WEED OF THE WEEK: Yellow guava in top 100 as a pest
YELLOW guava is native to Mexico, Central America, the Caribbean and tropical South America.
Yellow guava (psidium guajava) may be confused with Brazilian guava (psidium guineense) and cherry guava (psidium cattleianum). All of them are considered as serious environmental weeds in Queensland and New South Wales. People are urged to be careful where they plant these trees to prevent the spread of the seeds and where they dispose of fruit and garden waste.
They are also potential environmental weeds or "sleeper weeds" in other parts of Australia, and are regarded to be among the top 100 of the world's worst invasive alien species and so is listed in the top 100 Global Invasive Species Database (GISD).
As an environmental weed it has become invasive in bushland in coastal areas in Queensland.
Yellow guava (psidium guajava) is a widely cultivated species that has become invasive in the wetter areas of tropical and sub-tropical Queensland. It is a weed of waterways, pastures, open and closed native forests, forestry plantings, plantation crops, roadsides, disturbed sites and waste areas.
This species reproduces mainly by seed, but it can also re-shoot from stumps and produce suckers from damaged roots. Yellow guava is known to form dense stands, and the seeds are mainly dispersed by humans, fruit-eating birds and bats, livestock, as well as other animals such as rats, feral pigs, and some fruit-eating native animals. Even kangaroos have been seen eating fruit on the ground.
Its fruits have traditionally been used for juices and jams and are still used commercially. Adding to its undesirable status, the yellow guava is also host to the papaya fruit fly in Queensland. This makes its removal a high priority to the fruit industries.
Yellow guava is a small tree up to 10m. It has spreading branches, and characteristic smooth mouldy coloured bark (similar to gum trees) which flakes away to reveal the pale green layer beneath.
The prominent veined wide green leaves are oblong in shape, leathery, aromatic when crushed and downy on the underside. Leaf dimensions are 7-15 cm long and 3-5 cm wide.
The flowers are creamy white, and shed their petals to leave a tuft of yellow tipped stamens. The rounded highly seeded fruits have yellow skins when ripe, with pinkish red flesh, and can be between 5-10 cm in length.
How to control it
Do not dispose of the fruit loosely but bag the fruit before disposal.
Hand pull seedlings as soon as they are identified.
Be careful mowing around the tree surface roots as root damage results in shoots.
Cut off seedlings and apply herbicide quickly to the stumps.
Scrape and paint the bark of larger plants with herbicide.