Ecophysiological responses of individually and group reared Cydalima perspectalis (Lepidoptera: Crambidae) to alkaloid-containing host plants.

The box tree moth, Cydalima perspectalis (Walker), is an invasive pest of Hyrcanian forests in Iran. In the current study, the effects of two boxwood species, Buxus hyrcana Pojark and B. microphylla Sieb. and Zucc. (Buxales: Buxaceae), were examined on ecophysiology of the pest. The demographic parameters were evaluated based on the age-stage, two-sex life table theory. The physiological characteristics of C. perspectalis were considered through fresh/dry weights and individually/group rearing methods. The results showed that C. perspectalis larvae were able to develop, survive and reproduce on both boxwood species. The developmental times were 41.62 and 41.46 days on B. hyrcana and B. microphylla, respectively. The total lifespan did not differ on boxwood species. However, the difference of fecundity on B. hyrcana (412.82 eggs/female) and B. microphylla (286.06 eggs/female) was significant. The intrinsic rate of increase (r) and finite rate of increase (λ) were significantly higher on B. hyrcana than B. microphylla. The nutritional indices showed that the consumption index (CI) on B. hyrcana were significantly lower than on B. microphylla based on fresh/dry weights in both rearing methods. Conversely, the efficiency of conversion of digested food (ECD) and the efficiency of conversion of ingested food (ECI) on B. hyrcana were significantly higher than on B. microphylla. Despite nonsignificant differences in leaf nutrient contents (except calcium), total protein, triglyceride, and alkaline phosphatase activity were inversely different in larvae compared to adult stage on boxwood species. These findings could help to comprehensively understand the performance of the pest on boxwood species.

Methanolic Extract of Winter Cherry Causes Morpho-Histological and Immunological Ailments in Mulberry Pyralid Glyphodes pyloalis.

The effect of Withania somnifera a medicinal plant seed extract was tested against lesser mulberry pyralid, a potential pest of mulberry. The mulberry leaves were used for silk production in rural areas of northern Iran. The extract was administered orally by leaf dipping method in two lower (5%W/V) and higher (15%W/V) dosages to third instar larvae (<24 h) for biological assays and to fifth instar larvae (<24 h) for Physiological studies. The results showed formation of larvoids (Ls), larval-pupal intermediates (LPIs), pupoids (Ps) and pupal-adult intermediates (PAIs). The results showed increased larval duration by 1.7 and 2 folds in 5 and 15% treatment, respectively. Fecundity of resultant adults was decreased by 1.2 and 1.3 in 5 and 15% treatment, respectively. Except approximate digestibility (AD) and consumption index (CI) all other feeding indices showed reduction. The feeding deterrence was prominent at 15% (87%) and 5% showing 48% deterrence. Our enzymatic and non-enzymatic assessments upon treatment showed reduction in key components, except detoxifying enzymes. However, the activity of an important enzyme involved in cuticle hardening and immunity called phenoloxidase was reduced. We also investigated the histology of midgut for further analysis and found drastic changes in main cellular elements. Immunological changes following treatment was noticeable in reduced Total Hemocyte Count but surprisingly increased Differential Hemocyte Count. However, the hemocytes structure was extremely damaged. The reduced number of eggs in treated but survived adults indicated reduced ovaries, with vacuolization both in trophocytes and oocytes. The key chemical compounds showed reductions particularly at 15%. The present results are concomitant with few earlier studies on this medicinal plant and deserve further studies particularly in deriving key chemicals that alter metamorphosis similar to insect growth regulators.

Effect of thermal stress on the immune responses of Chilo suppressalis walker (Lepidoptera: Crambidae) to Beauveria bassiana.

Temperature is one of the important environmental elements affecting ecological fitness of insects through alterations in physiological systems. In the current study, a comparison was made on the cellular and humoral immune responses of the Chilo suppressalis larvae exposed to thermal stress (34 °C) and optimal rearing temperature (24 °C). Although total hemocyte count increased in the injected larvae by Beauveria bassiana, elevation of hemocyte numbers was significantly different in the larvae exposed to 34 °C for a short-time period compared to long-term exposure and control. A similar trend was observed in plasmatocyte and granulocyte counts as well as phenoloxidase activity. Gene expression of some antimicrobial peptides, including attacin1, attacin2, cecropin1, cecropin2, defensin, gallerimycin, lysozyme and prophenoloxidase-activating proteinase-3, was compared in the larvae exposed to thermal regimes and injection challenges. In all cases, expression of the target genes was relatively higher in the larvae injected by B. bassiana and short-term exposure at 34 °C. The present results confirmed that C. suppressalis could modulate the immune system in response to different thermal stress conditions mainly over a short period.

A Laboratory Study on the Modeling of Temperature-Dependent Development and Antioxidant System of Chilo suppressalis (Lepidoptera: Crambidae).

The developmental rates of Chilo suppressalis (Walker; Lepidoptera: Crambidae) were investigated at different constant temperatures of 11, 18, 22, 24, 26, 30, 32, 34, and 36°C to find out temperature thresholds, thermal requirements and larval antioxidant responses. The time to complete immature stages separately reduced by raising the rearing temperature except for eggs which showed no significant differences at 30-34°C. Data analysis by traditional and Ikemoto-Takai linear models determined Tmin of 10.0 and 9.92°C as well as thermal constants of 840.34 and 848.0 DD for the overall immature stages. The models including Analytis, Briere-2, Lactin-2, and Sharpe-Schoolfield-Ikemoto (SSI) calculated Tmin values of 9.15, 9.57, 10.0, and 11.37°C for overall immature stages while Tfast was found to be 33.8, 33.3, 33.7, and 33.0°C, respectively. Tmax was calculated as 35.12, 34.66, 34.56, 36.84, 34.11, and 35.15°C for Analytis, Briere-2, Lactin-2, SSI, Logan-6, and Logan-10. Topt using SSI was calculated as 24.42°C for total developmental time. The larvae exposure to 34°C in the short-term period demonstrated the highest activities of catalase, peroxidase, and superoxide dismutase compared to control (24°C). Activities of ascorbate peroxidase and glucose-6-phosphate hydrogenase also increased at 34°C in the short-term period for all preparations. The larvae exposed to 34°C in short-term period showed the highest amounts of Malondialdehyde and oxidized and reduced thiols (RSSR/RSH) ratio compared to control. These results may be useful to explain potentially ecological performance of C. suppressalis as the major pest of rice in Iran.

Modeling Temperature-Dependent Development of Glyphodes pyloalis (Lepidoptera: Pyralidae).

Development of Glyphodes pyloalis Walker was studied under laboratory conditions at constant temperatures of 12, 16, 20, 24, 28, 30, 32, and 36 °C. No development occurred at 36 °C. Although eggs hatched at 12 ºC, no larvae were capable of developing to adult stage. At 16 ºC, survival rate was low (4%) and prepupal stage lasted 101.68 ± 11.03 d. Larvae completed development through six stadia at 16, 30, and 32 °C. Developmental time of overall immature stages varied from 46.62 d at 20 °C to 22.04 d at 30 °C and increased at 32 °C. The lower temperature thresholds of 10.30 and 11.22 °C, and thermal constants of 429.18 and 401.88 DD were estimated by traditional and Ikemoto-Takai linear models, respectively. The Tmin values estimated by Analytis, Briere-2, Lactin-2, and Sharpe-Schoolfield-Ikemoto (SSI) for overall immature stages were 12.40, 12.92, 9.00, and 13.04 °C, respectively. The fastest development temperatures (Tfast) of 31.1, 31.1, 30.8, and 30.7 °C were estimated for overall immature stages based on Analytis, Briere-2, Lactin-2, and SSI, respectively. The intrinsic optimum temperature (Topt) estimated from the thermodynamic SSI model for total developmental time was 24.63 °C, in which the maximal active state enzymes involved in developmental process. The nonlinear models of Analytis, Lactin-2, Briere-2, and SSI estimated the upper temperature thresholds (Tmax) at 36.66, 35.97, 38.88, and 34.05 °C, respectively. These findings could be used to predict the population dynamics of G. pyloalis for an effective management.

Life table parameters and survivorship of Spodoptera exigua (Lepidoptera: Noctuidae) at constant temperatures.

Age-specific life table parameters, survivorship, and extra molting of the beet armyworm, Spodoptera exigua (Hübner), were determined at eight constant temperatures of 12, 15, 20, 25, 30, 33, 34, and 36°C with a variation of 0.5°C on sugar beet leaves. No development was observed at 12 and 36°C. The survivorship of overall immature stages was higher at 25°C than the other temperatures. The highest (0.276 d(-1)) and lowest (0.149 d(-1)) value of the intrinsic rate of increase (r) was observed at 30 and 20°C, respectively. Although the highest value of the net reproductive rate was at 25°C (377.7 female offspring at 25°C and 127.4 female offspring at 30°C), the highest value of r was at 30°C, which indicated the importance of shorter development time (16.9 d at 30°C and 27.2 d at 25°C) in enhancing r. The relationship between temperature and r was modeled using the Lactin-2 model. The lower temperature threshold, the upper temperature threshold, and optimal temperature for the r were estimated at 13.1, 32.2, and 34.1°C, respectively. The mean generation time decreased significantly with increasing temperature, with the longest (35.9 d) and shortest (15.1 d) mean generation time was calculated at 20 and 33°C, respectively.