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INSIDE THIS ISSUE:
5/6/03
* Corn survival and ponding
*Is Black Cutworm damage right around the corner?
*Keep your eyes peeled for Flea Beetles and Bean Leaf Beetles
www.Icorn.com
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This is the first installment to the igronomy flash newsletter for 2003. For those of you new to ICORN or recently registered, the igronomy flash newsletter will be sent to you periodically over the growing season as issues arise. Typically I will give a brief paragraph summary of a topic and link you to articles from various universities in our three state area. If nothing else, it should help you save the time of searching and
finding the articles. Feel free to call or e-mail me with your agronomic observations during the growing season to alert me to things I may not be seeing myself. With that said, let’s get to the first edition of 2003.
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Corn survival and ponding
Some areas have recently received heavy rains which have covered young corn seedlings. How long can the corn survive? As a general rule of thumb, I have always said they will survive 2-4 days under cool temperatures and 1-3 under hotter temperatures.
Here is a good article from Purdue: (Purdue 2003, Corn survival in Ponding)
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Is Black Cutworm damage right around the corner?
With all these low pressure systems coming up from the south this spring, many of them have brought Black Cutworm moths (that over-winter in the south) with them. Some fields have not been sprayed yet and may have had green plant mass that is an attractant to the female moths for egg laying. Scattered intense captures of BCW moths have been occurring since the first week of April in areas of Illinois, Indiana, and Ohio. Once the eggs have been laid, about 300 heat units need to accumulate in order for the larvae to reach to 4th instar stage (which is about the time they begin to cut). Right now, since the first of April, the southern portion of the three states
has generally received 400+ heat units, the central region around 275-350 and the north in the 250-350 heat unit range. Many of the intense captures occurred in the middle of April. What that means is that if temperatures remain warm, larvae will be reaching the 4th instar stage in the next week or two. So if the wet pattern keeps you out of the field until the first of next week, don’t hesitate to walk your fields to take a look, especially those of you who no-till. Here are a couple of good links:
(Purdue 2003)
(Illinois 2003)
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Keep your eyes peeled for Flea Beetles and Bean Leaf Beetles
As is usually the case, what happens in nature, is not what you expect. A month ago I predicted the cold weather would hurt Flea Beetle survival, and while it probably did, we still had a very high over-wintering population and some growers are reporting they have seen them. A customer in Central Ohio reported seeing a high number already. Most of the time, severe damage from Flea Beetle occurs in prolonged cool cloudy weather when the seedling cannot outgrow the tissue damage done by the beetle. Under bright sunshine and warm weather, corn typically keeps ahead of the damage, but I have seen a few cases the last couple of years where a spray was
warranted. The beetle can also be a vector of Stewart’s Wilt to the plant. In our hybrid lineup, keep your eye on 111.Y6 which seems to be a little more sensitive than others to Flea Beetle feeding.
(Illinois, 2003)
(Flea Beetle fact sheet)
For those of you who were fortunate enough to get your beans in early, keep your eye out for Bean Leaf Beetle damage. The adults over-winter in woods and field edges and search out early planted fields to curb their hunger. Damage consists of eating holes in the leaf tissue and cotyledons, sometimes so severely the seedling is killed. Keep in mind that soybeans can incur a pretty significant stand loss and still produce good yields. It is not very common in our area to spray for early damage, but it’s also not unheard of. There is also a school of thought emerging about the Bean Leaf Beetle feeding causing Bean Pod Mottle virus. Here is a very
good link to discuss the topic of feeding and the virus. It is the same Uof Il link I have listed above.
(Illinois 2003)
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