Uptick in Olive Fruit Fly Infestations Reported in Andalusia

As olive groves in Andalusia, the world’s largest olive oil-pro­duc­ing region, enter the pit-hard­en­ing phase of their phe­no­log­i­cal devel­op­ment, the num­ber of olive fruit flies reported in groves across the autonomous com­mu­nity has spiked.

While recent rain­fall in Andalusia is unlikely to sal­vage expec­ta­tions of another poor har­vest in Spain, the lit­tle rain that did fall cre­ated ideal con­di­tions for the pro­lif­er­a­tion of the olive fruit fly, the region’s most promi­nent olive tree pest.

According to the regional government’s phy­tosan­i­tary author­i­ties, the num­ber of flies cap­tured and the amount of fruit already dam­aged indi­cate an increased pres­ence of olive fruit flies in spring 2023 com­pared to pre­vi­ous ones.

However, the author­i­ties added that high tem­per­a­tures at the end of June com­bined with sus­tained efforts to treat groves has led to a recent decrease in fruit fly pop­u­la­tions and dam­age to olives.

The first dam­age caused by olive fruit flies in Andalusia was reported at the end of May.

Surveys con­ducted at the end of June by author­i­ties found that the province of Córdoba has seen the most dam­age, with 4.6 per­cent of olives sur­veyed with vis­i­ble olive fruit fly bites, a slight increase from the mid­dle of the month.

This has coin­cided with an increase in olive fruit fly plate cap­tures in the province. Authorities use plate cap­tures as a proxy for repro­duc­tive behav­ior since they use pheromones to attract the flies before they get stuck.

Meanwhile, in Jaén, the largest olive oil-pro­duc­ing province in Andalusia, author­i­ties saw a decrease in olive fruit fly bites, with a mid-month sur­vey find­ing 2.6 per­cent of fruits dam­aged and the end-of-month sur­vey show­ing 2.04 per­cent with dam­age.

However, author­i­ties also noted a sig­nif­i­cant increase in plate cap­tures over the same period indi­cat­ing olive grow­ers must remain vig­i­lant.

The province of Cadíz also demon­strated a con­cern­ing increase in olive fruit fly bites, while the province of Seville expe­ri­enced a slight decrease. Authorities had not pub­lished data from other provinces at the time of writ­ing.

However, author­i­ties said olive fruit fly cap­tures from all types of traps have been con­sid­er­ably higher in June than usual, even in areas where tra­di­tion­ally there have been fewer prob­lems with fruit fly infes­ta­tions.

Along with chem­i­cal and organic treat­ments, author­i­ties have rec­om­mended to olive grow­ers that they fos­ter appro­pri­ate envi­ron­ments for the olive fruit fly’s nat­ural preda­tors, includ­ing var­i­ous wasp and bee­tle species – Pnigalio mediter­ra­neus, Psittalia con­color, Eurytoma martel­lii, Cyrtoptyx latipes and Eupelmus uro­zonus.

Previously, Andalusian researchers pro­moted efforts to intro­duce bats to olive groves, another local olive fruit fly preda­tor.

• Junta de Andalucía