Olive Lace Bug Adds to Harvest Woes for Australian Farmers

Producers across Australia antic­i­pate mixed results as the 2024 olive har­vest gets under­way, with some fac­ing fur­ther com­pli­ca­tions due to a wide­spread lace bug infes­ta­tion.

The olive lace bug (Froggattia olivinia) is an Australian native sap-suck­ing insect that feeds off the under­side of leaves. In recent years, the insects have moved from native plants in the olive fam­ily to Olea euro­pea, the sci­en­tific name for the olive.

“Severe infes­ta­tions can defo­li­ate trees and even kill young trees,” said Robert Spooner-Hart, an asso­ciate pro­fes­sor of applied ento­mol­ogy and crop pro­tec­tion at Western Sydney University.

Spooner-Hart works with the olive indus­try in Australia and Europe fol­low­ing inte­grated pest man­age­ment (IPM) strate­gies, which use pes­ti­cide inter­ven­tion only when nec­es­sary and the least envi­ron­men­tally dis­rup­tive method­olo­gies.

While olive lace bugs have been reported in olive groves in South Africa, Pakistan and north­ern India, Spooner-Hart said the one in Australia is a dif­fer­ent species.

“Our species orig­i­nates from the east­ern states of New South Wales and Queensland but has now spread to all olive-pro­duc­ing states, mainly through move­ment of infested plants,” Spooner-Hart said, with the pest reported in Victoria, South Australia, Western Australia and Tasmania.

“It is regarded as the major olive insect pest in Australia,” he added, since the olive fruit fly, olive moth and olive thrips are not present on the island. ​“Olive black scale is a com­mon but less impor­tant pest,” Spooner-Hart said.

Based on a recent con­ver­sa­tion with a grower in north­ern Victoria, Spooner-Hart added that ​“it’s clear there that olive lace bugs have also uti­lized ash (Fraxinus excel­sior, also in the olive fam­ily Oleaceae) as a host.”

Amanda Bailey, a com­mit­tee mem­ber of the Australian Olive Oil Association, con­firmed that the olive lace bug has been an issue this sea­son.

“New infes­ta­tions occur reg­u­larly through­out the grow­ing sea­son,” she said. ​“In extreme cases, some groves have defo­li­ated trees due to olive lace bugs.”

She added that the stress and dam­age to trees caused by olive lace bugs could shock the plant out of pro­duc­tion for two to three sea­sons and even longer if the trees are left untreated.

Bailey said con­di­tions have been per­fect for olive lace bugs this sea­son. ​“In some areas, rain has pre­vented grow­ers from attend­ing to the issue because the ground has been too boggy to get equip­ment into the groves,” she explained.

Meanwhile, Ian Buchanan, the owner of Jandra Olive Farm near Eurobin in Victoria, told Olive Oil Times his farm has effec­tively lost its crop this year.

“We were due for a slow year – we have had three good har­vests in a row – but the lace bug infes­ta­tion has scoured all of our trees,” he said.

“From past expe­ri­ence, this means that even though there are still olives vis­i­ble on leaf­less trees, they will no longer accu­mu­late oil,” Buchanan explained. ​“I also expect that the next har­vest in 2025 will be poor, as the trees will put their effort into recov­ery. The 2026 har­vest might be spec­tac­u­lar, but that’s a long way away from now.”

As a result of the infes­ta­tion, Buchanan planned to pur­chase an entire crop of olives to mill this year ​“to keep the busi­ness run­ning.”

However, the olive lace bug infested the grove where he would have pur­chased the olives, and he expected they would also lose their crop.

To his knowl­edge, Buchanan believes Jandra is located within a 1,000 square kilo­me­ter area where most olive groves are entirely infested. ​“It could well be more exten­sive than that, but I haven’t seen addi­tional media cov­er­age on it,” he said. ​“I know it is bad in Western Australia.”

Buchanan fol­lowed the usual pre­ven­ta­tive mea­sures to ward off olive lace bugs, but he said the insects behaved dif­fer­ently this time of year and man­aged to sur­vive.

“We are nor­mally com­pe­tent at man­ag­ing the olive lace bug,” he explained. ​“We deal with it in small out­breaks every year.”

He said the best prac­tice is spot spray­ing, which he usu­ally does in an open vehi­cle with a small tank.

“My eye is trained to spot a clus­ter from a mov­ing vehi­cle,” he said. ​“We only have 750 trees, so one per­son can deal with it. We also usu­ally see it first on sen­tinel trees (mon­i­tored for the early detec­tion of harm­ful insects) on the perime­ter.”

But now things have changed.

“This year, the out­breaks were in the mid­dle of my pad­docks, indi­cat­ing the bugs have suc­cess­fully over­win­tered,” he said. ​“Normally, we are too cold for the olive lace bug to sur­vive win­ter; it’s orig­i­nally from the warmer north. In fact, this win­ter, we had frost­bit­ten olives for the first time in ten years; it was unusu­ally cold.”

Buchanan said this sug­gests that these bugs have adapted to the cold. ​“I think it is also fueled by the unusu­ally humid sum­mer we have had. The humid­ity has been tough,” he said.

After spot spray­ing in the spring, Buchanan did so again in January before hir­ing a com­pany to blast spray the entire grove twice.

“We def­i­nitely killed a lot of the bugs, but they regen­er­ated again,” he said. ​“In effect, all I have suc­ceeded in doing was delay­ing the end result by a few weeks.”

Buchanan also observed the pres­ence of the olive lace bug in mature ash trees around the region.

“You can drive around and see olive lace bugs in them. While olive grove own­ers might be inter­ested in man­ag­ing these bugs, pub­lic trees in parks and on the side of the road won’t be,” he said. ​“So it is dif­fi­cult to con­tain.”

He added that another com­pli­cat­ing fac­tor is that own­ers of orna­men­tal olive trees and hobby farm­ers may not notice the infes­ta­tions, prov­ing a haven for the lace bugs and mak­ing out­breaks dif­fi­cult to pre­vent.

“Near me are three such groves, all heav­ily infested with olive lace bugs every year,” Buchanan said. ​“Inevitably, some of those out­breaks blow my way.”

According to Spooner-Hart, two main cli­matic con­di­tions influ­ence the spread of the lace bug.

“Hot, dry con­di­tions cause high mor­tal­ity in the young nymphal instars (the devel­op­men­tal stage between a pupa and an adult insect), espe­cially in the crawlers (newly hatched insects),” he said. ​“Conversely, mild and humid con­di­tions result in high sur­vival rates to adult­hood.”

“Dry con­di­tions, espe­cially in non-irri­gated crops, mean trees are more stressed and less able to tol­er­ate dam­age from bugs,” Spooner-Hart added.

Two years of La Niña dur­ing the 2021/22 and 2022/23 crop years in Eastern Australia, fol­lowed by an unusual El Niño in which the cli­mate has behaved more like it does dur­ing La Niña, may also con­tribute to the spread of the insects.

“We have had con­di­tions suit­able for bug sur­vival and buildup of infes­ta­tions,” Spooner-Hart said. ​“Milder win­ters also prob­a­bly assist in increas­ing the num­ber of over­win­ter­ing adults and even the devel­op­ment of eggs dur­ing this time.”

During the warmer win­ter, many trees did not lose all their leaves, allow­ing more nymphs to sur­vive.

“Over the past two years, sev­eral loca­tions, par­tic­u­larly in east­ern Australia, have reported heavy bug infes­ta­tions,” Spooner-Hart said. ​“This is prob­a­bly due to a com­bi­na­tion of these con­di­tions.”

Spooner-Hart rec­om­mends reg­u­larly mon­i­tor­ing groves begin­ning in mid-spring to detect the emer­gence of the first cohort of lace bugs. There usu­ally are three cohorts in a sea­son.

This is crit­i­cal in the man­age­ment plan. ​“They are most vul­ner­a­ble at this time as crawlers (young nymphs) and don’t travel, remain­ing in gre­gar­i­ous clus­ters,” Spooner-Hart said. ​“Originally, infes­ta­tions start in hot spots, which can be man­aged.”

The other strat­egy is effec­tively timed pes­ti­cide appli­ca­tions tar­geted at newly emerg­ing nymphs in the first cohort.

“A num­ber [of pes­ti­cides] are reg­is­tered in Australia for olive lace bug, includ­ing organic options such as potas­sium soaps and oth­ers designed to fit into IPM pro­grams,” Spooner-Hart said.

“We have sub­stan­tial evi­dence that one or two well-timed appli­ca­tions are highly effec­tive for one or more sea­sons,” he added. ​“They are not highly dis­rup­tive to the ecosys­tem and are unlikely to result in pes­ti­cide resis­tance prob­lems.”

Pruning the trees to cre­ate a more open canopy is another strat­egy for remov­ing olive lace bugs in small groves, par­tic­u­larly if the hot spots are con­tained.

Buchanan said they have started imple­ment­ing some changes in their oper­a­tions to become more resis­tant to the olive lace bug. Along with blast spray­ing at the start of spring, he is also run­ning some preda­tor insect tri­als.

While the spread of the lace bug is well-estab­lished in Victoria, Stephen Tham, the co-owner of Cape Schanck Olive Estate on the south­ern Mornington Peninsula, said the pests had not yet reached their groves.

“Biosecurity by restrict­ing vis­i­tors to the grove is the main line of defense,” he said. ​“The olive lace bug poten­tially spreads widely through the infected leaves and other plant mate­r­ial of vis­i­tors and farm­work­ers, shared machin­ery and per­haps con­tract har­vest­ing and pro­cess­ing.”

“We stopped hav­ing con­tract work­ers the last six years or so and have only our reg­u­lar farm­work­ers, and my sis­ter and hus­band, dur­ing har­vest and hence have min­i­mized this risk of cross-con­t­a­m­i­na­tion,” he con­cluded.