Regional Surveillance plant pests are ones which exhibit pest characteristics, may become a problem over time or effective methods of control are unknown. The focus for managing these plant pests is preventing their spread in Hawke's Bay by voluntary control, and monitoring their presence to gather information. This information will help determine what problems they pose, and whether they will need more rigorous control in the future.
Regional Surveillance plant pests are banned from sale, propagation and distribution under the Biosecurity Act 1993.
Here is a list of Surveillance Plant Pests:
EGERIA (Egeria densa)
Aquatic - roots in mud or sand, 3mm diameter stems, whorls of four to five leaves at each node, flowers in summer.
Flowers/seeds: white three-petalled flowers.
Dispersal: boats, water-borne stem fragments with lateral buds which produce new shoots and roots.
Problems: dense growth to water surface from bottom of waterways means that it is a nuisance in recreational waters. Stem fragments can be a problem for hydroelectric power schemes.
HORNWORT (Ceratophyllum demersum)
Aquatic - fully submerged plant with green leaves up to 4cm long in groups of 7-12 around the stem.
Flowers/seeds: n/a as spreads form stem fragments.
Dispersal: water currents and waves.
Problems: forms a dense canopy below the surface. Wind can drive it against the shorelines where it smothers and shades other plants. Serious problem in hydroelectric lakes where it is easily dislodged and blocks penstock intake schemes.
HYDRILLA (Hydrilla verticillata)
Aquatic - submerged plant with very thin stems and leaves in whorls of 3-8 with toothed edges.
Dispersal: by rhizomes, runners, and stem fragments which are water borne.
Problems: forms dense canopies across the water surface to depths of 4m. It is very difficult to control.
Control/disposal: introduction of grass carp has been partially successful.
Flowers/seeds: mainly spreads by stem fragments but also seeds.
Dispersal: stem fragments and seed through water, machinery.
Problems: aggressive weed in drainage systems, shallow lakes and ponds and is difficult to control.
SOUTH AFRICAN OXYGEN WEED (Lagarosiphon major)
Aquatic - submerged perennial plant up to 6.5m deep. Leaves which have small serrated edges, are curled back and spiraled around the stem of the plant.
Flowers/seeds: n/a reproduces from stem fragments.
Dispersal: boats, trailers, eel nets.
Problems: smothers other aquatic vegetation and is a problem in recreational areas and streams.
NUT GRASS (Cyperus rotundus)
Perennial sedge with dark green leaves up to 20cm long. It develops a thick mat and has extensive underground root system of rhizomes and tubers.
Flowers/seeds: flower head up to 60cm high has three sided red purple stem.
Problems: outgrows the crops where it establishes, no chemical controls effective, roots grow through tubers and carrots so harvesting can be difficult. Clogs machinery used for cultivation.
Control/disposal: only method of control is prevention of establishment through hygiene, ensuring all equipment entering a property is clean.
PYP GRASS (Ehrharta villosa)
Pyp grass is native to South Africa, where is is commonly known as “pipe grass”. It is a perennial grass growing from long creeping rhizomes. The jointed stems are robust and usually around 90cm tall although they can be up to 150 or even 200cm tall. Leaves are bluish-green and short in proportion to the stems, about 1.5 - 13cm long. The leaves are not always present.
Problems: Pyp grass is a significant threat to sand dune systems throughout New Zealand. It may damage New Zealand’s threatened ecosystems, particularly back-dune habitats, affecting biodiversity, landscape, cultural and historic values.
It commonly grows as a dense sward displacing most other species.
Control/ Disposal: Spray.
WILD OAT (Avena fatua)
Looks like a narrow leafed variety of cultivated oat, seeds have tufts of hair at the base and a long bristle which becomes twisted when the grain is ripe.
Flowers/seeds: dark brown, cream or grey seed separates from husk, leaving a horseshoe-shaped scar on the seed base.
Problems: infestations can reduce the yield of wheat barley, linseed are peas by up to 66%. Other grass crops can be downgraded if wild oat is present. Seed is viable for up to 20 years and is difficult to dress out.
Control/disposal: pull out, paint with chemicals (roguing).
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