The subject of my study was the red-headed flea beetle which requires some introduction to anyone who is not in agriculture or ornamental production. This beetle causes damage by eating the leaves of a wide variety of plants. In the context of my study, I was concerned about the damage this beetle can do to ornamental plants such as hydrangeas, hollies, and sweetspires in commercial nurseries, specifically in eastern Virginia. The damage it causes is of top concern to growers who value and require their crops to be of high quality.  

This pest is likely a native species that has grown to be a problem within the last decade, being cited by Virginia nursery growers as their top pest of concern. The thing is that there isn’t much known about this pest the way there is about other common agricultural pests that have decades of research.  

In efforts to control the beetles, growers spray products as often as three times a week when beetle numbers are high. This brings me to one of the study objectives which was determining when the beetle numbers are high. Different climates affect their emergence and the numbers of generations that appear per year, and knowing when this is happening allows the growers to use certain products that have limits to the number of uses per year when they will be most effective.

 

 

What I did was go out to two commercial nurseries in eastern Virginia and every week from about March to October, for two years. My lab and I vacuumed sections of the nursery to count how many beetles per plant were present. We looked at three different plants that were known to have heavy beetle damage specifically, Hydrangea paniculatas in the variety limelight.  

 

 

We found that there were likely three generations a year with peaks in adult numbers occurring in June, late July, and late August. Each beetle life cycle takes about a month and at the end of the season, the eggs in the soil will overwinter to the next year. The larvae live in plant soil and feed on the roots but don’t cause visual damage.  

The other major section of this was to find when during the day the beetles were most active so that growers might time their spraying to most effectively target the beetles. I went out and counted how many beetles were doing what every 2 hours for a full 24 hours and found them to be active during the day especially between 11am-3pm. 

The last section of this paper looked at how many beetles caused what level of damage and to do this we put 0, 5, and 25 beetles in a cage with one hydrangea for 1 week and then assessing damage to leaves.  

Overall, we found that 5 individuals which according to the population studies, was a high density, can cause up to 4% damage which is more than you think.  Overall, this study provided information so growers now know when to expect high numbers of beetles, when during the day they are most active, and how much damage different numbers of beetles can cause so they can determine what their action threshold may be.   

There were so many moving parts to this project that worked together to tell the story of what the beetles were up to and what we could learn about them. There was even another section of the project that looked at a chemical attractant as a potential for a lure for the beetles but it was unsuccessful under the available conditions. 

There is still research that will be needed to bridge the remaining gaps such as if spraying at certain times of the day is more effective. But overall, that gives you a general idea of what I was up to for two years before starting at NPMA.  

Article by Ellie Lane

References

Lane, Eleanor L., and Alejandro I. Del Pozo-Valdivia. "Temporal and spatial factors influencing Systena frontalis (Coleoptera: Chrysomelidae) behavior in Virginia nurseries." Environmental Entomology 52.4 (2023): 730-739.

Lane, Eleanor L., and Alejandro I. Del Pozo-Valdivia. "Red Headed Flea Beetle in Virginia Nurseries." Virginia Cooperative Extension ENTO-464 (2021). https://www.pubs.ext.vt.edu/ENTO/ENTO-464/ENTO-464.html

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