Researchers in Canada have demon­strated that odor­ants released by sun­flow­ers may pro­vide an organic solu­tion to the grow­ing prob­lems caused by the brown mar­morated stink bug (Halyomorpha halys).

Native to Japan, China and the Korean Peninsula, the insect has spread widely from East Asia in the last decades to North America and the European Union.

The inva­sive species have become a scourge for farm­ers as the lar­vae, and adult insects feed on a range of high-value crops. The insects’ pres­ence has been repeat­edly asso­ci­ated with the green drop of olive fruit, a con­di­tion in which unripe dru­pes fall to the ground and become unus­able.

However, a newly-pub­lished study in the Journal of Chemical Ecology sug­gests that the odors of cer­tain chem­i­cals released by sun­flow­ers as they bloom may help curb the insects’ repro­duc­tion.

Researchers from Simon Fraser University’s bio­log­i­cal sci­ence research depart­ment exam­ined the olfac­tive reac­tions of the brown mar­morated stink bug to dif­fer­ent stages of devel­op­ment of the dwarf sun­flower (Helianthus annuus).

The sci­en­tists inves­ti­gated the insect’s behav­ior in still-air lab­o­ra­tory con­di­tions, with four pot­ted sun­flow­ers at dis­tinct phe­no­log­i­cal stages (veg­e­ta­tive, pre-bloom, bloom and seed­ing).

They found that most females were attracted to the bloom­ing plants but deposited their eggs evenly on all four.

The researchers then intro­duced the insects to a mov­ing-air two-choice olfac­tome­ter exper­i­ment, which tested their level of attrac­tion to each phe­no­log­i­cal stage and com­pared the results to the still-air trial.

“Blooming sun­flow­ers per­formed best over­all, but no one plant stage was most attrac­tive in all exper­i­ments,” the researchers wrote.

They cap­tured and ana­lyzed the head­space odor­ants of each plant stage, find­ing that sun­flow­ers had an increase in odor-emit­ting com­pounds, includ­ing monoter­penes, in the tran­si­tion­ing phase from pre-bloom to bloom.

The researchers then focused on find­ing the cor­rect mix of the odor­ants to attract the insects.

“Analyzing the head­space odor­ant blend of bloom­ing sun­flower by gas chro­mato­graphic-elec­troan­tenno­graphic detec­tion revealed 13 odor­ants that con­sis­tently elicited responses from female H. halys anten­nae,” the researchers wrote. ​“An 11-com­po­nent syn­thetic blend of these odor­ants attracted H. halys females in lab­o­ra­tory olfac­tome­ter exper­i­ments.”

The result­ing blend could be deployed in traps that would attract brown mar­morated stink bugs, keep­ing them away from the most valu­able crops.

“Particularly in spring, a sim­pler yet fully effec­tive sun­flower semi­o­chem­i­cal blend could be devel­oped and cou­pled with syn­thetic H. halys aggre­ga­tion pheromones to improve mon­i­tor­ing efforts or could improve the effi­cacy of mod­i­fied attract-and-kill con­trol tac­tics for H. halys,” the researchers wrote.

In Italy alone, the brown mar­morated stink bug causes about €85 mil­lion worth of dam­age to the agri­cul­ture sec­tor each year.

According to the U.S. Environmental Protection Agency, the insect has been iden­ti­fied in 38 states and the District of Columbia, with farm­ers report­ing dam­age to var­i­ous field crops, fruits and veg­eta­bles.

As a result, sci­en­tists are des­per­ately seek­ing to reduce their pop­u­la­tions, which often exceed those of endemic species.

One effort has seen Italian researchers intro­duce the samu­rai wasp, a nat­ural preda­tor of the brown mar­morated stink bug.

The goal of its deploy­ment is to con­tain the pres­ence of the bug by at least 60 per­cent in most areas, but the experts said it would take a few sea­sons to deter­mine whether the plan is work­ing.

• Journal of Chemical Ecology
• U.S. Environmental Protection Agency