Weed Control: Tackling the Fireweed Issue

Fireweed (Senecio madagascariensis) is an introduced weed to Queensland, originating from South Africa. The weed competes strongly with local pasture species, and is toxic to livestock if grazed; particularly cattle and horses, and can result in illness, slow growth, and a decline in condition, which can eventually lead to death.

fireweedFireweed is a member of the Asteraceae plant family, and is very daisy-like in its appearance. Fireweed has attractive bright yellow flowers, and has variable growth habits and leaf structures, meaning that it can grow from anywhere from 10 to 60cm in height. In most coastal zones, Fireweed is generally a low, heavily branched, short-lived perennial plant. Although leaf shape and structure may vary, leaves are commonly bright green and narrow in appearance, with serrated edges. Larger leaves are usually attached around the stem, and are typically 2-6 cm long, but can be anywhere from 2-10 cm in length on vigorous, or older plants.

Fireweed has a shallow root system, with roots reaching anywhere from 10 to 20 cm below the soil surface. The number of petals found on the Fireweed flower are usually found to be 13. Plants flower mainly from April to September, with individual plants often having a wide range of flowering stages at any one time. Seeds are small in size (1-3 mm long) and weight, with the weed producing large quantities of seed over a substantial period of time, which are easily dispersed by the wind. Each flower usually produces between 100 and 150 seeds. Long distance dispersal can occur in a large number of scenarios, and may include: by seeds on animals, in stock feed (predominantly through hay transport), or in mud on vehicles. The main disadvantage of Fireweed is that it can outgrow most useful pasture plants. Fireweed also readily invades pastures damaged by overgrazing and drought. Nearly all environmental settings in Queensland are favourable to Fireweed growth, as the plant can grow in low and high elevation areas, and in arid or moist settings.

Control Options

Herbicides have greater efficacy when applied to plants before they reach maturity.

Unfortunately Fireweed control is often not considered until after flowering, which is outside the ideal growth stage for spraying. When spraying later growth stages, the higher rates specified on the label may need to be applied. Before any spraying, read the herbicide label carefully to ensure the information it contains is clearly understood. The herbicide must be used always in accordance with label directions.

The table below lists some options for chemical control which we keep in store for fireweed control:fireweed-treatment-table

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For more information regarding the control of Fireweed, please contact your local Elders Agronomist.