One of the concerns that I have been encountering is regarding the use of a soil applied insecticide for fields that are going to be Corn on Corn in 2015, do I need it, and does it pay?
Some of the questions that need to be answered prior to making that decision are:
How many years has the field been Corn on Corn?
In most instances the longer the Corn on Corn rotation the higher the levels of corn rootworm larvae and beetles which translates into a reduced yield and income loss.
Are you planting a Corn Rootworm Traited Hybrid, which trait?
Some in the Industry are advising that if you are utilizing a Smartstax (SS) hybrid, you have 2 modes of action that are controlling rootworm larvae, and do not need a soil applied insecticide, but if you are planting conventional, VT Triple Pro, or Agrisure 3000GT you will need a soil applied insecticide. I do not agree with this statement especially with higher rootworm larvae population, in that corn rootworm larvae have to bite into the plant to be controlled regardless of the trait, you then have a wound for other pathogens to get into the plant and reduce yield.
Has that field had a history of down or lodged corn?
If you have had down or lodged corn in this field, odds are you have a higher population of rootworm larvae that if it numbers get high enough could overwhelm a traited hybrid.
What were the Corn Rootworm Beetle count numbers?
If you are finding 4-5 rootworm beetles per day in a sticky trap it points to an increased rootworm problem the following year. As we talked about this last fall we were finding 50-90 rootworm beetles per sticky traps per week in Corn on Corn fields and 4-32 beetles per sticky trap for Corn on Soybean fields.
The pictures below may remind you of how high the Beetle counts were last fall.
(The photo on the left is of a Northern Corn Rootworm beetle on a velvetleaf. The photo on the right is of Northern and Western Corn Rootworm Beetle on a velvetleaf. The Westerns have the racing strips on their backs)
What is the Return on Investment?
Recent data suggests a 6.6 bushel yield advantage for utilizing a soil applied insecticide for a traited hybrid. The average cost of a soil applied rootworm insecticide before grower programs is $19.75 per acre. If the value of corn is $3.85/bushel and we have a 6.6 bu/acre increase our Gross return is $25.41/acre or a 28.5% return
| Value/Bu | Yield Increase | |
| $ 3.85 | 6.6 | $ 25.41 |
| Insecticide Cost | $ 19.75 | |
| Net / Acre | $ 5.66 |
In conclusion, making decisions on what products or traits to use is about return on investment for that particular field. Not every field or hybrid may need to have a soil applied insecticide applied. If you have questions or concerns about what the return on investment a product has, contact your local Central Valley Agronomist to help sort out what would work for you on your farm.
