GDD AND ET DATA UPDATED DAILY

For those of you with internet access, daily updates of growing degree day (GDD) and evapotranspiration (ET) data provided by the NU High Plains Climate Center are available on the CropWatch Weather page at: http://cropwatch.unl.edu/weather/GDD-ET.html .  Sites available for information are located at Ainsworth, Alliance, Beatrice, Champion, Concord, Elgin, Grand Island, Holdrege, McCook, Mead, Monroe, Nebraska City, North Platte, O'Neill, Ord, Red Cloud, Scottsbluff, Sidney, West Point, and York

CONTROL OF VOLUNTEER CORN IN SOYBEAN

It is not surprising to see volunteer corn in soybean since the two crops are used in rotation.

However, volunteer corn is a weed and should be treated accordingly. It reduces light interception to soybean, interferes with harvesting procedure and makes the field look >messy=.  Growth of corn is generally >faster= than soybean, therefore if it is left uncontrolled, soon it will overtop the soybean canopy. Control can be achieved by mechanical means (eg. inter-row cultivation) and herbicides.

Timing of inter-row cultivation should depend on the weed pressure. If volunteer corn is a   predominant Aweed@, the timing of cultivation should be around the 5-6 leaf stage of corn. Growing point of corn remains in the ground until the 6^th leaf stage. Therefore any cultivation done prior to that leaf stage may result in regrowth of the plants and it will require a second cultivation. It is especially true with shallow cultivation.

If you have Roundup-Ready soybean, Roundup will control volunteer corn, unless you have had Roundup Ready corn in the previous year.  Roundup will not control volunteer RR-corn in RR-soybeans. 

Herbicides can also be used to very effectively control volunteer corn. There are several grass type herbicides (graminicides) that can be used postemergence in both conventional- and RR-soybean.  The list of herbicides includes: Assure, Fusilade, Fusion, Poast, Poast-Plus, and Select. Best control is achieved when herbicides are applied by the 3-4th leaf stage of corn. These herbicides will also control many grassy species, including barnyardgrass, green and yellow foxtail, fall panicum and sandbur. (SK)

Rescue treatments for postemergence weeds in corn

Unexpected breakdowns, rain or delays may have kept you out of the field when you would have liked to have been in it. If that's the case, Table 1 provides some herbicide rescue treatments that you can use for corn greater than 12 inches tall. Remember that all products control smaller weeds best and a certain herbicide may not have much impact on large weeds.

When deciding whether to spray, consider the potential for successful weed control and the chance of crop injury.

Table 1. Late season weed control in corn greater than 12 inches.

Accent -- Up to 36-inch corn. If taller than 20 inches, use drop nozzles.

Aim -- Up to 8-leaf corn (approximately 30 inches).

Callisto -- Up to 8-leaf corn (approximately 30 inches).

Clarity -- Up to 36-inch corn. Use caution with nearby sensitive broadleaf crops. Use directed application if possible.

Distinct -- Up to 24-inch corn. Use at 4 oz /A rate.

Liberty -- Up to 36-inch corn; requires Liberty Link corn.

Lightning -- 45 days before harvest; requires Imi/Clearfield corn.

Option -- Up to 36-inch corn. If taller than 16 inches, use drop nozzles.
Roundup UltraMax -- Up to 30-inch corn. If greater than 20 inches, use drop nozzles. Requires Roundup Ready corn.

2,4-D amine -- Up to tasseling. Use drop nozzles for corn taller than 8 inches. Use caution with nearby sensitive broadleaf crops.
This information is intended only to be a guide. Always read and follow label directions.

Brady Kappler, Extension Weed Science Educator

MANAGEMENT TIPS FOR IRRIGATED FIELDS

June 15 – July 15 “Before you irrigate check soil moisture in the active root zone. Below are the average root depths of selected corn and soybean stages.” (WK/DL/CS)

Root Depth (feet)	Corn Stage	Soybean Stage
1.0	4 leaf	Vegetative
2.0	8 leaf	Early bloom
2.5	12 leaf	Full bloom
3.0	16 leaf	Pod development
3.5	Silking	Seed development
4.0	Blister	Full seed fill