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Olive fruit fly pop­u­la­tions in Spain have devel­oped genetic resis­tance to a com­mon type of pes­ti­cide used to con­trol and elim­i­nate them, accord­ing to newly pub­lished research from the Complutense University of Madrid.

The study, which was pub­lished in the aca­d­e­mic jour­nal Insects, found that more than 80 per­cent of olive fruit fly pop­u­la­tions on the Spanish main­land have genes that con­fer a high level of resis­tance to the com­monly-used organophos­phate pesticides.

The lev­els of resis­tance to organophos­phate pes­ti­cides were found to be con­sis­tent in fruit fly pop­u­la­tions regard­less of the type of olive grove (i.e. organic, super-high-den­sity, tra­di­tional) in which they were found.

Normally, organophos­phate pes­ti­cides work by inhibit­ing the acetyl­cholinesterase pro­tein, which breaks down the chem­i­cal acetyl­choline, a neu­ro­trans­mit­ter respon­si­ble for mus­cle contraction.

“Organophosphate insec­ti­cides irre­versibly block acetyl­cholinesterase, there­fore, acetyl­choline is not degraded, which causes pro­longed paral­y­sis of the insect and with it, its death,” Esther Lantero, a researcher at the university’s depart­ment of genet­ics, phys­i­ol­ogy and micro­bi­ol­ogy said.

However, the researchers said that the overuse of these pes­ti­cides on olive trees across the coun­try have caused three dif­fer­ent types of muta­tions to the ace gene. Each of these muta­tions has an adverse effect on the way in which the pes­ti­cides inter­acted with the acetyl­cholinesterase pro­tein and decreased their efficacy.

“It is essen­tial to find effec­tive alter­na­tives that sig­nif­i­cantly reduce the den­sity of the olive fly pop­u­la­tions,” Lantero said. ​“For this rea­son, efforts should focus on the search for bio­log­i­cal, cul­tural, biotech­no­log­i­cal or phys­i­cal meth­ods that reduce the use of chem­i­cals, con­cen­trat­ing the approach based on bio­log­i­cal control.”

Along with test­ing olive fruit fly pop­u­la­tions from 12 dif­fer­ent Spanish regions, the researchers also tested pop­u­la­tions from 12 other regions spread across five coun­tries in the Mediterranean.

They found high degrees of resis­tance to organophos­phate pes­ti­cides from selected pop­u­la­tions in Greece and Italy (at least 95 per­cent), while pop­u­la­tions from Israel and Portugal had sig­nif­i­cantly lower lev­els of resis­tance (closer to 50 percent).

Meanwhile, pop­u­la­tions from Tunisia and Spain’s Balearic Islands had nearly neg­li­gi­ble lev­els of resistance.

• Insects
• Ecoticias