Invasive Aquatic Plant Dynamics in North Carolina. Rob Richardson Crop Science Dept.

Transcription

1 Invasive Aquatic Plant Dynamics in North Carolina Rob Richardson Crop Science Dept.

2 How Do Aquatic Plants Spread? Human activities (wildlife plantings, boating, fishing enhancement, aquarium dumping, water gardens, dredging, mechanical harvesting) Animals (wading birds, aquatic mammals) Water movement Transport by wind and rain (seeds, spores)

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5 Why Are Some Aquatic Plants Invasive? Large areas of clear, shallow water High levels of nutrients, especially N and P No natural enemies (introduced weeds) Characteristics which make them more competitive than native plants Adapted to low light or CO 2 Adapted to intense sunlight and high temperatures

6 Why Control?

7 Hydrilla in Lake Gaston

8 Focus on Hydrilla Called the perfect aquatic weed #1 aquatic weed in U.S. Leaves in whorls of Serrated leaf margins Tubers can remain in sediment for over 7 years Very shade tolerant Low CO 2 compensation

9 Hydrilla Hydrilla verticillata

10 Egeria densa Hydrilla verticillata

11 Hydrilla HYDRILLA ONLY Egeria densa (Brazilian Elodea)

12 Hydrilla Spread 1991 Lake McIntosh Eno River Chowan River 2002 Lake Tillery

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15 Biotypes Monoecious Native to tropics Introduced 1980 s Invading NC north Less robust Herbaceous perennial May produce seed Tubers: Formed June Nov. Weight 36 to 77 mg 200 1,228 / m 2 Dioecious Native to temperates Introduced 1950 s Invading SC south More robust Root crown persists No seed production Tubers: Formed Oct. April Weight 160 to 376 mg / m 2

16 Avian Vacuolar Myelinopathy Disease complex associated with dead of coots, bald eagles, and other birds Coots die within 5 days of first symptoms Bioaccumulates in birds Believed to be connection between hydrilla, cyanobacteria, and waterfowl Documented throughout southeastern US No long-term impact on grass carp

17 Stigonematales sp. culture 100X Light --Prime Suspect-- Stigonematales species-- Morphologically similar to 3 genera: Hapalosiphon, Fisherella, or Thalpophila Stigonematales sp. culture 100X Epifluorescence, Rhodamine filter Williams, S.K., S.B. Wilde, J. Kempton, and Alan J. Lewitus. (in prep) A novel epiphytic cyanobacterium associated with reservoirs affected by Avian Vacuolar Myelinopathy. To be submitted to Phycologia.

18 Stigonematales on hydrilla Toxin Production Diseased primary feeders (coots) Bioaccumulation Invasion Diseased secondary feeders (eagles) Hydrilla Natural Site

19 Hydrilla Turions Form main challenge to management Turion an overwintering bud structure Hydrilla forms both axillary turions or subterranean turions (tubers) Tubers more commonly formed than turions Tuber longevity estimated to be 4+ years, but turions only 1 year Long-term management plans must consider and monitor the tuber bank

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21 Tar River Tuber Counts Tar River Reservoir Tubers per m Year 1 77% decline Year 2 55% decline P<0.0001; r 2 =0.994 Col 1 vs Col 2 5% reference line Year 3 48% decline Tubers remaining (% of first sample) Time (days after first sample) 0

22 Tar River Tuber Counts Hypothetical Tuber Decline Tuber decline over time Yearly points Tubers remaining (%) % decline 99.95% decline Time (years)

23 Gaston Sample Site-Treatments Lakeview Hamlin Cotton Cold Springs Hawtree Poe Hubquarter Lyons Smith - No public treatments - Alternate year treatments fluridone No Treatment - Consecutive year treatments & 2008 fluridone

24 Lake Gaston Tuber Dynamics

25 Site Density Spring 08 Density Fall 08 tubers/m 2 tubers/m 2 Gaston control Gaston biennial Gaston annual Tar River Shearon Harris 1,275 1,700

26 Free-floating fern Giant Salvinia Descending spore capsules do not produce viable spores Pubescent leaves with egg-beater shaped hairs May double in biomass in 2 days About 10 A infested near Wilmington

27 Giant Salvinia Salvinia molesta

28 Molesta vs. Minima Characteristic Egg-Beater shaped hairs of Salvinia molesta Leaf hairs of Salvinia minima branch but do not rejoin as do molesta

29 US Distribution and Range Prediction

30 Salvinia On Ice, 1/27/03

31 NC Salvinia History 1998: found in Wake County (NC State Fair) 2000: confirmed in Brunswick, New Hanover, Pender, and Onslow counties 2004: Sampson and Craven counties added to infestation list Maximum salvinia infestation reached 10 sites and 40 acres The Southeast North Carolina Giant Salvinia Task Force was formed to develop and implement an eradication program

32 North Carolina Fall 2007 Distribution = eradicated = present * Currently 1 site with <5 acres

33 NC Giant Salvinia Task Force Cooperative effort of: NC Cooperative Extension NCDA NC Dept. of Environment & Natural Resources NCSU SePRO Corporation USGS Funding obtained from National Fish and Wildlife Foundation Pulling Together Initiative

34 Salvinia Treatment Three methods used: Herbicides Biocontrol: salvinia weevil (Cyrtobagous salviniae ) Limited hand removal Infested sites were considered eradicated if no salvinia was found for at least one year after last treatment

35 Salvinia Weevil Weevils collected in TX and shipped to NC by NCDA Infested pond adjacent to the Riverbend site was selected for release Pond was not treated with herbicides for two years after release The salvinia weevil survived and overwintered, but failed to reduce salvinia populations Weevils were more effective in controlling salvinia in full sunlight than in shade

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