Project : USDA ARS

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Research Project: Mitigation of Invasive Pest Threats to U.S. Subtropical Agriculture

Location: Subtropical Horticulture Research

2025 Annual Report

Objectives
1. Identify semiochemicals that mediate the behavior and physiology of exotic insect pests and develop semiochemical-based tools that lead to products for pest detection, behavioral disruption, and surveillance. [NP 304, Component 4, Problem Statement 4A] 1.A. Document behavioral responses and olfactory chemoreception to semiochemicals that have potential application in pest monitoring and control systems. 1.B. Identify and quantify insect semiochemicals; develop improved systems to collect, analyze and identify semiochemicals. 1.C. Develop synthetic and natural product lures based on host location and/or feeding cues that are formulated for effective use in IPM programs. 2. Evaluate ‘next generation’ technologies to advance methods for fruit fly detection and eradication, such as lasers, sonic methods, or nano-technologies. [NP 304, Component 4, Problem Statement 4A] 2.A. Compare available remote trapping systems that can automatically count and identify trapped insects; optimize automated detection systems for adult fruit fly pests. 2.B. Evaluate imaging techniques and non-destructive chemical analysis methods for detection of larval infestation within host fruit. 3. Evaluate essential oils for natural insect pest toxicants and elucidate the physiological mechanisms underlying resistance to conventional pesticides. [NP 304, Component 4, Problem Statement 4A] 3.A. Determine the molecular/physiological basis for development of pesticide resistance in adult fruit flies. 3.B. Identify plant essential oils and plant extracts that have insecticidal, repellent, or oviposition deterrent properties against adult fruit flies and other target pests. 3.C. Determine the specific chemical components responsible for the toxic/repellent effects of essential oils and plant extracts. 4. Integrate tools, technologies and management strategies to reduce the threat of pest establishment and mitigate the impact of exotic pest incursions. [NP 304, Component 4, Problem Statement 4A] 4.A. Develop new approaches to assess efficacy of lures, repellents, and control practices based on spatial statistics and contour analysis of trap captures in the field. 4.B. Develop improved IPM protocols for tephritid fruit flies, ambrosia beetles, and other target pests by integrating semiochemical-based technologies with other management options, such as biological control, judicious alternating use of insecticides to manage pesticide resistance, sanitation and other cultural practices.

Approach
Research will consist of field and laboratory experiments to investigate aspects of basic biology, physiology and chemical ecology that can be exploited to develop integrated pest management approaches for invasive insects that impact subtropical agriculture. Target species will include pests that threaten to invade or have recently established in south Florida, including fruit flies in the family Tephritidae (Oriental fruit fly, Medfly, and Anastrepha species) and ambrosia beetles that vector fungal pathogens (redbay ambrosia beetle and Euwallacea shot-hole borers). Strategies will include (1) identifying semiochemicals from natural product sources that can alter insect behavior, such as attractants, repellents, and oviposition deterrents; (2) developing new detection and delimitation tools that will include formulated lures, discrete attract-and-kill bait stations, next generation technologies like smart traps for automated pest surveillance, and non-destructive imaging techniques for detection of hidden infestation in agricultural commodities; (3) improving pesticide resistance management by identification of pesticide modes of action and physiological responses of fruit flies to toxicants; (4) evaluating plant essential oils as sources of natural toxicants (biopesticides) with less environmental impact; and (5) developing new approaches to assess efficacy of lures, repellents, and control practices based on spatial statistics and contour analysis of trap captures in the field.

Progress Report
Under Objective 1 repellents for pest ambrosia beetles piperitone and verbenone were identified as repellents for the redbay ambrosia beetle and tea shot-hole borer, reducing captures by 50-70% for 10-12 weeks. These beetles carry fungal diseases of avocado. This work provides an economical alternative for managing these avocado pests. ARS researchers at Miami, Florida identified host kairomones for lychee erinose mite (LEM). LEM can devastate Florida’s lychee. Research showed that lychee erinose mite (LEM) infestation induces changes in host emission profiles. Behavioral bioassays showed that chemical concentration influenced LEM attraction, providing information for LEM lure development. Potential oviposition deterrent for oriental fruit fly (OFF) identified. OFF is a destructive pest of tropical fruits. Laboratory bioassays showed that female OFF preferring fruit laid more eggs than those attracted to protein food odor, indicating a behavioral switch based on physiological state. Host-odor lures may be better for managing and detecting OFF. Evaluation of synthetic Anastrepha sp. fruit fly lures. Anastrepha sp. are major citrus pests and other tropical fruits. Lab and field studies comparing 2- and 3- component food cones lures for Caribbean fruit fly (CFF) showed the 2-component lure was more attractive and longer lasting (up to 8 weeks) than the 3-component lure. Results provide data requested by APHIS and benefits regulatory agencies for development of monitoring protocols. Functional roles of tea shot-hole borer (TSHB) symbionts. Volatile emissions from six symbiotic fungi associated with TSHB were investigated. Trans-p-menth-2-en-1-ol was identified as the primary attractant for female beetles, with limonene potentially serving as a secondary attractant. These results may guide future TSHB management. Risk assessment of Hass avocado and Mexican laurels for attack by redbay ambrosia beetle (RAB). Hass avocado Ocota sp. trees were highly attractive and susceptible to RAB attack. These results emphasize the need for early detection systems to prevent economic and ecological impacts of laurel wilt in the Western U.S. and Mexico. Developed a kairomone-based lure for cocoa pod borer (CPB). The CPB is a major pest of cacao. Pheromone lures are expensive for monitoring CPB populations. A lychee flavored extract demonstrated superior attractiveness and longevity compared to commercial pheromone lures, offering a promising alternative to CPB monitoring. Identified new attractants for medfly, a serious pest of fruits and vegetables. Trimedlure, a synthetic male medfly attractant, is expensive and has limited availability. Evaluation of essential oils (EOs) for male medfly attraction identified Artemisia absinthium EO, rich in a+ß-thujones, as highly attractive. Further studies showed similar attraction to a-thujone alone and a+ß-thujones together. These findings may inform the identification of new kairomones to improve medfly monitoring and control. Identified new male-specific attractants for medfly. Ten compounds were identified as effective short-range male medfly attractants from tea tree oil: terpinolene, a-terpinene, ¿-terpinene, p-cymene, (+)-terpinen-4-ol, (-)-terpinen-4-ol, a-phellandrene, myrcene, (+)-limonene, and (-)-limonene. These findings offer new sources of male medfly attractants to supplement or diversity reliance on trimedlure. Identification of Anastrepha sp. pheromone components. Caribbean fruit fly (CFF) and Mexican fruit fly (Mexfly) are serious pests of citrus and other fruit crops. To investigate new CFF and Mexfly lures ongoing research is investigating the production of male pheromone in both species. Key compounds have been identified, and laboratory experiments testing their attraction are in progress. Under Objevtive 2 AI-driven, image-based algorithm was used for identifying economically important Tephritid fruit fly pests. A prototype automated trap for tephritid fruit flies was developed which photographs. Over 1,000 images have been collected to train algorithm models, achieving 97% accuracy. Further image processing for sex classification is in progress. Non-destructive pest detection in fruits. Current inspection protocols of imported fruit are labor-intensive and only sample 2% of the incoming materials. Protocols using a Cyranose Electronic Nose were developed to recognize chemical odors associated with different developmental stages of guava fruit infested with CFF. This research highlights the potential for detecting fruit fly odors in infested fruits as a non-destructive method for detecting invasive fruit pests. Under Objective 3 ARS researchers at Miami, Florida used a development of ethyl formate fumigation protocols for fruit flies. The loss of methyl bromide necessitates the development of alternative fumigants. Fumigation protocols using ethyl formate (EF) were developed to control OFF and CFF. The addition of anisole improved EF efficacy, achieving complete pest control at lower concentrations. Further optimization tests are needed. Determination of insecticide resistance in Caribbean fruit fly (CFF). Results indicated mild resistance development to the insecticide methomyl in wild CFF. No cross-resistance was found among Spinosad, naled, cyfluthrin, methomyl. Synergists like PBO and DEM played roles in inhibiting resistance. Alternative control strategies are needed to prevent resistance development. Alternative control strategies for control of tephritid fruit flies. Thirteen phthalimide derivatives were investigated for their toxicity against female CFF. Three compounds demonstrated high potency, indicating their potential as environmentally friendly insecticide candidates. Systemic insecticides to control the Hibiscus Bud Weevil (HBW), a new invasive pest of tropical hibiscus in Florida. The efficacy of 21 insecticides and horticultural oils against HBW was investigated. Diflubenzuron showed significant mortality and reduced HBW reproductive rate and feeding behavior. Identified the most effective trap and commercial lure for HBW. The efficiency of commercially available traps and lures used for other weevil pests was investigated for their ability to capture and attract HBW. Results that yellow sticky traps baited with cranberry weevil lures were more effective in capturing HBW than other trap types and lures. TLC-bioautography for detection of acetylcholinesterase inhibitors. Thin-layer chromatography with biodetection was developed to identify potential natural products such as acetylcholinesterase (AChE) inhibitors. Manuka oil displayed considerable AChE inhibition. These results highlight bioautography’s effectiveness in identifying enzyme inhibitors, aiding biomarker development for toxicity in tephritid fruit flies. Plants compounds for insecticidal activity against CFF. Plant EOs from Asteraceae are being investigated for toxicity against female adult CFF. a,ß- Thujones showed stronger toxicity than a-thujones at median lethal LD50 but required a higher dose at LD99. These findings are critical for developing attract-and-kill management practices for CFF. Bioactivity-based molecular identification for the discovery of natural biopesticides. The two-spotted spider mite (TSSM) is a significant threat to ornamental plants. Preliminary findings suggest manuka oil has potential for TSSM control, with mortality observed within 24 hours after application. Manuka oil is being scaled to identify toxic compounds for potential biopesticide development. Under Objective 4 ARS researchers at Miami, Florida evaluated cultural practices for avocado trees. Growers use cultural practices like sanitation, pruning, stumping, and removal of infected trees to reduce the spread of the fungal pathogen laurel wilt in avocado. Monitoring for 12 months indicated that avocado groves with full canopy cover had the highest ambrosia beetles and the lowest light intensity. Topworked and newly planted groves showed the opposite. Increased light intensity through thinning canopy cover suppresses ambrosia beetles’ abundance, reducing laurel wilt spread. Developed a microencapsulated formulation of sugar alcohol as a control tool for the spotted wing drosophila (SWD), an invasive pest of small fruit production. Microencapsulated erythritol formulations at a 2-molar concentration were found to be as lethal as the insecticide delegate against SWD in laboratory and field trials. Erythritol shows promise as an alternative management option, with microencapsulation enhancing its longevity. Isolated and identified fungal symbionts associated with the tea shot hole borer (TSHB). Six fungal endosymbionts were isolated and identified from TSHB adults: Fusarium sp. FL-1, Fusarium sp. AF-8, Fusarium sp. AF-6, Graphium sp., Acremonium sp., and Acremonium murorum. Fusarium sp. FL-1 and Fusarium sp. AF-8 were found to support the highest percentage of larval development in feeding assays, highlighting their critical role as nutritional symbionts and targets for Fusarium dieback management. Identification of the phoretic mite Histogaster arborsignis associated with ambrosia beetles that carry the fungal pathogen causing laurel wilt disease in avocado. Histogaster arborsignis, a fungivorous phoretic mite, was found in association with several ambrosia beetle species known to carry Harringtonia lauricola, the causal fungal agent of laurel wilt disease in avocado. Feeding assays revealed that H. arborsignis can reproduce on H. lauricola. This enhances understanding of these associations, potentially contributing to biological control strategies for ambrosia beetles vectoring H. lauricola. Insect-host-pathogen study of ambrosia beetles that carry the fungal pathogen laurel wilt to avocado trees. Recent support from ONP has provided an opportunity to initiate studies examining the insect-host-pathogen interactions of this system.

Accomplishments
1. Identified the aggregation pheromone components produced by male hibiscus bud weevil adults. The hibiscus bud weevil (HBW), Anthonomous testaceosquamosus, is a significant invasive pest of tropical hibiscus, Hibiscus rosa-sinensis, in south Florida. While previous work by ARS scientists found that the cranberry weevil lure is moderately attractive to HBW, a more potent attractant is crucial for effective integrated pest management of this pest. In collaboration with the University of Florida, ARS scientists in Miami, Florida, investigated the aggregation pheromone components produced by male HBW. By collecting headspace volatiles from aggregating male HBW, four key components were identified: grandlure I, grandlure II, grandlure III, grandlure IV, and lavandulol. The five target components were subsequently quantified using octyl acetate as an internal standard. Average amounts in nanograms (ng) were calculated, and a ratio of 24.11 ± 0.44 % lavandulol, 8.75 ± 0.26 % Grandisol (Grandlure I), 62.62 ± 0.75 % Grandlure II, and 4.34 ± 0.36 % Grandlure III and (0.18 ± 0.01%) Grandlure IV was obtained. Laboratory and semi-field tests then determined the most attractive ratio of these pheromone components for eliciting female attraction. This discovery has led to a Cooperative Research and Development Agreement (CRADA) with Trécé INC., an insect semiochemical manufacturer, to develop a more effective attractive lure for HBW management.

2. Identified new Caribbean fruit fly and Mexican fruit fly pheromone components. The Caribbean fruit fly (caribfly), Anastrepha suspensa, is a production pest of guava and a quarantine pest of citrus, while the Mexican fruit fly (mexfly), A. ludens, is a significant quarantine pest of citrus in the USA. The development of advanced monitoring tools is crucial for precise pest management of both species. In a collaborative effort with APHIS scientists in Buzzards Bay, MA, ARS scientists in Miami, Florida, investigated the pheromone components produced by male caribfly and mexfly. This research led to the identification of two previously unknown minor pheromone components: ß-sesquiphellandrene and ß-bisabolene. Further analysis revealed variations in the ratios of pheromone components between caribfly and mexfly. Additionally, differences were observed in the pheromone component ratios produced by wild versus laboratory-reared caribfly populations. These results may impact the management of mexfly populations through the release of sterile male mexfly via the sterile insect technique (SIT). Additionally, wind tunnel bioassays demonstrated moderate attraction to individual pheromone components and their mixtures for both caribfly and mexfly. However, the complex synthesis and high cost associated with these compounds suggest that the identified aggregation pheromones are not viable as field attractants for either pest. These findings redirect research efforts toward alternative attractant discovery avenues for both caribfly and mexfly.

3. Identified new kairomones as an alternative to TML for medfly. The Mediterranean fruit fly (Medfly), Ceratitis capitata is one of the most destructive agricultural pests in the world. Currently, Medfly detection and monitoring relies on the parapheromone trimedlure (TML), a male-specific attractant. However, the cost and limited availability of TML, has prompted a search for the identification of alternative attractants. ARS scientists in Miami, Florida designed and synthesized 10 thymol and carvacrol ether derivatives for potential attraction of C. capitata as alternative to TML. Using a combination of short-range laboratory bioassays and electroantennography assays, thymol benzyl and octyl ethers, and carvacrol benzyl ether evoked significantly greater antennal responses than their parent compounds whereas carvacrol and thymol methyl ethers were not attractive to C. capitata. This result suggests that functional groups can signi¿cantly alter insect behavior. This study reveals some key structural features responsible for attraction, which serve as the basis for the design and developing alternative lures for C. capitata.

4. Identified oviposition repellents for caribfly. Guava production systems face significant challenges from large natural populations of caribfly and its resistance to chemical insecticides. Consequently, guava growers often rely on labor-intensive and environmentally concerning mesh coverings to protect developing fruits from infestation. In a collaborative effort with ARS scientists in Lincoln, Nebraska, and Hilo, Hawaii, ARS scientists in Miami, Florida, investigated compounds derived from coconut free fatty acids (CFFA) as caribfly deterrents. Laboratory studies demonstrated that five CFFA compounds—the complete CFFA blend, C8 acid, C10 acid, and derivatives of C8 and C10 acid—successfully deterred female caribfly oviposition. Further field trials showed that guava fruits in proximity to slow-release dispensers containing C8 acid and its derivative exhibited reduced caribfly infestations. These findings indicate that these oviposition deterrent compounds could be effectively deployed in commercial guava orchards via controlled-release dispensers to mitigate caribfly infestations.

5. First recordings of snail tentacle olfactory response to repellent compounds. Snails, including species like the giant African snail (Lissachatina fulica), brown garden snail (Cornu aspersum), horntail snail (Macrochlamys indica), and Asian tramp snail (Bradybaena similaris), are major agricultural and horticultural pests. Effective management strategies for these damaging gastropods are limited, necessitating the development of novel tools. In a collaborative effort with APHIS scientists in Miami, Florida, and ARS scientists in Lincoln, Nebraska, ARS scientists in Miami, Florida, conducted the first "electro-tentogram" (ETG) recordings from horntail and Asian tramp snails. These ETG recordings revealed that the potential repellent compounds, catnip oil and methyl benzoate, elicited significant physiological responses on snail tentacles. Subsequent behavioral assays confirmed these findings, demonstrating that catnip oil deters Asian tramp snails, and both catnip oil and methyl benzoate repel horntail snails. The ETG methodology established in this study offers a rapid screening tool for identifying additional attractive and repellent compounds for various snail pest species. Furthermore, catnip oil and methyl benzoate show promise for integration into invasive snail management programs aimed at protecting agricultural and horticultural commodities.

U.S. DEPARTMENT OF AGRICULTURE

Subtropical Horticulture Research: Miami, FL