Controling corn earworms

ponderpaul(7a)February 20, 2013

Wanting answers before I need them. How do you control corn earworms? What have you tried that worked?

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Okiedawn OK Zone 7

There's no single thing that is guaranteed to work, so I employ a vast array of techniques.

I plant several varieties every year, and at least one of them usually is either Texas Honey June or Country Gentleman because they have very tight corn husks that help exclude the earworms.

I always plant my early corn as early as possible--usually around the third week in March here, or whenever the soil temperatures hit the right range. If you use a short-season corn (I use Early Sunglow) for your early corn, it often will mature before the corn earworms even show up. If I plant Early Sunglow in the last week of March, it usually is ready for harvest by Memorial Day weekend and the corn earworms aren't even here by then most years.

Prior to planting, if you grow corn in the same place every year, if you'll plow or rototill your garden plot in the winter when it still is cold, you will kill some of the ones overwintering in the ground, or expose them to birds who then will eat them. I usually use my little Mantis to cultivate the soil in the corn patch twice in the winter, about 3 to 4 weeks apart.

Some people treat their soil with beneficial nematodes which attack the overwintering one. I am not thoroughly convinced it works, but some folks swear by it. When I did it, I couldn't tell that it made a difference.

I like to plant companion plants with tiny flowers (chamomile, yarrow, dill, etc.) to attract beneficial insects that attack corn earworms, like trichogramma wasps and green lacewings. You also can buy and release the predatory wasps or even minute pirate bugs. Normally, you release some predatory wasps weekly during the time the corn is tasseling and silking and the ears are enlarging.

Some years I spray the ears with Bt 'kurstaki', which will kill not only the corn earworms, but also the army worms and European corn borers.

If your planting is not too huge, you can apply mineral oil or soybean oil to the corn silks when they have just begun to turn brown on the tips. They used to recommend beginning this as soon as the silks appear, but then decided that using the oil that early interferes somewhat in fertilization of the silks, so now recommend you wait and start applying the oil as soon as fertilization is complete and the silks begin to brown and dry. The oil will smother the newly hatched corn earworms as they begin to travel down the silks to eat your corn kernels. You can increase its effectiveness by adding Bt 'kurstaki' to the oil you're using. It doesn't take too long to do this with a small home-garden sized patch of corn. You can use an eyedropper, a squirt bottle or something similar that allows you to put just a few drops on each set of silks. I cannot imagine doing it with an acre or two of corn though. With both the Bt and the oil you need to reapply every three days until you harvest.

Some people mix hydrogen peroxide with the oil (mineral oil or soybean oil) in a 50-50 mix and spray the silks with that, but I haven't tried it so cannot say whether or not it works.

Using all the above, you can probably get 80-90% of your ears worm-free most years. It is harder in a year when the air temps warm up really early (like last year) and the pests arrive really early.

Some years I haven't done anything at all with Texas Honey June and have found little to no hornworms in the ears, but that's not true of the newer supersweet types.

I have had some success spraying the whole corn patch every few days with Garlic Barrier which just seems to repel the pests and keep them away from the plants.

Spraying with spinosad is aid to help, but I won't do it because it is a broad-spectrum pesticide, and I don't want to use anything that is broad-spectrum because of its potential to harm the beneficial insects I rely upon to help control the pest insects. Some people spray with pyrethrums, but because we have pet cats and pyrethrum can cause nerve damage in cats, I don't use it.

My old farmer friend, Fred, sprays his plants with Sevin, though he doesn't always seem to be happy with the results.

When all else fails and the worms get into the ears, I just remove them and cut away the damaged part of the ear after harvest.

Hope this helps.


    Bookmark   February 20, 2013 at 11:11PM
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I would be sad if any of my neighbors sprayed their tassling corn with Sevin. That would kill quite a few bees. Though there is some doubt as to how well they can use it, it's undeniable that they often harvest corn pollen.

Tahlequah, OK

    Bookmark   February 21, 2013 at 10:40AM
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Okiedawn OK Zone 7


Well, it makes me sad too, but pretty much everyone around me who is not an organic gardener does use it, so that's why I mentioned it to Ponderpaul. least some of the folks who use it still have earworm damage to their corn anyhow, leaving me wondering how effective it is or isn't.

I would love it if everyone gardened organically and didn't use stuff that will harm the bees and other beneficial insects, least where I live.....many people still rely on synthetic pesticides.

I don't even like using organic pesticides, and rarely use them. Just because they are natural in origin, that doesn't mean they are "safe" and won't harm beneficial insects.

Because I don't use broad-spectrum pesticides at all, my garden is always full of insects, especially bees and wasps, and so much so that some of my friends who don't like bees and wasps don't even like to walk into my garden because they're afraid a bee or wasp will sting them. In the 15 years we've been here, I have been stung only twice....once near the front porch and once in the garden, but hearing that doesn't convince them to walk into "a garden full of bees".


    Bookmark   February 21, 2013 at 11:04AM
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Many of those wasps are eating harmful insects (yes, I know I'm "preaching to the choir ;)

I mentioned it because putting sevin on corn tassles or silk is absolutely a sure fire way to kill the bees which may live nearby.

I grew up gardening with insecticides. As a young adult I learned to garden organically; but not really because of a desire to be organic, rather because I didn't want to spend money on those things. Now I primarily garden organically, and that, for practical, monetary and health reasons.


    Bookmark   February 21, 2013 at 12:53PM
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Okiedawn OK Zone 7

I know. You are preaching to the choir.

I've been feeding the bees this winter, George, so you know that I never would poison them.

Do you know what they like? Cracked corn. When I put out cracked corn for the doves, the bees are busy at those little piles of corn all day long. Do you think that is odd? I've observed it for many years.


    Bookmark   February 21, 2013 at 9:45PM
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Thanks Dawn, I had never thought of cracked corn for the bees, but I will put some out today for them. I don't ever see the bees in winter but as soon as the clover and henbit begins to bloom they are here. After we mow the clover the honey bees are not around my yard much, but my garden gets a lot of bumble bees.

I have always wanted to have a beehive, but I know I would have to take care of it because Al is extremely allergic to their sting. The friend that he is visiting in Denver keeps bees and Al called me this morning to tell me how neat his operation is. He sent me pictures once of his hives right after he built them and they are not the typical square box type hive that I am familiar with. We may have to add bee keeping to the list of things we want to do at our son's place.
My Dad always had bees, but I don't remember a lot about how he took care of them. When I look at everything you need for start up, it looks expensive but when I see the price of honey it starts to look a little better. LOL I bought a gallon of honey through my co-op a couple of months ago and it was $32. My neighbor buys it at the feed store for $10.50 a quart, and it is even higher at the grocery store. I had a great source when I lived in Lone Grove and the guy had hives in Ardmore, down around Lake Murray and somewhere in Love County, I think.

I am going right now to put cracked corn out and see if I can bring in the bees. Thanks Dawn.

    Bookmark   February 22, 2013 at 2:07PM
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Okiedawn OK Zone 7

Carol, Well, I didn't really think of it, but the bees sure did! I've always put out bird seed for the birds in the winter, and the mourning doves like cracked corn scattered on the ground. Years and years ago I noticed bees hovering around the corn and landing on it in winter months. Then, in 2011 I was feeding all the wildlife a lot in the summer due to a lack of native vegetation and I noticed that the bees were going to the corn like they did in winter. I guess there was not a lot for them to eat otherwise in the horrible drought summer of 2011.

This winter, we have had a lot of days with highs in the 60s through the upper 70s and the bees have been out desperately looking for something. I have been putting out extra cracked corn for them and they stay at that corn all day. One day I ran out of corn, so I just mixed up sugar water for them using organic white sugar. They went crazy over it. I took the bee guards off the hummingbird feeders and put the sugar water in the feeders. I just have to remember to bring it in at night or the possums and coons climb the trees and knock down the feeders and drain them dry.

The whole issue the bees had, Carol, was that they were out before the henbit was blooming and I think they were desperately hungry. Now that we have henbit, daffodils and spring beauties in bloom, the sugar water feeders and corn aren't getting as much attention as they were previously, but the bees do still visit them.

The Methley plum tree is on the verge of blooming and has been for 8 or 10 days. Luckily, this cold spell hit at just the right time to keep them from blooming last week. Well, the bees are sitting there on the buds just waiting for them to bloom. It is almost comical. One thing I never have to worry about is that my fruit trees won't get pollinated. We also have chamomile with buds that will open any day now and then the bees will have one more food source.

Al's friend may have the top bar hives. I'll link something with an image of one. They are increasingly popular with hobbyist beekeepers. I'd love to keep bees, but it will have to wait until Tim retires. I refuse to take on one more outdoor task because I have too many to do during the growing season as it is. I just have reached the point where I know I cannot spend all day every day out in the garden in summer like I did 5 or 10 years ago. I have to pace myself better as I get older and come inside for more frequent breaks to cool off in the hot months.

The real estate agent who helped us find this place in the mid-1990s is a beekeeper, and I think he said his daughter is too. In the summer of 2011, there was a big wildfire near his house. We had most of the fire departments in the county out there trying to protect cattle and homes from the fast-moving fire. Chris drove way, way, way back behind a house and out into a field to stop the head of the fire. He told me that he barely stopped it before it reached a bunch of bee hives. That was a comment that sort of went in one ear and out the other on that busy day. A few months later Tim and I ran into our real estate agent and his wife at a Sam's Club store in Grapevine of all places and they told us it was their bee hives that Chris had saved that day. It sure is a small world sometimes.


Here is a link that might be useful: One example of a Top Bar Beehive

    Bookmark   February 22, 2013 at 3:13PM
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