Insects Create Problem For Alfalfa Fields

Date 2013/7/26 4:56:39 | Topic: News

Two insects are creating problems on alfalfa fields ready to cut for hay. Stealth scouting may be needed to see them, says a University of Missouri Extension entomologist. “These insects can be shy,” says Wayne Bailey. “The main message is go out and scout your fields.”

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The pests are not new, but can arrive in overwhelming numbers.

Potato leafhoppers cause leaves to yellow and fall off, reducing hay yields. The other, the striped blister beetle, can kill horses if the insects are crushed and baled during haymaking.

With both, a noisy approach makes the insects drop to the ground and hide.

The first telltale sign of potato leafhopper may be V-shaped yellowing at the tip of each leaf. Hoppers suck juice from the leaves. The yellowing precedes leaves dying and falling off.

First-year plantings of alfalfa are most at risk, Bailey says. Seedlings in new stands are most vulnerable. A stand that survives the second season can withstand more damage.

The leafhoppers are small, green triangular insects. They do hop.

Economic threshold for applying insecticide is only one hopper per sweep of a 15-inch insect net. Some alfalfa varieties have hairy leaves that repel the hoppers. Threshold on those varieties is three insects per sweep.

A lot of fields are above threshold, Bailey says. The hoppers migrate into Missouri from the south, mostly coming up the western side of the state, then moving north and east.

“Already we have heavy infestations in central Missouri,” he adds.

The other beetles cause blisters on human skin if they are squashed. The body fluids contain alkaloids that are part of their self-defense.



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