How do I protect plants from mold flies? - Knowledgebase Question

Name: Sherri Page
Granite Falls, WA (Zone 7b)
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Question by SherriRaye
September 10, 2017
I'm bringing in annuals to overwinter and need advice on how to protect my plants from mold flies. Last year I brought in cuttings and the mold flies were everywhere in my house for over 6 months until I took my plants outside for spring.

Name: Philip Becker
Fresno California (Zone 8a)
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A comment from Philipwonel
September 11, 2017
Ive heard people say sticy fly traps work.
Also, you can google DIY traps. Theres also pheromone recipies to attract flies/gnats to homemade sticky boards.
😎😎😎


A comment from Lharris492
December 16, 2017
Placing pennies on top of the potting soil worked to eliminate fungus knats. 5 or 6 per pot. After they corroded I replaced with new ones. A penny's best value.

Name: Sherri Page
Granite Falls, WA (Zone 7b)
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A comment from SherriRaye
December 16, 2017
What a unique idea. I'll give this a try.

Name: Cindy
Hobart, IN zone 5
aka CindyMzone5
Answer from Shadegardener
September 11, 2017

1

If you're talking about fungus gnats, they usually seek out damp places. Try to avoid overly wet soil. You could also use red wine traps - they love the stuff. You can also use yellow sticky traps. Or, if all else fails, you can dissolve some mosquito dunks (BTI) in water and water your plants with that.

Name: Sherri Page
Granite Falls, WA (Zone 7b)
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A comment from SherriRaye
September 11, 2017
For red wine traps, do you just put out red wine in a shallow dish? Also I don't know what mosquito dunks are. Can I find them at my local nursery?

Name: Carol
Santa Ana, ca
Sunset zone 22
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A comment from ctcarol
September 11, 2017
I don't know what stores you have there, but any place that has pesticides probably has either mosquito Dunks or Mosquito bits. Even markets and chain drug stores sometimes carry them.

Name: Sherri Page
Granite Falls, WA (Zone 7b)
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A comment from SherriRaye
September 11, 2017

Thank you, Carol.

Name: Will Creed
NYC
Professional indoor plant consultan
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Answer from WillC
September 15, 2017

1

Red wine and yellow sticky traps attract the adult, winged gnats but they do nothing about the larvae living in the soil that will continue to emerge. The flying adults are of lesser concern because they die of "old age" within a week.

You will have to treat the larvae in the soil. As Cindy indicated, the larvae thrive in damp soil and decaying organic matter. Plants that are planted in soil based mixes are much more hospitable to the larvae than peat-based soilless potting mixes that are best used for indoor plants.

The larvae live primarily in the top inch or two of the soil so they can emerge and fly out as they mature. Thus, if you allow the soil to dry as deep as possible into the pot, you will deprive the larvae of the dampness they require to survive. scraping off any loose soil on the surface will also help eliminate many of the larvae. Allow your plants to dry just short of the wilt point before adding a limited amount of water so that the soil dries again in a few days to a week. Other substances added to the soil, are not effective and often counterproductive if they are liquid.

Think DRY!

Name: Sherri Page
Granite Falls, WA (Zone 7b)
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A comment from SherriRaye
September 17, 2017
So nice to have a professional point of view. I'll buy some of the soilless potting mixes for my cuttings and water according to your instructions.

Name: Cindy
Hobart, IN zone 5
aka CindyMzone5
Answer from Shadegardener
September 11, 2017

0

Sherri - make sure to read the package on the mosquito dunks. Not all of them include BTI.
To make a wine trap - take a plastic soda bottle and cut the top off about 2/3 of the way up the bottle from the bottom. Take the top part that you cut off and invert it in the bottom part of the bottle. Will kinda look like a funnel inside of the soda bottle. Add red wine - not the good stuff - into the bottle. You don't need much and you don't want the wine to touch the inverted "funnel". You want the fungus gnats to be able to get in and then they'll be too drunk to get back out.

Name: Sherri Page
Granite Falls, WA (Zone 7b)
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A comment from SherriRaye
September 11, 2017
Thanks, Cindy, that sounds like a fun project. By the way, I've really gotten into gardening in my shady areas this year. I'll have to see if you've posted any photos of yours.

Name: Will Creed
NYC
Professional indoor plant consultan
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Answer from WillC
December 16, 2017

0

Sticky traps and red wine and other remedies that attract the flying adults have no effect on the gnat larvae so they are ultimately not very effective although somewhat satisfying to see the trapped adults.

Treat the larvae by drying them out and/or using Bti.

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