Abstract
The potential of semiochemicals to lure insect pests to a trap where they can be killed with biopesticides has been demonstrated as an eco-friendly pest management alternative. In this study, we tested two recently characterized male-produced aggregation pheromones of the bean flower thrips Megalurothrips sjostedti (Trybom), namely (R)-lavandulyl 3-methylbutanoate (major) and (R)-lavandulol (minor), for their field efficacy. Moreover, compatibility of these pheromones and two other thrips attractants, Lurem-TR and neryl (S)-2-methylbutanoate, with the entomopathogenic fungus (EPF) Metarhizium anisopliae ICIPE 69 has been determined. Our study revealed that the M. sjostedti aggregation pheromones have dose-dependent antifungal effects on the EPF viability, but showed no fungistatic effect at a field-realistic dose for attraction of thrips. (R)-lavandulyl 3-methylbutanoate had similar antifungal effects as neryl (S)-2-methylbutanoate 8 days after exposure; whereas, Lurem-TR had a stronger antifungal effect than other thrips attractants. In the semi-field experiments, all autoinoculation devices maintained at least 86% viability of M. anisopliae conidia after 12 days of exposure. Field trials demonstrated for the first time that (R)-lavandulyl 3-methylbutanoate increases trap catches. Our findings pave a way for designing a lure-and-kill thrips management strategy to control bean flower thrips using autoinoculation devices or spot spray application.
Highlights
Grain legumes are grown as staple crops by millions of smallholder farmers across sub-Saharan Africa and are important sources of protein to the urban and rural poor who cannot afford meat, fish, or milk products [1,2]
A potential of entomopathogenic fungus-based biopesticide such as Metarhizium anisopliae (Metschnikoff) Sorokin strain ICIPE 69 for sustainable pest management has been demonstrated in East Africa [3,11,12,13]
The semi-field experiment was conducted at icipe Duduville campus while the field experiment for screening effective dose of M. sjostedti aggregation pheromone was conducted at the icipe Thomas Odhiambo Campus (ITOC), Mbita, western Kenya (0◦26 06.19 S, 34◦12 53.13 E; 1137 m above sea level)
Summary
Grain legumes are grown as staple crops by millions of smallholder farmers across sub-Saharan Africa and are important sources of protein to the urban and rural poor who cannot afford meat, fish, or milk products [1,2]. Conidial transmission potential between thrips during aggregation could create an opportunity to develop improved biopesticides application techniques by exploiting semiochemical attractants for “lure-andkill” strategies using autoinoculation devices or spot spray applications. Such strategies have been shown to reduce the quantity of inoculum required and the cost of application while ensuring fungal persistence in the field [3,12,17]. The compatibility of M. sjostedti pheromone compounds was compared in the laboratory with two other commercial thrips attractants: Lurem-TR (methyl isonicotinate) and neryl (S)-2-methylbutanoate, which is the major component of the aggregation pheromone of the western flower thrips, Frankliniella occidentalis (Pergande). The development of semiochemical and biopesticide-based thrips management strategies will provide ecologically sustainable M. sjostedti control alternatives and help reduce reliance on harmful chemical pesticides
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