Spraying Too Much: Understanding the biology of the red headed flea beetle to inform IPM in nursery crops

Progress report for GS21-245

Project Type: Graduate Student
Funds awarded in 2021: $16,480.00
Projected End Date: 08/31/2023
Grant Recipient: Virginia Tech
Region: Southern
State: Virginia
Graduate Student:
Major Professor:
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Project Information

Summary:

The red headed flea beetle, Systena frontalis (Coleoptera: Chrysomelidae) is an emerging pest in nursery crops in the Southeastern US, costing millions of dollars for controlling this defoliator. Growers in Virginia spray up to three times 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 is 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 will let us elucidate the biology of this beetle. This proposal will also lay the foundation of knowledge and fill up information gaps on this pest, to propose the implementation of an IPM program to control this beetle. Seasonal as well as daily activity monitoring will be performed to determine times of the day and times of the year where less spraying of pesticides may be needed. Phenylethyl alcohol lures will be placed in the field in an effort to establish them as a viable method of cultural control to attract the red headed flea beetles away from target crops. Foliar damage quantification based on adult density will also help in ascertaining what damage quantity and type is being caused. The ultimate goal is 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.

Project Objectives:

The major goal of Ms. Lane’s research is to increase knowledge of the 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 are as follow:

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 and their tissue preference (young vs. old) within the canopy of Hydrangea plants under greenhouse and non-choice assays.

Cooperators

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Research

Materials and methods:

Obj. 1. The presence of both adults and larvae in infested container plants will be monitored throughout the growing season at two nurseries in eastern Virginia. Number of adults per plant and percent defoliation will be recorded weekly by visual examinations and sweep-netting, complemented with captures from translucent sticky cards. Number of larvae per container will be documented every other week. Scouting for this Obj. will be initiated during the second week of September in 2021, with the last monitoring activity done by the end of October 2021. Scouting for this beetle will be also initiated during May 2022 and continue up to the last week of October 2022. An additional scouting data set will be collected from May 2023 to the end of July 2023. These results will be shared as email communications or blog posts to inform county extension agents and growers on the timing of peak pest activity.

Obj. 2. Four types of sticky cards will be placed in two different nurseries to capture red headed flea beetle [RHFB] 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 RHFB adults in soybean fields (Braasch and Kaplan 2012). Cards with and without the lures will be hung on wood poles one-foot above the plant canopy. There will be three repetitions for each card type per trial, and cards will be arranged as a block design. The distance between cards will be at least 30 feet, and distance between reps will be 60 feet. Adult captures will be recorded daily for two weeks. This trial will be replicated twice (June and July during 2022 and 2023) at each nursery location, during the peak of activity of this beetle.

Obj. 3. RHFB live adults will be collected in early August from one commercial nursery and transported to the Hampton Roads Agricultural Research Station in Virginia Beach, VA for non-choice assays. Under greenhouse conditions, adults will be caged with insecticide-free hydrangeas. We will use one of most preferred plant hosts by the RHFB for this objective: Hydrangea paniculata var. ‘limelight’ (Joseph and Hudson 2020). One plant per cage will be exposed to: a) no adults, b) 5 adults, c) 20 adults and d) 50 adults per plant. Assays will be set up as a randomized complete block design, with four repetitions for each adult density. Defoliation will be assessed after seven days from the release day, damage location within the canopy (at the upper, middle or bottom part of the plant) and type of tissue damaged (young new growth vs. old fully formed leaves) will be recorded. This entire assay will be replicated twice (in September and October during 2021 and 2022).

Statistical analysis. All response variables, including insect densities and plant damage, will be subjected to ANOVA and analyzed using generalized linear mixed models. Some data sets will include the use of a repeated measure approach to analyze the effect of time (collection date) across treatments. Mean separation (post-ANOVA) among experimental treatments will be carried out using Tukey's test at α ≤ 0.05.

Potential problems, limitations, pitfalls. Experimentation under commercial field conditions could be challenging due to uncontrolled external parameters not managed by the researcher, including irrigation, fertilization, insecticide use and others. However, generating replicated field data is essential to providing pest management recommendations for a specific pest in commercial settings. To mitigate these unexpected challenges, experimental trials will be located with nursery growers who have experience collaborating with other researchers. Another challenge is finding reliable and consistent high infestation rates for this insect. To overcome this second challenge, experimental sites will be located in areas with previously recorded high infestation of RHFB. Collaborating growers will provide much needed insight to direct our efforts to areas with historical pest issues. Lastly, replication could also be a challenge. However, this proposal includes carrying out these experiments at two different nursery locations and during at least two years. Having replicated trials through time and placed in several locations increases our power to analyze any potential effect of the experimental treatments.

Research results and discussion:

Obj. 1

The seasonal monitoring procedure was improved during October 2021. The team decided to use a leaf blower, set for vacuum mode, to collect adults instead of using sweep nets. Now that we have refined the protocol, we are planning to use it to document the phenology of this pest during 2022. Despite this setback, we were able to see based on population levels and foliar damage, some adult activity of this pest during September and October 2021. The damage found in the foliage was high at the end of the season (September and early October) with beetle populations averaging close to 1 beetle per plant per week. This higher damage but lower number of beetles could simply be due to the full season’s cumulative damage.

Obj. 2

The team has coordinated with the two participating growers, discussing the location and logistic to set up these trials during spring and summer 2022.

Obj. 3

After seven days, the foliar damage was assessed from experimental cages. The plants with more beetles had more damage, as would be expected (df = 3, 12; F = 13.78; P = 0.0003). There was no statistically significant difference between different layer of the canopy and percent damage (df = 2, 24; F = 1.71; P = 0.2027). It appears to be no clear preference from RHFB adults for different layers of the canopy and that damage has been distributed across the entire canopy. Additional repetitions of this experiment will allow us to discuss implications on visual scouting protocols (selection of an specific plant strata) and foliar insecticide applications (use of drop nozzle vs. boom spay).

Participation Summary
2 Farmers participating in research

Educational & Outreach Activities

1 Curricula, factsheets or educational tools
2 On-farm demonstrations
3 Webinars / talks / presentations

Participation Summary:

4 Farmers
40 Ag professionals participated
Education/outreach description:

Consistent communication with the growers gave us the opportunity to let them know the status of the RHFB 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). This paper gives a brief overview of the issues Virginia nurseries face and what they can do to handle RHFB infestations.

The PI was able to present information on the RHFB in three extension meetings, reaching out to 40 agricultural professionals.

Project Outcomes

1 Grant received that built upon this project
3 New working collaborations
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 these growers as part of their decision making process before control tactics were implemented. 

Information collected from our non-choice and cage studies (Obj. 3) has increased the knowledge on the biology of RHFB. This project documented the feeding potential of this pest under controlled conditions. Clearly, a lack of management for the RHFB will result in significant losses for affected growers. Additional information on the biology of this pest, collected by upcoming experiments in this project, aims to strength the IPM program for ornamentals, ultimately reducing insecticide use, and by promoting the sustainability of the nursery sector.

Knowledge Gained:

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 a researcher. Conducting in-field scouting has also provided experience in learning and developing techniques.

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 RHFB under open-field nursery conditions.

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.