Armyworm

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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2019 Armyworm Trapping

2019 Armyworm Trapping

By Luis Espino, UCCE Rice Farming Systems Advisor

Looks like the number if moths we are catching is staying low, except for a couple of locations. By this time last year, we were averaging 18 moths per night, mostly all true armyworm. This year, we are not catching more than 10 per night, and in some cases the majority are western yellowstriped armyworm. I have not heard of heavy infestations on headed rice yet.

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Updating the Armyworm Battle

Updating the Armyworm Battle

By Luis Espino, UCCE Rice Farming Systems Advisor

For the last two weeks the number of true armyworm moths has declined, indicating that at this point there should be very little egg laying going on. In a couple of locations on the west and south part of the valley the number of western yellowstriped armyworm moths has increased. In the past, I have not seen western yellowstriped armyworm be a problem, I have only seen a few worms of this species in rice this year. Just in case, I’m providing graphs with total number of moths (the graphs on the left) and separated by species (on the right).

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Armyworm Numbers rising

Armyworm Numbers rising

From Luis Espino UCCE Rice Farming Systems Advisor

The number of moths trapped continues to increase. We are finding numerous medium sized worms, maybe second, third, and fourth instars in fields where moth counts are above 30 per night. Worms have moved from levees and borders to basins. This is the time to scout and look closely for defoliation in the upcoming two weeks.

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2019 Armyworm Trapping Update

2019 Armyworm Trapping Update

From Luis Espino UCCE Rice Farming Systems Advisor

The number of true armyworm moths has shot up quite a bit in several locations. True armyworm has been the problem species in the past. Western yellowstriped armyworm moths have been variable, increasing in some locations, decreasing in others, but in general, the numbers are much lower than at the beginning of the season.

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