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The following video demonstrates the set up for one of our projects at Michigan State
University studying winter annual weed seed germination and decay. This is the final year
of the two year project which was funded by the North Central Integrated Pest Management
Competitive Grants Program.
Winter annual weeds generally germinate in the fall and flower and produce seed in the
spring.
Though winter annual weeds are present when most field crops are not, they can still be
an issue because many can serve as alternate hosts or overwintering sights for crop pests
and diseases. One example is field pennycress (pictured here), which can be an alternate
host for the soybean cyst nematode.
For the purposes of this study we are examining 4 winter annual weed species.
Common chickweed, which is low growing and produces small, bumpy orange and brown seeds
the size of the head of a pin.
Henbit, a member of the mint family that is low growing and produces pinkish-purple flowers.
The seeds of henbit resemble spotted footballs with one flattened side.
Field pennycress, a member of the mustard family has a sulfur-like odor when crushed.
The seeds of pennycress are black and have an impression that resembles a thumbprint.
Finally, Shepherd's purse, another member of the mustard family, has the smallest seeds
of the winter annual studied, at about the size of a fine point pen.
To study the germination and decay of these weeds we created steel-framed cages. In the
germination area of the cages we covered the sides with a fine mesh tent screening to and
buried the cage sides to prevent seed movement during the year long experiment.
The germination of these winter annuals is being followed for one year, starting at the
end of the seed dispersal. In early June we placed the cages in an empty field at the
MSU Agronomy Farm. In the germination area we spread 500 seeds of one of the species
of interest. Each species has four replications. After the seeds begin to germinated we will
record emergence every 2-3 weeks and remove the seedlings that have emerged.
In the smaller portion to our cages we will study the decay of the winter annual seeds
over time. Before placing the cages outside small mesh bags containing 50 g of soil and
100 seeds of a weed species are prepared and strung with nylon twine. Once the cages are
in place the seed bags are place at one of three depths in the soil profile.
Four bags are placed on the soil surface using anchor pins.
Another four bags are placed 1" below the soil surface
And the final 4 bags are placed ~4" below the soil surface using a golf cup cutter.
Every three months a set of bags will be recovered and the seeds will be evaluated for decay.
Understanding the fate of winter annual weed seeds will provide insight into their importance
in agricultural systems and help improve cultural, biological, mechanical, and chemical management
strategies.