Thanks, again, to Justin Kroening, owner of Stone Stilo Prairie Gardens in DePere, Wisconsin, I learned something new this week about gardening. I had received shipment of Common Milkweed (Asclepias syriaca) plants from Monarch Watch for my Wild Ones Fox Valley Area chapter’s use and I noticed there were tiny little black flies buzzing around them. At first I paid no attention to them because I knew the plants would be outside and not near my house plants. But as the days went by, the milkweed seedlings didn’t perk up like I thought they should. Could it be because of the tiny flies?
So, I wrote to Justin asking if I could use soapy water against the flies without causing harm to future monarch caterpillars. He responded back with:
“Are they white or black? If black most likely fungus gnats or shore flies. Allow the soil to dry up really well between watering. The larvae in the soil can deplete roots. Soap won’t help much. Then drench and let the plants dry normally. That should do the trick.
If they are white flies, soapy water will help. Use a good spray that will blast them off.
The yellow sticky cards help for both.”
I’m not much of a gardener, so it’s not surprising I had never heard of Yellow Sticky Cards. But they’re wonderful for something like fungus gnats and shore flies. There are also Yellow Sticky Stakes.
The Yellow Sticky Cards or Stakes can be used anywhere insects are a problem, of course, but be mindful of their use around plants used by pollinators. For fungus gnats, the Yellow Sticky Cards or Stakes should be placed horizontally slightly above the soil’s surface. If that’s not possible, hang them over the plants.
Well, I’m following Justin’s instructions. So far, I see no insects whatsoever on the cards.
It may not be shore flies at all, but just the adjustment from the greenhouse to my yard. Our weather has been in the high 50’s/low 60’s during the day when the sun is out which means high 30’s/low 40’s at night. But the winds have been cold. My research indicates Common Milkweed is one of the last things to poke through the ground in the prairie; they prefer warm soil. Even though I had the trays sitting in a mini-greenhouse, covered with plastic film, perhaps it’s just too cool for them yet. I’ve started taking them into the garage for overnight.
I’ll let you know the outcome. For certain, I plan to remove the cards as soon as possible so as not to include beneficial insects in my monitoring.
Here’s an excellent article by Janet Allen on growing milkweed.