Repellent effect of essential oils on adult individuals of pollen beetle (Brassicogethes sp.)

Vrlo visoka razina rezistentnosti repičina sjajnika na insekticide onemogućava proizvođačima učinkovitu zaštitu uljane repice. Zbog toga je potrebno pronaći nova alternativna nekemijska rješenja, a jedno od njih je korištenje eteričnih ulja. Dosadašnjim laboratorijskim pokusima utvrđen je vrlo visoki repelentni učinak određenih eteričnih ulja na odrasle oblike repičina sjajnika u lociranju biljke domaćina. U praksi bi aplicirano eterično ulje moglo odbiti odrasle oblike repičina sjajnika od glavnog usjeva pri čemu bi primjena insekticida u potpunosti mogla izostati. U ovom istraživanju očekuje se utvrditi repelentno djelovanje eteričnih ulja na odrasle oblike repičina sjajnika. Tijekom 2021. prikupljeni su odrasli oblici repičina sjajnika otresanjem terminalnih cvatova u entomološki kavez, a prije postavljanja pokusa 40 sati bili su bez izvora hrane. Za provedbu pokusa korištena su eterična ulja zvjezdastog anisa, bosiljka, eukaliptusa, lavande, limuna i paprene metvice razrijeđena s acetonom u omjeru 1:10, a 40 μl primijenilo se na 3 cm2 filtar papira. Na 6-kanalni olfaktometar spojene su posude s tretiranim filtar papirom u koje je umotan netretirani terminalni cvat uljane repice, a kao kontrola korišten je filtar papir tretiran acetonom. U sredinu olfaktometra postavljeno je 10 odraslih oblika repičina sjajnika te je brojano koliko jedinki prijeđe završnu liniju prema određenom izvoru mirisa u 90 sekundi nakon puštanja. Rezultati pokazuju da je 60 % jedinki repičinog sjajnika odabralo izvor bez mirisa. Eterična ulja s mirisom bosiljka i eukaliptusa najmanje su privukla pozornost jedinki odnosno samo 4,5 % od ukupnog broja. Menta, kao i anis, privukla je 22,7 % kukaca dok aceton kao kontrola nešto manje od 20%. Limun se pokazao kao najlošiji miris te je privukao 26,1 % odraslih jedinki, međutim sva eterična ulja korištena u pokusu pokazala su repelentno djelovanje na odrasle oblike repičinog sjajnika.The very high level of resistance of pollen beetle to the insecticide makes it impossible for producers to effectively protect oilseed rape. For this reason, it is necessary to find new alternative non-chemical solutions, and one of them is the use of essential oils. Previous laboratory experiments have established a very high repellent effect of certain essential oils on the adult forms of the pollen beetle in locating the host plant. In practice, the applied essential oil could repel the adult forms of pollen beetle from the main crop, in which case the application of insecticides could be completely absent. In this research, it is expected to determine the repellent effect of essential oils on the adult forms of the pollen beetle. During 2021, the adult forms of the rape plant were collected by shaking off the terminal inflorescences in an entomological cage, and before setting up the experiment, they were without a food source for 40 hours. For the experiment, essential oils of star anise, basil, eucalyptus, lavender, lemon and peppermint diluted with acetone in a ratio of 1:10 were used, and 40 μl was applied to 3 cm2 of filter paper. To the 6-channel olfactometer, vessels with treated filter paper were connected, in which an untreated terminal flower of oilseed rape was wrapped, and filter paper treated with acetone was used as a control. In the middle of the olfactometer, 10 adult forms of the pollen beetle were placed, and it was counted how many individuals crossed the finish line towards a certain source of smell in 90 seconds after release. The results show that 60% of the only pollen beetle chose the odourless source. Essential oils with the smell of basil and eucalyptus attracted the least attention of individuals, i.e. only 4.5% of the total number. Mint, as well as anise, attracted 22.7% of insects, while acetone as a control slightly less than 20%. Lemon turned out to be the worst smell and attracted 26.1% of adults. In general, all the essential oils used in the experiment showed a repellent effect on the adult forms of the pollen beetle