Pest managers continue to monitor for the presence and density of western bean cutworm (WBC) larvae/ear damage. So far we have gotten reports of this pest’s damage in Lake, Newton, Jasper, St. Joseph, Starke, Pulaski, and Blackford Counties. Please let us know if you are finding larvae and ear damage elsewhere. Certainly the most interesting find was from Troy Millspaugh, just south of Hartford City. Though the density of larvae and damage was low, this is the farthest east and south reported for this pest in the state.
Unlike some pests, where populations develop in synchrony, WBC has a prolonged egg-laying period that is spread over several weeks. This means there is often a wide range of sizes of caterpillars in the same field at once. This explains how within the same field some damaged ears are vacated, larvae has dropped to the ground (see accompanying video), whereas others have small larvae feeding at the ear tip.
This has been a great opportunity to be able to distinguish WBC larvae and damage from the usually common corn earworm. This year, corn earworm’s moth flight and subsequent ear feeding have been extremely low. Corn earworm larvae are similar in appearance and damage to WBC, especially when the worms are small. This has lead to false reports of WBC damage in the past. With your observations from field visits, we can establish the WBC’s range (Ph: 765-494-8761).
Some pest managers looking for ear damage in fields have been seeing some very small, whitish worms. Often, these “worms” (actually grubs) are found in or around a plant wound site, which may or may not have been insect-induced. It is likely that these individuals are finding one of several sap beetle larvae, the most common being the familiar picnic beetle. These beetles, and their larvae, are commonly found in and around damaged and decomposing tissue. They are secondary invaders and will feed on decomposing, fermenting plant material and the sugars produced during this process (this is why they are attracted to beer, wine and other fermentation products). The beetles lay eggs in this rotting material (e.g., a damaged ear tip) so that the larvae have a food source to take them through their development. They are not considered pests, but you should be aware of what you are looking at.
Click on the above link to watch a video on where western bean cutworm larvae go after they're done feeding on the ear.
Picnic beetle, the most recognized sap beetle
Sap beetle larvae, note the two projections at the tip of the abdomen
Dusky sap beetles in leaf axil
Like the swallows that return to San Juan Capistrano every year, reports of Blunt Ear Syndrome (BES) or Beer Can Ear Syndrome (BCES) seem to surface every year sometime during mid to late August. This form of arrested ear development was first described in Colorado in 1989, was very prevalent across much of the Midwest in 1992, and has occurred in varying frequencies every year since.
The cause of this problem has never been conclusively determined. Some believe the occurrence of BES is associated with high soil pH or low-lying ponded areas of fields or herbicide injury. However, I have walked numerous fields with BES over the years that were not associated with any of these proposed causal factors.
NEPAC Weather 2009 - Example of timing of leaf stage and air temperature relative to the occurrence of BES in a field in NE Indiana, 2009
Figures 1-4. Images of BE from field in 2008 where problem was primarily locate in the first 10 rows or so aong the edge of a field.
• State (location) of the affected field.
• Planting date of the affected field.
• Seed company (e.g., Bob’s Pretty Good Hybrids).
• Hybrid number (e.g., BN2821).
• Approximate percent of field that is affected with BES.
• Approximate percent of ears affected with BES within the affected area.
• Average length (inches) of affected cobs.
• Average number of kernels per row on affected ears.
• Average number of kernel rows on affected ears.
• Soil pH levels of affected field.
• Other soil test information from affected field.
• General location of affected area within field (throughout, field edges, high ground, low ground, etc.).
• Relative soil drainage of affected area (well-drained, poorly drained, etc).
• Herbicides applied this year (product, rates, application times).
• Fungicides applied this year (including seed treatments)
Bechoux, N., G. Bernier, and P. Lejeune. 2000. Environmental effects on the early stages of tassel morphogenesis in maize (Zea mays L.). Plant, Cell & Environment. 23(1):91-98.
Lejeune, P. and G. Bernier. 1996. Effect of environment on the early steps of ear initiation in maize (Zea mays L.). Plant, Cell & Environment. 19:217-224.
Lejeune, Pierre, Prinsen, Els, Onckelen, Henry Van, and Bernier, Georges. 1998. Hormonal control of ear abortion in a stress-sensitive maize (Zea mays) inbred. Functional Plant Biol. 25, 481-488.
Nielsen, R.L. (Bob). 2001. ‘Beer Can’ Ear Syndrome - 2001. Corny News Network, Purdue Univ. [Online] <http://www.kingcorn.org/news/articles.01/Beer_Cans-0907.html>. [URL accessed 8/25/09].
Nielsen, R.L. (Bob). 2003. Blunt Ear Syndrome in Corn. Corny News Network, Purdue Univ. [Online] <http://www.kingcorn.org/news/articles.03/BeerCanEars-0812.html>. [URL accessed 8/25/09].
Nielsen, R.L. (Bob). 2007a. Ear Size Determination in Corn. Corny News Network, Purdue Univ. [Online] <http://www.kingcorn.org/news/timeless/EarSize.html>. [URL accessed 8/25/09].
Nielsen, R.L. (Bob). 2007b. Symptomology of Arrested Ear Development in Corn. Corny News Network, Purdue Univ. [Online] <http://www.kingcorn.org/news/articles.07/ArrestedEars-0904.html>. [URL accessed 8/25/09].
Nielsen, R.L. (Bob). 2008. Prevalent Purple Plants Possibly Puzzle Producers. Corny News Network, Purdue Univ. [Online] <http://www.kingcorn.org/news/timeless/PurpleCorn.html>. [URL accessed 8/25/09].
Pearson, Calvin. 1998. Evaluation of Golden Harvest Corn Hybrids for Blunt Ear Syndrome. Western Colorado Research Center 1998 Annual Report. Colorado State Univ., Fruita, CO. [On-Line]. Available at <http://www.colostate.edu/Depts/AES/Pubs/pdf/bluntear.pdf>. [URL accessed 8/25/09].
Pearson, Calvin and William E. Brown. 1999. Effect of Methyl Bromide and Golden Harvest and Pioneer Corn Hybrids under Two Irrigation Managements on Blunt Ear Syndrome at Fruita, Colorado 1999. Western Colorado Research Center 1999 Annual Report. Colorado State Univ., Fruita, CO. [On-Line]. Available at <http://www.colostate.edu/Depts/AES/Pubs/pdf/BES99.htm>. [URL accessed 8/25/09].
Pearson, Calvin. 2000. How Blunt Ear Syndrome of Corn is Affected by Hybrid and Irrigation at Fruita, Colorado 2000. Western Colorado Research Center 2000 Annual Report. Colorado State Univ., Fruita, CO. [On-Line]. Available at <http://www.colostate.edu/Depts/AES/Pubs/pdf/Pearson_BluntEarSyndrome.html>. [URL accessed 8/25/09].