Abstract
Except of pest control, insecticides have shown adverse effects on natural enemies as well. Thus, risk assessment of pesticides for biological control agents is critical for effective use in integrated pest management (IPM) schemes. In the present study, the lethal and sublethal effects of chlorpyrifos, a commonly used insecticide that may negatively affect biological control agents, were evaluated on a non-target predator, the Asian ladybeetle Harmonia axyridis. Previous studies have reported on lethal concentrations, but the effects of sublethal concentrations remain unclear. Lethal and sublethal concentrations of chlorpyrifos were applied to third instar larvae of H. axyridis, and different growth and developmental parameters were measured. Treatment with LC10 (4.62 mg a.i. L−1) significantly shortened the developmental period of third instar larvae, whereas it significantly prolonged those of fourth instar larvae and pupa. Treatment with LC30 (9.59 mg a.i. L−1) significantly increased the larval and pupal developmental period compared with that of the control, whereas feeding potential, female fecundity, and adult longevity significantly decreased after LC10 and LC30 treatment. The pre-oviposition period significantly increased compared with that of the control. Population growth parameters, the finite (λ) and intrinsic rate of increase (r) and the net reproductive rate (R0), decreased following exposure to sublethal concentrations of chlorpyrifos. According to the results, the use of chlorpyrifos in IPM schemes requires further research because even sublethal concentrations of this insecticide were harmful to H. axyridis population growth.
Highlights
Predators play a vital role in the regulation of a wide range of pests in agro-ecosystems [1,2] as they can control different insect pests from different families [3]
We evaluated the sublethal effects of chlorpyrifos on the developmental period of pre-adult stages (Table 2), male and female adult longevity, pre-oviposition period, and fecundity of H. axyridis (Table 3)
We evaluated the sublethal effects of chlorpyrifos on life applied in agriculture for pest control
Summary
Predators play a vital role in the regulation of a wide range of pests in agro-ecosystems [1,2] as they can control different insect pests from different families [3]. Many ladybeetle species (Coleoptera: Coccinellidae) are gregarious predators of several pest species, such as aphids [4,5], whiteflies [6], mealybugs [7], mites [8], and scale insects [9]. Owing to its global distribution and extensive ability to interrupt agricultural ecosystems, the Asian ladybeetle Harmonia axyridis ( known as the harlequin ladybird) is an important predator used in insect-based integrated pest management (IPM) schemes [10,11,12]. Voracity, and reproduction rate make this predator an effective biological control agent for different IPM strategies. This beetle is available commercially for insect pest management [15]. Previous studies have shown the effectiveness of H. axyridis for the biological control of different pests, such as the apple aphid Aphis spiraecola in apple orchards [16], yellow pecan aphid Monelliopsis pecanis in pecan orchards [17,18], Asian citrus psyllid
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