Alligator weed

1.    Alternanthera philoxeroides, commonly known as Alligator weed, is an immersed aquatic plant.

2.    Alligator weed is a Weed of National Significance.

3.    It is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts.

4.    It is an especially troublesome weed because it invades both land and water, and is very hard to control.

5.    Alligator weed can grow with roots embedded in the bank or on the bottom of shallow water bodies, or float freely on the water surface.

6.    It spreads its leaves across the water surface, forming dense mats.

7.    The long spreading stems are hollow, helping it to float.

8.    The roots are thin and stringy, and trail in the water from the joints between plant segments (the nodes).

9.    Alligatorweed is usually found growing in water, it is also capable of growing in a variety of habitats including dry land.

10. The stems of alligator weed are long, branched and hollow with 2 leaves opposite each other.

11. The flowers grow from the axils of the leaves.

12. They have five white sepals and appear as white balls.

13. Alligator weed is found in ponds, lakes, streams, canals and irrigation ditches and can form dense, sprawling mats.

14.  It originated in South America, but has spread to many parts of the world and is considered an invasive species in Australia, China, New Zealand, Thailand and the United States.

15. When alligator weed invades waterways it can reduce water flow and quality by preventing light penetration and oxygenation of the water.

16. It can also reduce water bird and fish activity and cause the death of fish and native plants.

17. Alligator weed mats create a favorable habitat for breeding mosquitoes.

18. Alligator weed is also difficult to control.

19. Insects have been released for the biological control of alligator weed.

20. The most successful and widely used is Agasicles hygrophila commonly called the alligator weed flea beetle; it has been released for biocontrol in Australia, China, Thailand, New Zealand and the United States.

21. Amynothrips andersoni, the alligator weed thrips, and Vogtia malloi, the alligator weed stem borer, have also been released in the United States.