Is it weedy rice or an imposter? UC has some answers

elongated internode

Elongated upper internode is a
genetic trait that produces plants
with really long internodes just
below the panicle, resulting
in a panicle that sticks above
all others. It can be confused
with weedy rice  — photo
courtesy University of California
Cooperative Extension

Rice is beginning to head in the California rice-production area. As you scout your fields, keep weedy rice in mind.

In the past few weeks, University of California Cooperative Extension farm advisers have received 10 suspect samples. Of these, two have been confirmed as weedy, three are being investigated and the rest have been ruled out.

They have also talked to several growers and pest control advisers about suspicious plants in their fields. One common question they have received has to do with the elongated upper internode (EUI) trait.

This is a genetic trait that produces plants with really long internodes just below the panicle, resulting in a panicle that sticks above all others. This trait is usually present at low frequencies, and therefore does not affect yield.

Because the panicle is higher, it can be confused with a weedy rice plant.

Plants with EUI will be the same as the field variety, except for the long internode. In medium-grain varieties, the leaves should feel smooth.

If the leaves feel rough, then it could be a contaminant, or weedy. If in doubt, give a farm adviser a call.

For more information on weedy rice in California, including photos of the five different biotypes, visit California Weedy Rice.