World first bio con­trol for pest

Whanganui Midweek - - COMMUNITY LINK -

Hori­zons Re­gional Coun­cil, on be­half of the Na­tional Bio­con­trol Col­lec­tive, has been suc­cess­ful in its bid to be the first in the world to use a mite for bi­o­log­i­cal con­trol against the in­va­sive weed old man’s beard.

The gall mite Ace­ria vi­tal­bae has been cleared by the En­vi­ron­men­tal Pro­tec­tion Au­thor­ity (EPA) to be im­ported and dis­trib­uted within New Zea­land. The im­port will mark a world first for a coun­try at­tempt­ing to con­trol old man’s beard by in­tro­duc­ing the in­sect from the north­ern hemi­sphere home range of the pest.

Hori­zons en­vi­ron­men­tal pro­gramme co-or­di­na­tor Craig Davey says the coun­cil has in­vested heav­ily in the fight to date.

“Old man’s beard cloaks veg­e­ta­tion, ul­ti­mately killing other plant species such as our na­tive trees and plants that make up our nat­u­ral bio­di­ver­sity,” he says.

“Ev­ery year Hori­zons spends more than $500,000 con­trol­ling the pest by spray­ing, cut­ting and sup­port­ing com­mu­nity ef­forts to do the same. To date this has stopped the spread of old man’s beard how­ever we are al­ways look­ing at what more can be done.

“While this will be a world first in terms of us­ing a mite against old man’s beard, we have at­tempted other forms of bio­con­trol in­clud­ing a sawfly, leaf mi­nor and fun­gus which haven’t been very suc­cess­ful. How­ever, we’re re­ally ex­cited by this new one as we have seen how suc­cess­ful gall mites have been on other pest plants.”

Mr Davey says im­port­ing the gall mite is an ac­cu­mu­la­tion of 10 years of hard work to or­gan­ise fund­ing, rig­or­ous test­ing and go­ing through a thor­ough EPA ap­pli­ca­tion process to en­sure the agent only af­fects the in­tended host.

“Bi­o­log­i­cal con­trol is a tech­nique used world­wide to re­store bal­ance be­tween a weed and the en­vi­ron­ment by re­cruit­ing some of its key nat­u­ral en­e­mies. Pest plants that have been in­tro­duced to New Zea­land are of­ten not con­sid­ered a weed in their home coun­try be­cause in­sects or dis­eases keep them in check.

“This mite forms galls on the host plant, which the plant redi­rects re­sources to, re­duc­ing its ca­pac­ity to flower, pro­duce leaves and pho­to­syn­the­sise. Ex­ten­sive test­ing has been com­pleted as part of the EPA ap­pli­ca­tion to en­sure the gall mite will not pose a dan­ger to other plant types.

“Dur­ing the process we were also con­sid­er­ing a bark bor­ing bee­tle that would have been very dam­ag­ing to old man’s beard, how­ever its taste for our na­tive clema­tis meant this was not a suit­able op­tion,” he says.

The gall mite is ex­pected to be im­ported into the coun­try in au­tumn 2019, for re­lease in ap­prox­i­mately spring 2019.

“We are plan­ning to make the first in­tro­duc­tion of the gall mite to the Tai­hape area. Many unique and won­der­ful habi­tats have been rav­aged by old man’s beard, and as we have a re­ally en­gaged com­mu­nity in the Ran­gi­tikei, we’d like to lo­cate these mites in the places too chal­leng­ing or risky for chem­i­cal con­trol.”

Hori­zons ap­plied to the EPA to in­tro­duce the gall mite on be­half of the Na­tional Bio­con­trol Col­lec­tive, com­prised of 14 re­gional coun­cils and the De­part­ment of Con­ser­va­tion.

Bio­con­trol has been un­der­taken by Hori­zons in a num­ber of other parts of the re­gion to ad­dress pest plants such as field horse­tail, broom, wan­der­ing willy and rag­wort.


Ran­gi­tikei River with old man’s beard on the left bank.

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