Australian Growers on Alert After Xylella Fastidiosa Found in China

Summary

Australian olive grow­ers are increas­ing prepa­ra­tions against Xylella fas­tidiosa after its spread was con­firmed in China, prompt­ing stricter pre­cau­tions for imported nurs­ery stock. Australian author­i­ties are imple­ment­ing emer­gency mea­sures to reg­u­late host nurs­ery stock at the genus level, as Xylella fas­tidiosa is con­sid­ered the coun­try’s high­est national pri­or­ity plant pest.

Australian olive grow­ers are step­ping up prepa­ra­tions against the risk posed by the bac­terium Xylella fas­tidiosa after its spread was con­firmed in China.

“At the begin­ning of this year, the Australian gov­ern­ment noticed a sci­en­tific paper report­ing Xylella had been found in wal­nuts in China,” Michael Southan, the chief exec­u­tive of the Australian Olive Association (AOA), told Olive Oil Times. 

“As a result, they con­ducted fur­ther inves­ti­ga­tions and con­firmed that Xylella is indeed present there,” he added.

The AOA noti­fied its mem­bers that China had been offi­cially regarded as a high-risk coun­try for Xylella fasti­siosa.

In response to the new sit­u­a­tion, imported nurs­ery stock from China that could poten­tially host Xylella fas­tidiosa will now undergo increased test­ing, treat­ment and pre-export cer­ti­fi­ca­tion.

“This means much stricter pre­cau­tions around plant mate­r­ial enter­ing Australia,” Southan said. ​“It’s now sig­nif­i­cantly harder to import plant mate­r­ial from China if iden­ti­fied as a sig­nif­i­cant or high-pri­or­ity host for Xylella fas­tidiosa.”

Additionally, Australian author­i­ties announced emer­gency mea­sures to reg­u­late host nurs­ery stock at the genus level rather than the broader plant fam­ily level.

This update allows for more tar­geted inspec­tions. Previously, con­trols were applied to all plants within an entire botan­i­cal fam­ily, includ­ing species not gen­uinely at risk.

Shifting to genus-level reg­u­la­tion enables inspec­tions to focus exclu­sively on plants truly at risk.

Further mea­sures imple­mented by local author­i­ties will include revi­sions to trade per­mits.

According to Australia’s Department of Agriculture, Fisheries and Forestry (DAFF), Xylella fas­tidiosa ​“is Australia’s high­est national pri­or­ity plant pest. It’s an inva­sive bac­te­r­ial pathogen caus­ing dev­as­tat­ing dis­eases in over 700 plant species.”

In a note, DAFF empha­sized that ​“if Xylella fas­tidiosa were to enter Australia, erad­i­ca­tion would be vir­tu­ally impos­si­ble, as no treat­ment or cure exists.”

A team from Xinjiang Agricultural University in Urumqi con­ducted the research, which con­firmed the pres­ence of Xylella fas­tidiosa in sev­eral wal­nut tree leaves.

The sci­en­tists iden­ti­fied the mul­ti­plex sub­species of Xylella fas­tidiosa, which is con­sid­ered low-risk for olive trees.

However, they did not exclude the pres­ence of other sub­species, indi­cat­ing a poten­tial risk for var­i­ous other plant species, includ­ing olives.

The bac­te­ria can spread unno­ticed for years before symp­toms become evi­dent, allow­ing ongo­ing epi­demics to remain unde­tected for con­sid­er­able peri­ods.

Previous stud­ies also sug­gest that when mul­ti­ple sub­species coex­ist, genetic exchange is pos­si­ble, poten­tially affect­ing the pathogen’s adap­ta­tion, host range and evo­lu­tion.

The pub­li­ca­tion of this research alerted Australian author­i­ties about the new risk, under­scor­ing the lack of an active inter­na­tional com­mu­ni­ca­tion chan­nel for such devel­op­ments.

“That’s inter­est­ing because con­sid­er­able time passes between con­duct­ing research, writ­ing a paper and hav­ing it approved for pub­li­ca­tion. This cre­ates a high risk period,” Southan said.

During this period, no spe­cific con­tain­ment mea­sures were taken.

In response to these find­ings, the Australian Olive Biosecurity Plan was updated. ​“The plan is part of Australia’s broader biose­cu­rity strat­egy,” Southan said.

He noted that, for the olive indus­try, ​“we are sig­na­to­ries to the Emergency Plant Pest Response Deed, a doc­u­mented agree­ment out­lin­ing our response to poten­tial incur­sions of pests sig­nif­i­cantly impact­ing our indus­try or mul­ti­ple indus­tries.”

“As part of this, each sig­na­tory indus­try main­tains a biose­cu­rity response plan, a doc­u­ment inform­ing the gov­ern­ment and other indus­tries about the most crit­i­cal pests and dis­eases threat­en­ing the olive indus­try,” Southan added.

“It also out­lines cur­rent mea­sures to min­i­mize the intro­duc­tion of these threats and actions we would under­take if an incur­sion occurs, includ­ing our imme­di­ate response to reduce spread and pre­vent fur­ther dam­age,” he con­tin­ued.

These biose­cu­rity plans pri­mar­ily focus on pre­ven­tion and iden­ti­fy­ing poten­tial risks at entry points such as ports and air­ports.

Among the iden­ti­fied risks are insects that could serve as vec­tors for the bac­te­ria, includ­ing spit­tle­bugs, which Australian researchers are cur­rently study­ing.

“We do not have the exact insects known as Xylella fas­tidiosa vec­tors in Europe, but we have related insects within the spit­tle­bug fam­ily that look some­what sim­i­lar,” Southan noted.

“They’re not iden­ti­cal, but we don’t know whether they could act as vec­tors if Xylella fas­tidiosa were intro­duced here,” he added, high­light­ing the com­plex­ity of poten­tial sce­nar­ios.

Every year, Australia allo­cates increas­ing resources to pre­vent and mit­i­gate agri­cul­tural threats. ​“Almost weekly, I encounter issues related to poten­tial incur­sions. It’s becom­ing increas­ingly com­mon,” Southan said.

Occasionally, threats are uncon­trol­lable. ​“I recall years ago, a strain of rust affect­ing wheat arrived in Australia car­ried by the wind,” he said. ​“It trav­eled across the ocean and landed here. How can you pre­vent that?”

International trade in plants and goods, com­bined with the increased move­ment of peo­ple, fur­ther height­ens biose­cu­rity risks.

“Sometimes pests sneak in and escape, mak­ing it essen­tial to have detailed pro­ce­dures in place for man­ag­ing new plant pests or dis­eases,” Southan said.

Olive Oil Times con­tacted the researchers in China involved in the study but did not receive a response by pub­li­ca­tion.

• Olive Biz
• Australian Department of Agriculture, Fisheries and Forestry