Goatweed hosts plant pathogens. For instance, it is a symptomless carrier of bacterial wilt (Ralstonia solanacearum), a host of the banana nematode (Radopholus similis), as well as the root knot nematatode (Meloidogyne javanica). There are reports as a host of virus diseases.
Ageratum conyzoides is on the Global Invasive Species Database (2020) of information about alien and invasive species that negatively impact biodiversity, managed by the Invasive Species Specialist Group of the IUCN Species Survival Commission.
Ageratum conyzoides; previously, known by a large number of different names in the genera Ageratum, Cacalia and Eupatorium. It is also said to be Ageratum conyzoides subspecies conyzoides. It is a member of the Asteraceae.
When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval. Recommendations will vary with the crop and system of cultivation. Expert advice on the most appropriate herbicides to use should always be sought from local agricultural authorities.
In Australia: glyphosate (and Fiji); glufosinate-ammonium, are registered. In Fiji, 2,4-D.
A similar species, Ageratum houstonianum, is recorded in the Pacific islands (Fiji, French Polynesia, New Caledonia, Papua New Guinea).
Goatweed is reported a problem in the following crops: maize (Ghana, Nigeria, the Philippines), peanut (Ghana, Indonesia, Sri Lanka), upland rice and chillies (Indonesia), cotton (Uganda), tea (Taiwan, India, Indonesia, Mauritius and Sri Lanka), cocoa (Brazil), potatoes (Colombia), oil palm (Nigeria), and over-grazed pastures (Australia, Hawaii, India). Yields are lower than expected, and labour costs for weed management are high.
A weed of gardens, roadsides, disturbed sites, waste areas, pastures, crops, wetlands and waterways in the tropical, sub-tropical and warmer temperate regions of Australia.
A short-lived herbaceous plant with softly hairy stems and leaves. Its toothed leaves are oppositely arranged at the base of the stems, but are often alternately arranged at the top of the stems. Its flower-heads are usually blue (occasionally pink or whitish) and lack any obvious ‘petals’these flower-heads have very hairy bracts and numerous long narrow projections. Its tiny black or brown ‘seeds’ (about 2 mm long) are topped with five whitish, hair-like, scales.
The stems are round, mostly green in colour, and softly hairy (i.e. pubescent). The leaves are mostly oppositely arranged, but can be alternately arranged on the upper parts of the stems. They are borne on stalks (i.e. petioles) 0.5-3 cm long and vary from being almost triangular in shape to egg-shaped in outline (i.e. ovate). These leaves (2-7 cm long and 1.5-6 cm wide) have bluntly toothed (i.e. crenate) margins and either blunt or pointed tips (i.e. obtuse to acute apices). Both surfaces of the leaves and the leaf stalks have a scattered covering of hairs (i.e. they are pubescent).
The flower-heads (i.e. capitula) are arranged in dense clusters at the tips of the branches (i.e. in terminal corymbs) and do not have any obvious ‘petals’ (i.e. ray florets). Each flower-head (5-8 mm across) has numerous tiny tubular flowers (i.e. tubular florets) that are surrounded by two or three rows of greenish-coloured bracts (i.e. an involucre). The florets (2-3 mm long) range from pale lavender to blue, pink or purplish in colour and each has two elongated projections (i.e. style branches). The bracts at the base of the flower-head (3-5 mm long) are elongated in shape (i.e. linear-lanceolate) and covered in sticky hairs (i.e. glandular pubescent). Flowering occurs throughout most of the year. The ‘seeds’ (i.e. achenes) are about 2 mm long, brown to black in colour, and topped with five awn-tipped scales (i.e. a pappus). These scales (2-3 mm long) are whitish in colour and resemble short bristles or hairs.
A short-lived (i.e. annual or biennial) herbaceous plant growing 0.3-1 m tall.