Olive Leaf Moth Threatens Brazilian Crops: Researchers Seek Solutions

Summary

Brazilian researchers con­ducted two stud­ies on man­ag­ing olive leaf moth infes­ta­tions in Rio Grande do Sul, test­ing a botanic insec­ti­cide and intro­duc­ing Darwin wasp species as poten­tial preda­tors. The botanic insec­ti­cide showed promise in con­trol­ling olive leaf moth lar­vae, while the Darwin wasps were able to par­a­sitize the cater­pil­lars, offer­ing a poten­tial Integrated Pest Management tool for olive grow­ers in the region.

A pair of stud­ies con­ducted by Brazilian researchers out­line new meth­ods for deal­ing with olive leaf moth infes­ta­tions, which are com­mon in the olive groves of the south­ern­most state of Rio Grande do Sul.

The lar­vae of the olive leaf moth, also known as the Palpita for­fi­cifera, feed on young olive leaves and branches, harm­ing the devel­op­ment of newly planted trees.

Currently, grow­ers con­trol infes­ta­tions after lar­vae have been detected by spray­ing insec­ti­cides. However, few syn­thetic insec­ti­cides are reg­is­tered with Brazil’s Ministry of Agriculture and Livestock.

Consequently, the researchers exe­cuted sep­a­rate stud­ies on the effec­tive­ness of a botanic insec­ti­cide for pop­u­la­tion con­trol and the intro­duc­tion of a tar­geted preda­tor. Their find­ings were pre­sented at the sec­ond Latin American Olive Oil Conference, which was hosted in Montevideo, Uruguay.

In the first study, the researchers tested a botanic insec­ti­cide with oxy­ma­trine as an active ingre­di­ent com­pared with a com­mon syn­thetic insec­ti­cide with spine­toram as its active ingre­di­ent.

They found that the oxy­ma­trine-based botanic insec­ti­cide per­formed sim­i­larly to the syn­thetic insec­ti­cide on the lar­vae of the olive leaf moth, though it was less effec­tive against adults.

“Results indi­cate that the botanic insec­ti­cide may be an eco-friendly and suit­able option for P. for­fi­cifera man­age­ment since it can cause mor­tal­ity lev­els sim­i­lar to the syn­thetic insec­ti­cide,” they wrote. ​“Field tri­als in com­mer­cial olive orchards are rec­om­mended to bet­ter ascer­tain oxy­ma­trine’s impact on P. for­fi­cifera.”

In the sec­ond study, per­formed in vitro, the researchers tested whether Darwin wasp species could exert nat­ural par­a­sitism on the olive cater­pil­lar. This pro­vided a new Integrated Pest Management tool to grow­ers in Rio Grande do Sul, the country’s largest olive oil-pro­duc­ing region, and neigh­bor­ing Santa Catarina.

According to the researchers, the two Darwin wasp species – Eiphosoma sp. nov. and Temeluche sp. nov. – were only recently dis­cov­ered in south­ern Brazil, and no pre­vi­ous stud­ies have exam­ined whether they would nat­u­rally prey on olive cater­pil­lars.

The researchers col­lected olive cater­pil­lar lar­vae from olive groves in Chapecó, Santa Catarina, and Pelotas, Rio Grande do Sul, before intro­duc­ing lar­vae from two species of Darwin wasps and leav­ing the infected sam­ples to incu­bate.

After 14 hours of incu­ba­tion, both lar­vae from Darwin wasp species emerged from the olive cater­pil­lar lar­vae, sug­gest­ing that they may nat­u­rally prey on the cater­pil­lars in an uncon­trolled envi­ron­ment.

Researchers in Italy have under­taken sim­i­lar stud­ies to deter­mine whether samu­rai wasps could be effec­tive nat­ural preda­tors of the brown mar­morated stink bug, a vec­tor for the deadly Xylella fas­tidiosa bac­terium.

Their results indi­cated that the wasp effec­tively par­a­sitized over one-third of stink bug eggs in one region in the coun­try’s north.

Similar efforts in south­ern Spain found that Iberian ants nat­u­rally prey on olive moth lar­vae in olive groves with­out dis­rupt­ing the rest of the ecosys­tem.

“These find­ings are impor­tant to prospect the nat­ural bio­log­i­cal con­trol of the olive cater­pil­lar in olive orchards,” the researchers con­cluded.