Researchers Chart Pest Sightings in Effort to Protect Against Xylella

As a pre­ven­ta­tive mea­sure against Xylella fas­tidiosa, sci­en­tists in the United Kingdom called on vol­un­teers ear­lier this year to record sight­ings of spit­tle­bugs and their residue. The researchers are using this data to chart their dis­tri­b­u­tion across the U.K.

Spittlebugs, also known as xylem-feed­ing insects, spread Xylella – which has destroyed scores of olive groves across Italy and the Mediterranean region – from one infected plant to another when feed­ing on them.

Spittlebugs are easy to iden­tify by the frothy spit­tle they pro­duce while feed­ing.

The U.K. research team con­sists of a con­sor­tium of 12 orga­ni­za­tions, includ­ing the Royal Horticultural Society and the U.K.-based Universities of East Anglia, St Andrews, Salford, Stirling and Sussex. Known as BRIGIT, the project involves sci­en­tists in the fields of ento­mol­ogy, plant pathol­ogy, ecol­ogy, epi­demi­ol­ogy, mol­e­c­u­lar biol­ogy, genomics and social sci­ence.

Claire Harkin, a post­doc­toral research fel­low at the University of Sussex and mem­ber of the BRIGIT con­sor­tium, told Olive Oil Times that under­stand­ing the nature of spit­tle­bugs is crit­i­cal to man­ag­ing the poten­tial for a Xylella out­break.

“If we can under­stand how far and how fast indi­vid­ual bugs move, what they pre­fer to feed on, and how much their pop­u­la­tions mix, we can bet­ter pre­dict how far and how fast Xylella might spread if it enters the U.K., and there­fore be bet­ter pre­pared to more effec­tively respond should it arrive here,” she said.

Harkin said this is an ongo­ing project.

“Although we are com­ing to the end of the spit­tle­bug sea­son now, we will be run­ning the spit­tle sur­vey in some form again next year,” she said.

Alan Stewart, another mem­ber of the BRIGIT con­sor­tium and an ecol­ogy researcher at the University of Sussex, said one of their tasks for the win­ter months will be to decide how best to do this and which infor­ma­tion gaps need to be filled.

Stewart said if Xylella-infected plants were imported to the U.K., there is poten­tial for the bac­terium to estab­lish and spread across the coun­try, ​“with poten­tially dev­as­tat­ing con­se­quences.”

He said as most research on Xylella and its insect car­ri­ers have been done in warmer cli­mates, not much is known about how the pathogen may spread in Northern Europe.

Stewart appeared on BBC Breakfast, BBC Radio 4 and BBC Online to launch the project.

Harkin – who described the response to the project as ​“incred­i­ble” – said it remained the top online story on the BBC News Science and Environment pages for one week, with around 1.25 mil­lion views. In addi­tion, BRIGIT called for vol­un­teers in print pub­li­ca­tions.

“This gen­er­ated a stag­ger­ing pub­lic response, with over 1,000 records sub­mit­ted on the first day alone,” she said. ​“We have now received over 14,000 records, over 80 per­cent of which include the cru­cial host plant infor­ma­tion.”

Harkin said 400 species of host plants have been reported, and the top three are laven­der, rose and rose­mary. She said they have had some records sub­mit­ted on olive trees, although ​“only a very small num­ber.”

She added that they need to check and ver­ify these records for the com­ing weeks.

“This is where the sub­mis­sion of pho­tographs to sup­port records has been enor­mously help­ful,” she said. ​“Around 40 per­cent of sub­mis­sions have asso­ci­ated pho­tographs, which will make the ver­i­fi­ca­tion task for these records much eas­ier. Once we have ver­i­fied the records, the inter­est­ing and impor­tant job of ana­lyz­ing the data will begin – data that will feed into the wider BRIGIT research project to help.”

“We also know that around 80 per­cent of records have been sub­mit­ted from pri­vate gar­dens,” Harkin added. ​“This is one of the huge ben­e­fits of run­ning a cit­i­zen sci­ence cam­paign; we sim­ply could not have accessed such data in any other way. We are enor­mously grate­ful to every­one… who has con­tributed data to this crit­i­cally impor­tant area of research.”

Harkin said while Xylella is not cur­rently thought to be present in the U.K., the insects that have been shown to be car­ri­ers in Mediterranean coun­tries are com­mon and wide­spread in the U.K. as well.

“Principal amongst these is the so-called com­mon froghop­per or meadow spit­tle­bug – Philaenus spumar­ius,” Harkin said, ​“which is one of our most com­mon insects. Ironically, it is also one of the most polyphagous, being known to feed on at least 400 dif­fer­ent plant species.”

“The rea­son Xylella has spread so widely and over such long dis­tances in recent years is because of humans mov­ing infected plants and plant mate­r­ial,” Harkin added. ​“For exam­ple, through trade and by peo­ple bring­ing plants back with them from hol­i­days abroad. This is the basis of the U.K. government’s ​“Don’t Risk It’ cam­paign.”

In a bid to pre­vent Xylella from spread­ing to the U.K, the gov­ern­ment has spent more than £4.5 mil­lion ($5.59 mil­lion) to strengthen their bor­der secu­rity.

“Whilst the bac­te­ria are trans­mit­ted between plants by the xylem-feed­ing insects, we believe the insects them­selves only travel rel­a­tively short dis­tances — per­haps up to 100 meters by hop­ping or fly­ing, but pos­si­bly fur­ther if they are car­ried on the wind,” Harkin said. ​“This is some­thing we are look­ing to defin­i­tively answer through the BRIGIT research project.”