Many of us have had difficulty growing a good crop of broccoli, collards, cauliflower or other vegetables in the brassica family in recent years. Other plants in this family include kale, Brussels sprouts and cabbage. There could be several reasons for this but very likely it is the Swede Midge.
The Swede Midge is an invasive fly that was first found in Minnesota in 2016. It is most often found in community gardens because it will find a feast there.
If you are planning to plant brassicas at Dowling, please do so with caution and prepare for active management to avoid a crop failure. Many gardeners have been disappointed, but some have had success with following the recommendations below.
Swede Midges do a lot of damage to brassicas. They cause distortion of the stems, can prevent flowering of broccoli or multiple smaller heads. You will often notice discoloration at new growth points.
Identification:
➔ Swede Midges are very small - adults are only 2mm in size so you will probably never see one. Their eggs overwinter in the soil around the areas that brassicas are grown. They can persist for several years until they get the right moisture and soil temps to hatch.
➔ There can be 2 to 5 generations per year so succession planting often doesn’t help. ➔ There are other insects and midges that can cause similar issues so look for tiny fly larvae near the growing points of the plant and in the crown.
How to manage them?
➔ Do not start seeds in soil that comes from an area where brassicas were grown. ➔ Practice good weed control. There are some weeds in the brassica family that can be hosts.
➔ Remove and destroy all vegetation after harvest. Practice good clean-up of your garden at the end of the season as the eggs will overwinter there. The eggs are laid in the crown so you may compost the rest of the plant.
➔ Sticky traps with lures can help you detect and monitor for Swede Midge but they are often difficult to distinguish from other insects. And remember that sticky traps lure more insects to your garden.
➔ Farmers would use crop rotation but because we have so many individual plots in close proximity, this is not an option that will work for us. Though they are not known as strong flyers, the recommended distance for crop rotation is 3000 ft. That’s more than ½ mile. ➔ There are currently no organic pesticides available on the market.
More information can be found at the links below:
https://extension.umn.edu/fruit-and-vegetable-insects/swede-midge
https://www.mda.state.mn.us/plants-insects/swede-midge
https://www.mda.state.mn.us/reportapest