Xtremehorticulture

Fungus Gnats Can Be Controlled With Special Bt Formulation

Q. I recently transplanted two house plants and now  have gnats coming out of the soil and infecting my entire house.  Is there any way to kill these little buggers or do I have to get rid of all the dirt and start over? A. Fungus gnats can be a serious problem with houseplants as they can feed on plant roots as well as the decomposing organic matter left in potting soils. The life cycle of fungus gnats (egg, larva, pupation and adult) are fairly short, perhaps two to three weeks. The destructive stage is the larva or worm stage. The pesky stage is the adult which can fly and be bothersome. These stages are overlapping so they will not all be flying at once but some will be in the egg stage, some in the larva stage, some pupating and some flying. You can attract the larva living and feeding in the soil to decaying vegetable pieces like small pieces of potato. You can lay pieces about the size of a French Fry on the soil surface and these larva will start feeding on them. You can collect these pieces and dispose of them and it will help get rid of a few of the buggers. Let me point you in the direction of an organic product that may work for you. This is supposed to be available at hardware stores and home improvement stores. It was originally labeled for controlling mosquitos but is now approved for fungus gnats. This is an “organic” product made from Bt (a bacterium) with a homeowner trade name of “Mosquito Bits”. There have been a few other homeowner products made from this Bt for indoor plants in the past but they have disappeared from many marketplaces I assume because the homeowner didn’t know about them and how to use them. Mosquito Bits is a formulation of a special Bt for controlling fungus gnats. A word of explanation. As I said, this is a Bt product. I have mentioned Bt in the past but this one is a DIFFERENT form of Bt so it will not work to use the Dipel or Thuricide product that you would use for grape leaf skeletonizer, tobacco hornworm, tomato fruitworm and other garden pests. This form of Bt is rather unique to certain types of insects such as mosquitos and fungus gnats. The commercial formulation of this product is called Gnatrol. Apply this product according to the label directions. Below I have pasted a document that explains the different types of Bt and how they might be used.

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What to Use on Vegetable Seedlings Decimated by Insects

Q. The day after I planted seedlings in my 4×8 raised bed I noticed they were decimated by some kind of insect. When I was amending the soil I noticed some small worm-like critters in the soil. I sprayed Bt but it evidently didn’t do anything to help the situation. I was told to use a powder called “milky spore disease” to kill any grubs or grub-like insects in the soil. Have you ever heard of this product? They said it works and I only have to apply it one time. Can you advise me on this product and where I might find it or some other solution?  Decimated pepper   A. The milky spore product only works on Japanese beetle and a few closely related insects which we do not have in southern Nevada. It is a bacterium and works rather slowly, if it will work at all, on pests we have in southern Nevada.             Bt works differently. It works on those insects that mature or pupate into either moths or butterflies. So if the immature insect turns into a beetle for instance it will not work. So without knowing which insect is doing damage it is hard to know what will work. Cutworm larva               The other alternative is to use a conventional pesticide approved for use on vegetables and has insect grubs or larvae on the label. These insecticides leave a poisonous residue for longer-lasting insect control.             This time of year Bt is a good product to use because it will control many of the insects causing damage right now. Look for products with a label that says Dipel or Thuricide. Forget the milky spore bacterium control in your case.             I am sending you a picture of what the cutworm larva looks like and its adult form, a moth. I will also post it on my blog. Bt can be sprayed on the soil and left undisturbed (no hoeing or irrigating after the application) for a few days but you have to repeat your applications to get any long term control. Corn earworm moth adult http://ipm.illinois.edu/ifvn/volume15/frveg1506.html             This is the time of year that moths are flying, mating, laying eggs and larvae are out looking for food. Usual cutworm damage is at the soil surface, not on the leaves.

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Milky Spore Product Probably Not Best Choice for Southern Nevada

Q. In my attempt to plant seedlings this year in my 4×8 raised bed, I noticed the day after I planted some pepper plants they were decimated by some kind of insect. When I was amending the soil a few weeks before, I noticed some small worm-like critters in the soil. I sprayed a bit of Bt on the soil but it evidently didn’t do anything to help the situation. I was told to use a powder called “milky spore disease” to kill any grubs or grub-like insects. Have you ever heard of this product? They said it works and I only have to apply it one time. Sounds too good to be true. This store said they used to carry the product but not any more for reasons unknown. I went to the Home Depot and Lowe’s, but neither store had the product. Can you advise me on this product and where I might find it or some other solution?  I removed the damaged plant and I’m trying to revive it. A. The milky spore product only works on some types of insects such as Japanese beetle which we do not have in southern Nevada, and a few closely related insects. “Milky spore” is a bacterium and works rather slowly, if it will work at all, on pests in southern Nevada.  Cutworm larva Bt works on those insect larvae that mature or pupate into either moths or butterflies. So if the larva turns into a beetle, for instance, it will not work. So without knowing which insect larva you have it is hard to know what will work unless you use a conventional pesticide approved for use on vegetables and has insect grubs or larvae on the label. This time of year Bt is a good product to use in home gardens because of the presence of cutworms. I am sending you a picture of what the cutworm larva looks like and its adult form (posted also on my blog), a moth. Bt can be sprayed on the soil and left undisturbed (no hoeing or irrigating) for a few days. Dipel in this form is a dry flowable product. Dry flowable pesticides are the same as what we call “water dispersable granules”. These can be mixed with water and they disperse in water easily and quickly BUT the spray mix MUST be constantly mixed or shook while applying or the pesticide with settle out and you will not be applying it anymore but will collect at the bottom of the sprayer This is the time of year that this moth is flying and laying eggs. Their larvae “hatch” from the eggs and are out looking for food right now. Usual cutworm damage is at the soil surface, not on the leaves. Other products to try to protect your plants are those that leave a poisonous residue for insects on the leaves. You can also use insect netting covering the rows in a low tunnel.  

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I Feel Really Bad for Sue and Her Grapes Frying After Dipel

Q. I e-mailed you awhile ago about issues with my grapes.  The GOOD news is, I had been pruning them totally wrong.  Following cane pruning instructions off of YouTube, in February I had more vines and grape clusters than since we moved in.  The bad news is that I was so excited about the grapes and worried about the pests (big black things and skeletonizers?) I followed your instructions and used Dipel Dust (just once) for prevention.  Everything was fantastic until two weeks ago.  I had beautiful green grape leaves and so many clusters of grapes and on the turn of a dime…everything fried and I mean I hardly have a leaf and the clusters are practically burnt raisins now if anything.  I am so sad.  What did I do wrong do you think?  My intuition is telling me that the Dipel, like other pesticides I have tried, burn the leaves in the sun when it gets into the high 90’s?  Ugh, I am so bummed.  Anyhow, let me know what you think.  Thank you so much. Sue A. I rather doubt it was the Dipel if you applied according to the label. I usually use the liquid form of Dipel or Thuricide when I use it. Or I will use Spinosad instead which does the same thing but hits a few more insects including the skeletonizers. This is Dipel DF or dry flowable and intended to be mixed with water, not applied as a dust. Please read the label before applying any pesticide. Regardless you still would want to apply any pesticide even if it is organic like Dipel, in the early morning hours or late afternoon when it is no longer hot outside. Dipel powder is hard to distribute evenly over a grape vine while the liquid form is much easier to spray as is spinosad. We use both products at the orchard and have had no problems with it when sprayed this time of year even around 8 or 9 am. I would next time though stick with a liquid product. It will give you better coverage over the leaf, both top and bottom, and is easier to apply. You should not be using the Dipel dust. Make sure you did not apply the Dipel DF as a dust. It is meant to be mixed in water and sprayed on. Has anyone else had this problem with Dipel on grapes? I would love to know. Please check the label before using just in case.

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