California Rice: 3 Steps for Managing Early Seeding Weeds

I went out on a few farm calls in the past week, and have noticed a trend. Due to the unusually wet weather this spring, some of the weeds are already producing seed out in the field! This occurs when the field was moist or wet in the spring, and was not tilled or sprayed prior to planting.

Herbicide Resistance Info

If you have weeds that are already setting seed, follow the steps below:

1. First, make sure to get proper identification of the weed species. Some weed species will produce seed and that seed can germinate and send up a second flush of weeds, in the same season! They are:

  1. Smallflower umbrella sedge
  2. Mexican sprangletop

NOTE: There are two types of sprangletop: Mexican and Bearded. Only the Mexican sprangletop will set seed that will germinate this season. Bearded sprangletop seed is dormant and won’t germinate until the 2018 season.

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Mexican sprangletop that has already set seed (about 20 days after rice seeding)
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Bearded sprangletop (left) and Mexican sprangletop (right). Photo: Matthew Quinton

2. If you have one of the above-listed species that is already setting seed, it is important to make sure that your follow-up herbicide application will control this second flush of germinating seeds. Otherwise, the amount of seed produced and deposited into the seedbank will be exponentially higher than in a normal year, because there will be two generations of plants that set seed in the same season!

3. If you have a weed species setting seed that is NOT listed above, you will likely not be able to do much this year, as the weeds are likely too large to control with herbicide and any impacts on yield have already occurred. Plan to have an aggressive program for next year (2018)!

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