Armyworm

Armyworm Monitoring is underway

Armyworm Monitoring is underway

Photo and article by Luis Espino, Rice Farming Systems Advisor, Butte and Glenn Counties

The armyworm monitoring season has started. The first traps were set on April 19, and two more sites were set up on April 30. More traps will be set up in the following weeks as growers finish their ground work and get ready for planting.

Interestingly, the first set of traps caught an unusual high number of western yellowstriped armyworm moths, about 20 per night for the last 10 days. It is not clear what this will mean for rice, but we will monitor closely.

Like last year, the trap numbers will be updated on the UC Rice On-line website once more sites are established.

More Armyworm Stories

Armyworm Season wrap up

Armyworm Season wrap up

By UCCE Rice Farming Systems Advisor Luis Espino 

Overall, 2019 was a year with strong armyworm pressure. In many fields, armyworm densities were high during the tillering stage, requiring a treatment. During the heading stage, densities were low in most fields; however, in several fields, panicle injury was high. 

On average, our moth trapping found that the first moth peak was similar in magnitude than last year’s, about 25 moths/trap/night. However, the first peak in 2019 was a week later than in 2018. We monitored several fields during this time, and infestations only became serious when traps were catching more than 30 moths/night, and the worm population peaked a week after the moth peak. The Intrepid Section 18 was approved earlier than previous years, so growers were able to make treatment decisions early. The heading peak was 12 moths/trap/night; in 2018 this peak was 18 moths/trap/night. Again, the 2019 peak was about a week later than 2018.

Later armyworm infestations should be less problematic than earlier infestations because rice has more foliage and could withstand more defoliation. During the heading stage, fields that were planted early and headed early escaped the most severe armyworm injury that I observed in late planted fields. 

An anomaly observed this year was the population pattern of the western yellowstriped armyworm. In the past four years, the true armyworm has been the species causing problems; while we caught yellowstriped in the pheromone traps, the numbers were low and I did not find any worms in rice fields. This year, yellowstriped numbers in the traps early in the season were high in Colusa and Glenn counties, and then, during heading, high in Colusa and Yolo. I did find some yellowstriped worms in the field during mid tillering, but their density was not high. I’m still puzzled about where these moths are going, and if they are resulting in worm populations.

We will analyze our yearly data and get back to you with some more thoughts during our winter meetings and other outreach events. Thanks to all the growers and PCAs that let us put traps in their fields, Corteva Agriscience for funding, and FarmDog for letting us use their scouting app for free. Also, many thanks to Marcus Rehrman, our Student Assistant that checked all traps weekly even though the AC in the truck is not the best.

Keep updated on this and other important issues by following our UC Rice Blog.

Armyworm Update Sept. 3

Armyworm Update Sept. 3

By Luis Espino, UCCE Rice Farming Systems Advisor

In all locations the number of moths trapped is coming down for the past two weeks of more. I have not been able to check fields for worms recently; I’m sure there are still a few worms out there. However, most of the rice is now past the point when panicles are at risk of significant injury. 

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Updating the Armyworm Fight

Updating the Armyworm Fight

By Luis Espino, UCCE Rice Farming Systems Advisor

By this time last year, we were seeing the peak of moth flight, with about 18 true armyworm moths per night, and almost no western yellostriped armyworm moths. This year, true armyworm moths are below 10 per night, except for a couple of locations in Glenn County. If we are going to experience an increase in flight, it might come in the next two weeks. 

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