How to use Bacillus thuringiensis (Bt) to Control Insect Pests

They can be used on foliage, food storage facilities, soil, or water environments.

Why are these bacteria so widely used? They occur naturally, affect very specific insects, and are relatively inexpensive and safe for humans, birds, fish, and most beneficial insects.

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However, for them to work effectively, you need to know what type of insect you want to target and make sure that you purchase a strain that will kill that particular species.

The National Pesticide Information Center reports that there are more than 180 pesticide products registered that contain Bt! And many have been approved for use in organic agriculture.

We at Gardener’s Path will cover the strains of Bt that are widely used. With thousands of strains out there, we can’t go over all of them!

We will list the strains that you are likely to encounter and describe how to use them.

How Does Bt Kill Insects?

Bt will only kill insects that eat the toxin and are susceptible to it. This is not a toxin that will kill on contact like most insecticides.

Once eaten, the toxin affects a specific switch in the stomach – like a lock and a key. This switch (a receptor) activates a reaction that makes holes in the stomach.

The contents, including the toxin and normal gut bacteria, spill out into the rest of the insect’s body, and it dies of infection and starvation.

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It can take the insect hours or days to die. Typically, the insect remains on the plant as it is dying, so don’t be alarmed if there are still insects on your plants even after treatment. They are probably on their deathbeds.

The insects are usually the most susceptible when the larvae are small.

How to Kill Beetles With Bt

You may or may not know that beetles comprise the largest number of species in the world, and there are more than 350,000 of them! Fortunately, most of them are not garden pests.

However, the Bt strains available only affect a few types of beetles. Some of them are major pests, though.

The bacteria to use to control beetle larvae are either Bacillus thuringiensis san diego or Bacillus thuringiensis tenebrionis.

Beetles that can be controlled include the Colorado potato beetle, elm leaf beetle, and willow leaf beetle.

Tips For Applying Bt

First, make sure you have the right strain for the pest you want to control! You should also make sure that the insect will be in its larval stage when you apply the Bt.

You will have better control if the larvae are small. There will be less damage to the plants because the little insects won’t eat as much.

If you treat larger larvae, they will eat more of the plants and cause greater damage. Also, they may morph into the reproductive phase and become insensitive to the toxin.

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And avoid high pH water! A pH greater than 8 is what activates the toxin in the insect’s gut, and you don’t want it to be activated ahead of time and then be useless by the time you apply it.

The spray will be more effective if you add a spreader or sticker to the tank mix. Use the spray within 12 hours of mixing. Make sure that you are spraying both the top and bottom surfaces of the leaves.

While it can survive for years in the ground if adsorbed to soil particles, Bt is rapidly inactivated by the UV radiation in sunlight.

Many people spray their plants in the evening, so the toxin can work overnight before being inactivated by the sun the next day.

The bacteria are sensitive to temperature and must be stored at 50 to 60°F. Do not expose the bacteria to hot or cold temperatures, which can kill them.

Precautions to Take

Bt has tested extremely well when examined for toxicity or the ability to cause cancer in animals – even at extremely high doses.

This microbe does appear to be truly safe for humans – even when eaten. Human stomachs are acidic, not alkaline, so they digest the Bt toxin.

However, some products are used in the form of a dust, and there have been a few instances of allergic reaction to the dust when the product was applied.

Just to be safe, you should wear gloves, long sleeves, and trousers when you apply the microbial insecticide. And then wash thoroughly afterwards.

Source: https://gardencourte.com
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