Final report for GS21-245
Project Information
The red-headed flea beetle, Systena frontalis (Coleoptera: Chrysomelidae) is a key pest in nursery crops across the Southeastern US, costing millions of dollars for controlling this defoliator. Some nursery growers could spray up twice a week, during the peak of the season, to control this pest. Excessive use of insecticides contradicts all the notions on sustainable agriculture, negatively impacting the environment, non-target organisms and the wellbeing of growers and consumers. This research effort proposed to better understand the biology, phenology, and damage potential of this devastating beetle in ornamentals. Both a combination of in-field and greenhouse work let us elucidate the biology of this beetle. This proposal aids filling up information gaps on this pest, impacting the implementation of an IPM program to control this beetle. Seasonal monitoring was performed to determine times of the year where less spraying of insecticides may be needed. Peaks of adult activity were recorded in eastern Virginia during June, late July, and from late August to early September, indicating the possibility of three generations. Adult lures with phenylethyl alcohol were placed in the field to establish them as a method of cultural control to attract the red-headed flea beetles away from target crops. This alcohol lures were ineffective to attract adults. Foliar damage quantification based on adult density helped in ascertaining what damage quantity and type is being caused. As expected, there was a linear and positive relationship between adult density and percent defoliation of hydrangea leaves. Densities of five adults per plant resulted in an average of 4% defoliation at the leaf level. The ultimate goal for this project was to establish an IPM program for this pest, improving the sustainability of nursery systems, and reducing the overall use of insecticides to protect the systems involved.
The major goal of this research effort was to increase knowledge of biology, ecology and management of the red-headed flea beetle under nursery conditions. Better informed decisions on pest control by growers will ultimately result in reduced operational costs, decreased insecticide use, and preservation of beneficial insects. The specific objectives for this proposal were as follows:
1) Document the phenology of adults under commercial nursery settings.
2) Compare the performance of yellow sticky cards vs. transparent sticky cards, with and without a lure of phenylethyl alcohol, to capture adults in commercial nurseries.
3) Document the foliar damage potential from different densities of adults within the canopy of hydrangea plants under greenhouse and non-choice assays.
Cooperators
Research
Obj. 1. The presence of both adults and larvae in infested container plants was monitored throughout two growing seasons at two commercial nurseries in eastern Virginia. Number of adults per plant and percent defoliation was recorded weekly by visual examinations and by using a bug vacuum. The number of larvae per container was documented every other week. Scouting for this Obj. was initiated during May in 2021, with the last monitoring activity done by the end of September 2021. Scouting for this beetle was also initiated during March 2022 and continued up to the last week of November 2022. The results from weekly scouting were shared, as text alerts, to inform growers of the timing of peak pest activity.
Obj. 2. Four types of sticky cards were placed in one commercial nursery to capture adults, including: a) yellow sticky card, b) clear/translucent sticky card, c) yellow sticky card with a phenylethyl alcohol lure, and d) clear/translucent sticky card with a phenylethyl alcohol lure. Previous research has shown that lures of phenylethyl alcohol attracted red-headed flea beetles in soybean fields (Braasch and Kaplan 2012). Cards with and without the lures were hung on wood poles one foot above the plant canopy. There were four replications for each card type, and cards were arranged as a block design. This trial was repeated three times during 2022. The distance between cards was at least 30 feet. Adult captures on sticky cards were collected twice, one week and two weeks after deployment.
Obj. 3. Live red-headed flea beetle adults were collected from a commercial nursery and transported to the Hampton Roads Agricultural Research Station in Virginia Beach, VA in preparation for non-choice assays. Under greenhouse conditions, adults were caged with insecticide-free hydrangeas. We used one of the preferred plant hosts by this pest for this objective: Hydrangea paniculata var. ‘limelight’ (Joseph and Hudson 2020). One plant per cage was exposed to: a) no adults, b) 5 adults, and c) 25 adults per plant. Assays were set up as a randomized complete block design, with four replications for each adult density. Defoliation was assessed seven days after the release day, damage location within the canopy (at the upper, middle or bottom part of the plant) was also recorded. This entire assay was repeated three times during 2022.
Statistical analysis. All response variables, including insect densities and plant damage, were subjected to ANOVA and analyzed using generalized linear mixed models. The adult phenology data included the use of a repeated measures approach to analyze the effect of time (collection date). Mean separation (post-ANOVA) among experimental treatments was carried out using Tukey's test at α ≤ 0.05.
Obj. 1
Consistently, red-headed flea beetle adults were present throughout the sampling season, extending from May to November during both years. In 2021, 558 potted plants were scouted across all locations and all affected crops. Scouting efforts were significantly increased the following year, in 2022, where 5,877 potted plants were sampled for recording the presence of adults. The first peak of adult activity was either documented during the middle of June in 2021, or during the last week of June in 2022. And during both years, the second peak in adult activity was registered during the last week of July, and the third peak during early September, respectively.
Knowing the expected peaks of adult activity could help growers do the scouting to fine-tune the timing of insecticide applications, increasing efficacy of applied insecticides.
Obj. 2
Data yielding captures of adults on sticky cards were collected from potted hollies at one commercial nursery in Virginia in 2022. Both factors, sticky card type (clear vs. yellow) and the presence of the PEA alcohol (lure vs. no lure), had no influence on the captures of red-headed flea beetle adults across the three repetitions of this trial.
Attractants could be an additional tool for managing these beetles; however the PEA alcohol was not a successful candidate of this type of semiochemicals for the red-headed flea beetle under the conditions of these experiments.
Obj. 3
The average defoliation rate at the leaf level for potted hydrangea plants, exposed to different red-headed flea beetle adult densities for one week, ranged from 3.06 to 3.11%. As expected, higher leaf defoliation rates were documented from plants caged with 25 adults, when compared with plants caged with 5 adults. Interestingly, there was not a consistent pattern where leaf defoliation rates varied among canopy sections (bottom vs. middle vs. top). And based on the positive and linear relationship between adult densities and damage rate at the leaf level, it is expected that one adult could remove up to 1.13% of the area of a leaf.
Red-headed flea beetles have a significant impact on leaf defoliation, if not control within a 7-day period. And growers could perform an scouting event using the top portion of plants to record defoliation, yielding reliable and representative data for the overall damage status of an infested plant.
Educational & Outreach Activities
Participation Summary:
Consistent communication with the growers gave us the opportunity to let them know the status of the red-headed flea beetle population. We made sure to let the growers know when we were seeing high levels of infestation in their fields. By informing them of when we saw high pest populations, the growers were able to act quickly to control this pest and prevent higher levels of economic losses due to damaged crops. This collaboration helped the growers be more aware of pest populations and timing of insecticide applications.
An extension fact sheet was published through the Virginia Cooperative Extension about the red headed flea beetle in Virginia nurseries (Lane & Del-Pozo, 2021). Additionally, a peer-review manuscript was published in the Journal of Environmental Entomology (Lane & Del Pozo-Valdivia, 2023), summarizing the results from this research proposal. Both papers give an overview of the issues Virginia nurseries face and what they can do to handle red-headed flea beetle infestations.
The PI was able to present information on this key pest in six extension meetings, reaching out to 80 agricultural professionals.
Project Outcomes
Participating growers have witnessed, firsthand, how field scouting could contribute on improving the timing for deploying control tactics. Our data from Obj. 1 has been used by participating growers as part of their decision making process before control tactics were implemented. Field testing attracts (Obj. 2) could result in an additional control tactic for this pest. Based on our results, the PEA alcohol was not a good candidate for a semiochemical of the red-headed flea beetle under nursery conditions.
Information collected from our non-choice and cage studies (Obj. 3) has increased the knowledge on the biology of this key pest. This project documented the feeding potential of this pest under controlled conditions. Clearly, a lack of management for this beetle will result in significant losses for affected growers. Information on the biology of this pest, collected from experiments in this project, aimed to strength the IPM program for ornamentals, ultimately reducing insecticide use, and by promoting the sustainability of the nursery industry.
By conducting these trials, Ms. Lane gained research experience. Setting up field trials and greenhouse trials, troubleshooting designs, and collaborating with growers has been a valuable experience and has allowed for growth as researchers. Conducting in-field scouting has also provided experience in learning and developing insect monitoring techniques.
The PI was also able to learn new aspects of the biology of this devastating pest. Scouting and biology data will inform suggestions on improving the management of the red-headed flea beetle under open-field nursery conditions.