Do you need to treat for adult corn rootworms?

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

As reported in an earlier article, corn rootworm egg hatch in 2012 was slightly ahead of a normal year. Adults were first detected in Illinois last week and around Iowa this week. We’ve been getting many questions about when or if it is appropriate to treat the adults. Three factors must be taken into account before a foliar insecticide application is warranted.

click image to zoomMarlin E. RicePhoto 1. Corn rootworm are strongly attracted to corn during pollination and can trim back silks to the husk. First, consider the growth stage of the plants. Adult corn rootworm will feed on leaves and cause some scarring; however, this will have little if any effect on yield. Adults can cause yield loss if they are present in the field when corn is silking, which is a critical time period to protect plants. Adults are strongly attracted to silks and will mass on plants to feed and mate (Photo 1). Adults that trim back silks to the husk during pollen shed will interfere with pollination.

Next, consider current growing conditions. Weather plays a huge role on how plants respond to silk feeding. Plants do not tolerate as much feeding during pollination in hot and dry weather. For example, under ideal moisture conditions, plants could tolerate 15 beetles per plant, but that number is reduced to just five per plant under drought stress (Photo 2).

click image to zoomVirgil Schmitt, ISU Extension and OutreachPhoto 2. Rolling corn leaves are an indication of moisture stress. If plants are droughty during silking, fewer beetles are needed to cause economic loss. Finally, consider plant maturity. Late-planted fields or late-flowering hybrids compared to neighboring fields are generally attractive to adult corn rootworm. Green silks will still be developing in these fields when older fields have brown or drying silks. Adults may migrate and aggregate in these later-maturing fields.

Management recommendations

It is always a smart idea to scout for insects in corn fields during pollination. But with adult corn rootworm becoming active before silking this year, we highly recommend keeping an eye on fields to protect yield. A foliar insecticide may be warranted if there are five or more beetles per plant, silks have been clipped to less than ½ inch of the ear tip, and pollination is not complete. Also take into consideration other insects that may be feeding on the silks at the same time (e.g., Japanese beetle).


Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...


Comments (0) Leave a comment 

Name
e-Mail (required)
Location

Comment:

characters left


Aluminum Grain Trailers

Maurer Manufacturing offers a complete line of high quality aluminum grain trailers. Manufactured in Spencer, Iowa, Maurer aluminum grain trailers ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form