Declared plant in Western Australia Alligator weed (Alternanthera philoxeroides)

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See also: Control Method | Weed description | Declared plants list

(Locality Code: C= City; S=Shire; T=Town)

Category: P1, P2

Location: for the whole of the State

Control Codes and Landholder Obligations

Recommended herbicides

:

Casoron Metsulfuron methyl Glyphosate

Herbicide	:	Casoron®
Active ingredient	:	67.5 g/kg dichlobenil                    ( Group K)
Rate of product use	:	22 g per square metre
Remarks	:	Normally applied as a granule treatment, but can be mixed with water and applied as a foliar spray. In this case add a wetting agent such as BS-1000 @ 1 mL/L. Do not apply to flowing water. Only apply to alligator weed mats.

Herbicide	:	Metsulfuron methyl (various trade names - AVPMA site)
Active ingredient	:	600 g/kg metsulfuron methyl             (Group B)
Amount of product per 10 litres water	:	1 g
Rate of product use	:	80g/ha.
Wetting agent dilution	:	1:1000  Non ionic surfactant such as BS-1000
Remarks	:	Follow up treatment will be required. Healthy plants may need to be treated at fortnightly intervals. The addition of glyphosate (360) at 100 mL/10 L may improve control.

Herbicide	:	Roundup  Biactive, Razor , Eraze, Weedmaster 360 Herbicide
Active ingredient	:	360 g/L glyphosate as the isopropylamine salt                                         (Group M)
Amount of product per 10 litres water	:	100 mL
Wetting agent dilution	:	1:1000 - Using a non ionic surfactant such as BS-1000
Time of application	:	Summer to winter

Herbicide	:	Nufarm Credit Broadhectare Herbicide
Active ingredient	:	540 g/L glyphosate present as the isopropylamine salt and mono-ammonium salts as the only active ingredient.                                    (Group M)
Amount of product per 10 litres water	:	66 mL – 86 mL
Wetting agent dilution	:	Nufarm Bonus adjuvant/surfactant. At rates for a 1:1 ratio ie. 66 mL of Bonus add 66 mL Credit and 86 mL of Bonus add 86 mL of Credit
Time of application	:	Summer to winter

Family :           Amaranthaceae

Form :             Aquatic

Status:            Present in WA

                    (click to view image)

Alligator weed is a perennial aquatic plant that can also grow on swampy land and in irrigated domestic gardens. On water, it forms dense floating or rooted mats up to one metre deep. It prefers static or slowly flowing fresh water with high nutrient levels, but will withstand brackish conditions. Alligator weed spreads by stolons that grow outwards, forming new roots at the nodes. Short lengths of stem can break off and develop into a new plant. It forms seeds, but they do not appear to be viable in Australia, therefore spread is entirely by vegetative reproduction. It is a Weed of National Significance.

Stem.           Hollow with hairy grooves on opposite sides of the internodes.

Leaves.        Dark green, opposite, joined directly to the stem (ie no leaf stalks) 2-7 cm long, 5-40 mm wide. Blade - waxy surface and conspicuous veins radiating from midrib.

Flowers.       Silvery white in sphericalor cylindrical heads 1.2-1.4 cm diameter, borne on hairless or only slightly hairy stalks 2-7 cm long arising from the leaf axils. Five petals 5-6 mm long 4 nerved and papery when mature.

Fruit.           Brownish, thin skinned - bladder like and flattened.

Seed.           Rarely, if ever produced in Australia.

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