Spotted Wing Drosophila (2016)

Lower Mainland Growers see more Spotted Wing Drosophila
by Ronda Payne February 16, 2016

Spotted Wing Drosophila (SWD) has been harassing Lower Mainland berry growers for five years and Tracy Hueppelsheuser, entomologist, Plant and Animal Health Branch with the BC Ministry of Agriculture, noted that 2015 was an even more exceptional year for the persistent pest.

Research has been ongoing to find and approve the tools farmers need to defend crops against SWD with no current biological control recommended by Agrifood BC and few chemical controls. Chemicals listed by the ministry are Delegate WG, Entrust SC, Mako EC and Malathion 85E. Mako and Malathion were both emergency registered for treatment of SWD in 2015, Entrust is OMRI approved for organic production and treatment guidelines for all products are available on the ministry production guide site.

Few tools to choose from means growers must be aware of all possible ways to manage SWD and Hueppelsheuser feels 2015 was a great example of preparedness and action.

“Winter and spring trapping along edges of Fraser Valley raspberry and blueberry fields from December to May has been done for the last five years,” she says. “The winter of 2014 to 2015 was warm and dry, resulting in much less SWD mortality than in previous years. Over this winter and spring, we caught six to nine times more flies than in previous winters.”

Summer was even worse with trapping showing seven to 122 times more flies in blueberry and raspberry fields when compared to previous summers. Hueppelsheuser says the numbers ramped up earlier and were exceptionally high in both summer and winter. Wild fruit saw heavy SWD infestations in 2015 even though previous years saw light infestations in wild fruit.

“The berry industry was bracing for the worst, and I think that was a good thing,” she says. “Growers were therefore more prepared to deal with the pest in a timely and proactive manner.”

This early preparedness combined with the hot, dry summer (SWD thrives in humid environments) allowed the programs of management to be implemented more accurately in terms of spray and harvest schedules. This didn’t necessarily keep SWD out of sight, but it certainly kept it at bay. A far better outcome than anticipated.

Hueppelsheuser is hoping more emergency registrations will be approved for the 2016 season. She encourages growers to stay on top of the activities outlined on the ministry site including traps, elimination of culled and old fruit from all areas, watching host plants in neighboring fields and most importantly is to pick early, clean and often.

“SWD is anything but routine,” she says. “The story has played out differently each of the five years we have had this pest and we would encourage growers to keep up to date with the information available.”

In summary, Heuppelsheuser’s biggest advice can be taken from how the 2015 season played out – anticipate SWD and plan for it to avoid being unprepared.