As Promising Harvest Nears in Italy, Favorable Conditions for the Olive Fruit Fly Too

Perfect weather over the last few months has cre­ated con­di­tions for a strong olive har­vest in Italy, both for quan­tity and qual­ity. But in recent days the cli­mate has also become quite favor­able for the pro­lif­er­a­tion of Bactrocera Oleae, also called olive fruit fly.

A patchy attack in var­i­ous parts of the coun­try, due to fre­quent rains and warm tem­per­a­tures have made this very last period of the grow­ing sea­son a chal­lenge for olive farm­ers against one of their most feared pests.

We met Riccardo Macari, an expe­ri­enced nurs­ery tech­ni­cian and expert pruner to talk about strate­gies for curb­ing the onset of this harm­ful insect.

“Much has changed regard­ing the man­age­ment of the fly and other olive dis­eases over the last thirty years. In the 1980s farm­ers used to sched­ule up to 7 or 8 treat­ments a year. Now this approach has been aban­doned in favor of a greater con­sid­er­a­tion of the envi­ron­ment, and because the pathogens ended up devel­op­ing resis­tance to prod­ucts.”

These days, the most com­monly used prod­ucts in con­ven­tional agri­cul­ture are organophos­phates like Dimethoate, with a broad-spec­trum and cytotropic action.

In recent years, the use of organic and inte­grated farm­ing meth­ods has increased, and some organic prod­ucts can have a good repel­lent action. ​“Under the 15 per­cent of infes­ta­tion, Neem oil, that comes from the pressed fruits and seeds of Azadirachta indica, can be dis­solved in water and sprayed,” Macari sug­gested.

“Kaolin is also help­ful in some cases, while Spinosad, an adul­ti­cide based on chem­i­cal com­pounds of the bac­te­r­ial species Saccharopolyspora spin­ose, which is con­sid­ered a nat­ural prod­uct and approved for use in organic agri­cul­ture by numer­ous coun­tries, can be very effec­tive if com­bined with traps.” A pheromone-based bait with the addi­tion of pro­teins or nitroge­nous sub­stances attracts the fly that is killed by an insec­ti­cide.

“In my opin­ion, what makes a dif­fer­ence is the aware­ness of appro­pri­ate prod­ucts and the eval­u­a­tion of the pres­ence of a pathogen in the olive grove,” he affirmed. ​“For instance, if I esti­mate that the pres­ence of the fly is more than 10 per­cent, at this point it is use­ful to apply a suit­able treat­ment, which I will avoid if the pres­ence is neg­li­gi­ble.”

Tailoring plans for spe­cific vari­eties is also impor­tant. The native cul­ti­vars are in gen­eral more resis­tant to the pathogen, and there is now a grow­ing ten­dency to pre­serve and restore them to bet­ter pre­vent dis­eases.

“In the area of Roman Castles, the fer­tile ter­ri­tory south­east of Rome where I man­age dif­fer­ent olive groves, in mid-July, we expe­ri­enced am ini­tial attack of the fly that did not have con­se­quences,” Macari explained. Due to tem­per­a­tures above 32°-33°C (89.6°-91.4°F) and low humid­ity, the ovipo­si­tion was not suc­cess­ful and the lar­vae did not develop.

“It is fun­da­men­tal for us to be in the olive grove, in order to eval­u­ate cli­matic fac­tors and deter­mine appro­pri­ate treat­ments,” he pointed out. ​“Now we are wait­ing to observe the behav­ior of the sec­ond gen­er­a­tion of insects. During the third week of August the tem­per­a­ture dropped to 26°-27°C (78.8°-80.6°F) and humid­ity increased, favor­ing ovipo­si­tion; there­fore, I inter­vened with Dimethoate in the case of con­ven­tional cul­ti­va­tion, while I used Bacillus thuringien­sis serotype kurstaki, Neem oil and pyrethroids in organic olive groves.

The first rem­edy against par­a­sites is the cold, and the warmer tem­per­a­ture in recent years has helped pests to pro­lif­er­ate, Macari said. But treat­ments in have become more focused and pru­dent and this approach allows us to pre­serve the del­i­cate ecosys­tem of the olive grove and there­fore the envi­ron­ment, and it is less expen­sive for farm­ers.

“Regarding pre­ven­tion, in addi­tion to mon­i­tor­ing traps, I rec­om­mend pay­ing atten­tion to plants from March or April (in the Northern Hemisphere) when the veg­e­ta­tive growth starts, and not wait until July as many farm­ers do,” he sug­gested.

“During that time you can also check the pres­ence of other pathogens like Prays oleae, also called olive moth, Palpita union­alis or Otiorhynchus, and you can apply a light treat­ment to impact the first gen­er­a­tion of the fly. It is much bet­ter to act before the olives sprout, in order to fight pathogens that involve the whole plant.”