Working for water plans for 2018

May 8, 2018

wattle

Working for water plans for 2018 ~ interview with Pieter Gerhardus (project manager for Working for water)

The key focal areas are two fold for the black wattle.

Firstly the initial clearing of the Black wattle and secondly follow ups where black wattle have been cleared to prevent the re infestation of the black wattle seedlings.

The initial clearing is going to be roughly 100 hectares. This will include the valley below Wildebeest plains going towards Insele lodge. The initial clearing has been done along the edges but the focus will now be to clear the entire valley. The next initial clearing area is at the top of the Whitehouse valley just below the predator bomas. The third initial area for clearing is below wildebeest dam going down the valley. These initials will prepare the way to start moving down the Whitehouse valley next year. If the initials are successful by incorporating clearing and fire this year, then we will be looking at doing more initials next year as the combination of clearing and fire will require less follow ups with longer intervals.

The follow ups for the black wattle for 2018 is on the 2300 hectares from Pieter’s se deck up the valley to Suurvlakte, the recently cleared new section close to Suurvlakte, over and across to Gate 1 and the area outside Mountain ridge. At least 2 treatments per block have been scheduled for the year.

Along with the mechanical and chemical treatment of the black wattle trees is a Biological component for control.

Hakea biological control is being introduced this year. Release sites will be identified to release different control agents depending on the age of the Hakea. Some agents control the Hakea saplings, others control Hakea plants around the age of two years and other agents control the adult trees and seed pods. These agents will be released in the hard to reach areas such as Trees loop and Protea forest.

The black wattle biological control is well established at Gondwana. The first galls were released in 2012/2013 .The larvae of the midge stimulates the wattle to grow and encapsulate the inflorescence leading to reduced seed production that takes place. Once the larvae has eaten off the inflorescence, the gall opens and the midge flies out to lay eggs in another inflorescence. The gall forming midge that encapsulates the inflorescence preventing pollination is everywhere, from the far east to the far west of the reserve. There is very little seed being produced with as much as a 90 percent reduction in seed germination. Key areas for sustaining the midges need to be identified so that they do not die out. The bomas is one key area along with a few other forests, where the wattle will be prevented from spreading but able to maintain and breed the midges. 

Another form of biological control was introduced in the form of weevils which destroy the black wattle seed. The effect of the weevils is visible in some areas of black wattle but is not being as effective at this stage with stopping seed production as the midge.

Text: Nadine Clarke
Photographs: Raquel de Castro Maia

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