Australia / NZ

A Better Method for Controlling Wild Olive Trees in Australia

A more affordable and time-saving method for culling wild olive trees in Australia has been found in basal bark spraying.

Jan. 16, 2017
By Mary Hernandez

Recent News

While the Aus­tralian olive oil indus­try con­tin­ues to thrive, increas­ing the demand for the olive plants to be imported and farmed, the olive tree has not been wel­comed in all areas of the coun­try.

When local birds and ani­mals con­sume its fruit, they inad­ver­tently spread its seeds into bush­land areas, where (if left unchecked) the seeds rapidly grow into feral’ woody weeds that invade and destroy local veg­e­ta­tion, as well as deprive sur­round­ing veg­e­ta­tion of ade­quate sun­light while they reach full height and breadth.

The feral olive trees are also cre­ated in instances when inex­pe­ri­enced farm­ers and gar­den­ers attempt to grow their own trees, which are then aban­doned or improp­erly har­vested.

Wild olive trees can live for cen­turies and are known to pro­vide breed­ing grounds for insects such as the apple wee­vil and the anthrac­nose fun­gus — both of which can harm the sur­round­ing plan­ta­tion and spread to healthy olive trees. It can also destroy valu­able live­stock graz­ing land and shore up pesti­lent ani­mals such as foxes and rab­bits.

All landown­ers are required by law to con­trol any olive plants on their prop­erty, under the Nat­ural Resources Man­age­ment Act of 2004 and South Aus­tralian Declared Plant Pol­icy.


Pre­vi­ous attempts at culling the wild olive tree (includ­ing cut­ting and poi­son­ing the stumps) as well as drilling and fill­ing stumps with a Glyphosate or Tri­clopyr mix­ture have proved unsuc­cess­ful, lead­ing to the need for a more effec­tive con­trol method — one that the Ade­laide and Mount Lofty Ranges Nat­ural Resources believe that they have found in basal bark spray­ing.

The basal bark method has been found to be cheaper and time effi­cient in terms of hours of labor required and the amount and type of tools needed. It involves spread­ing a her­bi­cide directly to the bark of a plant using a sprayer or sim­i­larly hand­held device, for­go­ing the usual power drills and chain­saws required by fill and drill’ meth­ods.

Pre­lim­i­nary find­ings show that this method takes roughly 3.5 hours to exe­cute at a cost of $386, com­pared to the fill-and-drill method which takes 44.5 hours and costs $2,913. It also can be done stand­ing up, can be sprayed with­out a spe­cific tech­nique and elim­i­nates the need to trim branches or sur­round­ing debris.

Experts are care­ful to point out that the basal bark method is not a replace­ment for other meth­ods of con­trol, but can pro­vide a lower cost alter­na­tive in areas with low wood­lands and juve­nile trees. In addi­tion, it can take up to a year to com­pletely elim­i­nate leaves, allow­ing these leaves to reshoot in the future.

The suc­cess of the basal bark method comes as wel­come news, with no end in sight yet to Australia’s past few months of record-level tem­per­a­tures and high winds.

Sev­eral areas of the coun­try have already started to insti­tute plant clear­ing mea­sures, and a fire ban has been issued in parts of New South Wales, the Greater Syd­ney and Hunter regions, parts of the Cen­tral Ranges, the South­ern Slopes and the North West.

Wild olive trees pose a par­tic­u­lar threat to spread­ing bush­fires, as its leaves are rich with oil, retain­ing heat and fuel­ing flames when alight. It’s removal — even tem­porar­ily — could have a sig­nif­i­cant effect on bush­fire risk.

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