By Thomas Kuhar
Corn earworm moth catch data from sweet corn farm locations around Virginia can be found in the table below. In summary, corn earworm activity has gone up this week in Accomack County, Virginia Beach, Amelia County, Frederick County, and Franklin County, but has dropped off in many other locations around Virginia. Thus, moth activity is quite variable right now, but should certainly be monitored carefully in the coming weeks.
Corn earworm pheromone trap catch per night in Virginia.
Insecticide Options for Insect Control in Sweet Corn
Pyrethroids are the most commonly used insecticides in sweet corn. They are relatively cheap, effective, and include many options such as (alphabetized):
Baythroid XL 1.6 to 2.8 fl oz/A
bifenthrin–2.1 to 6.4 fl oz/A Bifenture 2EC (Sniper, or others);
cyfluthrin–1.6 to 2.8 fl oz/A Tombstone 2EC (or OLF);
esfenvalerate–5.8 to 9.6 fl oz/A Asana XL;
lambda-cyhalothrin–1.28 to 1.92 fl oz/A Warrior II or 2.56 to 3.84 fl oz/A Lambda-Cy (LambdaT) permethrin–4.0 to 8.0 fl oz/A Perm-UP 3.2EC (or OLF)
zeta-cypermethrin–2.8 to 4.0 fl oz/A Mustang Maxx (or OLF)
zeta-cypermethrin+bifenthrin–4.0 to 10.3 fl oz/A Hero EC
Some drawbacks to pyrethroids are that they are broad spectrum contact poisons that are also quite toxic to natural enemies such as ladybeetles and minute pirate bugs, Orius spp., that frequent sweet corn in Virginia and which can destroy many eggs of CEW before the larvae can damage the ears. Pyrethroid insecticides are also toxic to bees. Frequent use of pyrethroids can also cause outbreaks of corn leaf aphids, which can build up on the ears causing honeydew and sooty mold, which can reduce quality and marketability of the produce. Corn earworm in Virginia is showing signs of resistance development to pyrethroids and therefore rotating different modes of action is recommended.
Other insecticide classes (different modes of action) that should be considered for use in sweet corn include:
- Lannate LV methomyl – Will not flare aphids. HAs not provided as effective control of corn earworm as the other products when used exclusively. Is a good rotation or tank mix option.
- Coragen 1.67SC chlorantraniliprole–3.5 to 5.0 fl oz/A – this diamide insecticide is virtually non-toxic to bees and natural enemies, and provides excellent control of corn earworm and other worm pests. Only about two applications can be used per season. It is an excellent choice during pollen shed.
- Besiege lambda-cyhalothrin+chlorantraniliprole–6.0 to 10.0 fl oz/A includes both the diamide and a pyrethoid.
- Blackhawk 36WG spinosad–2.2 to 3.3 oz/A or Radiant SC spinetoram–3.0 to 6.0 fl oz/A are spinosysns that provide very good control of corn earworm and other worm pests and are less harmful to many natural enemies.