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How to successfully collect and release leafy spurge beetles

NDSU man sweeping plants with net
BEETLE SWEEP: Sweep for leafy spurge flea beetles on warm sunny days. The sweeping motion should be in an arc from left to right over the top two thirds of the leafy spurge plant. Avoid hitting rocks and soil.
Avoid spraying chemicals by relocating beetles from one leafy spurge patch to another.

Leafy spurge beetles can be a great help when trying to control leafy spurge, but they don’t move far — especially if your leafy spurge patches aren’t connected.

But if you have an established leafy spurge beetle population on your farm or ranch, you can collect beetles from one patch of leafy spurge and release them in another patch to establish a new population.

“It pretty easy to do,” says Pete Bauman, South Dakota State University Extension range management specialist.

It’s also a pretty pleasant job — a lot easier than bouncing around on an ATV on a hot sunny day spraying chemical on leaf spurge patches, he says.

Rod Lym, North Dakota State University plant science professor, offers these tips on collecting and redistributing leaf spurge beetles:

1. Time of year to collect beetles. From early- to mid-June, before the females lay eggs, is the best time to collect beetles You want to them to lay eggs in the new location.

2. Time of day to collect beetles. The best time of day to collect beetles is from 10 a.m. to 3 p.m. It should be warm, more than 70 degrees F, with sunny skies and little or no wind. Leafy spurge should be dry when collecting beetles. Wet conditions will make sweeping difficult and reduce the adult survival during transportation.

Is the beetle population high enough to move some of the insects? Sweep a net five times covering an area of 10 square feet. If flea beetles are too numerous to count individually, remove excess trash and non-flea beetle insects and pour net contents into a graduated container. Every 10 milliliter of flea beetles is approximately 1,000 individuals. Redistribute flea beetles to other leafy spurge infestations when 500 to 1,000 beetles per five minute sweeping period are collected. Over-harvesting of beetles is not possible because many flea beetles fall to the ground prior to being swept or are on the soil surface laying eggs.

3. Move beetles in paper bags or containers. Do not use plastic containers because moisture condensing on the plastic can drown the insects. Add some leafy spurge to the bag or container and place it in a cooler containing ice. Do not allow the containers or cooler to sit in the sun.

4. Release beetles as soon as possible. Releasing the same day as collection is ideal; however, the insects can survive several days when refrigerated at 40 to 45 degrees F.

5. Place beetles on the edge of a dense patch. If you have a very dense patch of spurge, release the beetles on the edge of the patch, not in the middle. The female beetle lays eggs on the top of the soil. When the larvae emerge they have a few hours to burrow into the soil and find a leafy spurge feeder root to survive. If the litter from old leafy spurge stems is too thick, the larvae will never make it to the soil.

See related article: 5 things to know about leafy spurge biocontrol

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