Plant Invaders of Cortland County Results of 2004 Invasive Species Survey

Transcription

1 Plant Invaders of Cortland County Results of 2004 Invasive Species Survey Cortland County Soil and Water Conservation District 100 Grange Place, Room 202 Cortland, NY 13045

2 Plant Invaders of Cortland County The Cortland County Soil and Water Conservation District conducted an invasive plant species survey in the lakes and ponds of Cortland County. The purpose of this survey was to determine if invasive species were present, and if present, their general distribution within and around these bodies of water. This survey is the first step in controlling invasive species. It is necessary for us to know if invasive species exist in this county so steps can be taken to eradicate or control them before their population grows to a point where it is not economically or physically feasible to do so. This survey was conducted in July and August of 2004, and was completed with the assistance of funding through the Finger Lakes Lake Ontario Watershed Protection Alliance (FL LOWPA). Introduction: Invasive plants are species that are not native to a certain area, and that reproduce rapidly, spread over large areas of the landscape and have few, if any, natural controls, such as herbivores and diseases, to keep them in check (J. Swearingen et. al.). Some characteristics that many invasive plant species have in common include: spreading aggressively by runners or rhizomes; producing large numbers of seeds that survive to germinate; and dispersing seeds away from the parent plant through various means such as wind, water, wildlife and people (J. Swearingen et. al.). When these species are introduced, they create many problems for the native communities and ecosystems, some of which include growing and spreading rapidly over large areas, displacing native plants, including some very rare species, reducing food and shelter for 1

3 native wildlife, eliminating host plants of native insects and competing for native plant pollinators. Invasive species are capable of out-competing the native species until they become the only species present in the area, which obviously greatly diminishes biological diversity. In addition to the affects on nature, aquatic invasive plant species can also hinder recreational activities such as boating and fishing. For this study, the larger bodies of water in Cortland County were surveyed for the presence of invasive plant species (Figure 1). The bodies of water observed were Upper Little York Lake, Song Lake, Tully Lake, Green Lake, Goodale Lake, Cincinnatus Lake, Melody Lake, Lake Lorraine, Stump Pond, Solon Pond, and Glover Pond. We researched known invasive species in Central New York to focus the survey on species that were most likely to be present. The invasive plant species that we searched for and found in these lakes and ponds included: Eurasian watermilfoil (Myriophyllum spicatum), purple loosestrife (Lythrum salicaria), Japanese knotweed (Polygonum cuspidatum), water chestnut (Trapa natans), and curly-leaved pondweed (Potamogeton crispus L.) (Appendix A includes a summary describing each species and providing information on ways to identify and eradicate or control them). During our time on the lakes and ponds, we also searched for zebra mussels (Dreissena polymorpha), which have the potential to create a variety of negative impacts. Fortunately, we did not see any in the water bodies of Cortland County, although we have heard reports of zebra mussels residing in Upper Little York Lake. Materials and Methods: We began by investigating the largest lakes first, which included Upper Little York, Tully, Song, and Cincinnatus. We used a rowboat to travel around the perimeter of 2

4 3

5 each lake to observe whether or not the aforementioned invasive species were present. If found, various data was recorded, such as the name of the species, its general magnitude or coverage area, as well as its depth, distance to shoreline, and coordinates within the lake. A sample of each invasive species found from each lake was taken and placed in a labeled plastic bag for our record and identification purposes. Results: We found invasive species of plants in all but two of the water bodies in the survey. A summary of the survey for each water body is presented below. Song Lake Both purple loosestrife and Eurasian watermilfoil were flourishing in Song Lake. Purple loosestrife was seen in fairly large patches all along the shoreline of the lake, while Eurasian watermilfoil was growing densely in most areas. These two invaders were both especially noticeable in a shallow section on the northeast part of the lake. Tully Lake Our observations in Tully Lake were similar to Song Lake. There were many patches of purple loosestrife along the entire shoreline, however, the infestation of Eurasian watermilfoil was much less severe. There were only a few patches of Eurasian watermilfoil protruding through a thick mat of vegetation. Upper Little York Lake This lake also contained purple loosestrife and Eurasian watermilfoil. Purple loosestrife was very sparse. Only about five small patches were seen dispersed along the perimeter of the lake. Eurasian watermilfoil was abundant in every section of the lake between a depth of approximately 3 and 15 feet. 4

6 Green Lake Despite being connected to Upper Little York Lake via a stream, Green Lake was almost entirely free of invasive plant species. There were, however, a few purple loosestrife and Eurasian watermilfoil plants seen. Goodale Lake Goodale Lake is also connected to Upper Little York Lake, but contains many more aquatic weeds. We saw small patches of purple loosestrife along the entire shoreline. Thick patches of curly-leaved pondweed were present at the north end of the lake. Surprisingly, no Eurasian watermilfoil was seen, but many other aquatic plants were abundant. Cincinnatus Lake This was the only lake or pond observed in Cortland County containing Japanese knotweed and/or water chestnut. There were large patches of Japanese knotweed growing on the shoreline of the lake. The largest populations were seen on the north and east banks. Approximately five small patches (5-10 plants) of water chestnut were seen in the shallow waters on the west and north sides. Melody Lake Eurasian watermilfoil was growing in dense patches throughout most of this lake s perimeter, while only about four small patches of purple loosestrife were observed. Lake Lorraine We did not see any aquatic invasive plant species in Lake Lorraine, however, there were massive algae blooms during the time of observation, which greatly hindered visibility. 5

7 Stump Pond No invasive species were found in Stump Pond. It was completely dominated by an unidentified plant. Solon Pond Solon Pond contained small patches of both purple loosestrife and Eurasian watermilfoil scattered throughout the perimeter of the pond. Glover Pond Eurasian watermilfoil was a dominant plant in Glover Pond. This pond contained dense vegetation, and watermilfoil populated every section of it. Discussion: The aquatic invasive plant species that have become the most abundant in the lakes and ponds of Cortland County are purple loosestrife and Eurasian watermilfoil. Purple loosestrife was present in seven of the eleven lakes/ponds observed, while Eurasian watermilfoil was found in nine. In contrast, Japanese knotweed, water chestnut, and curly pondweed were each only found in one of the eleven lakes/ponds. Presently, it appears as if purple loosestrife and Eurasian watermilfoil pose a more significant threat to Cortland County s aquatic health, however, Japanese knotweed, water chestnut, and curly pondweed have the ability to spread very rapidly. Also, Japanese knotweed is more commonly found along streams and rivers, which is consistent within this county (J. Swearingen et. al.). Conclusion & Recommendations: The five invasive plant species observed in this study are potentially very threatening to the aquatic habitats of Cortland County. There are many mechanical, 6

8 chemical, and biological methods of controlling the spread of these invaders, some of which are more effective than others (See Appendix A). Because these species have the ability to spread rapidly, it is very important to implement these control methods as soon as they are found in a habitat. In particular, we recommend that the water chestnut in Cincinnatus Lake be addressed in Because of the relatively sparse population, we believe this plant can be eliminated or significantly controlled with a relatively small amount of effort. It is important to note that our study was limited. We were prepared to identify the five aquatic invasive species that were already known to exist in the Central New York area. It is quite possible that other invasive species inhabit these lakes and ponds. Also, our observations were limited to the perimeters and shallow sections of each lake and pond. The deeper portions, where we were unable to see the bottom, may harbor invasive species. To assist in maintaining the welfare of the lakes in this county, it is a good idea to form active lake associations. With the development of a lake association, the residents of the lake may be more efficient at noticing and dealing with problems within the lake. A lake association may also have the responsibility of collecting funding for projects such as control methods for invasive species. References: 1) Swearingen, J., K.Reshetiloff, B. Slattery, and S. Zwicker Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, Washington, D.C. 82 pp. 2) 3) 7

9 4) 5) 6) 8

10 Appendix A: Eurasian Watermilfoil (Myriophyllum spicatum L.) Origin: Eurasia and Africa Description: Eurasian watermilfoil, also called spike watermilfoil, is an emergent, herbaceous aquatic plant in the Water-milfoil family, or Haloragaceae. Stems grow to the water surface, usually extending 3 to 10, but as much as 33, feet in length and frequently forming dense mats. Stems of Eurasian milfoil are long, slender, branching, hairless, and become leafless toward the base. New plants may emerge from each node (joint) on a stem, and root upon contact with mud. The grayish-green leaves of Eurasian watermilfoil are finely divided and occur in whorls of three or four along the stem, with pairs of fine, thin leaflets about 12 inches long. These leaflets give milfoil a feathery appearance that is a distinguishing feature of the plant. Eurasian watermilfoil produces small yellow, 4-parted flowers on a spike that projects 2-4 inches above the water surface. The fruit is a hard, segmented capsule containing four seeds. Habitat in the United States: Typical habitat for Eurasian watermilfoil includes fresh to brackish water of fish ponds, lakes, slow-moving streams, reservoirs, estuaries, and canals. It is tolerant of many water pollutants. Eurasian watermilfoil tends to invade disturbed areas where native plants cannot adapt to the alteration. It does not spread rapidly into undisturbed areas where native plants are well established. By altering waterways, humans have created a new and unnatural niche where milfoil thrives. Problem: Dense canopies of Eurasian water-milfoil shade out native vegetation, alter the species composition of aquatic invertebrates and may impair the ability of some fish species to spawn. Due to the plant s ability to form dense stands, water recreation activities such as swimming, boating and fishing are impaired. The sheer mass of plants can also cause flooding and the stagnant mats that can create good habitat of mosquitoes. Milfoil mats can rob oxygen from the water by preventing the wind from mixing the 9

11 oxygenated surface waters with deeper water. The dense mats of vegetation can also increase the sedimentation rate by trapping sediments. Control Methods Prevention through education is very important Mechanical Rotovation (underwater rototilling), installation of bottom barriers, hand pulling by divers, and dredging harvesters are the most common methods of Eurasian water-milfoil control. To be effective, all fragments must be collected and removed from the site. Manipulations of the water level, where feasible, may have an effect on the plant. Low water levels can desiccate populations and high levels will cause plants to decline by not giving them access to enough light. Harvesting has been conducted on lakes in Cortland County in the past. Chemical In smaller water bodies (350 acres or less), there has been some success using fluridone to control Eurasian water-milfoil and other aquatic weeds. Chemical controls would likely need to be approved by the NYS Department of Conservation. Biological A native North American weevil (Eurhychipsis lecontei) has been found to feed and reproduce on Eurasian water-milfoil. This insect may be a useful biocontrol agent; however, although it seems to prefer Eurasian water-milfoil, it also feeds on native water-milfoils including M. exalbescens and M. verticillatum, both of which are state endangered species. Another invertebrate that has been found to feed on Eurasian water-milfoil is the European aquatic moth. Studies have shown the presence of this insect significantly declining the population of Eurasian water-milfoil. Other biological control methods, including a fungus (Mycoleptidiscus terrestris), are currently being studied. In some very limited situations triploid (sterile) grass carp may be useful. Stocking with grass carp is regulated by the Pennsylvania Fish and Boat Commission. Cornell University is currently conducting research into better understanding biological control of this plant. 10

12 Purple Loosestrife (Lythrum salicaria L.) Origin: L. salicaria, a plant of European origin, has spread and degraded temperate North American wetlands since the early nineteenth century. The plant was introduced both as a contaminant of European ship ballast and as medicinal herb for treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores. Description: L. salicaria is a herbaceous, wetland perennial that grows in a wide range of habitats. Established plants can reach heights of 6 feet with stems forming wide-topped crowns that dominate the herbaceous canopy. One mature plant can produce more than 2 million seeds annually. Seeds are easily dispersed by water and in mud adhered to aquatic wildlife, livestock and people. High temperatures (>68 F) and open, moist soils are required for successful germination. A woody rootstock serves as a storage organ, providing resources for growth in spring and regrowth if the above-ground shoots are cut or damaged. Distribution and Spread: By the 1830's, L. salicaria was well established along the New England seaboard. The construction of inland canals and waterways in the 1880's favored the expansion of the plant into interior New York and the St. Lawrence River Valley. The continued expansion of L. salicaria coincided with increased development and use of road systems, commercial distribution of the plant for horticultural purposes, and regional propagation of seed for bee forage. As of 1996, L. salicaria is found in all contiguous states (except Florida) and all Canadian provinces. Problem: Invasion of L. salicaria into a wetland can result in the suppression of the resident plant community and the eventual alteration of the wetland's structure and function. Large monotypic stands of L. salicaria jeopardize various threatened and 11

13 endangered native wetland plants and wildlife by eliminating natural foods and cover. Dense plant establishments in irrigation systems has impeded the flow of water. Previous Control Methods: No effective method is available to control L. salicaria, except where it occurs in small localized stands and can be intensively managed. In such isolated areas, uprooting the plant by hand and ensuring the removal of all vegetative parts can eliminate L. salicaria. Other control techniques include water-level manipulation, mowing or cutting, burning, and herbicide application. These control methods are costly, require continued long-term maintenance and, in the case of herbicides, are non-selective and environmentally degrading. Biological Control: Ideally, natural enemies, as well as competition with other plants, prevent many plants from expanding their distributions. In turn, the abundance of the plant (acting as a host) influences the abundance of its natural enemies. L. salicaria was introduced to North America without its natural enemies. Four host specific insect species approved by USDA-APHIS have been released in the US. These species are Hylobius transversovittatus, a root-mining weevil, Galerucella calmariensis and Galerucella pusilla, two leaf-eating beetles, and Nanophyes marmoratus a flowerfeeding weevil. Nanophyes brevis, a seed feeding weevil, has been approved for introduction, however, European specimens are infested with a nematode, and this infection has prevented its introduction. Although infested adults of N. brevis do not show reduced life-spans or increased mortality and females lay fertile eggs, the potential for harmful effects of the nematode to indigenous North American insects exists. 12

14 Water Chestnut (Trapa natans) Origin: Europe, Asia and Africa Background Water chestnut was first observed in North America near Concord, Massachusetts in The exact path for the introduction is unknown. Description and Biology: Plant: an annual aquatic plant with a submerged stem; stems can reach 12 to 15 feet in length; very fine roots anchor the plant into the mud. Leaves: at the water's surface, the plant contains a rosette of floating leaves. The saw-tooth edged leaves are triangular in shape and connect to an inflated petiole, which provides added buoyancy for the leafy portion; additional, feather-like leaves can be found along the submerged stem. Flowers, fruits and seeds: four-petaled white flowers form in June and are insectpollinated. The fruit is a nut with four 1/2-inch, barbed spines. Seeds can remain viable for up to 12 years, although most will germinate within the first two years. Spreads: by the rosette and fruits detaching from the stem and floating to another area on currents or by fruits clinging to objects, birds and other animals. Distribution and Ecological Threat Water chestnut can grow in any freshwater setting, from intertidal waters to 12 feet deep, although it prefers nutrient-rich lakes and rivers. Presently, the plant is found in Maryland, Massachusetts, New York and Pennsylvania, with most problematic populations occurring in the Connecticut River valley, Lake Champlain region, Hudson River, Potomac River and the upper Delaware River. It is increasingly becoming a problem in Central New York. Water chestnut can form dense floating mats, severely limiting light -- a critical element of aquatic ecosystems. This plant can also reduce oxygen levels, which may increase the potential for fish kills. It competes with native 13

15 vegetation and is of little value to waterfowl. Water chestnut infestations limit boating, fishing, swimming and other recreational activities. Further, its sharp fruits, if stepped on, can cause painful wounds. Water chestnut has been declared a noxious weed in Arizona, Massachusetts, North Carolina and South Carolina. Its sale is prohibited in most southern states. Prevention and Control Methods Manual, mechanical and chemical techniques are used in its control. Complete removal of plants is imperative, as floating, uplifted plants and plant parts can spread the plant to new locations. It is critical that any removal take place in the summer before the nuts have a chance to mature and drop off the plant. Eradication is difficult because water chestnut seeds may lay dormant for up to 12 years. Once water chestnut is pulled out or cut, removal and disposal away from the water is essential to prevent re-establishment of the plants. Control programs and individual efforts can be successful in reducing and controlling infestation. Many areas that support monocultures of water chestnut may be freed of nuisance levels. Public agency control efforts, as well as increased citizen awareness and participation in hand pulling to control the spread, and preventing introduction to bodies of water are all necessary for future water chestnut management to succeed. Biological controls are being investigated, but no species have been approved for release. Cornell Cooperative Extension of Onondaga County has an active program to address water chestnut and other invasive species. 14

16 Japanese knotweed (Polygonum cuspidatum) Origin: Native to Japan, also North China, Taiwan, and Korea. Description: Japanese knotweed is a herbaceous perennial that grows very quickly on thick single stems, which appear reddish brown, and includes simple branches when large. Each joint is surrounded by a membranous sheath, making the joint seem swollen. It is notable for extreme height of branches which arch over and remain, brown, through the winter. Clumps of dark green oval leaves grow 8-10 inches long, 3-6 inches wide, and are pointed at the tip. Small greenish white flowers appear in the full summer. Seeds are minuscule, and the plant reproduces predominately via rhizomes. New growth emerges through the dead brown stems of the previous season, leading to dense thickets. Site and Date of Introduction: It was intentionally introduced to UK from Japan as an ornamental in 1825 (according to Leslie Seiger, Nature Conservancy, Element Stewardship Abstract). From there made it to U.S. by late nineteenth century. Habitat in the United States: It is found in at least 36 states in USA including northeastern U.S., California, Pacific Northwest, and Alaska (but not Hawaii, and not usually found south of North Carolina). Reason(s) Why it has Become Established: It grows extremely quickly: within 6 days, a viable plant exists from a rhizome as small as.7 grams, especially when rhizome is in water, which is why river/stream banks tend to get overwhelmed. It grows over 6 feet in first couple months of spring, shading out all other species around it. Even when the visible parts of the plant are cut away, the rhizomes sustain it, making it extraordinarily persistent. Japanese knotweed can withstand almost 15

17 all types of soil, light, and drought conditions. Its rhizomes will survive to grow plant even if buried 3 feet deep, or under asphalt. Benefit(s): Japanese knotweed can be eaten and is a good source of vitamin C. It has been used as an ornamental plant along pathways and to create hedges. Due to its ability to grow quickly and reproduce rapidly, it is useful in erosion control. It is also considered a medicinal herb. Threat(s): Japanese knotweed reduces biodiversity, because it forces out native plants through shade and thick ground cover. It damages wildlife habitat by reducing plant biodiversity, is expensive to treat, aesthetically displeasing, and causes damage to sidewalks and pavement. This invader is extremely difficult and time consuming to eradicate once it is established. Hybridization has already occurred on a wide scale, and the potential exists for much greater interbreeding/evolution, making it even more difficult to control. It has been declared a noxious weed in several states. Because the leaves and stems fall thickly and take a long time to decompose, no other plants (except the new Japanese knotweed shoots) can grow in an affected area, so it has the real potential to wreak havoc on native ecosystems. Control Method: Thoroughly digging out roots and stems takes years to succeed, if it ever does because even if a tiny speck of stem remains, the plant will regenerate. It is vital to burn or otherwise properly dispose of the plant scraps. Japanese knotweed can even ruin a compost pile. It takes a minimum of three years to get rid of it, either by cutting away to the stems and treating each stem with an herbicide such as Roundup or by covering the ground with black plastic and heating the soil to the point where the rhizome dies. Grazing animals can be used to consume the shoots, but this doesn t completely eradicate the plant. Types of biological control agents (BCA) are being studied. It is known that there are many insects and fungi that control the plant's spread in its native range, so prospects are hopeful (according to the Japanese Knotweed Alliance). 16

18 Curly-leaved pondweed (Potamogeton crispus L.) Description Potamogeton crispus is a submersed aquatic perennial that can reach 1-2.5feet in length. The turions of this plant are spindle-shaped, measure inches and can be located terminally or axillary. The stems of this plant are flattened. There are two ranks of leaves that are arranged spirally. The leaves are linear-oblong in shape, measure 1-3 inches long and inches wide. The leaf margins are undulate and the apex of the leaf is obtuse. The base of the leaf is sessile. The stipules of the leaf are small, thin and paper-like, and disintegrate early. The peduncles are inches in length and can be recurved when the plant is in fruit. The spike is dense and measures inches in length. The body of the red to reddish-brown achene is ovoid and measures 0.1 inches. The achene has 3 keels, with the middle keel having a small tooth projecting out from the base. The beak of the achene is conic and erect, measuring 0.1 inches. This plant has an unusual life history because it flowers and fruits in the late spring to early summer. The plant then dies, leaving only fruits and turions (vegetative reproductive structures) to survive the summer. The turions produce new plants in the late summer or fall, leaving small plants to overwinter, even sometimes under the ice. 17

19 Reproductive/Dispersal Mechanisms This plant spreads mostly by means of its vegetative turions that germinate in the fall. Potamogeton crispus does produce fruits and flowers, but the seeds do not appear to be viable. Distribution Potamogeton crispus is native to North Africa, India, the Middle East, Australia and Europe, from Portugal to Turkey and France to Italy, and also in Ireland to the north. It has been reported from all of the states of the U.S. except Alaska, Hawaii, Maine and South Carolina. In New England, this plant occurs in Vermont, New Hampshire, Massachusetts, Connecticut and Rhode Island. History of Introduction in the United States This plant was first collected in the U.S. in Wilmington, Delaware in The first New England record for this species was in 1880 near Arlington, Massachusetts. In 1900, it was collected from the southeastern part of New York and Long Island. Vermont first reported the plant in 1911, and Connecticut in Potamogeton crispus was most likely introduced accidentally with fish hatchery stock. However, another possibility it was introduced as a part of the aquarium trade. In all likelihood it was introduced in multiple places and spread from these different points of introduction. Habitats in New England Potamogeton crispus is tolerant of slightly brackish as well as fresh water. It can survive in low light, low temperatures and prefers high nutrient or alkaline water. Threats Potamogeton crispus can form dense mats of vegetation on the surface of the water. These mats inhibit the growth of native aquatics, as well as interfere with boating and other water recreation. Since these plants germinate in the fall, they overwinter under the ice and are therefore among the first plants out in the spring, giving it a competitive advantage. When the plants die off in the summer, the decaying plant matter can make the water extremely eutrophic. 18