). This native insect damages watermilfoil plants and is frequently associated with declining watermilfoil populations

Eurasian watermilfoil biomass associated with insect herbivores in New York

A study of aquatic plant biomass within Cayuga Lake, New York spans twelve years from 1987-1998. The exotic Eurasian watermilfoil ( Myriophyllum spicatum L.) decreased in the northwest end of the lake from 55% of the total biomass in 1987 to 0.4% in 1998 and within the southwest end from 50% in 1987 to 11% in 1998. Concurrent with the watermilfoil decline was the resurgence of native species of submersed macrophytes. During this time we recorded for the first time in Cayuga Lake two herbivorous insect species: the aquatic moth Acentria ephemerella , first observed in 1991, and the aquatic weevil Euhrychiopsis lecontei , first found in 1996 . Densities of Acentria in southwest Cayuga Lake averaged 1.04 individuals per apical meristem of Eurasian watermilfoil for the three-year period 1996-1998. These same meristems had Euhrychiopsis densities on average of only 0.02 individuals per apical meristem over the same three-year period. A comparison of herbivore densities and lake sizes from five lakes in 1997 shows that Acentria densities correlate positively with lake surface area and mean depth, while Euhrychiopsis densities correlate negatively with lake surface area and mean depth. In these five lakes, Acentria densities correlate negatively with percent composition and dry mass of watermilfoil. However, Euhrychiopsis densities correlate positively with percent composition and dry mass of watermilfoil. Finally, Acentria densities correlate negatively with Euhrychiopsis densities suggesting interspecific competition.

Euhrychiopsis lecontei distribution, abundance, and experimental augmentations for Eurasian watermilfoil control in Wisconsin lakes

The specialist aquatic herbivore Euhrychiopsis lecontei (Dietz) is currently being researched as a potential biological control agent for Eurasian watermilfoil (Myriophyllum spicatum L.). Our research in Wisconsin focused on 1) determining milfoil weevil distribution across lakes, 2) assessing limnological characteristics associated with their abundance, and 3) evaluating milfoil weevil augmentation as a practical management tool for controlling Eurasian watermilfoil.

Temporal and spatial changes in milfoil distribution and biomass associated with weevils in Fish Lake, WI

During the course of an eight year monitoring effort, the Wisconsin Department of Natural Resources documented a significant decline in milfoil biomass and distribution in Fish Lake, Wisconsin. Average milfoil biomass declined by 40- 50% from 374-524 g dw m -2 during 1991-93 to 265 g dw m -2 during both 1994 and 1995. Milfoil recovered fully in 1996- 98 to 446- 564 g dw m -2 . The size of the milfoil bed, as discerned from aerial photographs, shrank from a maximum coverage of 40 ha in 1991 to less than 20 ha during 1995. During the “crash” of 1994-95, milfoil plants exhibited typical signs of weevil-induced damage, including darkened, brittle, hollowed-out growing tips, and the arching and collapse of stems associated with loss of buoyancy. Monitoring of weevils and stem damage during 1995-98 showed highest densities and heaviest damage occurred near shore and subsequently fanned out into deeper water from core infestation sites each spring. The extent of milfoil stem damage was positively correlated with weevil densities (monthly sampling). However, weevil densities and stem damage were lower during 1995 (when milfoil biomass was in decline) than during 1996-98 (when milfoil biomass was fully recovered).

A decline of Eurasian watermilfoil in Minnesota associated with the milfoil weevil, Euhrychiopsis lecontei

Euhrychiopsis lecontei RAYMOND M. NEWMAN 1 AND DAVID D. BIESBOER 2 ABSTRACT The native milfoil weevil, Euhrychiopsis lecontei Dietz, is a candidate biological control agent for the exotic Eurasian watermilfoil ( Myriophyllum spicatum L.) in northern North America. Declines of Eurasian watermilfoil populations have been associated with the weevil but many of these examples are poorly documented. We report the first documented decline of Eurasian watermilfoil in Minnesota due to the milfoil weevil.

Relationship between water quality, watermilfoil frequency, and weevil distribution in the State of Washington

During the summer of 1997, we surveyed 50 waterbodies in Washington State to determine the distribution of the aquatic weevil Euhrychiopsis lecontei Dietz. We collected data on water quality and the frequency of occurrence of watermilfoil species within selected watermilfoil beds to compare the waterbodies and determine if they were related to the distribution E. lecontei . We found E. lecontei in 14 waterbodies, most of which were in eastern Washington. Only one lake with weevils was located in western Washington. Weevils were associated with both Eurasian ( Myriophyllum spicatum L.) and northern watermilfoil ( M. sibiricum K.). Waterbodies with E. lecontei had significantly higher ( P < 0.05) pH (8.7 ± 0.2) (mean ± 2SE), specific conductance (0.3 ± 0.08 mS cm -1 ) and total alkalinity (132.4 ± 30.8 mg CaCO 3 L -1 ). We also found that weevil presence was related to surface water temperature and waterbody location ( = 24.3, P ≤ 0.001) and of all the models tested, this model provided the best fit (Hosmer- Lemeshow goodness-of-fit = 4.0, P = 0.9). Our results suggest that in Washington State E. lecontei occurs primarily in eastern Washington in waterbodies with pH ≥ 8.2 and specific conductance ≥ 0.2 mS cm -1 . Furthermore, weevil distribution appears to be correlated with waterbody location (eastern versus western Washington) and surface water temperature.

Factors to consider when using native biological control organisms to manage exotic plants

Biological control of exotic plant populations with native organisms appears to be increasing, even though its success to date has been limited. Although many researchers and managers feel that native organisms are easier to use and present less risk to the environment this may not be true. Developing a successful management program with a native insect is dependent on a number of critical factors that need to be considered. Information is needed on the feeding preference of the agent, agent effectiveness, environmental regulation of the agent, unique requirements of the agent, population maintenance of the agent, and time to desired impact. By understanding these factors, researchers and managers can develop a detailed protocol for using the native biological control agent for a specific target plant. . We found E. lecontei in 14 waterbodies, most of which were in eastern Washington. Only one lake with weevils was located in western Washington. Weevils were associated with both Eurasian ( Myriophyllum spicatum L.) and northern watermilfoil ( M. sibiricum K.). Waterbodies with E. lecontei had significantly higher ( P < 0.05) pH (8.7 ± 0.2) (mean ± 2SE), specific conductance (0.3 ± 0.08 mS cm -1 ) and total alkalinity (132.4 ± 30.8 mg CaCO 3 L -1 ). We also found that weevil presence was related to surface water temperature and waterbody location ( = 24.3, P ≤ 0.001) and of all the models tested, this model provided the best fit (Hosmer- Lemeshow goodness-of-fit = 4.0, P = 0.9). Our results suggest that in Washington State E. lecontei occurs primarily in eastern Washington in waterbodies with pH ≥ 8.2 and specific conductance ≥ 0.2 mS cm -1 . Furthermore, weevil distribution appears to be correlated with waterbody location (eastern versus western Washington) and surface water temperature.

Panel Discussion - Management of Eurasian watermilfoil in the United States using native insects: State regulatory and management issues

While researchers have evaluated the potential of native insect herbivores to manage nonindigenous aquatic plant species such as Eurasian watermilfoil ( Myriophyllum spicatum L.), the practical matters of regulatory compliance and implementation have been neglected. A panel of aquatic nuisance species program managers from three state natural resource management agencies (Minnesota, Vermont and Washington) discussed their regulatory and policy concerns. In addition, one ecological consultant attempting to market one of the native insects to manage Eurasian watermilfoil added his perspective on the special challenges of distributing a native biological control agent for management of Eurasian watermilfoil.

Hydrillae (Hydrocharitaceae) in Europe. [translation of key to Hydrilla only] [Translation from: Goettinger Floristische Rundbriefe 14 33-56, 1980]

This partial translation of a bigger publication provides an identification key to the aquatic plant Hydrillae (Hydrocharitaceae) in Europe. Illustrations are included.

The scope for biomanipulation in improving water quality

Biomanipulation is a form of biological engineering in which organisms are selectively removed or encouraged to alleviate the symptoms of eutrophication. Most examples involve fish and grazer zooplankton though mussels have also been used. The technique involves continuous management in many deeper lakes and is not a substitute for nutrient control. In some lakes, alterations to the lake environment have given longer-term positive effects. And in some shallow lakes, biomanipulation may be essential, alongside nutrient control, in re- establishing former aquatic-plant-dominated ecosystems which have been lost through severe eutrophication. The emergence of biomanipulation techniques emphasises that lake systems are not simply chemical reactors which respond simply to engineered chemical changes, but very complex and still very imperfectly understood ecosystems which require a yet profounder understanding before they can be restored with certainty.

水生植物凤眼莲的种内基因型差异与入侵模式

原产于亚马逊河流域的水生植物凤眼莲（Eichhornia crassipes）在花部结构上有三种花型（L、M和S），故其配殖系统（mating system）为典型的三型花柱（tristyly）。但在入侵地区，它却常只有M和L两种花型，其中尤以M型占据绝对优势，使有性繁殖水平大为下降。为了解释凤眼莲在入侵过程中，花型频率为何发生变化以及该变化对其在入侵地的适应性进化上有何影响，作者在中国西南的两个居群中连续两年开展了野外生长和人工授粉实验，对比分析水面和泥地两类不同生境中M和L在克隆生长、生物量积累以及有性繁殖水平等方面的异同，并利用RAPD、 ISSR片段比较了具M型和L型花植物个体间的遗传变异水平。对三型花柱这一长期引人注目的遗传模式的分子位点也尝试了连锁片段的克隆和测序。 克隆生长的对比实验发现，在2004年，漂浮生长的M个体平均克隆分株数为25.37，L为21.20，前者显示较强的克隆生长能力（t＝2.252， P< 0.05）;2005年的实验再次证实M（每个个体19.83个分株）比L（每个个体15.53分株）表现出了显著较强的克隆优势（t＝2.631，P<0.001）。M较L多产生克隆约24%。 但在岸边泥地上固着生长时，2004年L个体平均克隆分株为16.20，M 为10.17个分株。L表现出了更强的克隆生长能力（t＝4.788，p<0.001），与漂浮生长状况下的情形恰恰相反，暗示M与L个体可能存在一定的生态位分化。这种分化可能是在入侵过程中形成的，也可能反映了原产地亚马孙流域旱涝交替造成的固着生长与漂浮生长交替发生的种内适应性。 生物量（干重）的对比分析发现，M个体在漂浮生长和固着生长的情况下都比L有着更高的生物量积累（漂浮生长实验：t＝6.173，p<0.005（2004年）;t＝6.99，p<0.001（2005年）。固着生长实验：t＝4.029，p<0.001）。生物量对凤眼莲的竞争和过冬有着一定的作用，因此较大的生物量积累可能是M个体在当地气候和环境中逐渐适应的一个结果。 有性繁殖的实验包括了实验个体的花序数与花朵数、自交与异交人工授粉的结实情况以及种子萌发率等方面的对比分析。结果表明，虽然M和L个体在花序数和花朵数上不存在显著差异，但是M个体在自交和异交的种子产量上比L略高，尤其是自交的种子产量，M显著高于L（M平均每个蒴果的自交种子产量为139.8，L为76.2）。以各100粒种子进行萌发实验，发现两花型之间在种子萌发率上不存在显著差异。对于M而言，其自交种子产量远大于异交种子产量 （139.8 vs. 93.3），且种子萌发率也略大于异交的种子萌发率（自交种子萌发率45.47％，异交种子萌发率 30.73％）。结合以上的实验结果，本文认为M基因型优势的形成可能与M个体与当地环境长期适应导致的生长与繁殖 上的优势有关。M的本地适应性是建立在特定的遗传背景上时，异交反而会破坏这种遗传组合，造成远交衰退。 对40个M和30个L个体进行20个RAPD引物和20个ISSR引物的遗传分析时发现，所有个体在RAPD表型上没有区别，但是在M中出现了3个ISSR表型，在L中出现了2个ISSR表型。本文还尝试利用RAPD技术扫描与三型花柱的遗传位点连锁的DNA片段。在146个RAPD随机引物中，初步发现两个候选片段，一个750bp，另一个2 000bp;已对它们进行了克隆、测序。 这些初步实验表明凤眼莲在我国的入侵可能伴随着基因型的差异表现和居群遗传分化，这种基因型的差异表现对该植物的成功入侵具有作用。其中，花型为M的个体的优势生长解释了该花型在中国分布区内的主导地位。推测该生长优势的遗传基础可能来源于基因组内较高的杂合子水平和在入侵地较长的适应历史，但最终结论尚有待进一步的实验证据。

Agri-aqua farming in Thailand

Integrated agriculture-aquaculture systems have been in existence in Thailand for centuries. This country has the most varied integrated farming operations in southeast Asia; pig, cattle, buffalo, chicken, duck, vegetable, aquatic plant, rice and orchard in combination with fish are practices. The systems most preferred by subsistence farmers are rice-fish, duck-fish and chicken-fish culture. A brief outline is given of these 3 systems.

Combining global climate and regional landscape models to improve prediction of invasion risk

Aim
It is widely acknowledged that species distributions result from a variety of biotic and abiotic factors operating at different spatial scales. Here, we aimed to (1) determine the extent to which global climate niche models (CNMs) can be improved by the addition of fine-scale regional data; (2) examine climatic and environmental factors influencing the range of 15 invasive aquatic plant species; and (3) provide a case study for the use of such models in invasion management on an island.

Location
Global, with a case study of species invasions in Ireland.

Methods
Climate niche models of global extent (including climate only) and regional environmental niche models (with additional factors such as human influence, land use and soil characteristics) were generated using maxent for 15 invasive aquatic plants. The performance of these models within the invaded range of the study species in Ireland was assessed, and potential hotspots of invasion suitability were determined. Models were projected forward up to 2080 based on two climate scenarios.

Results
While climate variables are important in defining the global range of species, factors related to land use and nutrient level were of greater importance in regional projections. Global climatic models were significantly improved at the island scale by the addition of fine-scale environmental variables (area under the curve values increased by 0.18 and true skill statistic values by 0.36), and projected ranges decreased from an average of 86% to 36% of the island.

Main conclusions
Refining CNMs with regional data on land use, human influence and landscape may have a substantial impact on predictive capacity, providing greater value for prioritization of conservation management at subregional or local scales.

Effects of Elodea nuttallii on temperate freshwater plants, microalgae and invertebrates: small differences between invaded and uninvaded areas

The invasive aquatic plant species Elodea nuttallii could pose a considerable risk to European freshwater ecosystems based on its current distribution, rate of spread and potential for high biomass. However, little research has been conducted on the impacts of this species on native biota. This study takes an ecosystem-wide approach and examines the impact of E. nuttallii on selected physicochemical parameters (dissolved oxygen and pH), algae, invertebrate and macrophyte communities. Elodea nuttallii had small but significant impacts on plant, invertebrate and algal species. The richness of algal periphyton was lower on E. nuttallii than on native macrophytes. The taxonomic composition of invertebrate communities associated with E. nuttallii differed from that associated with similar native plant species, but did not differ in terms of total biomass or species richness. Macrophyte species richness and total cover were positively correlated with percentage cover of E. nuttallii. Not all macrophyte species responded in the same way to E. nuttallii invasion; cover of the low-growing species, Elodea canadensis and charophytes were negatively correlated with E. nuttallii cover, whilst floating-rooted plants were positively correlated with E. nuttallii cover. All observed differences in the macrophyte community were small relative to other factors such as nutrient levels, inter-annual variation and differences between sites. Despite this, the observed negative association between E. nuttallii and charophytes is a key concern due to the rarity and endangered status of many charophyte species.