Abstract
We investigated the repellent effect of 12 Apiaceae plant essential oils on nymphal and adult (male and female) forms of the bean bug, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae), using a four-arm olfactometer. Among the essential oils tested, ajowan (Trachyspermum ammi Sprague) essential oil showed the strongest repellent activity against the nymphal and adult bean bugs. For female adults, the repellent activity was significantly different between an ajowan oil-treated chamber and an untreated chamber down to a concentration of 14.15 μg/cm2. We also investigated the repellent activity of individual ajowan essential oil constituents. Of the compounds examined, carvacrol and thymol showed the most potent repellent activity against the nymphal and adult bean bugs. Carvacrol and thymol exhibited 73.08% and 70.0% repellent activity for the bean bug nymph at 0.71 and 2.83 μg/cm2, respectively, and 82.6% and 80.7% at 5.66 and 11.32 μg/cm2, respectively, for male adults. Carvacrol and thymol exhibited strong repellent activity against female adult bean bugs down to a concentration of 2.83 μg/cm2. Ajowan essential oil, thymol and carvacrol elicited a negative electroantennogram (EAG) response from adult bean bugs. This could explain the repellent activity of ajowan essential oil and its constituents. Our results indicate that ajowan essential oil and its constituents carvacrol and thymol can be potential candidates as the ‘push’ component in a ‘push-pull’ strategy for bean bug control.
Highlights
The bean bug Riptortus clavatus Thunberg (Heteroptera: Alydidae) has caused serious damage to soybean and tree fruits in Korea and Japan [1,2,3]
We evaluated the repellent activity of 12 Apiaceae plant essential oils and ajowan essential oil constituents against nymph and adult male and female bean bugs to select a specific repellent suitable for use in a push-pull system
We evaluated the repellent activities of the plant essential oils and their constituents for nymphal and adult bean bugs using a four-arm olfactometer with a slight modification of a prior study [20]
Summary
The bean bug Riptortus clavatus Thunberg (Heteroptera: Alydidae) has caused serious damage to soybean and tree fruits in Korea and Japan [1,2,3]. Rahman et al [16] reported that aggregation pheromone traps did not reduce the bean bug population or crop damage. They found that aggregation pheromone traps were not effective for controlling bean bugs and new bean bug control strategies are necessary. Providing insects with a choice between more attractive odors such as host plant volatiles or pheromones (pull) and host plants containing repellents (push) could be a good strategy for enhancing the effectiveness of current control methods. Natural repellents based on plant essential oils have already been commercialized and used for this ‘push and pull’ strategy in insect management [17,18], though there have been no reports on the repellent effect of plant essential oils and their constituents on R. clavatus
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