Foiling fungus gnats

Foiling fungus gnats

Brian Austin of Dutch Heritage Gardens shares his tips for stopping fungus gnats, shoreflies and botrytis.

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December 11, 2016

Brian Austin, head grower at Dutch Heritage Gardens, propagates “every annual under the sun and quite a few perennials as well” at the 10-year-old Colorado grower. Dutch Heritage Gardens propagates about 95 percent of its plants in-house. However, it only produces herbaceous plants, so Austin faces some different challenges than tree or woody shrub propagators.

Botrytis is the no. 1 fungal issue for Austin, but for pests, it’s fungus gnats and shoreflies. His prevention and treatment for those particular pests depends on the crop and how important it is. For spring production annuals, for example, he uses more biological controls, like nematodes. However, when it’s vital that absolutely no pests appear, he takes preventative measures through chemical control.

“I try to focus on more biological approach first, then go to chemicals,” Austin said. “But with poinsettias, it’s really important to not have those at all, so I just do a preventative Safari sprench early on those and not even deal with them.”

Austin’s operation has more of a problem with shoreflies than other growers because he relies on flood floors in his greenhouse. The shoreflies congregate under the pipes under the concrete where they are difficult to dislodge.

Perennial direct stick propagation at Dutch Heritage Gardens.

He’s found that proper water management can help with his big three: fungus gnats, shoreflies, and botrytis.

“With anything you’re propagating, you want to be aggressive with cutting your mist back,” Austin said. “That really starts from day 1, on. Especially with night mist; cut that out as soon as you can. Don’t wait. I train my assistant growers to be aggressive with cutting mist back, because if you overmist you tend to open yourself up to those pests even more.”

Austin has been with Dutch Heritage Gardens for eight years, and in that time has developed a system to minimize pest and disease problems. Through years of trial and error and careful note-taking, he developed a mist schedule that accounts for crop type and how far along in the propagation process a crop is. After weathering a few years of grower turnaround, he realized how beneficial it would be to have a system written down on paper in a way that would be easy for anyone to pick up and understand.

“We post the mist schedule on every boom, we classify the crops by low mist, medium mist, or high mist," he said. "Then all my grower has to do is follow the schedule.”

The schedule will provide misting information so that a grower can set the irrigation boom for a particular speed and duration for a low, medium or high mist crop. Then, it provides the information for boom settings for day two, day three, etc.

“The big thing is being consistent year to year,” he said.

Top photo: Poinsettia propagation at Dutch Heritage Gardens. Photos provided by Dutch Heritage Gardens.