New bio­con­trol agent re­leased

The Orchardist - - Biosecurity - By He­len Barnes

The long-awaited and much an­tic­i­pated new bio­con­trol agent,

Ta­mar­ixia tri­ozae, a par­a­sitoid wasp which de­stroys the Tomato Potato Psyl­lid (TPP) pest, has been re­leased in Hawke’s Bay and Can­ter­bury.

About 400-500 Ta­mar­ixia were re­leased by Plant & Food Re­search at three sites in Hawke’s Bay in Au­gust, and a fur­ther 150 were re­leased at two sites in Can­ter­bury in early Septem­ber. They were re­leased onto African box­thorn plants, where over­win­ter­ing pop­u­la­tions of TPP can be found.

These ini­tial re­leases are the start of a wider planned re­lease and mon­i­tor­ing project, sup­ported with fund­ing through the gov­ern­ment’s Sus­tain­able Farm­ing Fund (SFF). That project is be­ing man­aged by the Veg­etable Re­search and In­no­va­tion Board and in­cludes Tomatoes NZ, Veg­eta­bles New Zealand, Pota­toes New Zealand, the NZ Ta­mar­illo Grow­ers As­so­ci­a­tion and Heinz-Wat­tie’s NZ Ltd. In June 2016, the group gained En­vi­ron­men­tal Pro­tec­tion Author­ity (EPA) ap­proval to im­port and re­lease Ta­mar­ixia into New Zealand.

Al­though the win­ter re­lease was not ideal tim­ing, it came about be­cause the first ship­ment of Ta­mar­ixia (re­ceived from Mex­ico ear­lier this year) was found to have fun­gal con­tam­i­na­tion, so could not be re­leased.

The Ta­mar­ixia project group col­lec­tively de­cided that they did not want to wait un­til spring to try and bring in an­other batch. We wanted to be sure that Ta­mar­ixia would be avail­able in

time for the com­ing sea­son so that the Sus­tain­able Farm­ing Fund mon­i­tor­ing and re­lease project could get un­der­way, and pos­si­bly have some avail­able for oth­ers who wish to re­lease it.

Plant & Food Re­search worked with the Ta­mar­ixia sup­plier and suc­cess­fully im­ported a “clean” batch in July. Those in­di­vid­u­als were reared, and the sec­ond gen­er­a­tion “F1” prog­eny were those ap­proved by the Min­istry for Pri­mary In­dus­tries (MPI) for the re­cent first re­leases in Can­ter­bury and Hawke’s Bay. A con­di­tion of the cur­rent MPI im­port per­mit is that “im­ported par­a­sitoids will be reared in quar­an­tine through one gen­er­a­tion, and once this is com­pleted, all Ta­mar­ixia tri­ozae adults from the orig­i­nal im­ported prod­uct will be de­stroyed”.

The project group is now look­ing at ways of es­tab­lish­ing a sup­ply of Ta­mar­ixia for this sum­mer. One op­tion be­ing looked at is us­ing the ser­vices of com­mer­cial bio­con­trol agent sup­plier Bio­force, who are in­ter­ested in rear­ing and sup­ply­ing the par­a­sitoid. Rear­ing a Ta­mar­ixia colony in cap­tiv­ity re­quires a sup­ply of live TPP and host plants, mak­ing it a lit­tle bit more dif­fi­cult to sup­ply than some other bio­con­trol agents, such as En­car­sia, which can sur­vive and re­pro­duce on an ar­ti­fi­cial diet. As a par­a­sitoid, Ta­mar­ixia needs a live TPP nymph to re­pro­duce, mean­ing that a live sup­ply of TPP is needed as part of the rear­ing sys­tem. The Tomato Potato Psyl­lid has caused enor­mous prob­lems for the potato, tomato, cap­sicum and ta­mar­illo grow­ers in New Zealand since it was dis­cov­ered here in 2006.

Since then, the in­dus­try has been wag­ing a bat­tle to con­trol this in­sect pest. Ta­mar­ixia, a tiny wasp that lays its eggs on the psyl­lid, which then hatch and eat the psyl­lid, is a bi­o­log­i­cal con­trol op­tion. Ta­mar­ixia is found in the USA and Mex­ico as a nat­u­rally oc­cur­ring par­a­sitoid of Tomato Potato Psyl­lid.

The long-term hope is that Ta­mar­ixa will es­tab­lish self­sus­tain­ing pop­u­la­tions in the nat­u­ral en­vi­ron­ment, there­fore re­duc­ing the pres­ence of TPP and the pest pres­sure for tomato, potato and ta­mar­illo grow­ers through­out New Zealand.

One of the vials that con­tained Ta­mar­ixia tri­ozae adults at­tached to African box­thorn, a host plant of tomato potato psyl­lid. Photo cour­tesy of Me­lanie David­son, Plant and Food Re­search

Ta­mar­ixia tri­ozae about to par­a­sitise a TPP nymph. Photo sup­plied by Plant & Food Re­search

From left:

A healthy TPP nymph along­side a par­a­sitized nymph (show­ing exit hole). Photo sup­plied by Plant & Food Re­search

Photo cour­tesy of Natasha Agnew, Plant & Food Re­search

One of the re­lease sites for Ta­mar­ixia tri­ozae in the Hawke’s Bay. The par­a­sitoid was re­leased near the African box­thorn, an al­ter­na­tive host for the tomato potato psyl­lid, in Au­gust 2017.

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