`Unraveling the Mystery Behind Slovenia's Dramatic Fruit Drop - Olive Oil Times

Unraveling the Mystery Behind Slovenia's Dramatic Fruit Drop

By Nedjeljko Jusup
Jul. 25, 2022 13:16 UTC

The joy of abun­dant flow­er­ing was fol­lowed by sad­ness a month after fer­til­iza­tion as olives turned brown and fell from their branches. This is a sum­mary of this year’s olive grow­ing sea­son in Slovenia.

Sandwiched between the Alps and the Adriatic Sea, olives have been cul­ti­vated since ancient times in the coastal areas of​the Brdi, Goriška, the Vipava Valley, Karst and Slovenian Istria.

Olive farm­ing has great poten­tial, both from the point of view of a sus­tain­able food sys­tem and from the point of view of pre­serv­ing the qual­ity of the envi­ron­ment and sus­tain­able tourism,” said Maja Podgornik, the head of the Institute for Olive Growing at ZRS Koper.

See Also:Droughts Are More Frequent, Last Longer and Accelerate Water Shortages, U.N. Says

Slovenian extra vir­gin olive oil is reg­u­larly rec­og­nized for its qual­ity at inter­na­tional com­pe­ti­tions. At the NYIOOC World Olive Oil Competition, the world’s largest qual­ity con­test, Slovenian pro­duc­ers have earned awards each year since its incep­tion in 2013.

Olives are grown on 2,389 hectares in Slovenia by around 4,200 grow­ers. The total income gen­er­ated by the sec­tor reaches €10 to €15 mil­lion each year. As a result, olive grow­ers are des­per­ately seek­ing answers to this year’s fruit drop.


The cur­rent dry­ing and falling of the fruits can­not be con­nected with the attacks of dis­eases and pests,” the Agricultural Forestry Institute of Nova Gorica replied deci­sively.

Due to the lack of pre­cip­i­ta­tion and the result­ing extremely dry con­di­tions this year few dis­ease out­breaks were reported.

While some cases of pea­cock’s eye (Spilocaea oleag­ina) and olive spot (Mycocentrospora cla­dospo­ri­oides), two fun­gal dis­eases, were reported, timely spray­ing pre­vented any dam­age from occur­ring. The phe­nom­e­non was less pro­nounced than in pre­vi­ous years.

With the help of pheromone traps, farm­ers were also able to fol­low the flight and repro­duc­tive cycles of the olive moth (Prays oleae). They said that they have not noticed much dif­fer­ence in the time and num­ber of pest out­breaks com­pared to pre­vi­ous years.

For sev­eral years now, we have been reg­u­larly mon­i­tor­ing the pres­ence of the mar­ble bug (Halyomorpha halys) in olive groves,” offi­cials from the insti­tute wrote in their report. The pest was reg­u­larly observed in indi­vid­ual olive groves, but in fewer num­bers than last year.”

Native olives (nor­mally devel­oped, dried and fallen) are reg­u­larly sam­pled and inspected for pos­si­ble dam­age caused by black bug bites,” they added. We did not notice any dam­age from pests.”

Therefore, they con­cluded the dur­ing and falling of the fruit was not con­nected with attacks of the mar­ble bug or the pres­ence of other pests in olive groves.

Since the begin­ning of this year, the most sig­nif­i­cant olive pest – the olive fruit fly (Bactrocera oleae) – has been mon­i­tored at dozens of loca­tions with the help of pheromone traps.

The fly was iden­ti­fied in larger num­bers from the end of March to the begin­ning of May, the period before the olive trees blos­som. Later, olive fruit fly pop­u­la­tions decreased sig­nif­i­cantly.

The cur­rent weather con­di­tions are not favor­able for the appear­ance of pests, which is con­firmed by the small num­ber iden­ti­fied in pheromone traps. However, offi­cials still rec­om­mend that farm­ers set traps in their groves to deter any poten­tial infes­ta­tions.


Additional mea­sures against pests are cur­rently not nec­es­sary, accord­ing to experts.

Instead, they believe that the cause of the dry­ing and drop­ping relate more to abi­otic fac­tors such as air tem­per­a­ture, soil tem­per­a­ture and rain­fall.


In the period from flow­er­ing to ripen­ing, a suf­fi­cient amount of water is very impor­tant for the devel­op­ment of the olive fruits. It has been sci­en­tif­i­cally proven that on trees exposed to higher tem­per­a­tures there is an increased fruit drop and con­se­quently a smaller har­vest.

Based on pre­cip­i­ta­tion mon­i­tor­ing, Slovenian experts said the win­ter and spring of 2022 have been the dri­est since 1993. Overall, they expect 2022 will be the dri­est year of the past three decades.


In the first six months of 2022, only 193 mil­lime­ters of rain fell in Slovenia. From September 2021 to April 2022, the total amount of pre­cip­i­ta­tion was about 300 mil­lime­ters. A min­i­mum of 500 mil­lime­ters of rain­fall is required for opti­mal olive devel­op­ment.

The scale of this year’s drought exceeds those of 2003, 2012 and 2017, when olive grow­ers pro­duced 40 to 70 per­cent fewer olives, and the drought was declared a nat­ural dis­as­ter at the state level,” offi­cials said.

The lack of rain­fall in the win­ter and spring brings plenty of headaches to olive farm­ers as mois­ture does not build up in the soil. By the end of the spring – in the period before and dur­ing flow­er­ing – too lit­tle rain­fall means the trees are unable to fer­til­ize the blos­soms nor­mally and receive nutri­ents.

Experts believe this led to weaker devel­op­ment of the flo­ral organs and com­plete fer­til­iza­tion, which may have resulted in the brown­ing and fruit drop.

Another con­se­quence of the country’s ongo­ing drought has been ram­pant wild­fires burn­ing across Slovenia.

According to data from the European Forest Fire Information System (EFFIS), five fires have burned 2,384 hectares in Slovenia in the first six months of 2022. From 2008 to 2021, 10 wild­fires burned 1,095 hectares, less than half of this year’s dam­age.

In the Karst region, on Slovenia’s west­ern bor­der with Italy, the Carso wild­fire is cur­rently wreak­ing havoc. Photos from local media sug­gest some olive trees have burned and smoke has forced local res­i­dents to flee.

According to EFFIS, 2022 is on pace to be the worst wild­fire sea­son in Europe since records began.

Daniel Dawson con­tributed to this report.


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