Ord Land and Water, with support from Rangelands NRM have been undertaking an extensive weed eradication program over the last 12 months on Nicholson Station in the East Kimberley.
Dick Pasfield, Coordinator at Ord Land and Water said the weed mesquite had great potential to spread and that seedlings were likely to be carried upstream in the Nicholson River to the Ord river catchment.
Mesquite, originally from Northern Mexico and the southern United States was introduced on a number of pastoral stations in the past as it was drought tolerant and produced pods and leaves that were nutritious for cattle.
“Mesquite is a multi-trunk tree that can grow to 5-6 metres high and are covered in very sharp spines of up to 8 cm long,” Dick said.
They are also reported to have the most extensive root system of any plant on Earth, with roots measured about 80 metres deep.
This creates problems for land managers as the trees reduce the moisture in the soil and can effect pasture productivity. Growing around water bodies, they also reduce the water available for stock and replace native plants, causing changes also in the native fauna.Originally the trees were fairly sparse (about 20-30 metres apart) but more recently there have been many seedlings popping up and feeding into the Nicholson River.
Ord Land and Water have used an integrated approach to control the weed. A bulldozer has been used in the thickest areas, with outlying plants reached by quad bike or ute and sprayed with herbicides.
We also plan to use fire after the wet season to see the effect on new germinations.
Dick said a form of biological control had also been working in form of the Leaf Tying moth (Evippesp) which has found its own way to the Kimberley.
“Originally released by CSIRO in the Pilbara where the other known infestation of mesquite is located, the moth has helped defoliating trees and stopped setting seed this year,” Dick said.
The program has now effectively taken out almost every mesquite tree that is in the 17,600 ha area on Nicholson Station.