Digestive pectinolytic activity in the Sunn pest,Eurygaster integriceps Puton (Hemiptera: Scutelleridae)

Adults of Eurygaster integriceps were collected from the wheat field, dissected and their midguts and salivary glands were removed out. After centrifugation of the homogenates, the resulted supernatants were used as the source of enzyme. Pectinase activity was assayed using agarose plate and colorimetric assays. Pectinesterase and polygalacturonase activity was detected in the first and fourth part of the midgut, respectively. Colorimetric assays revealed more pectinase activity in the first part than the fourth part. No activity was detected in the salivary gland. Optimal pH for pectinase activity in the first part of the midgut was determined at pH set of 3, 4, 5, 6, 7, 8, 9 and 10. The results showed the optimum pH for pectinases occurred at pH 6. Maximum activity for the enzyme incubated at 20,30,35,40, 45, 50, 60, 70, 80, 90 and 100°C for 60 min was observed at 50°C. This is the first report of the presence of pectinases in a scutellerid bug.     

Comparison of glutathione S-transferase and general esterase in two bugs, Eurygaster integriceps Puton (Heteroptera: Scutelleridae) and Brachynema germari Kolenati (Heteroptera: Pentatomidae)

Glutathione S -transferases (GSTs) and general esterases play important roles in the detoxification of many substances including allelochemicals from plants and chemical pesticides. In this study, to determine the feeding status and effects of agronomical practices on GST and general esterase, two bug species, Eurygaster integriceps and Brachynema germari , were selected with differences in these cases. GST and general esterase responses varied when switching from 1-chloro-2,4-dinitrobenzene (CDNB) and α -naphtyl to 1,2-dichloro-4-nitro-benzene (DCNB) and β -naphtyl in E. integriceps and B. germari , respectively. The activities of GST and esterase by using CDNB and α -naphtyl were higher than that of DCNB and β -naphtyl for both insects. It was shown that the optimal pH for GST and general esterase activity varied between pH 5.5 and 6. While the Michaelis constant (K_m) value related to E. integriceps toward CDNB and α -naphtyl was lower than K_m for B. germari , K_m values calculated for E. integriceps toward DCNB and β -naphtyl corresponding to those related to A. hejeri were similar to CDNB and α -naphtyl values. The maximal reaction velocity (V_max) values related to E. integriceps for both substrates (CDNB and α -naphtyl) were always higher than those from B. germari and showed significant differences. At the basement of the native-PAGE electrophoresis, five bands were observed in for GST and three were visualized for B. germari , with a large, darker band for E. integriceps in the case of esterases. Studies on the detoxification enzymes of herbivores should be undertaken to determine accurately the effect of the host plants on the organisms eating them, particularly in terms of biochemical and ecological advantages.     

Temperature and Ca2+ ion as modulators in cellular immunity of the Sunn pest Eurygaster integriceps Puton (Heteroptera: Scutelleridae)

Environmental conditions in addition to divalent cations may affect the interactions between pathogens and insects. Elucidation of factors which modulate insect immune responses could be a significant part of investigations in this area. In this study, adults of Eurygaster integriceps, as the destructive pest of wheat, were kept at different temperatures in addition to injection with different concentrations of Ca²⁺ to find the effect on cellular immune reactions against Beauveria bassiana. Results showed that total and differentiate hemocyte numbers, nodule formation and phenoloxidase activity increased with elevation of temperature so that the higher values were obtained at 30 and 40°C at various intervals. Higher concentrations of Ca²⁺ ion (5 mM) caused an increase in plasmatocyte length and width especially after 60 min. Similar results were observed for nodule formation and phenoloxidase activity of E. integriceps adults after injection by B. bassiana spores and phenoloxidase activity. It is clear from the current study that thermoregulation and Ca²⁺ ion can positively affect the hemocyte numbers especially plasmatocytes and granulocytes, nodule formation and phenoloxidase activity in E. integriceps. The understanding of modulators of the insect immune response may directly influence novel approaches to obtain safe and effective biological control agents.     

新烟碱类杀虫剂对麦扁盾蝽若虫和成虫的毒效（英文）

在伊朗, 麦扁盾蝽Eurygaster integriceps是小麦和大麦上的主要害虫。新烟碱类杀虫剂是一类具有较强活性的杀虫剂, 对刺吸式口器害虫具有良好的效果。本研究应用触杀和熏蒸两种生测方法测定了4种新烟碱类杀虫剂（噻虫嗪、吡虫啉、呋虫胺和啶虫咪）对麦扁盾蝽3龄若虫和成虫的毒效。触杀法生测结果显示, 各杀虫剂对麦扁盾蝽没有强烈的触杀活性, 但是在高浓度下（5 000 mg/L a. i.）, 可见较高的死亡率。熏蒸法生测结果显示, 所有杀虫剂对麦扁盾蝽的若虫和成虫均有较好的毒性。结果提示应用熏蒸方法可能是治理这一重要害虫的新方法。     

Purification and characterization of the cuticle-degrading protease produced by the entomopathogenic fungus,Beauveria bassiana in the presence of Sunn pest,Eurygaster integriceps (Hemiptera: Scutelleridae) cuticle

The extracellular protease from the entomopathogenic fungus, Beauveria bassiana in the presence of Eurygaster integriceps cuticle was isolated, purified and characterized. Isolate B1 of B. bassiana that shows high virulence against E. integriceps was examined for the production of the cuticle-degrading proteases. Results showed that both subtilisin-like (Pr1) and trypsin-like (Pr2) cuticle-degrading proteases were produced and the enzyme kinetic properties showed better activity of Pr1 in comparison with Pr2. The proteases were purified using acetone precipitation, Sephadex G-100 gel filtration and CM-Sepharose ion exchange chromatography, with a 5.09-fold increase in specific activity and 21.86% recovery. The enzyme molecular weight was estimated to be 47 kDa and the optimal pH and temperature were 8 and 45°C, respectively. The purified protease was activated by divalent cations, Ca^{2 +} and Mg^{2 +}, and inhibited by NaCl, KCl and determined as a serine protease by inhibition of its activity due to using PMSF, EDTA, mercaptoethanol and SDS. Studies on the timing of the protease secretion in the presence of cuticular substrates could provide information about the role of the accumulated hydrolytic enzymes during pathogenesis to better understand these processes.     

Beauveria bassiana for the control of Sunn Pest (Eurygaster integriceps) (Hemiptera: Scutelleridae) and aspects of the insect's daily activity relevant to a mycoinsecticide

A series of investigations was carried out at ICARDA during April-June 2004 and May-June 2005 to investigate the use of the entomopathogenic fungus Beauveria bassiana to control Eurygaster integriceps and to determine aspects of the insect's biology that could be relevant to control with the fungus. Application in 2004 of an oil-based formulation of B. bassiana showed distribution of the spray decreasing from the top of the wheat to the bottom, although the proportion of tillers with coverage at the base was still 80%. Seventy percent of Sunn Pest had received direct hits, with the highest amount on the dorsal surface, followed by the ventral surface, then the legs and antennae. Mortality of field-treated, then laboratory-maintained insects, ranged from 47.6% for insects exposed only to the B. bassiana spray, 74.2% for unsprayed insects exposed to treated wheat and 86.4% for insects receiving direct spray and being exposed to treated wheat. Some field results demonstrated mortality. Mortality assessments following the 2005 treatments were conducted solely in the field, there was no apparent effect upon Sunn Pest numbers. The majority of studies on Sunn Pest biology were carried out on untreated insects outside the trial plots. Different assessment methods resulted in varying estimates of adults and juveniles in the field. The numbers of Sunn Pest found and the proportion of these at the top of the wheat crop, declined after early morning and increased again in the early evening, suggesting sheltering deeper in the crop or in the soil during the middle part of the day. Mobility and location of marked insects was followed in micro-plots and by mark and recapture studies, demonstrating a range of activities, from movement around the crop for a number of metres, including contact with numerous tillers to almost total immobility; Sunn Pest generally avoided movement on the soil. The potential for Sunn Pest control with a mycoinsecticide and how Sunn Pest behaviour is relevant to a mycoinsecticide application are discussed.     

Effect of the entomopathogenic fungus,Beauveria bassiana,and its secondary metabolite on detoxifying enzyme activities and acetylcholinesterase (AChE) of the Sunn pest,Eurygaster integriceps (Heteroptera: Scutellaridae)

The effects of Beauveria bassiana spores and its secondary metabolite on insect resistance to an organophosphorus insecticide, fenitrothione and secondary metabolite effects on acetylcholine esterase inhibition were investigated. Findings showed that fungal spores and its secondary metabolite increase total esterase and glutathione S-transferase activities in the hemolymph of infected and treated adults of Eurygaster integriceps. But the fungal secondary metabolite had an adverse effect on AChE activity of adults that decreased its activity level and isoforms of this enzyme in polyacrylamide gel electrophoresis. Fungal infection decreased the susceptibility of E. integriceps adults to fenitrothione, in comparison with uninfected individuals. Possible involvement of detoxifying enzymes in the development of insect resistance to fenitrothione should be considered in combined usage of chemicals and microbial agents for integrated pest management programs.     

Inhibitory effect of proteinaceous seed extract of three Iranian wheat cultivars on Eurygaster integriceps (Sunn pest) digestive enzymes

Abstract

To investigate interaction between proteinaceous extracts of three Iranian wheat cultivars and digestive enzymes of Sunn pest, a population of adult insects was collected in summer from a wheat field located in Borkhar Region, Isfahan, Iran. Seed proteins were extracted by 0.15?M NaCl solution and partially purified using ammonium sulphate. Spectrophotometric assays were implemented to determine enzyme activities. Results indicated cultivar- and dose-dependent efficacy of seed protein extracts. Inhibition percentages of α-amylase, α-glucosidase, β-glucosidase and proteolytic activities at concentration of 32?μg/mL and saturation percentage of 70% ammonium sulphate were 54, 37, 25 and 59% by Hamoon, 16, 28, 18 and 19% by Karkheh and 15, 16, 15 and 23% by Dena, respectively. Zymography also confirmed the effect of inhibitors on α-amylase activity. Among wheat cultivars, Hamoon has the highest biological activity against Sunn pest major digestive enzymes and could contribute towards the development of new insect pest control strategies.     

Phospholipid and triacylglycerol fatty acid composition of major life stages of sunn pest,Eurygaster integriceps (Heteroptera: Scutelleridae)

Phospholipid and triacylglycerol fatty acid compositions of whole animals from all life stages of Eurygaster integriceps, including eggs, nymphs, pre-diapausing adults and diapausing adults, were determined. The fatty acid composition of total lipids of their food, wheat, was also determined. The major components of the insects and their food were the expected C16 and C18 saturated and unsaturated fatty acids. Since fatty acid compositions of third-stadium nymphs were not similar to the profiles of their food, most likely, dietary fatty acids are modified by the insect. The fact is that the food does not provide C20 polyunsaturated fatty acids, but the insect tissue lipids include these components. We suggest biosynthesis of the C20 components by elongation/desaturation of C18:2n-6, an abundant component of the diets. We also show differences in fatty acid profiles from each of the life stages.     

Purification and characterization of phenoloxidase from the hemocytes of Eurygaster integriceps (Hemiptera: Scutelleridae)

Insects protect themselves from microbial invaders by two main immune activities, namely the cellular and humoral reactions. Phenoloxidases are oxidative enzymes that have an important role in both cell-mediated and humoral immunity. In this study, the purification and biochemical characterization of a phenoloxidase from the hemocytes of the Sunn pest Eurygaster integriceps Puton (Hemiptera: Scutelleridae) were carried out. After the final purification step, the enzyme was purified 7.31-fold with a recovery of 3.94% and a specific activity of 4.95U/mg protein. Results of the biochemical characterization showed that the purified phenoloxidase has a maximum activity at pH 6 and at 30-35°C and is stable for 24-36h. Divalent cations such as Ca(2+) and Cu(2+) significantly increased the enzymatic activity and synthetic inhibitors such as phenylthiourea significantly decreased it. The purified phenoloxidase has a molecular mass of 22kDa. The current paper represents a further step towards the characterization of humoral immunity of E. integriceps in order to develop new strategies for the biological control of the Sunn pest.     

Distribution of Sunn Pest,Eurygaster integriceps Puton (Hemiptera: Scutelleridae), in overwintering sites

Sunn Pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae), is the most serious pest of wheat in West and Central Asia. Following harvest, the pest migrates from wheat fields to high elevations to escape high summer temperatures and, the following spring, moves back to the fields. In this work, Sunn Pest populations were monitored in 21 overwintering sites located in seven provinces (with 800–2500 m elevation) in Iran. Litter samples were taken twice in each site, once in July–November 2002 and again in March 2003. At each site 60 Artemesia sp. bushes were selected at random and litter from each bush was collected and the number of live male and female adult Sunn Pest counted. More Sunn Pests were collected in higher elevations in the first sampling. Golestan (893 m), Kermanshah (1583 m), and Qazvin (1675 m), located in valleys and surrounded by mountainous areas, had < 5 adults/bush. However Azarbayejan (1750 m), Markazi (1883 m), Kordestan (2067 m), and Esfahan (2141 m), located in mountainous areas and/or close to mountains, had 10–52 adults/bush. No noticeable changes in Sunn Pest populations were observed in 17 overwintering sites among 21 between the two sampling times. These results suggest that, after Sunn Pest moves to more highly elevated sites at aestivation time, most of them remain in these sites during overwintering before migration to wheat fields in the spring. Sunn Pest can be targeted for management in these areas during the fall and/or early spring as their movement is clearly limited.     

Investigation of the internal bacterial flora of Eurygaster integriceps (Hemiptera: Scutelleridae) and pathogenicity of the flora members

Eurygaster integriceps (Hemiptera: Scutelleridae) is one of the most serious pest of wheat and other cereal crops throughout the Near and Middle East including Turkey. To contribute biological control of this pest, we investigated the culturable bacterial flora of E. integriceps and their virulence against it. We also tested different entomopathogenic fungi (Isaria fumosorosea ARSEF8356, Beauveria bassiana ARSEF8356, Metarhizium brunneum ARSEF8671 and Nomurae rileyi ARSEF1670) against this pest under laboratory conditions. Bacterial isolates were characterized based on morphological, biochemical, physiological and molecular characteristics (16S rRNA sequencing). The isolates were identified as Pantoea sp. (S1, S5, S7, S8, S10 and S11), P. agglomerans (S2, S3 and S4), Pseudomonas sp. S6 and Micrococcus luteus S9. The highest mortality within bacterial isolates was observed from Pantoea sp. S1, P. agglomerans S4 and Pantoea sp. S7 with 100%. Mortality of other bacterial species ranged from 33% to 88%. The highest mortality among the tested entomopathogenic fungi was obtained from Isaria fumosorosea ARSEF 8333 with 100%. Mortality of other fungi ranged from 33% to 50%. Consequently, Pantoea sp. S1, P. agglomerans S4, Pantoea sp. S7, Beauveria bassiana ARSEF 8356 and Isaria fumosorosea ARSEF 8356 seem to be promising candidates in the control of E. integriceps.     

Esterase activity in summer population of sunn pest, Eurygaster integriceps Put. (Hemiptera: Scutelleridae)

A key constraint on increasing wheat production in Iran and some neighbouring countries is Sunn pest which cause severe damage to vegetative growth stage of plant in the early season. It also feeds on wheat grain in late growth stage of plants thus damaged wheat grains loose their bakery properties. Because of injecting protease enzymes into the grain during feeding, enzymes degrade gluten proteins and cause rapid relaxation of dough which results in the production of bread with poor volume and texture. Organophosphorus insecticides are the main pesticides used to control the insect pest. However, suitable reduction in pest population has not been achieved partly due to resistance to pesticides. Esterase plays crucial roles in insect physiology and detoxifies a broad range of xenobiotics including insecticides. Enhanced esterase activity is a major mechanism if insecticide resistance and has been detected in a number of insects. To evaluate esterase activity adult bugs were collected from wheat field in Karaj area of Iran and transferred to the laboratory. For biochemical assay, two adult bugs (either males or females) were homogenized in 500 microl Na-phosphate buffer pH 7.2. The homogenates were centrifuged at 14000 g for 10 minutes at 4 degrees C. The supernatants as the enzyme source were pooled and stored at -20 degrees C for later use. For enzyme assay, 300 microl of supernatant was mixed with equal volume of substrates (30 mM alpha-naphthyl acetate or 30 mM beta-naphthyl acetate) and incubated at 30 degrees C for 30 minutes. Then, 50 microl of fast blue solution (150 mg fast blue B in 15 ml distilled water plus 35 ml 5% SDS) was added and esterase activity was determined in a spectrophotometer at 595 nm. Data showed that there are no differences in esterase activity between male and female. However, There was significant differences between hydrolysis of substrates, alpha-naphthyl acetate and beta-naphthyl acetate. Insect esterase hydrolyzes alpha-naphthyl acetate much more than beta-naphthyl acetate.     

A amylase activity of nymphal stages of sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae)

Wheat production in Iran has changed substantially over the past one or two decades with development of higher-yielding cultivars and improved methods of planting. Sunn pest, Eurygaster integriceps (Heteroptera: Pentatomidae), is the most important cereal pest in Iran. Sunn pest like other insect pests of wheat lives on a polysaccharide-rich diet and depends to a large extent on effectiveness of their alpha-amylases for survival. alpha-amylase (1-4-alpha-D-glucan glucanohydrolase) hydrolyses starch, and related polysaccharides by randomly cleaving internal alpha-1,4-glucosidic linkages and has a major role in the utilization of polysaccharides. The recent increase in study of insect digestive enzymes seems to make sense in the realization that the gut is the major interface between the insect and its environment. Hence, an understanding of digestive enzyme function is essential when developing methods of insect control such as the use of enzyme inhibitor's and transgenic plants to control phytophagous insects. The aim of the current study is to identify and characterize alpha-amylase activity in order to gain a better understanding of its digestive physiology, which hopefully will lead to new strategies of the insect control. In order to analyze a-amylase activity adult and different nymphal stages were collected from wheat field from Karaj area and midgut complex from these individuals were dissected under a light microscope in ice-cold saline buffer (0.006M NaCl). After homogenization in buffer, homogenate was centrifuged at 15000 g for 20 min at 4 degrees C. The supernatant was pooled and stored at -20 degrees C for subsequent analysis. alpha-amylase activity was assayed by the dinitrosalicylic acid (DNS) procedure using soluble starch as substrate (starch 1%). Our result showed that enzyme activities in different nymphal stages (first, second, third, fourth and fifth stadium) were 0.19, 0.78, 1.21, 1.23, 1.25 units/mg protein, respectively.     

Analysis of the spatio-temporal distribution of Eurygaster integriceps (Hemiptera: Scutelleridae) by using spatial analysis by distance indices and geostatistics

Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is the most serious insect pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in Iran. In this study, spatio-temporal distribution of this pest was determined in wheat by using spatial analysis by distance indices (SADIE) and geostatistics. Global positioning and geographic information systems were used for spatial sampling and mapping the distribution of this insect. The study was conducted for three growing seasons in Gharamalek, an agricultural region to the west of Tabriz, Iran. Weekly sampling began when E. integriceps adults migrated to wheat fields from overwintering sites and ended when the new generation adults appeared at the end of season. The adults were sampled using 1- by 1-m quadrat and distance-walk methods. A sweep net was used for sampling the nymphs, and five 180° sweeps were considered as the sampling unit. The results of spatial analyses by using geostatistics and SADIE indicated that E. integriceps adults were clumped after migration to fields and had significant spatial dependency. The second- and third-instar nymphs showed aggregated spatial structure in the middle of growing season. At the end of the season, population distribution changed toward random or regular patterns; and fourth and fifth instars had weaker spatial structure compared with younger nymphs. In Iran, management measures for E. integriceps in wheat fields are mainly applied against overwintering adults, as well as second and third instars. Because of the aggregated distribution of these life stages, site-specific spraying of chemicals is feasible in managing E. integriceps.     

变温条件下禾谷缢管蚜发育起点温度和有效积温研究

在室内自然变温条件下测定了禾谷缢管蚜的生长发育速率。对试验结果采用2种计算方法,结果表明,直接最优化法稍优于直线回归法,由前者得出的发育起点温度为：无翅蚜全若蚜期5．50℃、有翅蚜全若蚜期5.36℃和全世代5．26℃;有效积温分别为105．69、132．28和125．40日度。根据发育起点温度和有效积温,预测了199年平凉、甘谷和兰州的理论发生代数;用有效积温公式预测了各发育阶段的历期;各发育阶段的最适温度由多项式回归法求得。     

Fine structure and chemical analysis of the metathoracic scent gland of Eurygaster maura (Linnaeus, 1758) (Heteroptera: Scutelleridae)

The morphology and ultrastructure of the metathoracic scent glands (MTG) of Eurygaster maura were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also, extracts of the volatile fraction of the MTG secretion from males and females were analyzed by capillary gas chromatography-mass spectrometry (GC-MS). In SEM investigations, MTG are composed of a reservoir and a pair of lateral glands connected to the reservoir by a duct. MTG are open in between the meso- and the metacoxae. These areas, called evaporation areas, are composed of mushroom-like elements. In TEM investigations, the reservoir walls contained two types of cells. Generally, a reservoir is lined by a single layer of epithelial cells, type I cells, which have numerous organelles. Type II cells are found only in a certain area of the reservoir wall. These cells have large secretory ducts lined by a cuticular intima layer. The lateral glands are lined by secretory cells and a secretory duct found in their cytoplasm. Nuclei of secretory cells are closed to the basal region of the cells and circular-shaped. In GC-MS investigations, the MTG exhibited a typical scutellerid composition. In general, (E)-2-hexanal, (E)-2-hexenyl acetate, n-tridecane, n-hexanoic acid, octadecanoic acid, and n-dodecane compounds were present, while diisooctyl acetate and 14-Beta-H-Pregna were detected only in the male extracts of Eurygaster maura.     

Laboratory experiments on certain aspects of the feeding of young adult Eurygaster integriceps put. (Hemiptera, Scutelleridae) in Iran

Experiments are described in which young adult Eurygaster integriceps were kept in cages on various diets including dry wheat ears, ears in the stage of milky ripeness, green camel-thorn (Albagi camelorum) and water in various combinations. The sufficiency of the various diets was compared by estimating the mortality, change in live weight and final fat content of the insects, and by the extent of feeding as shown by feeding scars on the wheat grains.

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Resume Des expériences en cage sont décrites, faites dans la région de Varamine près de Téhéran, Iran, avec pour buts de rechercher si les grains de blé mûrs et durs conviennent pour l'alimentation des adultes nouvellement sortis de Eurygaster integriceps (Hemiptera; Scutelleridae), comment on peut les comparer, avec les grains tendres au stade plus précoce de maturité laiteuse et dans quelles circonstances les grains durs peuvent être effectivement ingérés et assimilés.On conclu que les insectes ne peuvent utiliser le blé sec sans eau. Celle-ci peut être fournie sous la forme d'eau ordinaire, ou peut être également obtenue des plantes fraiches, telles que les mauvaises herbes qui poussent dans les champs de blé, le camel-thorn (épine de chameau) Albagi camelorum Fisch. étant utilisé dans ces expériences. Les expériences indiquent que de cette manière, le blé sec fournit de meilleures conditions d'alimenattion que le blé tendre. On obtient également quelques indications que le camel-thorn vert est meilleur que l'eau ordinaire comme addition au blé sec, peut-être parce qu'il fournit des éléments nutritifs aussi bien que de l'eau.L'aptitude des différentes combinaisons alimentaires utilisées dans les différentes cagés a été comparée par l'estimation de la mortalité des insectes, les changements dans leur poids vif, le contenu en graisse des insectes survivants à la fin de l'expérience, et l'activité alimentaire indiquée par le nombre de traces d'alimentation.Les conclusions tirées des expériences sont d'une importance économique du fait qu'elles indiquent, dans les régions où la pluie d'été est inexistante ou négligeable, et où la récolte de blé mûrit avant que les adultes nouvellement sortis aient terminé leur très importante alimentation et leur accumulation de réserves alimentaires, qu'Eurygaster integriceps peut seulement le faire si des plantes sauvages vertes, telles que le camel-thorn sont présentes; l'élimination de ces mauvaises herbes, comme politique à long terme peut de ce fait avoir pour effet de réduire le nombre d'Eurygaster. Les expériences suggèrent aussi que des expériences ultérieures sur les éléments nutritifs les meilleurs pour l'élevage de laboratoire d'Eurygaster, en vue de la propagation de parasites oophages, seraient intéressantes.

     

Impact of Eurygaster maura (Heteroptera: Scutelleridae) feeding on quality of bread wheat in relation to attack period

Sunn pest (or cereal bug) (Heteroptera: Pentatomidae and Scutelleridae) infestations of wheat, Triticum aestivum L., in the grain filling stage have the potential to adversely affect the quality of harvested grain for bread making. In the absence of resistant wheat cultivars, producers must rely on chemical control to protect their crop from sunn pest infestations. To implement an efficient environment friendly control strategy, there is a need to pinpoint the relationships between the timing of the bug attack and gluten degradation. Recent outbreaks of Eurygaster maura (L.) in northwestern Italy have increased the local concern toward this problem. A 3-yr study was carried out by caging plants of two bread wheat cultivars, characterized by different seed texture and bread-making quality, and introducing adults of E. maura in four periods corresponding to different grain filling stages: heading, early milk-ripe, milk-ripe, and late milk-ripe. The degree of bread-making quality depletion was assessed by analytical and biochemical methods and related to the attack period. Using analysis of variance, significant differences were found in the quality traits of kernels attacked by E. maura in different grain filling stages, the maximum damage occurring with bug feeding at the late milk-ripe stage. Biochemical investigations on gluten confirmed analytical results; in grain samples infested at the late milk-ripe stage, SDS gel electrophoresis revealed the degradation of some components of the high-molecular-weight glutenins, and high-performance liquid chromatography analyses showed a breakdown of the first peak of the insoluble fraction, mainly containing polymeric proteins highly related to dough strength.     

Effects of temperature on the development and survival of an endangered butterfly, Shijimiaeoides divinus barine (Leech) (Lepidoptera: Lycaenidae)

The effects of temperature on the development and survival of Shijimiaeoides divinus barine were examined in the laboratory in 2008. The eggs and larvae were reared at temperatures of 15, 17.5, 20, 25, 30 and 35°C with a long-day photoperiod of 16 h light : 8 h dark (16L : 8D). The highest hatchability of eggs was 88.0% at 20°C, but hatchability at high temperatures of 30 and 35°C was 30 and 0%, respectively. The lowest and highest survival rates from the first to third instar were 18.8% at 15°C and 76.9% at 20°C. Few deaths were observed after the fourth instar. The shortest developmental periods of the eggs and larvae were 4.0 and 15.8 days at 30°C, and the durations of the egg and larval stages increased significantly as the temperature decreased. The developmental zero and thermal constants were 9.6°C and 82.6 degree–days for the egg stage, and 10.7°C and 306.8 degree–days for the larval stage. The developmental period of the natural population of S. divinus barine in Azumino City, Nagano Prefecture was calculated using the developmental zero, thermal constants and Azumino City temperature data.