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Monday, 25 January 2016 22:18
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At the Cullinan Conservancy, New Year’s Day was used to battle invader plants. Joan-Louise Du Toit from the conservancy said that she took her family for a picnic and then they monitored the five biological control sites on the game farm.

Joan-Louise du Toit from the Cullinan Conservancy

In December the Plant Protection Institute released biological control on some yellow bells (Tecoma stans) in the area. This is a species of flowering perennial shrub in the trumpet vine family, Bignoniaceae, which is native to the Americas. It is the official flower of the United States Virgin Islands and the floral emblem of the Bahamas. It is drought-tolerant and tends to take over in warm climates.

Pom pom weed

The biological control on queen of the night cactus has been ongoing since 2000 with very positive results in the conservancy. The last release in summer was in the Pienaarspoort, Rietfontein and Elandshoek area.

Queen of the night is approximately 10-15 metres tall with erect, columnar stems, often with a short trunk. This species complex is cultivated as ornamentals and living hedges. Bird-dispersed seeds have resulted in the spread of the cactus into the savanna of the warmer and arid parts of South Africa, where it reduces the carrying capacity of land by preventing livestock and game to shelter under shade trees during the hottest parts of the day.

Queen of the night

Conservancy members were assisted by Anthon Maluke from the Department of Agriculture Fisheries and Forestry (DAFF) to release the biological control agent Hypogeococcus pungens, a mealy bug species, on the queen of the night cacti at ten new sites.

The community was asked to inform the conservancy if there are any queen of the night plants on their properties so that the biological agent could be released on the cacti. GPS co-ordinates were taken and mapped by the Biological Control Centre of the Plant Protection Research Institute.

A conservancy member releasing biological agent
Photo: Haakdoring

Last year the conservancy was approached by a herbicide company for permission to conduct herbicide trials in the area. After getting permission from the property owners the first two trials were started on milkweed and syringa. These sites will continuously be monitored by the conservancy. The aim is to evaluate the efficiency of the herbicides for registration purposes.

Milkweed is an American genus of herbaceous perennial plants that contains over 140 known species. It previously belonged to the family Asclepiadaceae, but is now classified as the subfamily Asclepiadoideae of the dogbane family, Apocynaceae.

Milkweed is named for its milky sap, which consists of a latex containing alkaloids and several other complex compounds. Some species are known to be toxic.

Yellow bells (Tecoma stans)

Pom pom
“We have also released biological control on pom pom, which is not doing too well because of the drought,” Joan said.

Pom pom weed (Campuloclinium macrocephalum) is an ornamental South American herb belonging to the daisy family, Asteraceae. It is rapidly becoming the most serious threat to the conservation of grasslands in South Africa.

Infestations become conspicuous when the plants are in flower between December and March, transforming the veld from green to pink. The plant initially establishes itself in disturbed sites such as roadsides, but then invades grasslands, open savanna and wetlands. This weed displaces native species.

Milkweed being sprayed during trials
Photo: Haakdoring

All control sites in the Cullinan Conservancy are mapped on the national database and conservancy members monthly monitor the sites themselves.

“We just have to realize that climate (extreme frost, and drought) affects the success of the biological control. Sites have to be carefully selected as veld fires kill most of the agents,” Joan said.

Joan said that the conservancy plans on expanding their biological control to other declared weeds in 2016.

Seeds emerging from a follicle on a milkweed plant


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