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  #1  
Old 05/30/10, 08:03 PM
 
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Corn earworm

Last year's corn crop was a wipeout.

I am going to try mineral oil this year. Is it applied as soon as the silk appears?

I understand that a lot of people use eye droppers. Today, one of the gardening radio talk show hosts stated that he also uses eye droppers because he only has a few dozen stalks, but if he had more, he would use a sprayer. Anyone ever use a sprayer? Did you use full strength?

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  #2  
Old 05/31/10, 08:45 AM
 
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primroselane,

I have grown lots of sweet corn, but never did anything about earworms..... Since it was for home use, I just broke off the tip of the ear and used the rest anyway. At that time I had a big old coon dog that loved fresh sweet corn, and he gobbled them up. Those further down were just cut out with the knife before processing. Obviously, I did not sell any corn. So, from what I read,(Google) the mineral oil is applied to the silk after the kernels have been pollinated--which means after the silk turns somewhat brown and dry. Earlier will interfere with pollination and kernel development. So,,,,,, applying oil to the silk will suffocate those worms already inside the corn, under the husks, and you may still find a dead worm and some damage.

Here's one website that looks pretty complete for information on organic production for sweet corn, maybe you will find what you need in it. One mention of veg. oil mixed with Bt, sold by Johnnie's, may be what you can use?
Hope this will help.
geo

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  #3  
Old 05/31/10, 10:48 PM
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Wait until after the ear has been pollinated. That will be around a week or so after the silk appears. It will be when the silk is just starting to turn brown. Only takes a drop right in the center and it will follow the silk down into the ear.

Martin

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  #4  
Old 06/01/10, 07:55 AM
 
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OK, I'm cornfused.

Martin, are you saying to treat for earworms when the silk begins turning brown?? I had earworms long before that stage. We begin treating (spraying.....lots of corn) as soon as silk appears.

We treat w/ Bt, if that makes a difference.

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  #5  
Old 06/01/10, 08:56 AM
 
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Would the use of DE on the silks as soon as they appear interfere with pollination?

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  #6  
Old 06/01/10, 11:07 AM
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Originally Posted by Txsteader View Post
OK, I'm cornfused.

Martin, are you saying to treat for earworms when the silk begins turning brown?? I had earworms long before that stage. We begin treating (spraying.....lots of corn) as soon as silk appears.

We treat w/ Bt, if that makes a difference.
Using mineral oil is not for the prevention of earworms but killing any which may already be in the ear. The same applies for Bt. The only way to prevent earworms would be to spray and kill the moth.

Martin
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  #7  
Old 06/01/10, 11:27 AM
 
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Originally Posted by Paquebot View Post
Using mineral oil is not for the prevention of earworms but killing any which may already be in the ear. The same applies for Bt. The only way to prevent earworms would be to spray and kill the moth.

Martin
Right, but wouldn't there be more damage to the ear from waiting until the silk begins turning brown? Would spraying/treating earlier kill the larvae before it can do extensive damage?
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  #8  
Old 06/01/10, 11:40 AM
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Originally Posted by Txsteader View Post
Right, but wouldn't there be more damage to the ear from waiting until the silk begins turning brown? Would spraying/treating earlier kill the larvae before it can do extensive damage?
Silk turning brown and totally dry and brown are two different points in the ear development. When the silk appears and is ready to be pollinated, it is fluffy, somewhat erect, and vibrant. A week or so after pollination, it looses those qualities and begins drying and turning brown. That's when the mineral oil goes on. One is then assured that it can not interfere with pollination.

Martin
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  #9  
Old 06/01/10, 11:53 AM
 
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Quote:
Originally Posted by geo in mi View Post
primroselane,

I have grown lots of sweet corn, but never did anything about earworms..... Since it was for home use, I just broke off the tip of the ear and used the rest anyway. At that time I had a big old coon dog that loved fresh sweet corn, and he gobbled them up. Those further down were just cut out with the knife before processing. Obviously, I did not sell any corn. So, from what I read,(Google) the mineral oil is applied to the silk after the kernels have been pollinated--which means after the silk turns somewhat brown and dry. Earlier will interfere with pollination and kernel development. So,,,,,, applying oil to the silk will suffocate those worms already inside the corn, under the husks, and you may still find a dead worm and some damage.

Here's one website that looks pretty complete for information on organic production for sweet corn, maybe you will find what you need in it. One mention of veg. oil mixed with Bt, sold by Johnnie's, may be what you can use?
Hope this will help.
geo
OOPS, forgot the website....http://www.pfi.iastate.edu/ofr/Crops..._and%20Btk.pdf
geo
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  #10  
Old 06/01/10, 12:57 PM
 
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Quote:
Originally Posted by Paquebot View Post
Silk turning brown and totally dry and brown are two different points in the ear development. When the silk appears and is ready to be pollinated, it is fluffy, somewhat erect, and vibrant. A week or so after pollination, it looses those qualities and begins drying and turning brown. That's when the mineral oil goes on. One is then assured that it can not interfere with pollination.

Martin
Ok, now I see what you're getting at....the mineral oil interfering w/ pollination. That wouldn't apply if one were using Bt, correct?

Also, from your experience, is one treatment more effective than the other; mineral oil vs. Bt?

Sidenote: Planted Honey Select for the 1st time this year. We picked the first ears this a.m. & had them for lunch. Gosh, they were good! I see why they were given that name. Too bad they're hybrid.
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  #11  
Old 06/01/10, 01:07 PM
 
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Thanks for the link, George.

Something I noticed.....the footnote at the bottom of that chart mentioned that the Bt used wasn't fresh.

How long does Bt stay 'fresh'? We suspected that the leftover bottle we used last year (from the previous year) had lost its' effectiveness as we had a LOT of damage in spite of spraying diligently.

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  #12  
Old 06/03/10, 06:19 AM
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Quote:
Originally Posted by oneokie View Post
Would the use of DE on the silks as soon as they appear interfere with pollination?
I'm also wondering about using diatomaceous earth for ear worms.
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  #13  
Old 06/03/10, 12:53 PM
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DE would not bother the worms in any manner since it would not come in contact with them.

Martin

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  #14  
Old 06/03/10, 06:58 PM
 
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Quote:
Originally Posted by Txsteader View Post
Thanks for the link, George.

Something I noticed.....the footnote at the bottom of that chart mentioned that the Bt used wasn't fresh.

How long does Bt stay 'fresh'? We suspected that the leftover bottle we used last year (from the previous year) had lost its' effectiveness as we had a LOT of damage in spite of spraying diligently.
I can't find any answer to your question. The labels for Dipel and Thuricide don't show any life span for the powder. The b.t. fact sheet http://npic.orst.edu/factsheets/BTtech.pdf does mention some half life information, and that b.t. does degrade rapidly with exposure to UV light.

Did your leftover bottle have any stamped expiration date, or use by date on it?

geo
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  #15  
Old 06/03/10, 08:26 PM
 
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Quote:
Originally Posted by geo in mi View Post
I can't find any answer to your question. The labels for Dipel and Thuricide don't show any life span for the powder. The b.t. fact sheet http://npic.orst.edu/factsheets/BTtech.pdf does mention some half life information, and that b.t. does degrade rapidly with exposure to UV light.

Did your leftover bottle have any stamped expiration date, or use by date on it?

geo
There was/is no 'use by' or expiration date on the bottle. It was leftover from the previous season, but who knows how long it's been sitting on the store shelf.

I just found this:
http://findarticles.com/p/articles/m...2/ai_15232832/
Quote:
Under ideal storage conditions, many chemicals remain effective for 7 to 10 years or longer. Exceptions are biological pesticides, such as Bacillus thuringiensis. Since these are made from living organisms, they're much more vulnerable to temperature extremes. Above 90 |degrees~ shelf life is about a month. When stored in cool, dry conditions, liquids can last for a year, powders up to three years.
And this:
http://www.vegetablegardener.com/ite...bial-pesticide
Quote:
Bt products available in garden shops are commonly sold as wettable powders that can be mixed with water and sprayed on plants with conventional garden spray equipment. A wettable powder goes into solution easily and has a long shelf life. Once the powder is mixed with water, however, it will last for only a few days, so prepare only what you think you will use and don’t try to save it for another time.

Because Bt is actually a living organism, the pH of the water used to make the solution is important. Many failures with Bt happen because it is mixed with hard water (which is alkaline and high in calcium).
And...
Quote:
If your water is hard, buffer it with citric acid before using it for a solution.
Bingo! I'm betting that's a big part of our problem, because the sunlight/temperature issues don't apply (dark bottle/cool garage) but we do have HARD water.

Also, we planted late this year and earworms get worse as the season progresses. Almost every ear we've harvested has damage, although mostly confined to the tip.
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  #16  
Old 06/03/10, 10:15 PM
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Originally Posted by Txsteader View Post
Also, we planted late this year and earworms get worse as the season progresses.
You are quite correct there. Up here, we figure on at least 2 generations per year. Parts of the South may have 4 or 5 with each being much larger numbers than the previous one.

Martin
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