Fall Armyworms and Paul Revere

With so many outbreaks of fall armyworms being reported in our neighboring counties, I can’t help but to feel a little like Paul Revere.  However, don’t expect me to go for a midnight ride through McLean County on horseback shouting “The Fall Armyworms Are Coming!” once they are spotted crossing county lines. 

As much as we all have enjoyed these late summer rains, they can cause increased survival of small fall armyworm caterpillars, which can lead to outbreaks.  Thus far, reports in Western Kentucky (including neighboring counties) have shown fall armyworms showing up in home lawns, grass pastures and in soybean fields.   Fall armyworms spend about 3 weeks as caterpillars but 80% of their feeding occurs in the last few days of their development. While devastating damage appears overnight, the worms have been present for some time before reaching their prime eating stage.

The key to preventing significant losses is early detection of infestation.  Watch for chewed leaves, the earliest signs of an infestation. Caterpillars are up feeding on leaves during the evening or on cloudy days but hide under surface residue or in soil cracks during the day.  An average of 2 to 3 worms per square feet may justify treatment.  Malathion is the only insecticide with a 0 (zero) day harvest or grazing interval but control may be limited.

A few things to keep in mind about fall armyworms:

·         Double crop beans could be problematic, especially if:

o   They are less mature than R6

o   The field borders a pasture/hay field

o   Fields are infested with grass weeds

·         Forage fields of mixed alfalfa/grass & pastures could be at risk.  Established fields will probably not be killed but a compete cutting may be lost.  By far the greatest risk would be newly established grass or alfalfa/grass stands.

·         Home lawns would typically be in the same danger as grass/hay pastures. A good established stand will probably not be killed, but a new stand certainly could be.  Home owners wishing to apply a control should see an insecticide that carries “armyworm” on the label.

Producers are encouraged to scout their fields and be on the lookout for fall armyworms.  For more information on fall armyworms, please contact the McLean County Cooperative Extension Office at (270)273-3690.  Educational programs of the Cooperative Extension Service serve all people regardless of race, color, sex, religion, disability or national origin.