The potential immune alterations in insect pests and pollinators after insecticide exposure in agroecosystem

Agroecosystems are the habitat of pests and beneficial insects from different orders, which are exposed to agro-practices, especially treatments with chemicals. Insecticides are a wide group of chemicals used in agroecosystems that affect insect ecology and physiology in different ways. Among physiological components affected by insecticides, the immune system (IS) is an important one, enabling insects to resist against invading microorganisms and parasitoids thanks to the action of hemocytes and humoral components. So the determination of any immune alterations should be considered as a critical issue in insecticide application within agroecosystems. Insecticides of synthetic or natural origin, e.g. insect growth regulators (IGRs) and botanicals, are frequently cytotoxic and alter hemocyte morphology and number, impairing cellular-based immune responses in addition to humeral responses. Exposure of pollinators to neurotoxin insecticides like neonicotinoids may inhibit the immune-related transcription factor, NF- B, with a negative impact on the expression of antimicrobial peptides, melanization and clotting. In contrast, some IGRs may have enhancing effects on hemocyte spreading mainly plasmatocytes and cellular-based immune responses. Chemical insecticides have several impacts on the physiology of insects in which immune modulation is one of the most important cases because any alteration may alter their ability to respond toward invading pathogens and directly their survival. This is more severe once pollinators are in contact with chemicals because of the presence of several pathogenic agents that directly influence their performance

Virulence determination of Beauveria bassiana isolates on a predatory hemipteran, Andrallus spinidens Fabricius (Hemiptera: Pentatomidae)

Virulence of the two isolates of Beauveria bassiana, BB2 and AM-118, were evaluated on adults of a predatory hemipteran, Andrallus spinidens Fabricius by conidial bioassay and enzymatic activities. Results of the bioassay revealed LC50 of 37×104 and 15×103 spore/ml for isolates BB2 and AM-118, respectively. Activities of chitinase, lipase and ALP showed the higher activity in the media inoculated by AM-118 while no statistical differences were observed in activity of ACP. Although no statistical differences were found in general protease and Pr1 activities but activity of Pr2 in AM-118 was significantly higher than that of BB2. Activity of general esterases demonstrated no statistical differences when α- and β-naphtyl acetate were used as substrates but activity of glutathione S-transferase in AM-118 was higher than that of BB2 by using CDNB and DCNB as specific reagents. Results of the current study indicated higher virulence of isolate AM-118 against adults of A. spinidens by lower LC50 value and higher activities of the enzymes involved in pathogenicity. Recruiting of these isolates against C. suppressalis must be considered by their adaptability of A. spinidens. Moreover, AM-118 has been isolated from rice fields of northern Iran, so it may somehow indicate a type of host-microorganism interaction

Cellular immune reactions of the sunn pest, Eurygaster integriceps, to the entomopathogenic fungus, Beauveriabassiana and its secondary metabolites

In this study, five morphological types of circulating hemocytes were recognized in thehemolymph of the adult sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae),namely prohemocytes, plasmatocytes, granulocytes, adipohemocytes, and oenocytoids. Theeffects of the secondary metabolites of the entomopathogenic fungus Beauveria bassiana oncellular immune defenses of Eurygaster integriceps were investigated. The results showed thatthe fungal secondary metabolites inhibited phagocytic activity of E. integriceps hemocytes andhampered nodule formation. A reduction of phenoloxidase activity was also observed. The datasuggest that B. bassiana produce secondary metabolites that disable several immune mechanismsallowing the fungus to overcome and then kill its host. This characteristic makes B. bassiana apromising model for biological control of insect pests such as E. integriceps

Influence of different densities and nymphal instars of Aphis gossypii (Hemiptera: Aphididae) on developmental time and feeding rate of larvae of Episyrphus balteatus (Diptera: Syrphidae) under greenhouse conditions

Several aphidophagous insects such as predators and parasitoids are known to respond positively to aphid infested plants. This  study was intended to evaluate the effect of different densities (40, 60, 80, 100) and nymphal instars (1st, 2nd, 3rd, 4th) of the cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae) as prey on developmental time and feeding rate of the larvae of the syrphid fly Episyrphus balteatus DeGeer  on cucumber leaves. The experiment was conducted at the greenhouse condition (22± 5°C, 55± 10% RH and 14L: 10 D h photoperiod) with 10 replications. Our study indicated that lower density and poor quality of prey caused higher larval mortality. Feeding on 3rd and 4th nymphal instars and higher density of prey (80 and 100 prey/day) caused shorter developmental time of E. balteatus. The larvae fed on densities of 40 and 60 prey, even though fed on higher nymphal instars, failed to complete their larval development. It is concluded that higher prey densities (80 and 100 prey) were highly suitable for predator's larval development and significantly reduced the developmental period of E. balteatus. These findings provide further evidence that E. balteatus has high predation capacity on aphids, and therefore can be used as a successful biocontrol agent against A. gossypii

Life table parameters and digestive enzyme activities in Chrysodeixis chalcites (Esper) (Lepidoptera: Noctuidae) fed on some commercial cultivars of tomato

Effects of six commercial tomato cultivars, Super Strain B, Super crystal, Hed rio grande, SUN 6108 f1, Rio grande UG and Cal.JN3 were determined on digestive physiology and life table parameters of Chrysodeixis chalcites (Esper). The highest values of consumed foods were determined in the larvae fed on Rio grande UG and Cal.JN3 while the lowest values were observed on SUN 6108 f1. Statistical difference was found in the pupal weight by the highest value on SUN 6108f1. The highest values of intrinsic rate of increase (rm) and the net reproductive rate (R0) were obtained on SUN 6108 f1 but the lowest values were obtained on Cal.JN3. Significant differences were also found in activities of digestive enzymes including specific proteases, α-amylase, glucosidases and TAG-lipase. Our findings showed that the highest and the lowest activities of specific proteases and TAG lipase were obtained on Rio grande UG and SUN 6108 f1, respectively. In addition, activities of the carbohydrases were the highest in the larvae fed on Cal.JN3. The demographical and physiological findings here revealed Cal.JN3 and Rio grande UG as the partially unsuitable cultivars for C. chalcites in comparison with other ones which may be recommended in integrated pest management

Comparison of feeding indices and digestive enzymes of pomegranate neckworm, Ectomyelois ceratoniae (Lep.: Pyralidae) on three pomegranate cultivars

In this research nutritional indices of pomegranate neckworm on the three cultivars of pomegranate including Malas-Daneh-Sia, Gabri and Shahvar were studied under controlled conditions (30 ± 1ºC, 70 ± 5% RH and 16L: 8D). Enzymatic activity in the midgut of larvae reared on these cultivars was also compared. Results indicated that the relative consumption rate (RCR) was significantly different among three cultivars. The highest amounts of the relative growth rate (RGR), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were observed on Shahvar cultivar. The approximate digestibility (AD) on Malas-Daneh-Sia was the highest. The highest enzymatic activities of α-amylases and lipases were observed in the midgut of larvae reared on Shahvar cultivar. In contrast, proteases demonstrated the lowest activity in these larvae. The present findings showed that the shahvar cultivar has a higher feeding quality for pomegranate neckworm

Effects of different prey regimes on activities of digestive enzymes in Andrallus spinidens (Hem.: Pentatomidae)

The responses of digestive enzymes of the midgut of Andrallus spinidens Fabricius nymphs, toward feeding on Chilo suppressalis Walker, Galleria melonella (L.), Plodia interpunctella (Hübner) and Ephestia kuehniella Zeller were analyzed to find the most satisfactory species for a mass rearing program. The nymphs were fed from 2nd instar until 24 hours after the emergence of the 5th instar. The highest weight gain was recorded in the nymphs that fed on C. suppressalis and G. melonella, and the highest amount of total protein found in the nymphs feeding on G. mellonella. Carbohydrase activities including α-amylase, α- and β-glucosidase were the highest in the nymphs that were fed on C. suppressalis and E. kuhniella. The highest TAG-lipase activity occurred in the nymphs feeding on G. mellonella and the related gel electrophoresis showed distinctive zones in comparison with the rest. General proteolytic was performed at two pH values and the highest activity recorded in G. melonella (pH 8) and E. kuehniella (pH 6). The highest activities of serine proteinases, cysteine proteinases and two exopeptidases were found in the nymphs fed on G. mellonella and E. kuehniella. Correlation between digestive enzyme activities in A. spinidens and nutritional composition of their feeds may reflect the adaptive nature of the enzymatic profile. These findings can efficiently help to find the most suitable species for an efficient control program and successful mass rearing of the biocontrol agent

Efficacy of essential oil of Lavandula angustifolia on mortality and physiological parameters of diamondback moth, Plutella xylustella (Lep.: Pyralidae)

Efficacy of the essential oil of the plant species Lavandula angustifolia on the mortality, physiology and biochemistry of diamondback moth, Plutella xylustella L., was studied under laboratory conditions (24 ± 2ºC, 75 ± 5% R.H. and 16 L: 8 D hours). The LC10, LC30 and LC50 values of the essential oil were estimated as 0.0857%, 0.270% and 0.599% (V/V), respectively. The repellency effect for the LC10 and LC30 concentrations on third instar larvae were 19.2 ± 3.61 and 34.29 ± 4.87, respectively. The approximate digestibility (AD), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), relative growth rate (RGR) and relative consumption rate (RCR) for the treated larvae in three days showed significant differences compared with the controls. The effectiveness of plant essential oils on digestive enzymes, total protein, triglycerides, alkaline phosphatase, protease, lipase, alfa amylase, glutathione S-transferase and esterase were also significantly different. Our finding suggests that the essential oil of L. angustifolia can be efficiently used as a botanical insecticide

Effect of Sweet Wormwood Artemisia annua Crude Leaf Extracts on Some Biological and Physiological Characteristics of the Lesser Mulberry Pyralid, Glyphodes pyloalis

The lesser mulberry pyralid, Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) is a monophagous and dangerous pest of mulberry that has been recently observed in Guilan province, northern Iran. In this study, the crude methanol extract of sweet wormwood Artemisia annua L. (Asterales: Asteracaea) was investigated on toxicity, biological and physiological characteristics of this pest under controlled conditions (24 ± 1 °C, 75 ± 5% RH, and 16:8 L:D photoperiod). The effect of acute toxicity and sublethal doses on physiological characteristics was performed by topical application. The LC50 and LC20 values on fourth instar larvae were calculated as 0.33 and 0.22 gram leaf equivalent/ mL, respectively. The larval duration of fifth instar larvae in LC50 treatment was prolonged (5.8 ± 0.52 days) compared with the control group (4.26 ± 0.29 days). However larval duration was reduced in the LC20 treatment. The female adult longevity in the LC50 dose was the least (4.53 ± 0.3 days), while longevity among controls was the highest (9.2 ± 0.29 days). The mean fecundity of adults after larval treatment with LC50 was recorded as 105.6 ± 16.84 eggs/female, while the control was 392.74 ± 22.52 eggs/female. The percent hatchability was reduced in all treatments compared with the control. The effect of extract in 0.107, 0.053, 0.026 and 0.013 gle/mL on biochemical characteristics of this pest was also studied. The activity of α-amylase and protease 48 hours post—treatment was significantly reduced compared with the control. Similarly lipase, esterase, and glutathione S-transferase activity were significantly affected by A. annua extract