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market-farming - Re: [Market-farming] Bt Sweet Corn

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Chronological Thread  
  • From: "Wiediger, Alison" <alison.wiediger AT hart.kyschools.us>
  • To: "Market Farming" <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] Bt Sweet Corn
  • Date: Mon, 25 Jan 2010 14:27:10 -0600

Lots of good information here to help with decision making.  By the way, Josh, if you decide to use something like the Zea-Later, here is a link for earworm lures:
 
http://www.johnnyseeds.com/p-6973-corn-earworm-lure.aspx
 
Combined with a sticky trap, it will help  you monitor adults for deciding when to spray, use the Zea-Later, etc.  The trap also works very well trapping cucumber beetles (use the cucumber beetle lure), a pest difficult to control organically.  It gave us beautiful cucumbers last season.
 
Alison Wiediger, Au Naturel Farm


From: market-farming-bounces AT lists.ibiblio.org [mailto:market-farming-bounces AT lists.ibiblio.org] On Behalf Of Chris Reid
Sent: Monday, January 25, 2010 2:06 PM
To: market-farming AT lists.ibiblio.org
Subject: Re: [Market-farming] Bt Sweet Corn

Josh,
You were wondering about growing Bt corn.  Especially since you are in the Corn Belt, local experience may be really relevant.  Have you talked to Purdue or a county extension agent about what they are seeing and hearing?
 
From afar I took a look to see what Purdue is saying in its publications about ear worm and Bt corn. Other sources have said that the primary target pest of Bt corn is the borer, and ear worm control is more variable.  Carla in OK is having what sounds like pretty good success.  It may be slightly different in Indiana - see below.
 
You didn't say what part of Indiana you are in.  Purdue extension talks about carefully selecting planting time as a strategy to avoid corn ear worm damage:
 

"CEW  (corn ear worm) usually will not survive winters north of about Bloomington, Indiana. In southern Indiana, this insect may attack both early and late planted corn. In central and northern Indiana, CEW generally affects only the late-maturing crop. Following mild winters, CEW may survive further north, and early-planted sweet corn may be attacked. Throughout the state, corn maturing in mid-season is less likely to be injured, because CEW are between generations at that time, however monitoring populations is important."
 
They also make it clear that in their experience, Bt corn is still not a substitute for at least some spraying.  Here is a quote:
 

"Bt SWEET CORN

There are varieties of sweet corn available that have had a gene inserted in them that causes the plant to produce the same toxin as the bacterium, Bacillus thuringiensis, or Bt. This toxin will provide considerable control of corn earworm.
 
However, planting Bt sweet corn will NOT eliminate the need to spray insecticides. Bt sweet corn will often have large numbers of small earworms in the tip of the ears, making those ears unacceptable in most markets. Particularly in late season sweet corn, it is advisable to plant Bt sweet corn if your market will accept it. Used in combination with insecticides, Bt sweet corn will allow production of high quality sweet corn, even when corn earworm populations are extremely high."
 
One thing they don't say but I do wonder is whether Indiana is experiencing increases in populations of Bt resistant ear worms. The pest pressure Purdue describes sounds higher than what Carla in OK was reporting.
 
 
I read a piece from the mid-80's that suggested the length of the corn wrappers can affect the ability of the ear worms to infest the top of the corn.  I don't know if anyone regards using corn with longer wrappers as useful to do now or not.  At the time, some seed companies were trying to find varieties of corn that had physical characteristics making them less susceptible.
 
Widespread use of the same pesticide pretty inevitably leads to pesticide resistance.  Some IPM fact sheets I looked at recommended specific planting patterns of Bt and non Bt corn and used e.g. 30-40% NON-Bt corn for the purpose of making sure there was a group of non-BT resistant ear worms to mate with any survivors in the Bt corn.   They are called refuges. 
 
Here is an example of that approach to avoiding developing resistant insects:
 
 
You asked about organic methods.  Johnny's sells a corn silk applicator that uses vegetable oil plus Bt.  This may or may not be a viable alternative time-wise, depending on how much you are growing. 
 
 
Is there any price/competitive advantage of diversifying out of corn into a less common crop that also  can be timed to get the max out of your market price?  With so many corn pests around that make corn a challenge to grow, a series of vegetable crops that corn pests do not also attack might have pretty low pest pressure.
 
 
Chris Reid
Stamford, CT
 
 
 

 




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