Mild Temperatures Worry Olive Growers in Central and Northern Italy

Summary

Cooler tem­per­a­tures and July rains in cen­tral and north­ern Italy have cre­ated ideal con­di­tions for the spread of the olive fruit fly, lead­ing grow­ers to inten­sify mon­i­tor­ing and treat­ment efforts to pro­tect the upcom­ing har­vest. The olive fruit fly infes­ta­tions have been reported in var­i­ous regions of Italy, with dif­fer­ent areas expe­ri­enc­ing vary­ing lev­els of infes­ta­tion and author­i­ties advis­ing grow­ers to take timely inter­ven­tions to com­bat the pest.

The com­bi­na­tion of July rains and cooler-than-aver­age tem­per­a­tures in cen­tral and north­ern Italy has cre­ated ideal con­di­tions for the spread of the olive fruit fly.

Growers and regional author­i­ties are inten­si­fy­ing mon­i­tor­ing and treat­ment efforts to pro­tect the upcom­ing har­vest.

According to the lat­est data from the European Union’s Copernicus Climate Change Service, in large areas of Europe, July has proved slightly cooler than recent years.

In Italy, cen­tral and north­ern regions expe­ri­enced repeated sig­nif­i­cant rain­fall, which also con­tributed to reduced sur­face tem­per­a­tures. Data show that in those areas, July was the coolest July of the last ten years.

Following an oppo­site trend, in those same weeks, most of south­ern Italy expe­ri­enced a new heat­wave that brought tem­per­a­tures there to record lev­els, accom­pa­nied by a dras­tic lack of rain­fall.

For olive grow­ers in the cen­tral and north­ern regions, mild aver­age tem­per­a­tures raised the risk of olive fruit fly infes­ta­tions.

While sev­eral cen­tral and north­ern regions are report­ing active infes­ta­tions, national-level pro­jec­tions remain uncer­tain. Monitoring oper­a­tions are active across the whole coun­try.

The pest thrives with tem­per­a­tures in the range of 20 ºC. Only extreme tem­per­a­tures, such as above 35 °C, can halt infes­ta­tions or even reduce their impact.

Abundant rain­fall is also ben­e­fi­cial to the olive fruit fly, as water fur­ther stim­u­lates repro­duc­tion.

In their con­tin­u­ous mon­i­tor­ing oper­a­tions, Latium regional author­i­ties and the pro­duc­ers’ orga­ni­za­tion OP Latium, in cen­tral Italy, released a series of bul­letins about the cur­rent fruit fly sit­u­a­tion.

The organization’s mon­i­tor­ing involves inspect­ing 20 ran­domly selected olives from each of ten olive trees per hectare, for a total of 200 olives exam­ined per hectare.

In south­ern Lazio, up to the areas north of Rome, olive fruit fly dam­age has been found in two to five per­cent of the sam­pled olives.

Treatments are sug­gested when four to five per­cent of the olives are esti­mated to have been con­t­a­m­i­nated by an egg.

Farther north, in Canino, renowned for its extra vir­gin olive oil, infes­ta­tions are now reach­ing 10 per­cent.

Growers in neigh­bor­ing areas reported slightly lower infes­ta­tions to Olive Oil Times.

Meanwhile, in another cen­tral region, Abruzzo, author­i­ties updated their fruit fly warn­ing to local olive grow­ers.

At the end of July, they sug­gested inter­ven­ing when olive trees bear­ing medium to large olives that had been infected. As August kicked in, they asked for broader mon­i­tor­ing of the cur­rent infes­ta­tions.

“Maximum atten­tion should be paid to olive fruit fly attacks fol­low­ing this week’s rain­fall and the drop in tem­per­a­tures, which are expected to remain rel­a­tively low for the next few days,” the author­i­ties wrote.

“The cur­rent weather con­di­tions are favor­able to fly activ­ity, and indeed, imme­di­ately after the rain, stings have been observed on olives, typ­i­cally the larger ones, some of which are fer­tile,” they added.

Stings are con­sid­ered fer­tile only when they come from flies deposit­ing their egg in the olive. Even if not fer­tile, a sting found on an olive fruit can still sig­nal a pos­si­ble ongo­ing infes­ta­tion.

“However, there are also olive sam­ples from the coastal area that show no stings at all,” Abruzzan author­i­ties wrote.

They asked grow­ers to treat their olives against the fly even when only a min­i­mal pres­ence of the insect is found.

The note also remarked that in the absence of infes­ta­tion, no treat­ment should be car­ried out, as it has no pre­ven­tive effect.

The agro­nomic ser­vices mon­i­tor­ing infes­ta­tions in Tuscany noted that, in mon­i­tored areas, infes­ta­tions have been found in sam­pled olives 15 to 35 per­cent of the time, and are cur­rently under treat­ment.

They are sug­gest­ing con­ven­tional olive grow­ers pro­ceed with treat­ments against the adult flies as soon as a five per­cent infes­ta­tion is found.

“Plan adul­ti­cide treat­ments using insec­ti­cide and bait, antic­i­pat­ing the resump­tion of fly activ­ity given the favor­able con­di­tions for the pest’s devel­op­ment, and keep the fruits pro­tected with anti-ovipo­si­tion prod­ucts (kaolin, rock dust, man­isol),” they wrote.

Tuscan author­i­ties rec­om­mended that organic olive grow­ers cover the foliage and fruits with anti-ovipo­si­tion prod­ucts.

“When daily catches exceed three or are increas­ing, apply treat­ments with adul­ti­ci­dal prod­ucts and an attrac­tant bait,” the author­i­ties wrote.

According to the lat­est infes­ta­tion map, updated in the first week of August, a large num­ber of grow­ers in Tuscany are report­ing more than a ten per­cent fruit fly pres­ence in their olives.

In north­west­ern Italy, in Liguria, as the pres­sure of the fly is found in all main grow­ing areas, regional author­i­ties are advis­ing grow­ers to pro­ceed with treat­ments in August even if tem­per­a­tures are now expected to rise.

In Veneto, in the north­east­ern part of the coun­try, mon­i­tor­ing oper­a­tions are show­ing that a timely inter­ven­tion helped many grow­ers keep infes­ta­tion vol­umes down.

In their August bul­letin, the regional author­i­ties are sug­gest­ing con­tin­u­ing treat­ments where needed and main­tain­ing the max­i­mum degree of vig­i­lance on the infes­ta­tions.

Experts noted how the abun­dant pres­ence of the olive fruit fly in some areas also stems from the mild win­ter, which favored the sur­vival of the last gen­er­a­tion of flies from the pre­vi­ous sea­son.

While the pest can sig­nif­i­cantly affect both qual­ity and yield, timely inter­ven­tions, both con­ven­tional and organic, appear to have been effec­tive so far.

As for the prospects of the new olive sea­son, the results are still too early to call. 

Most of the Italian olive and olive oil pro­duc­tion comes from the south­ern regions. It is the per­for­mance of olive farms in those areas that will deter­mine the vol­umes of the 2025/26 crop year.

The next olive har­vest in Italy is expected to start in some areas in the first weeks of September, and to pick up pace between October and November.