Abstract
The ectoparasitoid wasp, Habrobracon hebetor (Say, 1836) (Hym.: Braconidae) is one of the most important natural enemies of many pests in Iran. In this study, the effects of sublethal concentrations of malathion (LC10 and LC25) on biological parameters of the adult wasp including parasitism percentage, male production and longevity of the parasitoid in different growth stages (larvae, pupae and adult) were investigated. The experiments were conducted at 26 ± 1 °C, 60 ± 5 % RH, and 16L:8D h photoperiods. The effect of sublethal concentrations of malathion on adults was determined by exposure of wasp to insecticide, and in the case of larvae and pupae, immersion method was used. Based on the results, with the increase of toxic dose, the percentage of parasitism in adult decreased from 95.6 5% to 87.78 %, compared to the control treatment. Male production increased from 22.73 % in control to 56.38 % at LC25 concentration. Also, the percentage of parasitism of the malathion-impregnated wasp larvae decreased from 87.78 to 22.92%, compared to the control treatment. Male production from 30.94 % in the control increased to 39.63 % at the LC25 concentration. In addition, the percentage of parasitism in the wasp pupae impregnated with malathion was reduced from 93.33 to 88.89 %, respectively. Male production increased from 22.98 in the control to 37.23 % in the LC25 concentration. The data showed that pupae were more susceptible to sublethal concentrations than the larvae.
Highlights
Most insecticides have harmful effects on non-target organisms, especially natural enemies (Croft, 1990)
According to analysis variance of the the data obtained from H. hebetor adult, rate of parasitism percentage was found to have a significant difference at 1 % level in the sublethal concentrations of malathion (F2, 6 = 6.7; P
The results showed that the highest percentage of parasitism in the control treatment was 95.56 ± 1.11 % and the lowest in the LC25 concentration was 87.88 ± 1.11 %
Summary
Most insecticides have harmful effects on non-target organisms, especially natural enemies (Croft, 1990). Biocontrol agents are commonly susceptible to insecticide applications. In recent years, integrated pest management systems attempt to use natural enemies in combination with lower doses of insecticides for pest control. The combined use of biocontrol agents and insecticides to manage pests requires adequate knowledge about the aspects and selective effects of insecticides on natural enemies (Croft, 1990; Dent, 1995; Banks & Stark, 1998; Bajc et al, 2017; Laznik & Trdan, 2014). Several natural enemies can be used for biological control of lepidopteran pests. Habrobracon spp. are used as effective parasitoids of different pests specially in stored products and crop plants (Navaei et al, 2002)
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