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Fall armyworms may threaten

Thursday, September 19, 2002

OREGON COUNTY -- University Extension Agronomy Specialist Vance Hambelton said he received the first sign of an armyworm problem in the area by way of a telephone call Labor Day. The call was from Ozark County where the worms had done severe damage to an alfalfa field. "On Sept. 3 I received a call from a Howell County producer with the same problem. I have not observed damage to grass pastures or hayfields but have heard of some possible problems. The dry conditions the past several weeks have decreased natural controls regarding the worms," Hambelton said.

The agronomist reminds area farmers that alfalfa fields, summer annuals and newly seeded fields are most susceptible to fall armyworms. "Lawns, grass pastures and hay fields may also be attacked. Close observation and early treatment, if necessary could prevent large losses," he said.

"The larvae (worm) of this insect can be devastating to grasses and other plants. The larvae are about one and one-fourth inches long when full grown. They are smooth skinned and vary in color from light tan or green to almost black. Running from head to tail are three very thin yellow-white lines. On each side is a wide, dark stripe and below this is a wider, wavy yellow stripe that may be splotched with red. The fall armyworm and the true armyworm look similar but the fall armyworm usually has a prominent white and inverted Y (upside down) on front of the head. This characteristic may be difficult to detect on some individual worms," Hambelton said.

The agronomist said according to his information, the fall armyworm does not over-winter in Missouri. He said this means the adult moths migrate from the deep south, lay their eggs and begin the reproduction process. "Several generations may occur in an ideal year. The eggs are laid in shady areas and not in plant seed heads. They are not spread by seeding, to my knowledge," he said

Hambelton said after the eggs hatch two to three weeks of feeding by the larvae can be expected before they go to the pupation stage where they become encased in a semi-hard coating. "They undergo the change from the larvae to the adult moth, through this pupation stage, in 10 to 14 days and emerge as an adult moth to begin another life cycle," the agronomist said.

For more information concerning the fall armyworm in Oregon County, call the University Extension Center at Alton at 778-7490.



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