Fungus Gnats !!!

This has really been a trial this year. The gnats are destroying my seedlings. The zinnias seem to be especially hard it. After doing some research, I decided to try using mosquito dunks in the water to combat the larva. I have been spraying the gnats with soap to get rid of them, but need to ensure that the cycle is broken with the larva since they actually do more damage eating the roots.

It is killing me to see perfectly healthy plants become stunted, and discolored.

My zinnias are always the ones that attract the fungus gnats. This year has been a really bad year for them (even seen them in the local plant stores) Last year was my first year dealing with them. Couldn't figure out why my zinnias wouldn't grow. Freaked out when I went to reseed and saw the maggots in my soil-so immediately tried everything to get rid of them. The only thing I could find to kill them was strong solutions of malathion which in turn killed the seedlings anyway. Even with sterilized trays, dirt, store-bought seeds, and dryer conditions they are back again this year. I bought sticky fly strips and made sticky cards with them. I placed them right into the dirt next to the zinnias. This has considerably helped to control them. I still see a few around, but my zinnias are growing well now.
I've read a few posts about the benefits of chamomille tea-maybe that will help. I also read somewhere about placing 1/4" potato slices on the dirt. Remove the potato after a couple days, and you can tell how large your population is. Maybe if you try this in dirt away from the zinnias, it will attract them and you can easily remove the larvae without damaging the seeds.
Please post if the mosquito dunks work without damaging the seedlings.

How about putting 1/4" of sand on top your soil. I've done that for house plants before. The gnats have a hard time getting thru the sand

I've heard of using sand before, but I am concerned about using it for my seeds. Sands retains a lot of moisture and compacts, so I don't know how well the seeds will germinate, I'd be worried they might rot. If I have a problem next year with the fungus gnats and the sticky fly strips don't control it, I was considering trying it. Luckily, I don't have a problem with my houseplants, just my zinnia seeds.

I will let you know what happens with the dunks. I just started using them yesterday. I also saw a product that Gardens Alives carries that I am thinking about.

http://www.gardensalive.com/product.asp?pn=3440

Heat your soil a head of time. Oven at 220 or some people use a microwave. That will make sure your soil starts off sterile.

Don't know if this is gnats but I have one tray of seedlings that something is eating off the cotyledons. I will pot them and a few hours later all I have is a twig.
Yesterday I put a couple fo "Cherry Brandy" plants (they are several weeks along)in the tray and something chewed off the leaves. I'm hoping whatever it is it left the bud as I only have a couple of them. Any ideas what this is. I removed the light tray and all and brought it into the house. I swear this is wearing me out.

I have had the same thing happen Indy....just stems a day later after transplanting.

What's the deal?

Debbie

Adult fungus gnats don't usually eat the laves and cause that much damage. It's the larvae they lay in the soil that will cause damage, eating the tiny roots on seedlings. If you don't see any infestation of bugs, my guess is it's something larger like a caterpillar or slugs eating the leaves. I had a swedish ivy plant that I brough inside and everyday the leaves were disappearing. Couldn't find anything for a while, and one night very late I went down there to check it out and found a caterpillar wreaking havoc on my plant.

I didn't think caterpillars and slugs were out yet. And in my garage???? Anyway I trudged up the stairs and back and forth carrying everything and have it set up in an unused bedroom. So far so good.

Well, I am trashing a tray of osteospermum thanks to the gnats and aphids. The osteos were kind of lank to begin with, so I had repotted them deep, and they all looked better. Over time, I noticed that the leaves were curled and not attractive. I thought that this was because of the gnats. Today, when I was examining them closely, I realized that there were aphids helping the gnats to destroy my seedlings.

I actually started some more osteo seeds last week. Even if these don't make it to maturity, I refused to buy some at the nursery!

I don't care how long or how much money I spend this will work. LOL> Been there done that.

Exactly.

I was moving some large boulders in my side garden next to the driveway last week. When I moved the large boulders they were MANY maggots underneath the boulder. I did not know what they were but I destroyed them by crushing them with my fingers., Actually I thought they were flies and why werte they under the Boulder???? Yes, I did have on gloves. The next day the same thing. What am I dealing with here????

Indynannyof8-I didn't think I would have caterpillars or slugs in my basement. 'Hungry' bugs will find their way to just about anywhere. I've never had a slug in my basement before and haven't brought in any new plants or dirt for a long time. Found a slug a couple days ago going after my seedlings...

Maybe a slug hitched hiked in or slug egg hatched in one of your pots/trays if they were outside for a while

Try watering with chammomile tea and hydrogen peroxide to prevent fungus and kill gnat larvae. And if you use sticky traps to catch the adults they must be the yellow ones, not the white ones. Works great for me.

Everything's been in the basement since Oct. except for seed packs. I don't know how the slug got down there and it looked way too big to be just hatched from an egg.
I agree with the yellow sticky cards, unattractive but work well. I don't have any visible fungus or mold growth, but something about the zinnia is attracting them. The gnats aren't too much of a problem(luckily it's not infested), I just know they're there...
Will chammomile tea or hydrogen peroxide hurt the seedlings(well, not really seedlings any more-some have their sixth/seventh set of leaves)? What ratio do I use?

HP will not hurt seedlings, it actually is just water with an extra oxygen molecule so it stimulates root growth, prevents dampening off and kills fungus & soil insects. I use 1 part H2O3 (drugstore strength 3%) to 4 parts water or chammomile tea.

Things seem better after the move upstairs. Hope Hope. I had to plant more melampodium seed as the monster ate all their tops. They have sprouted so I will be potting them maybe tomorrow. I still have some petunias that have not sprouted and some yellow statice. I am about ready to finish up, I hope.
I have a ? about the chammomile tea. Where can I purchase just some chammomile tea and not ha ve to get a mixed pkg? I got one tea bag at the Holiday Inn Express lol and now how doI mix it. I doubt if 1 tea bag is going to help but I had looked at Wallyworld and only found the mixed pkg.

I have had some success getting rid of fungus gnats by soaking pots in isopropyl alcohol until they stop bubbling, letting them soak for 10 or 15 minutes, then draining them. It seems to kill the larvae, though whether it's a chemical kill or drowning, I am not sure. This also works on root mealy bugs where it is definitely a chemical kill. It's a bit of a pain to do with large numbers of pots or with large size pots. I strain any dirt out of the alcohol after so I can reuse it as long as possible. I haven't ever tried it with seedlings, so cannot say how it might affect their root systems. Alcohol does wick into damaged tissue, and does a certain amount of new damage when it does. But the usual 70% strength you find at drugstores can be diluted by half with water and still work well as an insect spray, for scale, mealies & spider mites, so that might work for seedlings as a soak. You'd have to try with one or two and see what happens.

Yellow sticky cards work really well, but they are not always available locally, and can be pricey. When I could not find any some years ago, I made my own, that could be reused many times. I took two sheets of bristol [poster] board and glued them together for strength. It was what I had on hand at the time, but carton cardboard would work in one layer, I think. I painted the board brilliant yellow with exterior rust paint on all sides. I used two coats of paint, because the board needs to be completely sealed. If not, the sticky gel will soak in and ruin it. Only needed a small can of paint. Once dry, I cut it into various size cards and punched hanging holes in each one, not too close to the edges. Then I put on the sticky layer, using Tanglefoot, coating each card with a thin layer of it. Tanglefoot comes in a small tub and while it's a bit expensive, one tub goes a very, very long way, used for these cards. It's a gel paste designed to be smeared thickly on a foam wrapper around tree trunks to stop caterpillars and such from climbing up from the ground. They crawl over it and get stuck. Works very well in thin layers for gnats, white flies and to some extent for fruit flies, though fruit flies are not as attracted to the yellow colour as the others. Tanglefoot does not dry out, and a nice thing about these cards is that once you make them, you can use them over again many times, instead of tossing after just one use. Just scrape them off with a blade when they get covered with bugs and put on a new coating of Tanglefoot. Eventually they get worn out, or discoloured but they last much, much longer than commercial versions do, and you can make any size you need. Tanglefoot's pretty easy to coat the cards with, and I used a ruler edge to scrape it into the thinnest possible layer. If I wanted it on both sides, I hung two cards back to back, or stuck them together with some tape. The original double layer sheet of bristol board made enough that I've still got quite a few, that still work, and I made them about ten years ago.

I like your reuseable sticky cards. I made mine, but out of the sticky fly strips that hang from the ceiling. I cut out cardboard a little wider then the strip and about 6" long. Taped the strip to the bottom on one side, pulled it over the top, and taped at the bottom on the other side. It wasn't as messy as I originally thought, I figured I'd glue myself to everything. I'll have to remember that -Tanglefoot-any idea where to get it?
I had a hoya that attracted mealybugs. I used alcohol and it worked great, one time I got sick of the bugs so I just dumped the bottle on the plant (thoroughly rinsed afterwards). It didn't damage the plant but I'd be worried to soak seedlings in it. If I ever had a serious problem with the gnats I might try it though,can't be any more harmful then the awful insecticides I tried last year.

I buy the yellow sticky traps and have them shipped to my local Ace Hardware for free. http://www.acehardware.com/product/index.jsp?productId=1280343&cp=&sr=1&kw=sticky&origkw=sticky&parentPage=search&searchId=36783871643

They are quite large so I cut them into halves or even thirds.




This message was edited Apr 6, 2009 6:16 PM

Tanglefoot is available at a lot of places.. hardware, garden centres, etc. I think Lee Valley carries it, for mail order. Here's the URL for the company that makes it. http://www.tanglefoot.com/

I think hoya plants are secretly ringing dinner bells we can't hear, to alert mealy bug and scales to come on over and have a feast :-) ! Seriously, I've found that many plants that keep turning up with mealy bug over and over, often turn out to have root mealies, in the soil. I am not sure if root mealy bugs are a different kind, or if the regular ones just go underground and feed on roots, but the result is the same. You carefully kill them off the leaves and stems, thinking you have taken care of the problem and suddenly they're back. Part of the problem is they have a long life cycle, about a month, and the nymphs are invisible to the eye, so we don't see them 'till they become adult and turn opaque. Spraying twice two weeks apart can help catch anything that was missed the first time.

I make a practice now of checking new plants for mealy in the soil soon as I get them home. I just pop them out of the pots, and if they're there, they are usually visible on the outside of the root ball. Even if you can't see any on the outside, I'd suspect their presence if you keep getting reinfested. My mother had a big hibiscus standard that kept turning up with mealy, along with a Christmas & Easter cactus doing the same. I'd sprayed them all for her a number of times, so the next time I took them all out of their pots and they all had root mealies. The root mealies were just a reservoir sending out new nymphs constantly to reinfest the leaves.

In small pots, I've had some success killing root mealy by soaking the pot in alcohol until it stops bubbling, letting it sit for a half hour or so, then draining. But it's too difficult & expensive to do that with big pots, and it's not always successful with really heavy infestations.The only reliable cure I know for those situations is a lot of work, but it's effective. You have to remove as much soil as possible from the roots, preferably all of it. Then wash the roots with soapy water, rinse and after that, spray the entire plant including the roots with either alcohol or one of the new horticultural oil sprays thoroughly. Then repot in fresh, clean soil, and if you reuse the old pot, wash it well too. It's a lot of work for more than a few plants, and can be a back breaker for a big tub like my Mom's hibiscus was in, but I can say that since I treated Mom's plants this way, the mealies have not reappeared, and it's been over 3 years now. Other plants of my own have also remained clean after this kind of treatment.

This procedure can do a fair amount of damage to roots, so don't do it to a plant that is known to dislike having the roots disturbed. Also so be prepared to tent or bag the plant for a few weeks afterward, because the leaves may need the extra humidity inside a bag to prevent them from wilting, much like a cutting. I had to prune Mom's hibiscus until it would fit in a giant size clear garbage bag, because it lost all of it's feeder roots, and the bag kept it happy until it grew new ones. It had it's best ever flowering season that summer.

I've come to prefer the new horticultural oil above anything else, for mealy, scales, mites and white fly, because it works very well. It's also so Non toxic it's approved for organic farming. It has no smell, is quite safe to use indoors and the bugs don't become resistant because it works by smothering them. It's a relatively new product, so it's not labeled for use on very many plants yet. But I've used it successfully on all kinds of leafy tropicals, some ferns, some crassulas [ jade] plants, Christmas and Easter cactus, and a variety of other succulents. Crassulas & ferns, among others are known to be sensitive to many pesticides. Alcohol seems to be one of the few that won't bother them much. To be safe with those plants I wash the oil off after about a half hour with soapy water, and so far have seen no ill effects on anything. Make sure that wet plants are not exposed to sunlight until fully dry, as that will tend to increase the chances of possible leaf damage from the oil. Succulents with a waxy or whitish bloom will lose it if oil is used, but new growth will be normal. I use alcohol for them, as it won't remove the whitish coating.

i recommend sand. i am germinating plumeria seeds in a sandy mix. i use course sand. the seedling are fine. the top layer of sand dries out fast and that's what you want. you don't want the gnats to have access to moist soil. you will not have that with a layer of course sand on the top of your seedling mix.

GRRRR! My one slug has now turned to five-in my basement! I have not had this problem before and am not very happy about it. We did get like 2" of rain last week, maybe that's the cause.....

yuck

Slugs are pretty gross, for sure. Have you heard of the beer trap for slugs ? You just pour beer into a shallow dish or lid, you only need an inch or so of depth, I think. In a garden you'd place that into a shallow hollow in the ground near the plants. The slugs love beer, and will crawl in and drown. Maybe you could do the same with potted plants, just use a really small container for the beer, maybe a gallon jug lid or something like that ? I've also seen thin copper sheeting or foil & copper mesh sold for deterring slugs and snails. You place it around the plants and the critters won't cross it, something about their secretions and the copper don't mix. Lee Valley sells heavy copper foil for this purpose, and you can get copper mesh in small quantities made up as pot scrubbers. You can just pull those apart and arrange it around a plant. The foil would go around a flat pretty easily, I'd think.

I read in another forum that you can put coffee grounds down for the slugs .... I haven't tried it yet.. but I am going to put some under my containers that always attract them this year

Well, nothing has worked with the gnats. I went back again, and read through some of the old threads, and it reminded me that I went through this same scenario last year. I have tried ammonia, Murphys Oil Soap, insecticidal soap and mosquito dunks to no avail. I had my husband buy some camomile tea to try tonight, but I just got fed up. Then I noticed that several people suggested using Neem Oil, and I thought to myself that if I could find some at 8:30 on a Sunday night, I would use it.

I went to my potting bench to try to figure out my next course of action, and decided that I would just use some seaweed fertilizer tonight and think about the gnat tomorrow. When I picked up the bottle, I found Neem Oil Insecticide Soap concentrate behind it!

I had completely forgotten that when the same thing happened last year, I went out and bought this bottle. I do remember that it had a horrible odor - especially in the small bedroom that I use for planting (luckily the plants are the only ones that sleep there!). I think that last year I sprayed all the plants in the room. I'm guessing that it worked because I don't really remember having any problems afterwards. This time I made a weak solution and used it as a soil drench to get rid of the larvae. Hopefully, this will work.

The window is open, and the fan is on to get rid of the smell.

I just read a fascinating article posted on another thread, about using coffee grounds as an insecticide. It was specifically for mealy bug and scales, but it was the alkaloid compounds in the coffee grounds that killed the insects. You put the grounds around or on the plant and as you water, the alkaloids are washed down, into the soil, and that has the toxic effect on the bugs. Don't know if it's been tried for gnats, but it sure wouldn't be hard to try it out. One thing, it does not work instantly, but over a period of a few weeks. But it keeps working for up to ten months. You can also water with a form of 'coffee tea', sort of like manure tea. Much weaker than actual brewed coffee. The chap who wrote the article was getting his grounds free from Starbucks, who were happily giving them away to anyone who wanted them for organic mulch or composting. I plan to try coffee grounds on the very next plant I find with any critters, just to see what happens. The article, in PDF format, is in the Ferns, Fungi & Mosses forum, under the heading, coffee grounds on staghorn ?, April 11, 2009. Check it out, it is absolutely worth reading.

Fungus gnats...they're little flies that like warm constantly moist soil in which to lay their eggs. The larvae can, but don't always, injure little rootlets. What they really like is the fungus in the soil (thus the name). Larvae are VERY small and transparent, with black heads. You'll need a magnifier to see them clearly. Commercial and research greenhouses have a big problem with them because of the climate conditions, and because they also thrive in the moist soil on the greenhouse floor (making a good case for cement floors). BTi, not just BT, kills fly larvae. BT does not. Has to be BTi. And you have to treat the soil on the greenhouse floor, not just the pots. And you have to do it more than once...read the label. Sand doesn't really hold water in the soil unless you have inches of it...1/4" of light/white sand tends to fend off adult fungus gnats. BTi, sand, and cleanliness should reduce their numbers below the point where they'll do any real damage...Remember to let the soil dry out a bit; constant water=fungus=fungus gnats.

sand does the trick.

Pennefeather if that neem dip your doing works well, please let me know. I have been using a product that listed fungus gnats and larvae but it doesn't seem to be working. I have seedlings ranging in size fromonly a couple weeks old to a couple months. I am concerned with the youngest ones possibly not being able to handle the treatment.

In case you didn't see it, this weeks Dave's Garden newsletter had an article about BT. I always thought it was just for caterpillars, but the article mentioned a specific type of BT that works on fungus gnat larvae. It would not harm seedlings, it's a type of bacterial treatment that only works on specific larvae of specific insects. Check the newsletter article, it's got all the details.

Thanks I'll check it out! : )

I've been using it a couple of weeks now, but I'm not convinced. To be fair, sometimes, it is hard to tell what is working, and what is not. I actually think that I am getting more damage from aphids than gnats now. I'm not even sure that the neem is working well, but that is probably because my solution is so weak - I've purposely made is weaker than recommended.

Fortunately, my last frost day is April 20. Next weekend, I'll start setting my annuals outside, and that will take care of all of my problems!

I've had the same problem with what I tried. They seem to keep showing up- more each time I notice them. It is really stinky for me because I can't plant out for at least another month maybe longer.

I put out a sock bird feeder that feeds very small birds. I purchased it at a grocery store. It holds very small seed., These small birds feed at the sock and then go around the garden and eat all the aphids. It has worked for three years. They also get rid of the horn worms on the tomato plants. It is late but I will send you the name of the bird seed tomorrow.....I also have a water fall feature for the birds for their water needs.