Biocontrol in­sects re­leased

Afro Voice (Western Cape) - - Western Cape News - NA­DINE FORD-KRITZINGER nadinef@afro­

THE city of Cape Town has an­nounced that more than 243 000 biocontrol in­sects, also known as agents, have been reared for re­lease into the en­vi­ron­ment to de­stroy alien in­va­sive plants across the city.

This comes af­ter coun­cil­lor Brett Her­ron, may­oral com­mit­tee mem­ber for trans­port and ur­ban de­vel­op­ment, vis­ited the Cape Town’s in­sect mass rear­ing fa­cil­ity in West­lake this week to meet the city’s biocontrol agents.

This in­no­va­tive project forms part of the city’s ef­forts to cre­ate jobs and man­age in­va­sive plants to en­sure a more sus­tain­able en­vi­ron­ment.

Since its launch in Septem­ber 2014, the Cape Town’s in­va­sive species unit’s in­sect mass rear­ing fa­cil­ity in West­lake had been us­ing an or­ganic, cost­ef­fec­tive and en­vi­ron­men­tally safe bi­o­log­i­cal con­trol method to curb in­va­sive plants by breed­ing and re­leas­ing their nat­u­ral en­e­mies, in­sects. To date, the fa­cil­ity has reared more than 243 000 in­sects for re­lease in the city to help root out alien in­va­sive plants.

The fa­cil­ity rears agents for four aquatic in­va­sives, namely wa­ter hy­acinth, par­rot’s feather, Kariba weed and wa­ter let­tuce, which are con­sid­ered the worst in­va­sive weeds in South Africa.

The fa­cil­ity also rears biocontrol agents for terrestrial in­va­sive plant, the prickly pear. The Cape Town bi­o­log­i­cal con­trol pro­gramme is a part­ner­ship be­tween the de­part­ment of en­vi­ron­men­tal af­fairs and Rhodes Uni­ver­sity’s de­part­ment of en­to­mol­ogy.

Dur­ing his visit to the fa­cil­ity, Her­ron saw first­hand how the in­sects were col­lected and pack­aged, ready for their next mis­sion.

“The visit to the in­sect­rear­ing fa­cil­ity has been most fas­ci­nat­ing.

“In or­der to rear the agents, our team ac­tu­ally grows the plant which the agents are in­tended for. The aquatic in­va­sive plants are grown in ar­ti­fi­cial ponds at our fa­cil­ity and this is also where the agents grow and com­plete their life­cy­cle.

“The agents are then col­lected from these ponds when they are ready to be re­leased on their mis­sion,” Her­ron said.

Ac­cord­ing to the city, each of the in­sects are phys­i­cally counted and then placed in plas­tic con­tain­ers. Within hours they are trans­ported and re­leased on the spe­cific in­va­sive plant. Gen­er­ally, the in­sects are re­leased ev­ery two weeks. The num­ber of in­sects that are re­leased de­pends on the size of the mis­sion field. Suc­cess in the field de­pends on the sea­son and other ac­tiv­i­ties that may be tak­ing place in the area.

Her­ron said: “When the con­di­tions are right and the op­ti­mal num­ber of agents are re­leased onto the in­va­sive plant, it can take only a few days for the agents to start es­tab­lish­ing on site.

“Once they have set up camp, it could take weeks for the agents to de­stroy the plant, depend­ing on the size of the area that needs to be cov­ered.

“It is im­por­tant to note that, af­ter the agents have been re­leased, they also con­tinue to prop­a­gate and com­plete their life­cy­cle.

“Their off­spring also con­tinue to de­stroy the tar­geted in­va­sive plant un­til the whole in­va­sive plant has been de­stroyed and then their life­cy­cle comes to an end.”

The West­lake River, which was pre­vi­ously choked with Kariba weed, is an ex­am­ple of a mis­sion ac­com­plished.

Bi­o­log­i­cal con­trol is in­creas­ingly be­com­ing a cost­ef­fec­tive method of con­trol in the war against in­fes­ta­tions of in­va­sive aquatic weeds and prickly pear.

Other meth­ods in­clude the re­moval of aquatic weeds with ma­chines, labour­in­ten­sive man­ual con­trol and chem­i­cal con­trol. The best suc­cesses are re­alised when biocontrol is em­ployed as part of an in­te­grated con­trol ap­proach, us­ing a com­bi­na­tion of one or more of the avail­able meth­ods. In ad­di­tion to the en­vi­ron­men­tal ben­e­fits, the biocontrol project pro­vides a plat­form for green job cre­ation, skills de­vel­op­ment and ed­u­ca­tion. Some of the staff have been trained at Rhodes Uni­ver­sity, a leader in biocontrol re­search in South Africa.

Five staff are em­ployed un­der the Ex­panded Pub­lic Works Pro­gramme (EPWP) to assist with the day to day ac­tiv­i­ties in the biocontrol fa­cil­ity.

The ac­tiv­i­ties in­clude, but are not lim­ited to, clean­ing the fa­cil­ity (in­clud­ing the ar­ti­fi­cial ponds), mak­ing sure there is fer­tiliser in the ponds and col­lect­ing (and count­ing) the agents for re­lease in the field. The EPWP work­ers are also trained to lead tours, in­for­ma­tion ses­sions and pro­vide en­vi­ron­men­tal ed­u­ca­tion through the fa­cil­ity for school pupils, com­mu­nity friends’ groups and other in­ter­ested groups.

Her­ron said: “Since the in­cep­tion of the biocontrol project, a num­ber of peo­ple have been trained on how to rear and col­lect the biocontrol agents as well as to re­lease them in the field.

“We are very im­pressed by the com­mit­ment and pas­sion that the staff have for this project.

“We are also very proud to know that the pub­lic, es­pe­cially our pupils from var­i­ous schools, are re­ceiv­ing first­hand ex­pe­ri­ence on the ap­pli­ca­tion of bi­o­log­i­cal con­trol as an ex­cit­ing part of in­va­sive plant man­age­ment.”


IN­NO­VA­TIVE PROJECT: Stu­dents ob­serve how biocontrol works.

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