Time To Scout For The Armyworms On Wheat

SPRINGFIELD, MO.

    Although early season trapping of moths indicated Spring infestations of armyworms would be small, some southwest Missouri wheat famers are still reporting armyworm damage.

   In fact, according to Jay Chism, agronomy specialist with University of Missouri Extension, some area wheat fields may need insecticide because the armyworms are at threshold.

   “However, there is no way to know without scouting fields, even when it is wet,” said Chism.

   Scouting for armyworms is best done at night or during early morning. Armyworm larvae are nocturnal (night) feeders and generally remain hidden during bright, sunny days.

   Treatment is justified when an average of four non-parasitized, half-grown or larger worms can be found in every square foot during late spring and before more than two to three percent of the heads are cut from wheat.

   “Most fields are not at that point but the window of opportunity for spraying is short. If the armyworms are stripping leaves you need to get in there and get them under control,” said Chism.

   Insecticides recommended for control of the armyworm in fescue include Mustang Max, Sevin XLP Plus, Penncap-M or Warrior.

ARMYWORM CHARACTERISTICS

    “In the wheat fields I looked at this week the armyworms had eaten the head off,” said Chism.

   Typically, armyworms will strip the foliage by eating the flag leaf on wheat. When that happens the total wheat yield is greatly reduced, sometimes by as much as 70 percent.

   “The flag leaf makes up a big part of the total wheat yield. That means keeping that flag leaf healthy is really important,” said Chism.

   Larvae typically feed on foliage from the soil surface upward. This results in the canopy of an infested crop field look normal on one day and then disappear the next as larvae complete their feeding on the host plant by consuming the remaining upper foliage.

   Research has also shown that true armyworm larvae are most destructive to wheat and other small grain crops when wet weather causes lush growth and lodging in the field.

   Full-grown, armyworms are nearly 1.5 inches long. Larvae have a greenish brown body, nearly hairless, smooth, with a thin stripe down the center and two orange stripes along each side. The head is brown in color and often exhibits a honeycomb pattern of markings, or inverted “V” marking. Each proleg has a dark band on its outer side and a dark tip on the inner side.

   For more information on dealing with armyworms in wheat contact Chism at (417) 682- 3579 or read MU Extension guide sheet G7115, “Management of the Armyworm Complex in Missouri Field Crops.” Δ