Aziz Sheikhi Garjan

Abstract Effects of hexaflumuron at 10% lethal concentration (LC10) and LC25 on development and reproduction parameters of the diamondback moth, Plutella xylostella (Linnaeus, 1753) (Lep.: Yponomeutidae) were investigated. Estimated LC50, LC10 and LC25 values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P. xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre-pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre-adult stages declined significantly at LC25 concentration. Reproduction parameters such as reproductive rate (R0) and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate (GRR) at the LC10 concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time (Dt). We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P. xylostella.

The two-spotted spider mite, Tetranychus urticae Koch, one of the major pests of various agricultural plants, causes many problems on agricultural, horticultural and ornamental plants. In recent years, using plant-derived compounds such as essential oils and extracts was attended for their insecticidal and acaricidal properties. Mentha pulegium is a native plant of temperate Asia, was identified as an acaricidal plant for the first time in this study. The impact of essential oil of this plant on fumigant toxicity, LT50, oviposition deterrent activity and repellency against Tetranychus urticae was studied at different concentrations. The results stated that M. pulegium oils had high toxicity on eggs and adults of two-spotted spider mite (LC50 was 2.57 and 2.25 μL L−1 for eggs and adults, respectively). In addition, all tested concentrations had oviposition deterrent activity and repellency on adults of this mite.

To introduce ecologically safe acaricide, effects of essential oils derived from Cuminum cyminum (Cumin), Syzygium aromaticum (Clove), and Mentha spicata (Spearmint) were determined on Tetranychus urticae at 25±1 � C, 65±5% RH and a photoperiod of 16:8 (L:D) hour. The essential oils extracted by hydro-distillation were characterized by means of GC and GC–MS. Bioassays were performed by filter paper diffusion without allowing direct contact. Cumin, clove, and spearmint oils contained �- Pinene (29.1%), eugenol (78.5%) and carvone (59.4%), respectively, as the major compounds. The lowest LC 50 value for adults was recorded for cumin oil (3.74 µL L -1 air) followed by clove (6.13 µL L -1 air) and spearmint (7.53 µL L -1 air). The highest ovicidal activity was recorded for cumin oil (LC 50 = 7.65 µL L -1 air) followed by clove (LC 50 = 8.73 µL L -1 air) and spearmint (LC 50 = 9.01 µL L -1 air). According to repellency tests, by increasing concentration of oils, the repellency effects were increased. The most potent repellency effect was recorded for clove, followed by spearmint and cumin oils. The three extracted essential oils seem to be suitable sources of active vapors that can be used as alternatives for chemical pesticides for controlling this pest.

An understanding of the sublethal effects of pesticide residues on phytoseiid mites is important to successful augmentation and conservation programs. We assessed the residual and sublethal effects of four concentrations of fenpyroximate (LC5, LC10, LC20 and LC30) and three concentrations of abamectin (LC10, LC20 and LC30) on prey consumption rates of exposed females of Phytoseius plumifer (Canestrini & Fanzago) and their offspring when fed Tetranychus urticae Koch. Prey consumption of female mites was strongly affected by treatment with all concentrations of the two acaricides. Throughout the study, females exposed to fenpyroximate showed a more extreme reduction in prey consumption than those exposed to abamectin. In contrast, abamectin affected the prey consumption of the subsequent generation of females to a greater extent than fenpyroximate. Of the subsequent generation, total protonymphal and total nymphal prey consumption were adversely affected by both acaricide treatments at the highest concentration. Deutonymph prey consumption of fenpyroximate exposed females was reduced, but not of abamectin exposed ones. Total nymphal offspring prey consumption did not significantly differ between the two acaricide treatments. In conclusion, use of either acaricide decreased the predation rate of P. plumifer, and this effect should be considered when designing integrated management programs.