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Fungus Gnats

Very recently, I've seen that some fungus gnats have been popping out of one of me D. capensis pots and I don't really mind it, but I see a couple of new ones every day. Would you guys consider this something to be concerned about, because if there is a BIG amount of larvae beneath the soil, I definitely don't want them to mess up my plant's roots.
 
Yes, the larvae can feed on the roots. The larger the infestation the greater the likelihood of that happening.

Some people consider fungus gnats as harmless and at most a nuisance from the adults flying around if indoors. Many states Agriculture Departments have reconsidered fungus gnats as a serious problem causing much crop damage.

The easiest method I've found to control them is to use sticky traps to capture as many adults as possible. And to treat the soil with Bacillus thuringiensis ssp israelensis (Bti). Bti will slowly kill the larvae. If you treat long enough to cover all the possible generations in your pot you'll be fungus gnat free until it gets reinfested.

Bti is readily available in stores as Mosquito Dunks or Mosquito Control by Bayer Advanced. Just add a little to some water and water your pots with it or break off a chunk (if using Dunks) and put it in your water tray.

Since it is a bacteria take care to wash your hands thoroughly before touching you eyes or mouth.

In the mean while, let your Sundews have a good feed.
 
Yeah, your dews will readily take care of any flying adult gnats. They're the perfect size for most dews to capture and consume.
 
Never had a problem with them on dews...the plants will control them by feeding on them.
If they get to some seeds pots them it can be trouble...the very small plants can be affected by the root damage made by the larvae.
 
Well there is a relatively young plant in the pot. It's only about a month old but it's grown a lot ever since I gave it more light and fed it some springtails.

Here it was a couple of weeks ago.

<a href="http://s235.photobucket.com/albums/ee112/faraphx234/?action=view&current=Picture018.jpg" target="_blank"><img src="http://i235.photobucket.com/albums/ee112/faraphx234/Picture018.jpg" border="0" alt="Photobucket"></a>

And now

<a href="http://s235.photobucket.com/albums/ee112/faraphx234/?action=view&current=Picture034.jpg" target="_blank"><img src="http://i235.photobucket.com/albums/ee112/faraphx234/Picture034.jpg" border="0" alt="Photobucket"></a>

<a href="http://s235.photobucket.com/albums/ee112/faraphx234/?action=view&current=Picture032.jpg" target="_blank"><img src="http://i235.photobucket.com/albums/ee112/faraphx234/Picture032.jpg" border="0" alt="Photobucket"></a>

Yummy : ]

<a href="http://s235.photobucket.com/albums/ee112/faraphx234/?action=view&current=Picture033.jpg" target="_blank"><img src="http://i235.photobucket.com/albums/ee112/faraphx234/Picture033.jpg" border="0" alt="Photobucket"></a>

Think I should change its soil just to be safe?
 
i treated my fungus gnat problem with bon neem (neem oi) and it seemed to work if applied multiple times . I think it took me about 2 or 3 applications once a week to clear it up. So far there have been no signs of fungus gnats its been about 1 or 2 months so far
 
You can change the soil as may times you want...the "problem" will appear again. If you give your plant good conditions it will grow well no matter what the larvae do to it.
 
You can change the soil as may times you want...the "problem" will appear again. If you give your plant good conditions it will grow well no matter what the larvae do to it.

Well it is growing REALLY fast; two new leaves are springing up and I get new a trap about every 4-7 days : ] I'm still finding some fungus gnats in its pot, but I"m only finding them in the top layer of LFS. I bet this is where most of the activity is, with a few gnats maybe under the actual soil surface. I'm not caring much for it anymore. I used to see em' flying lots o' times into my baby D. capensis, but now there are none getting caught, but there's still a sufficient amount left to feed my sundew. Most of them are actually dropping into my water trays and drowning there! xD LAWL
 
I put one quarter of a "mosquito dunk" in my "watering can" and use sticky traps for the adults. The Mosquito dunks contain BT which kills the larvae.
 
  • #10
It's probably not a big deal, but I found when I grew some of my plants in a sandier mix, there are no fungus gnats at all. Hardly any springtails either compared to my 2:1 or 3:1 peat:sand mixes. Gnats seem to like stagnant soggy soils. I used neem oil in the past to kill them off, and it really took care of them. No damage to the plant whatsoever. Just keep feeding it like you are, and you should have a flowering adult plant in no time, regardless of how many gnats there are.
 
  • #11
Gnats seem to like stagnant soggy soils.

That's why I thought they were growing in the LFS...it stays moist so it makes for a good breeding ground. Now though, I haven't seen any...they don't seem to like warm weather so I guess that's why they're gone.
 
  • #12
That could be the major factor. I know temps get fairly high in my setup, so that along with a drier mix must completely discourage them.
 
  • #13
Fungus gnats larvae live in the top inch or so of very damp soils. The easiest recommended control for house plant infestations is to allow the top few inches of the soil to dry out completely between waterings. This is not advisable for carnivorous plants. Another preventative is to put a top mulch of sand at least 1/4 inch thick. The adults are not able to lay their eggs through this layer or are fooled into thinking the soil is too dry for them. The mulch should be applied before an infestation begins.

I've tested this method in my Sarracenia rosea pot and it works quite well. The added plus (or perhaps a minus) is that none of the other mosses grow in the pot either.

Read more about fungus gnats here:

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7448.html
http://www.ipm.ucdavis.edu/PMG/r280300811.html

And for those who think the larvae are harmless (from above):

Only fungus gnats commonly damage plants. Larvae of these flies feed on roots, thus stunting plant growth. Root damage can occur in interior plantscapes and in houseplants if high populations infest moist, organic-rich soil. Fungus gnat larval damage can be especially serious in greenhouses, nurseries, and sod farms. In addition to larvae chewing on roots, both larvae and adults can spread plant pathogens and may promote disease in commercial crops.​

and

DESCRIPTION OF THE PESTS
Fungus gnats are small (2–5 mm long) mosquitolike flies with dark wings, delicate legs, and long antennae. They lay their eggs in soil, and the eggs hatch about 4 days later. There are four larval instars that increase in size up to about 0.33 inch (8 mm). Larvae are clear, with visible internal organs, and have shiny black head capsules. Initially larvae feed on root hairs and algae; later, larvae may feed on the insides of roots. When populations are high, larvae may bore into larger roots or stems that are in the soil. Larvae will also feed on leaves touching the soil. One generation may complete development in 21 (72°F) to 40 (61°F) days.

DAMAGE
Larvae usually feed on roots and algae within 1 inch of the soil surface. Root feeding by larvae can allow entry of plant pathogens. Direct damage through root feeding can cause wilting even though the plants are being sufficiently watered. Damage is particularly severe in propagation areas, in seedling flats, and with especially sensitive crops. Adult fungus gnats also disseminate soil-inhabiting pathogens on their bodies and in their feces. Fungus gnat adults can be a nuisance when present in large numbers.​

Fungus gnats are a vector in spreading the Fusarium fungus which is responsible for rhizome rot in Sarracenia.
 
  • #14
....Fungus gnats are a vector in spreading the Fusarium fungus which is responsible for rhizome rot in Sarracenia.

They are also one of the suspects in the spreading of Ceph sudden death syndrome
Av
 
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