Our Research
Annual Wheat Stem Sawfly Survey
Each year, our lab surveys 15+ Colorado counties for sawfly infestation. This data is then used to monitor sawfly movement and provide a database for use in future projects. See the image below for our recent survey results.
2024 Wheat Stem Sawfly Infestation in Colorado. Image Credit: Adam Osterholzer
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This graphic can be downloaded here:
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Wheat Stem Sawfly Flight Timing
We conduct sweeps to track the timing of when adult sawflies emerge and target wheat crops. This data helps us predict future flights.
Graphic Depicting WSS Flight Data 2021-2024. Updated by Ana de Zoten and Adam Osterholzer.
Solid Stem Assessment Screening
Breeding wheat to have semi-solid stems remains the main control measure for mitigating sawfly damage. Increasing the stem solidity makes it more difficult for sawflies to lay their eggs. Semi-solid stems are also less suitable for larvae to develop in than hollow stems.
We cooperate with Dr. Esten Mason of the CSU Wheat Breeding and Genetics Program to help further this research. We screen stem solidity for a variety of experimental lines. This data is utilized to predict a line's resiliency to sawfly infestation. It can also be used to determine how environmental conditions impact solid stem gene expression.
We cooperate with Dr. Esten Mason of the CSU Wheat Breeding and Genetics Program to help further this research. We screen stem solidity for a variety of experimental lines. This data is utilized to predict a line's resiliency to sawfly infestation. It can also be used to determine how environmental conditions impact solid stem gene expression.
Parasitoid Wasp Studies
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Parasitoid wasps are a potential control measure for sawflies. These wasps will seek out sawfly larvae in wheat stems. After paralyzing a sawfly larva, these wasps lay their own egg inside the stem. The offspring consumes the sawfly larva, killing it before it becomes an adult.
Colorado currently has populations of two types of parasitoid wasps, Bracon cephi and Bracon lissogaster. Both populations are insufficient in size to mitigate sawfly damage. Bracon cephi is the more abundant species. Even though these wasps are effective control measures for sawflies in other states, they have yet to cause a decrease in sawfly infestation in Colorado. We conduct a variety of field and lab studies with these parasitoids. We are taking part in field releases and genetic studies. We hope to improve the effectiveness of the parasitoids against the sawflies. |
​Parasitoid Wasp (Bracon cephi). Image Credit: Paetra Vroman-Lucas
​Parasitoid Wasp (Bracon cephi). Image Credit: Zhi Mei Maria Lee
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Ancestral Wheat Screening
We screen for novel sources of resistance to sawflies in ancestral wheatgrasses. Breeding programs are utilized to incorporate these resistances into commercially viable wheat. We test for sawfly resistance by deliberately exposing plants to adult sawflies in the field. By evaluating the oviposition and larval survival data, we determine whether resistance has been achieved. We partner with the Wheat Genetics Resource Center at Kansas State University on this project.
Unloading experimental lines for sawfly exposure.
Image Credit: Henrique Vieira
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Sawfly infesting experimental lines.
Image Credit: Henrique Vieira
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Evaluating Use of Fusarium spp. Fungi in Sawfly Control
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We are evaluating the ability of Fusarium spp. fungi to cause sawfly mortality. Our current results look promising! Significant mortality has been observed following exposure. Results will be released in the upcoming seasons.
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Fusarium spp. samples on sawfly larvae.
Image Credit: Adam Osterholzer
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Degree Day Model for Predicting Sawfly Emergence
Our Ph.D student Henrique Vieira conducted this research. CoAgMet weather data was used with historical sawfly infestation to help growers predict sawfly flights. Based upon Henrique's model, we predict that sawflies will begin emerging at 148 growing degree days (GDD). Growers can expect the most adults at 224 GDD, followed by severe decline at 354 GDD.
We recommend scouting stubble for sawfly infestation (looking for stubs, cutting open stems to find larvae, etc.) prior to 148 growing degree days. This will let growers see if sawflies will emerge and infest their nearby wheat fields. Growers can monitor GDD accumulation at: pnwpest.org/cgi-bin/ddmodel.us?spp=aaa&uco=1
We recommend scouting stubble for sawfly infestation (looking for stubs, cutting open stems to find larvae, etc.) prior to 148 growing degree days. This will let growers see if sawflies will emerge and infest their nearby wheat fields. Growers can monitor GDD accumulation at: pnwpest.org/cgi-bin/ddmodel.us?spp=aaa&uco=1
Graphic depicting the relationship between growing degree day accumulation and WSS abundance. (Vieira et al., PLOS One)
