Pompom Weed (Campuloclinium Macrocephalum)

October to February is the time of the year when the war against the pink peril is at its most intense. The alien invader pompom (Campuloclinium macrocephalum) is at once costly and attractive with a showy bright-pink powder puff flower.

Those complying with the law and controlling the Pink Peril, know the investment in controlling the invasion is high. But not as high as the cost of doing nothing. The flower head produces copious amounts of seed; the plant is extremely resilient; it propagates from seed and underground tubers. Most traditional controls do nothing more than stimulate growth!

The stems, leaves, flowers and seeds are suspected of containing allelochemicals which inhibit the growth of other species. The invasive nature of this weed and the chemical response can very quickly turn lush grassland into a pink wasteland.

Biological control

The Agricultural Research Council has researchers working to find the natural enemies of the pompom weed. Biological control research is underway, and this will involve introducing, testing and releasing natural enemies of pompom weed.

Researchers have been to Argentina and Brazil to get to know the enemies of pompom weed in its natural habitat.

Biocontrol scientists have released a tiny insect to wage war on the pompom weed,  a Category 1 invasive alien species.  The pompom outcompetes local grasses and easily becomes the dominant plant in grasslands, effectively turning productive land into a wasteland.

Pompom weed has had only a minor rust as a natural enemy. Adding to the arsenal, biocontrol scientists have released a tiny insect known as the pompom thrips (Liothrips tractabilis).

Recruited from Argentina, where pompom weed is indigenous, the newly-released pompom Liothrips causes significant damage to the stems and leaf tissue at the growing tips. This causes deformities in plant growth, reducing the height, biomass and flower production of this unwanted weed.

This is not a “silver bullet”.  Scientists warn that it will take several seasons for entomologists to build up large enough populations of Liothrips to halt the spread of pompom weed.  And the infected pompom will take at least two seasons to die off.

Tips

• Fire does not destroy the pompom. It lies dormant, with nutrients in the underground tuber ready to grow again.
• Digging it up it time consuming, and any small part left behind, will grow again.
• Cutting the flower head results in branched growth, and within 2 weeks, between 3 and 5 new flowerheads will have the replaced the one snipped off.
• Herbicide is the most effective control method. Spray before the heat of the day. When the temperature exceeds 29 degrees, the plant’s own controls prevent the herbicide from being taken up. The spray must be on the plant for more than 2 hours , if using Plenum and 6 for Access – so avoid applying when rain threatens.
• Commence applying the herbicides BEFORE the flowers appear. This is the most effective way of combating the spread.
• Effective herbicides are Access, Brushoff and Plenum