Developing near and long-term management strategies for Lebbeck mealybug (Nipaecoccus viridis) in Florida citrus

Developing near and long-term management strategies for Lebbeck mealybug (Nipaecoccus viridis) in Florida citrus

Report Date: 04/13/2022
Project: 20-002C   Year: 2022
Category: Other
Author: Lauren Diepenbrock
Sponsor: Citrus Research and Development Foundation

1. Please state project objectives and what work was done this quarter to address them:

1. Near term field management

(a) Develop methods to time management actions

Working with 6 commercial citrus growers throughout central Florida, we have been developing a robust dataset to describe the seasonal phenology (“life cycle”) of lebbeck mealybug populations. Describing the seasonal life cycle of this pest helps determine key timepoints for management of its population in relation to tree development and/or time of year.

Findings through March 2022:

Similar to data from 2021, we have seen lebbeck mealybug populations grow alongside with fruit development. During bloom, we have also documented mealybugs arriving to flowers during bud swell, suggesting that there may be an odor-based attractant. We have seen similar recruitment of mealybugs to tree damage. Based on our observations, we have collected volatile odors from various stages of flower and fruit development as well as from mechanically induced damage. These will be used to determine if specific odors are attractive to lebbeck mealybug in ongoing research. This will help us to understand additional drivers of attraction of lebbeck mealybug to better target management.

The ongoing lure trial has proved unfruitful. Pheromone lures from our colleagues in Isreal were compared to traps baited with virgin females and blank traps. Only traps baited with virgin females attracted male mealybugs. This needs to be refined before it could be useful for local mealybug detection.

(b) Expand laboratory insecticide and adjuvant screening.

Adjuvant screening: A total of 10 adjuvants, including and 4 from Helena Agri Enterprises were mixed with DI water at label rates and sprayed until dripping on leaves with adult female mealybugs and ovisacs. Three adjuvants resulted in high mortality of mealybug adults (comparable to mortality from applications of Delegate (Spinetoram)), and 1 resulted in higher mortality of eggs within ovisacs.

(c) Evaluate promising materials in open grove setting

A drench trial began on March 8, 2022 comparing Admire Pro, Platinum 75 SG, Belay, Sivanto Prime, Verimark, Aldicarb, and an untreated control for management of lebbeck mealybug. In the absence of a field population, we are bringing back field-aged treated expanded soft leaves to challenge with mealybugs. This test will continue for 90 days after application.

(d) Fire ant management as part of lebbeck mealybug management

Data collection has concluded for management of fire ants, sampling of ants associated with mealybug clusters, and cluster collection to determine impact of management on establishment of predators. While we are still exploring the data, we do see a clear impact of fire ant removal whereby a higher abundance of predators are found in ovisacs and mealybug clusters without fire ants present than clusters where fire ants are actively tending clusters. We do not see a the same association with any other ant species present in our research site, which suggest the importance of fire ant management for control of this pest. Additionally, treatments to remove fire ants result in lower numbers of mealybug clusters and ovisacs found during visual surveys.

II. Long term management

a. Assessment of predator- what is currently in the system, can they be enhanced, how to implement use of predators alongside insecticide use for ACP and mealybugs

In total, six different species of predators have been identified actively preying on lebbeck mealybug, including both generalists and mealybug specialists. Four other generalist predators found in Florida citrus have been confirmed to consume lebbeck mealybug in lab trials, and likely prey on mealybugs in groves as well. Results on these predators have been written up and are currently being submitted for publication.

In addition to predators previously found in fields, we have now found at least two species of parasitoid that are promising for management. A taxonomic specialist identified them as Anagyrus dactylopii and Aprostocetus sp. Future work will focus on establishing a laboratory colony to better understand the potential of this predator for control in citrus groves.

b. Determine how to implement mealybug management concurrent with other pest management programs

No new data to report this quarter

c. Determine what insecticide chemistries inhibit feeding

Continuing baseline feeding interaction work. Documentation will continue throughout spring and summer, with continued funding insecticide assays should begin in summer/fall 2022.

d. Develop tools to minimize spread

Data have been submitted for publication and the manuscript is currently under review. Recommendations using isopropanol and steam to treat infested materials will be ready to share in spring 2022.

2. Please state what work is anticipated for next quarter:

Most of these are in the beginning stages and will be continued through the coming year

1b c. Field testing of insecticides and promising adjuvants (for ovisac penetration). This will include combining adjuvants with Delegate to determine if the combination of adjuvant and insecticide results in increased mealybug instar and ovisac mortality.

We plan to treat and field-age insecticides similar to the drench study throughout the spring, summer, and fall to determine efficacy on mealybugs in lab assays.

1d. Develop fire ant management recommendations based on 2021-22 data

2a. Further testing of predators for management in CUPS, field mesocosm studies of predators (bagged trials on infested trees) to determine efficacy in groves compared to controlled lab study.

2b. Field evaluations of management incorporating data from 1b, c, and d

2c. Continued documentation to develop robust feeding interaction understanding. Based on this, we can evaluate impacts of specific insecticides on this interaction (Can we block it? Can we kill the feeding adult? Can we kill her offspring?)

2d. Develop test to evaluate sanitation procedures for larger equipment (trucks, tractors). Develop protocol for sanitation using solarization and freezing.

3. Please state budget status (underspend or overspend, and why):

On track, however some objectives are taking longer than anticipated and we have requested a continuation of current funding and additional funding through a 3rd year of work to complete our objectives.

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