Insect Can Be Effective Predator of Meadow Spittlebug Vector of Xylella

An entomologist found evidence that North American insect can be used to limit the presence of Meadows Spittlebugs vectors of the Xylella fastidiosa CoDiRO strain on olive trees.

Zelus renardii
Oct. 23, 2017
By Ylenia Granitto
Zelus renardii

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Research con­ducted at the Uni­ver­sity of Bari Aldo Moro pro­duced use­ful find­ings on the employ­ment of the assas­sin bug Zelus renardii in tack­ling the onset of Phi­laenus spumar­ius, bet­ter known as the Meadow Spit­tle­bug, which is the known vec­tor of Xylella fas­tidiosa pauca that causes the Olive Quick Decline Syn­drome OQDS (or CoDiRO).
See more: Arti­cles on Xyella Fas­tidiosa
Every year, we intro­duce to our coun­tries sev­eral new species of insects,” said the asso­ciate pro­fes­sor of gen­eral and applied ento­mol­ogy at the Depart­ment of Soil, Plant and Food Sci­ences of the Apu­lian uni­ver­sity, Francesco Por­celli who con­ducted the study.

In the case of adult Phi­laenus, since the ear­lier stages of the pro­ce­dures for con­tain­ment of Xylella, we could rely only on chem­i­cal treat­ments to be applied in a short period dur­ing the flow­er­ing of olive trees,” he explained. Nowa­days, our goal is to include an effec­tual bio­log­i­cal con­trol action in con­ven­tional and organic IPM that can inte­grate or replace chem­i­cal con­trol with an organic one.”

Francesco Porcelli with his researchers at the University of Bari Aldo Moro

Por­celli and his group of researchers (Francesca Gar­ganesa, Roberta Roberto, Lina D’Ac­colti, Ugo Pic­ciotti, Laura Diana, Valentina Russo, Mar­tina Salerno, Francesco Diana, Ric­cardo Gam­mino, Angela Schi­avarelli, Valdete Sefa, Ahmed El Kenawy, Daniele Cornara) met the Zelus, which is native to North Amer­ica, five years ago in the con­text of their research on Macro­ho­mo­toma glad­i­ata, an Asian Ficus pest recently intro­duced to Europe.

Hav­ing noted that Zelus was an active preda­tor of this trop­i­cal insect, they bred it in a lab and tried to use it against other pests. Dur­ing an exper­i­ment, in the frame­work of doc­toral research on Aleu­ro­can­thus spiniferus and on Phi­laenus, they put an adult insect along­side some spit­tle­bugs and it was love at first sight,” Por­celli affirmed. Zelus turned out to be fatal for adult Phi­laenus and now, after sev­eral tests, we are able to con­firm the first evi­dence.”

© Olive Oil Times

Now, the researchers should be able to breed the insect on a mass scale, in order to use it as liv­ing insec­ti­cide. Accord­ing to their eval­u­a­tions, a new bal­ance between pop­u­la­tions of the insects already exists since Zelus was found in Italy in 2012 and no major demo­graphic explo­sions of this species occurred. This means that the car­ry­ing capac­ity of the ecosys­tem with regard to Zelus pop­u­la­tion is mod­est,” the Apu­lian ento­mol­o­gist observed.

Just to give you an exam­ple, on a tan­ger­ine tree intensely infested by Aleu­ro­can­thus spiniferus and Aleu­rothrixus floc­co­sus, of which our insect is not a preda­tor, we can find only two or three egg masses and a cou­ple of adults of Zelus,” he clar­i­fied.

Zelus renardii

This is a strong indi­ca­tor that if large quan­ti­ties of adult Zelus (which already live in our olive trees in small quan­ti­ties) were intro­duced to the envi­ron­ment at the time when Phi­laenus reaches adult stage dur­ing the last week of April and the first or sec­ond week of May (depend­ing on sea­son), these preda­tors will start starv­ing since the ecosys­tem does not sup­port them. More­over, to the ben­e­fit of bal­ance, Zelus is a can­ni­bal, prey­ing on its juve­niles or on adults of the same age as is the case of non-recep­tive females on mat­ing-attempt­ing males.

Fur­ther­more, the inter­est­ing thing is that this insect can be used as a multi-pur­pose organic insec­ti­cide. In my opin­ion, chem­i­cal inter­ven­tions against Xylella vec­tors will be grad­u­ally reduced,” the ento­mol­o­gist observed.

In this sense, a ben­e­fi­cial organ­ism which feeds on one pest alone is not enough for an organic man­age­ment of olive tree, whereas we need a sta­bi­liz­ing fac­tor within the olive tree ecosys­tem. And Zelus showed a great abil­ity to attack also other insects harm­ful to the olive grove, but not all the insects fre­quent­ing olive trees.”

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