NQ DRY TROPICS WEED FREE pg . 81
WATER LETTUCE
Pistia stratiotes
DESCRIPTION
This spongy perennial resembles a small , floating , open head of lettuce .
Leaves are a floating rosette of pale green , fan shaped and covered with hairs . The leaves are up to 14 centimetres long and 8 centimetres wide .
Flowers when mature the plants produce lots of small , green flowers in their centre , between 7 to 12 millimetres long . A membrane separates the male and female flowers .
Fruit resembles a berry , 5 to 8 centimetres wide . Seeds are small and oblong and are tapered at each end . Roots are unbranched tufts and fibrous up to 80 centimetres long .
Habitat water lettuce prefers nutrient rich , stationary water bodies or slow moving streams .
Weed characteristics it rapidly forms dense mats covering rivers , dams and irrigation channels . It interferes with irrigation and stock watering , and large infestations can damage wildlife habitats and put children and livestock at risk if they become entangled in the roots . It can restrict water flow , increase water loss by transpiration and serve as a breeding ground for mosquitoes .
Dispersal it spreads both by vegetative reproduction and by seeds .
BIOSECURITY MATTER
Restricted . This species is Category 3 Restricted matter under Queensland Legislation .
HOW TO ACT
Prevention is the best control method . Control of nutrient inputs into waterways will reduce rate of infestation . Early detection and rapid response will provide the best chance of control . Integrated control combining mechanical , biological and chemical methods with long term monitoring and follow up is required . Hand removal of small infestations is recommended . Biological control agents have proven to be effective throughout eastern Queensland . Apply herbicide strictly as per label recommendations .
WATER WEEDS DELTA ARROWHEAD OR SAGITTARIA