Two months ago I posted a blog, encouraging farmers to scout every field for rootworm.  Because of the wide variance in planting dates in 2013, it’s important to continually inspect every field – regardless of seed selection – for insect pressure.

With adult corn rootworm becoming active during silking this year, we highly recommend keeping an eye on fields in order to protect yield.  Now it is a good time to assess corn rootworm activity: score injury caused by larvae, and monitor adult activity in corn.  Late-planted fields or late-flowering hybrids are generally attractive to adult corn rootworm beetles.  Silks will still be developing in these fields when older fields have brown or drying silks.  Adults may migrate and aggregate in this later-maturing fields.

Also evaluate root injury to better understand the efficacy of your management program.  Monitoring over several years will help establish a historical record of how larvae respond to management tactics (e.g., crop rotation, Bt corn, soil insecticides, etc.). One common outcome of severe larval feeding is lodging of corn plants.  However, it is important to confirm that feeding from corn rootworm was the cause of lodging and that it did not results from other factors such as strong winds.

To help assess injury, ISU Entomologist Aaron J. Gassmann developed an Interactive Node Injury Scale.  Injury assessment made now and field notes taken will help you select seed products for 2014.  To prevent corn rootworm damage from reaching devastating levels, plant a portfolio of products.

Continued use of the same rootworm-resistant trait in corn hybrids, an increase of corn-on-corn areas, plus a lack of refuge acres, has caused rootworm resistance to become an issue in some areas.  Best management practices to reduce corn rootworm pressure in the future include: crop rotation, trait rotation and respecting the refuge.

Respecting the refuge just got easier thanks to the EPA last week granting approval of Agrisure Duracade E-Z Refuge trait stacks.  New, for 2014 planting, Latham® Hi‑Tech Hybrids is offering Agrisure Duracade^TM as another option in the fight against corn rootworm.  

Farmers have a chance to see Latham’s new 2014 products this Saturday, Aug. 24, when we host the 5^th Annual Latham Freedom of Independence Ride.  This year’s ride begins and ends in Lewis & Clark State Park in Onawa.  It’s free and open to motorcycles, classic cars and even pickup trucks.  For more details, visit our company website lathamseeds.com.  Then click on the Freedom Ride icon.  Pre-register today, and we’ll see you Saturday on the open road!

With most of the 2013 crop in the ground, it’s time to walk fields.  Crops should be scouted within 3 to 5 days of planting and then regularly throughout the growing season.  Be on the lookout for: (1) crop emergence; (2) nitrate leaching and (3) insect and disease pressure

It’s a good idea to walk fields within 5 days of planting.  Evaluating current stands can indicate whether to replant portions of the field.  Notes you take now also could impact your seed buying decisions this fall.  Plus, evaluating current stands can help determine if adjustments should be made to your equipment or planter speed next spring.

When checking fields where the corn is more developed, look for signs of nitrogen loss.  Iowa State University Nutrient Management Specialist John Sawyer says the best options for sidedressing, in order from most to least preferable, include:

1. injected anhydrous ammonia, UAN or urea,
2. broadcast dry ammonium nitrate, ammonium sulfate or urease treated urea,
3. surface dribbling UAN solution between rows,
4. broadcast UAN, and
5. broadcast urea.

Also walk every field for signs of corn rootworm (CRW), regardless of what traits they planted.  The corn rootworm hatch is underway, so larvae will soon begin feeding on roots if they aren’t already doing so.  Corn development, although delayed, still provides plenty of plant material for the CRW larvae to feast upon. Severe infestation can destroy nodes 4-6, which effect water and nutrient uptake.

Because of the wide variance in planting dates this year, rootworm beetles can move between fields in search of the best “buffet.”  A late maturing corn field may attract a large numbers of beetles if neighboring corn stopped producing pollen, for example.  Beetles may also move into corn and/or soybean fields that have an abundance of pollen-producing weeds, including volunteer corn, ragweed or foxtails.

Weed control is important for several reasons.  Crops have a better chance of reaching optimal yield when they’re not competing with weeds for sunlight, water and nutrients.  Plus, controlling weeds helps control corn rootworm populations.  The rootworm hatch is underway; expect 50 percent hatch between 684-767 degree days.  Click here for current degree day accumulation for corn rootworm provided by the Iowa Environmental Mesonet, ISU Department of Agronomy.

Cool, wet spring weather delayed corn planting and the corn rootworm hatch, which is largely dependent upon soil temperature.  When soil temperatures accumulate between 684-767 degree days, 50 percent of the rootworm hatch occurs.

Although corn is not as far along in its development as it normally is at this time of year, there is still plenty of plant material available to provide a feast for the CRW larvae.  It won’t be long before newly hatched larvae begin feeding on corn roots.  Severe infestation can destroy nodes 4-6, which effect water and nutrient uptake.

Shortly after larvae begin feeding on roots, adult beetles begin to emerge from fields and begin feeding on pollen, green silks and leaves. The males emerge first, and the females follow about 5 to 7 days later.  Mating takes place, and then females will lay eggs toward the end of July through August.

Because of the wide variance in planting dates this year, it will be important to inspect every field – regardless of seed selection.  Rootworm beetles can move between fields in search of the best “buffet.”  A late maturing corn field may attract a large numbers of beetles if neighboring corn stopped producing pollen, for example.  Beetles may also move into corn and/or soybean fields which have an abundance of pollen-producing weeds, including volunteer corn, ragweed or foxtails.

Note areas where corn rootworm damage is the highest and create a plan of action if root injury is high.  To help assess injury, ISU Entomologist Aaron J. Gassmann developed an Interactive Node Injury Scale.  To help develop an action plan, keep best management practices in mind.

Field notes from 2013 will help you select seed products for 2014.  To prevent corn rootworm damage from reaching such devastating levels, plant a portfolio of products.  Remember, that in 2104 Latham® Hi‑Tech Hybrids, will offer Agrisure Duracade^TM as another option in the fight against corn rootworm.