Combating Lantana

Through the introduction of the Lantana herringbone leaf miner, the biocontrol of this weed has significantly improved.

Lantana weeds are some of the worst in the world, and a Category 1b species in South Africa in terms of the National Environmental Management: Biodiversity Act No. 10 of 2004: Alien and Invasive Species Regulations, 2014. Land occupiers are legally obliged to either control it or to remove and destroy it if possible. No planting is allowed.

Lantana is a genus of about 150 species of perennial flowering plants in the verbena family (Verbenaceae).

The genus includes both herbaceous plants and shrubs growing up to 2m.

The Lantana’s aromatic flower clusters (umbels) are a mix of red, orange, yellow, or blue and white florets.

The flowers typically change colour as they mature, resulting in two- or three-coloured inflorescences.

Dispersed by fruit-eating birds, Lantana is established along fence lines and under trees, where it outcompetes indigenous plants and forms impenetrable thickets that reduce natural pasturage, productivity of cattle farming, access to water supplies and tree plantations, biodiversity and land values.

The Lantana herringbone leaf miner ( Ophiomyia camarae) is one of several biological control agents used against the plant.

LIFE CYCLE

The adult herringbone leaf miner is a small (1,5mm to 2mm), shiny, black fly. Egg laying commences one to two days after the adults emerge from the leaves of the plant. The female inserts a single egg into a leaf vein, and lays one to three eggs per leaf.

Eggs hatch after about eight days. The larvae mine within the leaf for eight to 10 days, and pupate for nine to 12 days inside the leaf. The adult-to-adult generation time is between 27 and 32 days.

During its 18-day adult lifespan, a female will lay around 92 eggs. The Lantana herringbone leaf miner has many overlapping generations a year, and therefore has the capacity to rapidly increase in numbers.

Female flies puncture the leaf veins with their egg-laying organs. As they feed within the leaf tissue, the young larvae form dark, narrow mines that meander from the leaf veins. The tunnels become visible about 10 days after the adults have emerged.

Older larvae form pale, yellowgreen or brown fishbone-shaped ‘herringbone’ mines, often centred along the midrib, with side shoots along the lateral veins.

Mining along the veins damages the leaves’ fluid transport system, reducing water flow to the leaf and nutrient flow from the leaf to the shoots and roots. The damaged leaves often fall prematurely.

The leaf miner will augment the effect of the biological control agents already established on Lantana in South Africa. Increased suppression of the growth and reproduction of the weed will further reduce the cost of conventional control.

And conventional control is indeed needed. The Lantana biocontrol agents currently established are simply unable to stop the weed densifying and spreading.

• Source: arc.agric.za/arc-ppri > search ‘Ophiomyia camarae’.

FLICKR Lantana camara is one of the 150 species of the Lantana genus. It might look pretty, but lantana is an invasive alien species, and landowners are required by law to remove and destroy the plant.