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: 06/11/2022
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 actionsWe have completed one year of lifecycle documentation, finding as previously noted, that populations begin to grow concurrent with fruit production until mid-summer when we see some fluctuation and reduction in mobile life stages (crawlers, 2nd-3rd instar nymphs) concurrent with the heavy rains of June and July. We again see a rise in the juvenile life stages in the fall after rains and intense heat of late summer cease. While there is a fluctuation in the juveniles in these periods, the number of females with ovisacs remains constant suggesting that there is higher natural mortality during this period. Natural mortality could be due to consumption, physical removal from hosts by rain, and death due to regional temperatures (this last factor should be further evaluated).         Concurrent with population development, we have been evaluating a method for population estimates that would be user-friendly if accurate. This method entails minor damage to a branch (e.g. pocket knife scraping) and covering the damage with cardboard to create a tight place for mealybugs to settle as they like these tight points and appear to have an attraction to damage. We are nearing completion of this test and will relate the data to field populations at those same locations.  (b) Expand laboratory insecticide and adjuvant screening.Adjuvant screening: We evaluated 6 adjuvants relative to water and an insecticide control (spinetoram). The insecticide control was chosen based on efficacy for mealybugs in previous trials and being less impactful on beneficial organisms that are important for control of lebbeck mealybug. This design allows us to see the impact of adjuvant alone on mortality with promising materials moving forward to field trials in combination with insecticides. The goal of this work is to enhance efficacy of insecticides while maintaining populations of key predators.         Several materials are promising based on this trial for use as adjuvants to enhance mortality of most mealybug life stages with minimal impacts on the primary predator of lebbeck mealybug. Incorporating adjuvants such as Clearsurf 90 (NIS), Trio, 800 Plus, and Suffoil and similar products into tank mixes should enhance efficacy of insecticides. 435 oil and Wake Up had 70% and 80% mortality respectively of mealybug destroyer juveniles and should not be used in the latter portion of the season when predators are more active and less direct damage should be occurring to fruit. Based on preliminary lab studies (data not shown), similar testing on agricultural detergents is worthwhile, however these will require detailed phytotoxicity studies prior to field use. (c) Evaluate promising materials in open grove settingA 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 consistent field population, we are brought back field-aged treated expanded soft leaves to challenge with mealybugs in the laboratory every 2 weeks until no available soft leaves were available for a total of 6 weeks after application.         At two weeks after application, Aldicarb yielded the greatest mortality with 67% of 2nd-3rd instar juveniles dead compared to 36% from Admire, 21% from Belay, and all other comparable to the untreated control. In week 4 mortality was similar across treatments, and in week 6, Aldicarb continued to have the highest mortality, with Admire, Belay, and Platinum performing better than the control. (d) Fire ant management as part of lebbeck mealybug managementNo new data this quarter- data analysis and manuscript preparation is underway. It is clear that fire ant management is important to lebbeck mealybug management and the most effective tools to keep fire ant populations down is through (e) Evaluate management options for IPCs No work done this quarter. II. Long term managementa. 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 mealybugsIn 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 feedingContinuing baseline feeding interaction work.  d. Develop tools to minimize spreadNo new data to report this quarter 2. Please state what work is anticipated for next quarter: Note: several of these goals were intended to be completed in the March-May quarter, however the postdoc working on this left for a faculty position and recruitment of a new postdoc was delayed until funding could be ensured. I am attempting to fill the position by the start of August 20221b 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.  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. We have a planned open field release of mealybug destroyers with a grower in late June/early July. 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): With additional funding now secured, we are on track to complete this work.     


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