In the last few days Central Valley Agronomists and Interns have found Hop Vine Borer (pictured below and on the left) and also Common Stalk Borer (pictured below and on the right) in fields of Conventional and herbicide resistant corn. (Pictures courtesy of Dalton Kampsen, summer intern in the Ellendale location)
Hop Vine Borer and Common Stalk Borer are generally found on field edges or fields with large amounts of crop residue (reduced tillage). In the past I have normally found Common Stalk Borer in fields with heavy Giant Ragweed pressure especially after we have sprayed the Giant Ragweed plants the Borer will start to transition from the Giant Ragweed to the Corn plant.
Hop Vine Borer and Common Stalk Borer will tunnel into the plant and start to eat towards the growing point, by doing this it will kill the newest leaves and create a plant that has a green lower leaves but dead leaves at the center or “Dead Heart Plants”, this does kill the plant.
If your hybrids have SmartStax, VT Triple Pro or Agrisure Viptera in it you do have a level of protection from these pests. With that being said even with this built in protection, if we have heavy infestations of Hop Vine Borer or Common Stalk Borer they can overwhelm the plant. The concern here is that the pest needs to ingest part of the plant before control will be achieved, if enough pests ingest the plant, the plant will be overrun. The analogy is you might have food for 50 people but if 150 people come to eat you will run out of food fast.
Treatment levels for Hop Vine Borer and Common Stalk Borer are 10 % of the plants at the V6-V7 growth stage. I have seen Fields with high Giant Ragweed pressure with corn at V8 that needed to be treated.
If you have questions or concerns regarding Hop Vine Borer or Common Stalk Borer contact myself or your local Central Valley Agronomist.
