Insect Can Be Effective Predator of Meadow Spittlebug Vector of Xylella

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 Also: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.”

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.”

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.

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.”