Abstract
This study was conducted to evaluate the insecticidal effects of ethyl formate (EF), methyl bromide (MB), and phosphine (PH3) fumigants against PH3-susceptible and -resistant strains of the rice weevil (Sitophilus oryzae), a major rice pest. The highest lethal concentration time 50 (LCt50) values of the PH3-susceptible strains were 255.797, 21.104, and 6.171 mg h L−1 for EF, MB, and PH3, respectively, at pupal stage. The highest LCt50 values of the PH3-resistant strains were 149.028 and 48.170 mg h L−1 for EF and PH3, respectively, at late larval stage, and 43.520 mg h L−1 for MB at pupal stage. In comparison to the susceptible strains, the PH3-resistant strain collected in South Korea had a resistance level 4 to 56 times higher. Use of the major quarantine fumigants EF, MB, and PH3 indicated the existence of PH3-resistant rice weevils in South Korea for the first time.
Highlights
Stored pests are known to cause damage to stored products, such as reduced grain weight, quality, commercial value, and seed survival [1]
Pupae treated with 4.00 mg/L, the highest treatment concentration, showed an insecticidal rate of
20 mg/L for late larvae (Figure 4). These results indicate that PH3 -susceptible S. oryzae is most tolerant in the pupal and late larval stages
Summary
Stored pests are known to cause damage to stored products, such as reduced grain weight, quality, commercial value, and seed survival [1]. MB is an old fumigant discovered in 1932 that has been used in virtually every field of disinfection and disinfestation, such as fruit, grains, wood, and necessities [9]. It has been designated as an environmentally destructive substance causing ozone depletion [10], and its use has been completely prohibited except for quarantine and pre-shipment purpose under the Montreal Protocol [11,12]. PH3 is known to spread rapidly during fumigation, has low fumigant residue after treatment, and has no side effects on seed survival [13,14]
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