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November 2014

 

As predicted, the summer rains are late but hopefully by the time this article is published, they will have arrived and summer plant growth will be in full swing. Regrettably this also means that our alien invasive plants will also be awakening from their winter dormancy. It is perhaps opportune that we now review and summarize what we discussed last year, so that, (hopefully) you are well prepared to take on the aliens this season!!
Invaders currently flowering are: Syringa (Meliaazerderach), Yellow Bells (Tecomastans), Crofton Weed (Ageratinaadenophora), Cat’s Claw Creeper (Dolichandra unguis-cacti) and Jacaranda (Jacaranda mimosifolia), so look out for these and prepare to eradicate them BEFORE they set seed. Other weeds discussed in previous issues are: Pompom (Campulocliniummacrocephalum), Lantana (Lantana camara), Bugweed (Solanummauritianum), Pine and Gum (Eucalyptus spp) species.
Identification and control methods are as follows:

Syringa (Maksering):

a well-known fast growing tree with dark- green, glossy, compound leaves with serrated margins, lilac flowers, green berries becoming yellow and wrinkled when ripe.

 

Yellow Bells (Geelklokkies):

a small tree or shrub with compound leaves with sharply serrated margins, bright yellow, trumpet-shaped flowers, fruit a 150 mm long pod splitting to release wind dispersed, papery, winged seeds.

Control: both the above species can be controlled by an application of 5% Hatchet or Chopper in water, applied to a freshly, low-cut stump with a low pressure hand sprayer, avoiding run-off onto soil.

Pompom:

as it is a perennial herb which dies back each winter, it is unlikely to be seen currently in grassland. However the pink, fluffy flower-heads are most evident from December onwards. It grows to 1,5 m and the stem and leaves are covered in rough, bristly hairs. Leaves are light green with serrated margins.

Control: Plants can be dug out taking care to remove the entire deep rootstock. If it is a low infestation flower-heads can be cut off and burned to prevent seed dispersal. , but take care to mark plants for treatment with Brush Off or Nicanor (16 gm in water in a 16 liter knapsack sprayer) or if not near a water source a 5% solution of Plenum can be used. Ensure that the entire plant is drenched.

Lantana:

Probably does not require a description but is an untidy scrambler, up to 2 m tall, covered in stiff hairs or re-curved prickles, crushed leaves are pungent smelling and are a skin irritant, flowers in compact clusters and multi-coloured; fruit is a green berry turning black at maturity.

Control: hand-pull small plants, but large plants need to be cut back and stumps painted with a 5% solution of Chopper or Hatchet or a 2% solution of Plenum in water. Plants up to 1 m can be foliar sprayed.

Bugweed: (Luisboom):

Also well known, a shrub or tree with pale green foliage covered in felty hairs; leaves strong smelling when crushed; flowers purple in terminal clusters and fruit is green turning yellow in terminal clusters.

Control: plants up to waist height can be sprayed with Starane (20 ml per 16 liter water in a knapsack sprayer). Larger plants need to be cut back  and a stump treatment applied (3% solution of Hatchet or Chopper or 500 ml per 16 liter sprayer).

Pine and gum:

most pines can simply be cut down and do not re-grow.  All gums require cutting down and a stump treatment of 5-10% solution of Chopper or Hatchet in water applied mainly on the cambium (inner bark layer) Stump re-growth requires a foliar treatment of Nicanor or Brush Off when knee high (125 gm per 100 liter water).

In all the above cases, the addition of a wetter agent to prevent run-off of herbicide is recommended.

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