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Semiochemicals / Pheromones Technologies
Insect pheromones are specific natural compounds that meet modern pest control requirements, such as species specificity, lack of toxicity to mammals, and environmental benignity. They are also a component of the Integrated Pest Management of agricultural pests.
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The pheromones can be utilized in two main ways: as mating disruptors and as part of mass trapping and attract-to-kill strategies. In mating disruption, female pheromones are released in large quantities to interfere with male detection of mates, thereby reducing the reproduction of pest species (Welter et al., 2005). Mass trapping, on the other hand, employs sex or aggregation pheromones and food or host attractants to lure herbivores into traps where they can be killed locally, minimizing environmental harm (Witzgall et al., 2010).
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​Mass trapping and mating disruption strategies using sex pheromones have significantly reduced the use of conventional insecticides. To achieve effective results, it is essential to carefully design an appropriate blend of pheromones, determine the correct doses, and establish the proper release rate (Yew & Chung, 2015).
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This chapter summarizes the developments in pheromone research and its practical application in agricultural pest management in Southeast Asian countries and China.
Sex pheromones and pheromone use for early monitoring in Indonesia
Study 1: Sex Pheromone of Cocoa Pod Borer, Conopomorpha cramerella: Field Activity Evaluation of Pheromone Formulations in an Indonesia Plantation
This study is part of a collaboration with the United States Department of Agriculture (USDA) that helped restart the work on pheromones to develop an efficient Cocoa Pod Borer (CPB) management system. The objectives were to re-evaluate the attractive activity of the sex pheromone of C. cramerella in Indonesia and Malaysia and determine whether the commercial formulations could be used as an accurate and efficient monitoring system.
The female sex pheromone of the cocoa pod borer was tested for its ability to attract male insects using six different formulations on Indonesian cocoa plantations. In a dose-response experiment, a pheromone concentration of 0.1 mg demonstrated significantly greater attractiveness to male cocoa pod borers (CPB) than the lower doses tested. Additionally, during the initial four-week trapping period, USDA lures containing 0.1 mg of the synthetic pheromone blend were significantly more attractive than a commercial lure from Alpha Scents, Inc., which contained 0.1 mg of pheromone.
Pic 1. The infested cocoa pod by CPB
Source: Rahmawati et al., 2017
The study also found that after the first week, there was a significant decline in captures, which continued to decrease over the following three weeks. The 100 μg lures lasted 4 to 5 weeks, consistent with previous findings suggesting a lifespan of 1 to 2 months. In contrast, the 1 mg lures remained attractive for up to 7 months. This extended longevity of the lures supports mass trapping and mating disruption strategies. Trials with mass trapping demonstrated a reduction in male captures and cocoa pod damage. Additionally, infestation rates were significantly decreased when pheromone lures were combined with insecticides in an attract-and-kill approach.
Study 2: Population dynamic and pheromone use for early monitoring of Spodoptera exigua Hübner (Lepidoptera: Noctuidae) in Indonesia
Sex pheromone traps are helpful for the early detection and monitoring of pest infestations and may help control these pests. These traps effectively captured Spodoptera exigua moths (Kusumawati et al., 2022). It is recommended to use three traps per 2000 m² for effective pest monitoring (Lestari et al., 2020). Additionally, Moekasan et al. (2013) noted that the control threshold for S. exigua, based on the capture rates using Pheromone Exi traps, is ten or more individuals per trap per day. By applying this control threshold, the use of insecticides can be reduced by 35.71%, resulting in a yield of 13.46 tons per hectare, similar to the effects of using insecticides twice a week.
There is a strong correlation between the capture of S. exigua adults using pheromone traps and the extent of plant damage. Significant positive correlations were observed between moth populations and damage intensity in a pheromone-treated field from 3 to 7 days after monitoring. The pheromone used in this study was Pheromone EXI RB (Z-9-tetradecanol: 10 μg/ dispenser; Z-E-9-12-tetradecadienyl acetate: 90 μg/ dispenser) produced by CV. Nusagri. This demonstrates that pheromone traps can serve as an effective monitoring tool for S. exigua.
Sex pheromone precursors from engineered oilseed plants study in China
Study 1: Insect pest management with sex pheromone precursors from engineered oilseed plants
Camelina sativa seeds have been genetically modified to express (Z)-11-hexadecenoic acid, a precursor to the sex pheromone of several moth species. The oil from these seeds is the source from which the precursor is isolated, purified, and transformed into the pheromone. Camelina's high yield and oil content make it particularly suitable for producing pheromone precursors. Genetic modifications also enhance the production of monounsaturated fatty acids, which are essential for pheromone synthesis. The stable production of these precursors was achieved after three generations of careful field selection to optimize yields.
Pic 2. Workflow of the production of a transgenic line of Camelina sativa
Source: Wang et al., 2022
​Field trials and efficacy studies indicate that plant-derived pheromone lures can attract moths as effectively as synthetic pheromones. Additionally, mating disruption trials demonstrated that these natural lures are as effective in preventing male moths from finding mates, suggesting their potential for lower-dose applications in large-scale pest control programs.
​A study examining this approach's costs and economic benefits yielded positive results. Conventional pheromone production is quite expensive, ranging from $1,000 to $3,500 per kilogram, which limits its use to niche markets. In contrast, bioproduction using Camelina significantly reduces costs to approximately $10 to $25 per kilogram for the precursor and $70 to $125 per kilogram for the final active ingredient. This bio-based method also decreases dependence on petroleum-derived raw materials and enhances supply chain stability.
​The findings of this study indicate that genetically modified Camelina can serve as a scalable and cost-effective solution for producing pheromone-based pest control products.
Pheromone mass trapping of bagworm moths and an economic evaluation of Integrated Pest Management against fall armyworm in Malaysia
Pheromone mass trapping of bagworm moths, Metisa plana Walker (Lepidoptera: Psychidae), for its control in mature oil palms in Perak, Malaysia
This study evaluated the effectiveness of using live, virgin female moths to attract and trap male bagworm moths. The results confirmed earlier research by Norman & Othman (2006) on younger oil palms (4 years old). The primary goal of this method is to reduce the male moth population, thereby decreasing mating opportunities and the subsequent generation of larvae. The findings indicated that continuous trapping significantly reduced the bagworm population. Fewer males led to less mating, resulting in a decline in the next generation of larvae. Similar results have been observed in studies targeting other pests, such as the Sweet Potato Weevil (Cylas formicarius) by Yasuda (1995), the Banana Corm Weevil (Cosmopolites sordidus) by Haka, and the oil palm pest Oryctes rhinoceros by Norman et al. (2007), which managed to reduce populations to below 10 individuals per square meter in replanting areas.
Pic 3. Sticky vane traps hung onto wooden poles. Top, along transects; bottom, close up of male moth captures.
Source: Kamarudin et al., 2010
​As the larval populations decreased, the damage to the fronds also decreased. In the trapping plots, the decrease in damage ranged from 35% to 45%, while in the control plots, the reduction was between 20% and 27%. Interestingly, one control plot experienced a 17% increase in damage due to a rise in bagworm numbers. These findings align with those of Braun and Van de Fliert (1999), who observed reduced damage in fields with pheromone traps when pest pressure was low.
In conclusion, pheromone-based mass trapping is an effective strategy for controlling bagworm infestations. This method decreases larval populations, leading to lower frond damage and increased yield.
Study 2: An economic evaluation of Integrated Pest Management against the invasive fall armyworm (FAW) in Malaysia
​MARDI (Malaysian Agricultural Research and Development Institute) researched the effectiveness of three commercial pheromones that are available in Malaysia: P061-90Lure (Costa Rica), FAW Lure (India), and Trece Pherocon® Fall Armyworm (USA) to attract adult male FAW moths. Laboratory tests showed all three pheromones were equally effective. However, field trials at MARDI Bachok Station, Kelantan, revealed that the Costa Rican pheromone was 3.5 times more effective in attracting FAW males and had a longer field lifespan. Thus, the Costa Rican pheromone was recommended for FAW monitoring in Malaysian corn crops.
​Economic Analysis of FAW Control Methods
​The study examined the costs and benefits of controlling fall armyworm (FAW) in the cultivation of grain corn and sweet corn, comparing conventional pesticide methods to IPM. The cost components included fees for service providers, plant materials, fertilizers, and pest control. A significant distinction between the two methods was the drying cost associated with grain corn, which is unnecessary for sweet corn. IPM utilizes pheromones from Costa Rica along with biological insecticides, such as Emamectin benzoate and Chlorantraniliprole, as alternatives to the chemical pesticides used in conventional methods.
​Partial Budget Analysis: Financial Impact on Farmers
Integrated pest Management (IPM) increased grain corn yields by 300 kg, leading to an additional RM300 in revenue and reducing insecticide costs by RM240. However, the extra costs of pheromones (RM496) and Chlorantraniliprole (RM140) resulted in a net loss of RM96, making IPM less financially viable for grain corn.
IPM increased sweet corn yields by 12% (3,180 cobs), generating RM2,385 in additional revenue. The system also reduced insecticide costs by RM1,596.30, cutting pesticide sprays from 18 to 5 applications. Despite an additional RM496 cost for pheromones and RM123.10 for Emamectin benzoate, farmers saw a net financial benefit of RM3,363.19.
Philippines
Study 1: Field evaluation of the sex pheromone of the cacao pod borer (Conopomorpha cramerella Snellen) in the Philippines
A field bioassay was conducted in the southern Philippines to evaluate the effectiveness of a new blend of CPB (Cacao Pests and Bugs) sex pheromones and to determine the optimal trap height placement in a cacao field. This information is essential for maximizing the efficiency of sex pheromone traps as part of an integrated pest management (IPM) program for CPB.
​In the study, pheromone lures were placed at four different heights: 1.0 m above the canopy, 0.5 m above the canopy, at the canopy level (0.0 m), and 0.5 m below the canopy. A blank lure (control) was also positioned 1.0 m above the canopy. The main objective was to evaluate male CPB trap catches at these various heights.
The pheromone lures used were polyethylene vials (Just Plastic Ltd) that contained 100 µg of the synthetic new pheromone blends acquired from the Invasive Insect Biocontrol and Behavior Laboratory at USDA-ARS, Beltsville, MD, USA. The lures included a mixture of E, Z, Z- and E, E, Z-4,6,10-hexadecatrienyl acetates and their corresponding alcohols in a ratio of approximately 40:55:4:6, along with an equal weight of 2,6-di-tert-butyl-4-methylphenol (BHT) as an antioxidant (Vanhove et al., 2015).
Pic 4. (A) Empty delta trap with sticky liner, (B) delta trap with a pheromone lure showing male CPB trap catch, and (C) delta trap placed 1.0 m above the tree canopy.
Source: Amalin et al., 2023
Results showed significantly higher male CPB trap catches when installed at least 0.5 m above the canopy, while minimal to zero male CPB catches were obtained from the control traps with blank lures, confirming the attractiveness of the new blend of the CPB sex pheromone in the field. Using the optimum trap height obtained from the first field trial, pheromone activity evaluation in the 9-ha cacao field likewise showed the attractiveness of the sex pheromone lure as compared to the blank lures. This result suggests that 0.5 m above the canopy could be the most appropriate placement of the pheromone traps in the cacao field.
​This study also indicated that pheromones can effectively enhance the CPB's pest management program. There was a significant increase in male CPB caught in traps equipped with the new CPB pheromone blend, compared to minimal or no catches in control traps with blank lures. This demonstrates the attractiveness of the CPB sex pheromone in the field.
Further Resources
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