Dietary Protein and Carbohydrate Levels Affect Performance and Digestive Physiology of Plodia interpunctella (Lepidoptera: Pyralidae).

In this study, life history and nutritional indices of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) was evaluated on six food commodities: dried fig, dried wheat germ, dried white mulberry, groundnut, pistachio, and raisin, compared with artificial diet. The influence of dietary macronutrient content on digestive α-amylase was also assessed. A delay in the developmental time of P. interpunctella immature stages was detected when larvae were fed on raisin. The highest survival rate of immature stages was on the artificial diet, and the lowest was on raisin. The highest realized fecundity and fertility were recorded for the females reared on artificial diet. Overall, fourth instar P. interpunctella reared on artificial diet had the highest relative consumed and growth rate, and lowest rates were observed in larvae fed raisin. Amylolytic activity and isoform patterns varied depending on larval instar and diets, but were higher for larvae fed artificial diet with moderate carbohydrate and protein. Zymograms showed the presence of three isoforms of α-amylase in midgut extracts of P. interpunctella fed different diets. Larvae fed dried white mulberry, fig, and raisin had one (A2) α-amylase isoform. The data suggest that dietary carbohydrate and protein content induce changes in nutritional efficiency, development, and α-amylase activity. A survey of the differences in digestive enzyme activity in response to macronutrient balance and imbalance highlight their importance in the nutrition of insects.

Inhibitory effects of an extract from non-host plants on physiological characteristics of two major cabbage pests.

The diamondback moth (Plutella xylostella) and small white cabbage butterfly (Pieris rapae) are the two main serious pests of cruciferous crops (Brassicaceae) that have developed resistance to chemical control methods. In order to avoid such resistance and also the adverse effects of chemical pesticides on the environment, alternative methods have usually been suggested, including the use of plant enzyme inhibitors. Here, the inhibitory effects of proteinaceous inhibitors extracted from wheat, canola, sesame, bean and triticale were evaluated against the digestive α-amylases, larval growth, development and nutritional indecs of the diamondback moth and small white cabbage butterfly. Our results indicated that triticale and wheat extracts inhibited α-amylolytic activity in an alkaline pH, which is in accordance with the moth and butterfly gut α-amylase optimum pH. Dose-dependent inhibition of two crucifer pests by triticale and wheat was observed using spectrophotometry and gel electrophoresis. Implementation of specificity studies showed that wheat and triticale-proteinaceous extract were inactive against Chinese and purple cabbage amylase. Triticale and wheat were resistant against insects' gut proteases. Results of the feeding bioassay indicated that triticale-proteinaceous extract could cause a significant reduction in survival and larval body mass. The results of the nutritional indecs also showed larvae of both species that fed on a Triticale proteinaceous inhibitor-treated diet had the lowest values for the efficiency of conversion of ingested food and relative growth rate. Our observations suggested that triticale shows promise for use in the management of crucifer pests.

Fumigant Toxicity and Sublethal Effects of Artemisia khorassanica and Artemisia sieberi on Sitotroga cerealella (Lepidoptera: Gelechiidae).

Fumigant toxicity and sublethal effects of essential oils from Artemisia khorassanica Podl. and Artemisia sieberi Bess were investigated against adults of Sitotroga cerealella Olivier. To assess the sublethal effects, adult moths were exposed to the LC30 of each essential oil, and life table parameters of the surviving S. cerealella were studied. Higher fumigant toxicity of A. khorassanica (LC50: 7.38 µl/liter air) than A. sieberi (LC50: 9.26 µl/liter air) was observed against S. cerealella. Also, the insecticidal effects of A. khorassanica (LT50: 9.01 h) were faster than A. sieberi (LT50: 14.37 h). A significant extension was observed in the developmental time (egg to adult) of S. cerealella treated with the essential oils. In addition, fecundity of S. cerealella reduced by 25.29 and 35.78% following exposure to sublethal concentrations of A. sieberi and A. khorassanica, respectively. Both tested essential oils caused a significant reduction in the gross and net reproductive rates, intrinsic rate of increase (rm), and finite rate of increase of S. cerealella. The rm values following exposure to A. sieberi, A. khorassanica, and control were 0.098, 0.094, and 0.107 d-1, respectively. The results of this study suggest that tested essential oils have a good potential to apply in integrated pest management of S. cerealella.

The Effect of Maize Hybrid on Biology and Life Table Parameters of the Trogoderma granarium (Coleoptera: Dermestidae).

The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a polyphagous pest that infests many stored grains and products. The effect of nine maize hybrids including 704, AR 89, AS 71, AS 77, BC 678, KSC 703, PL 472, SC 704, and Simax was studied on biology and life table parameters of T. granarium at controlled conditions (33 ± 1 °C, 65 ± 5% RH, and a photoperiod of 14:10 [L:D] h). According to the results of this study, the immature period was the longest on BC 678 (56.79 ± SE: 1.51 d) and the shortest on PL 472 (39.90 ± 0.48 d). The highest values of fecundity and fertility were observed on PL 472 (67.95 ± 1.23 eggs and 74.81 ± 0.68%, respectively) and the lowest values were on BC 678 (40.00 ± 1.63 and 48.24 ± 1.35, respectively). The net reproductive rate (R0) of T. granarium ranged from 10.40 ± 0.11 offsprings on BC 678 to 30.43 ± 0.20 offsprings on KSC 703. The highest intrinsic rate of increase (rm) was for T. granarium reared on KSC 703 (0.0773 ± 0.0001 d-1), and the lowest was on BC 678 (0.0390 ± 0.0002 d-1). According to the obtained results, BC 678 is an unfavorable hybrid for population increase of T. granarium, which can be recommended to be grown in regions where the damage of T. granarium is considerable to minimize maize infestations by this pest.

Effects of Food Quality on Biology and Physiological Traits of Sitotroga cerealella (Lepidoptera: Gelechiidae).

Biology and physiological traits of Sitotroga cerealella Olivier, a world-wide insect pest of cereals, were investigated on different grains (barley, maize, rye, sorghum, triticale, and wheat). Larval and pupal duration was the shortest on wheat and triticale, and the longest on sorghum. There were significant differences in survival rate of immature stages on grains with different seed hardness. The highest realized fecundity and egg fertility was observed on triticale and the lowest was seen on sorghum. Larvae fed on triticale and wheat showed higher amount of α-amylase activity than larvae fed on other grains. Maximum Vmax/KM ratio was determined for the midgut α-amylase of S. cerealella larvae fed on wheat. Whole-body protein, lipid, and glycogen contents of pupae reared on sorghum and rye were significantly lower than those reared on other grains. The statistical analysis showed that the clear correlation could be drawn between the biological characteristics and energy contents of S. cerealella on one side and seed hardness, amylolytic activity, and food consumed on the other. According to the findings of this study, the variable responses of S. cerealella to feeding on different host grains could be attributed to the quality of diets tested.

Susceptibility of Five Sugar Beet Cultivars to the Black Bean Aphid, Aphis fabae Scopoli (Hemiptera: Aphididae).

The black bean aphid, Aphis fabae Scopoli (Hemiptera: Aphididae), is one of the important pests of sugar beet. The relative impact of resistance, including antibiosis and antixenosis of five sugar beet cultivars (Doroti, Perimer, Pershia, Rozier and 006) on A. fabae was studied under laboratory conditions using clip cages. The antibiosis test was based on life table parameters. Significant differences on developmental time, mean number of nymphs/aphid/day, fecundity, and adult longevity of A. fabae were found across tested sugar beet cultivars. In addition, there were significant differences among the sugar beet cultivars for population growth parameters such as the intrinsic rate of natural increase (r m ), net reproductive rate (R 0), finite rate of increase (λ), doubling time (DT), and mean generation time (T) of A. fabae. The highest and lowest (r m ) values were observed on Pershia (0.449 nymphs/female/day) and Perimer (0.358 nymphs/female/day), respectively. No significant differences were found for the preference of the black bean aphid, and antixenosis had no effect on resistance against this aphid. As a result, our findings showed that the Pershia cultivar was a relatively susceptible host plant. Two cultivars (Perimer and Rozier) were relatively resistant to A. fabae, which could prove useful in the development of IPM programs for this aphid in sugar beet fields.

Wheat cultivars affecting life history and digestive amylolytic activity of Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae).

The life history and digestive α-amylase activity of the Angoumois grain moth, Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae) were studied on six wheat cultivars (Arg, Bam, Nai 60, Pishtaz, Sepahan and Shanghai) at 25 ± 1°C, relative humidity of 65 ± 5% and a photoperiod of 16:8 (L:D) h. A delay in the developmental time of S. cerealella immature stages was detected when larvae were fed on cultivar Sepahan. The maximum survival rate of immature stages was seen on cultivar Bam (93.33 ± 2.10%), and the minimum rates were on cultivars Nai 60 (54.66 ± 2.49%) and Sepahan (49.33 ± 4.52%). The highest realized fecundity and fertility were recorded for females which came from larvae fed on cultivar Bam (93.30 ± 2.10 eggs/female and 91.90 ± 3.10%, respectively); and the lowest ones were observed for females which came from larvae fed on cultivar Sepahan (49.30 ± 4.50 eggs/female and 67.4 ± 11.1%, respectively). The heaviest male and female weights of S. cerealella were observed on cultivar Bam (2.97 ± 0.02 and 4.80 ± 0.01 mg, respectively). The highest amylolytic activity of the fourth instar was detected on cultivar Bam (0.89 ± 0.04 mg maltose min-1), which had the maximum mean hundred-wheat weight (5.92 ± 0.19 g). One α-amylase isozyme was detected in the midgut extracts from the fourth instar larvae fed on different wheat cultivars, and the highest intensity was found in larvae fed on cultivar Bam. Correlation analyses showed that very high correlations existed between the immature period, fecundity and fertility on one side and inhibition of α-amylase, soluble starch content and hundred-wheat weight on the other. According to the obtained results, cultivar Sepahan is an unfavorable host for the feeding and development of S. cerealella.