Saeid Moharramipour

Diaeretiella rapae (M’Intosh) (Hymenoptera: Braconidae) is one of the most important biological control agents of aphids on crucifer and cereal plants. The reproduction and demographic parameters of D. rapae were investigated at six constant temperatures (10, 15, 20, 25, 27.5, and 30 °C) on the greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) reared on wheat (var. Pishtaz). No development was observed at 30 °C. The highest value of mummified aphids per parasitoid female was obtained at temperature of 20 °C (120.08). However, the highest (0.374 day-1) and lowest (0.019 day-1) values of the intrinsic rate of increase (r) were observed at 25 and 27.5 °C, respectively. The shortest times for doubling and mean generation of parasitoid were resulted at 25 °C (1.85 and 7.73 days, respectively). Based on the results, a range of 20 to 25 °C is the most suitable temperature regime for D. rapae population growth on S. graminum. These findings have potential implications for integrated S. graminum management in wheat fields. However, semi-field and field studies are needed to obtain more environmentally relevant results.

The sugar beet moth, Scrobipalpa ocellatella (Boyd), one of the most severe sugar beet pests, causes quantitative and qualitative yield losses late in the autumn. Previously, it was shown that low temperature and short‐day photoperiod together cause diapause induction in pupae. Here, the interaction of the critical elements of the diapause induction, including the period (PER), timeless (TIM), prothoracicotropic hormone (PTTH), and ecdysteroid titer, were investigated. Immunohistochemistry results showed that the number of period immunoreactivity (PER‐ir) and TIM‐ir cells in nondiapause pupae (NDP) was lower than in the brain of the diapause pupae (DP). Moreover, the number of PER‐ir and TIM‐ir cells in the protocerebrum and optic lobe (OL) of NDP was lower than DP. Moreover, lower PTTH content in the brain and hemolymph of DP was confirmed by competitive enzyme‐linked immunosorbent assay. Enzyme immunoassay showed a lower 20‐hydroxyecdysone (20E) titer in the hemolymph of the DP compared with the NDP. Within a short‐day condition, PER and TIM titers increased in the brain leading to decreasing PTTH titers in the brain and hemolymph that caused decreasing 20E titer in the hemolymph, leading to the induction of diapause. This study suggests that PER and TIM could be one of the brain factors that play an essential role in regulating diapause in S. ocellatella.

The contact insecticidal activity of in natura and maltodextrin/Angum gum nanoencapsulated essential oils of Eucalyptus globulus Labill and Zataria multiflora Bioss was evaluated against the third instar larvae of Ephestia kuehniella (Lepidoptera: Pyralidae). The essential oil from E. globulus exhibited an average yield of 1.19%, and presented 1,8-cineol (59.08%) as the major component, while Z. multiflora essential oil, with an average yield of 1.5%, was characterized by thymol (26.12%) and carvacrol (25.31%) as the main components. The encapsulated particles presented spherical morphology with regular and homogeneous external surfaces, ranging from 60 to 130 nm in diameter. Laboratory bioassays estimated the contact LC₅₀ of in natura and encapsulated essential oils as 13.07 and 1.34 µL L⁻¹ for E. globulus and 1.47 and 5.87 µL L⁻¹ for Z. multiflora, respectively. The results presented here, which are probably the first to be reported, suggested that essential oil nanoencapsulation represents an efficient method for enhancing both insecticidal activity and the durability of the active ingredients for sustainable pest management.

Scrobipalpa ocellatella (Boyd) (Lepidoptera: Gelechiidae) is one of the most important pests of sugar beet that causes quantitative and qualitative yield loss in the late summer. To locate the position for diapause induction, combinations of constant temperatures at 15, 18, 20, and 25°C and day lengths of 8, 10, 12, 14, 16, and 24 h were studied from egg to adult emergence. The incidence of diapause peaked at 15 and 18°C, with the day lengths of 12 and 11 h, whereas low temperatures did not improve the effects of short photoperiods (day lengths of 8 and 10 h) in diapause induction. The results showed that the critical day length for diapause induction was 12.8 h at overall 15 and 18°C. It was observed that the third instar larvae were the most sensitive stage to the inductive photoperiod (12:12 [L:D] h). The non-24-h light-dark experiment showed that the nigh length is more important than the day lengths measurement. In a set of 24-h light-dark cycles at 2:12 (L:D) h, a 1-h light pulse declined diapause induction markedly 1 h after scotophase. Field monitoring of the S. ocellatella for 2 yr (2015 and 2016) showed that the 50% of larvae enter winter pupal diapause in early September and this proportion increases in response to a decrease in the day lengths and temperature. From this study, it was concluded that low temperature acts in conjunction with short-day photoperiod in diapause induction of S. ocellatella.