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

Early life nutritional quality effects on adult memory retention in a parasitic wasp

Nutritional quality during early life can affect learning ability and memory retention of animals. Here we studied the effect of resource quality gained during larval development on the learning ability and memory retention of 2 sympatric strains of similar genetic background of the parasitoid Trichogramma brassicae: one uninfected and one infected by Wolbachia. Wolbachia is a common arthropod parasite/mutualistic symbiont with a range of known effects on host fitness. Here we studied, for the first time, the interaction between resource quality and Wolbachia infection on memory retention and resource acquisition. Memory retention of uninfected wasps was significantly longer when reared on high quality hosts when compared to low quality hosts. Furthermore, uninfected wasps emerging from high quality hosts showed higher values of protein and triglyceride than those emerging from low quality hosts. In contrast, the memory retention for infected wasps was the same irrespective of host quality, although retention was significantly lower than uninfected wasps. No significant effect of host quality on capital resource amount of infected wasps was observed, and infected wasps displayed a lower amount of protein and triglyceride than uninfected wasps when reared on high quality hosts. This study suggests that the nutritional quality of the embryonic period can affect memory retention of adult wasps not infected by Wolbachia. However, by manipulating the host’s obtained capital resource amount, Wolbachia could enable exploitation of the maximum available resources from a range of hosts to acquire suitable performance in complex environments

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

Identification, differential and total count on haemocytes of Hyphantria cunea (Lep.: Arctiidae) and Glyphodes pyloalis (Lep.: Crambidae), and investigation on the effect of juvenile hormone I on these cells

Haemocytes of two lepidoptrans Hyphantria cunea (Drury) and Glyphodes pyloalis Walker were studied using light microscopy. Based on available literature, six types of haemocytes were recognized of each species: prohaemocyte, plasmatocyte, granulocyte, oenocyte, spherulocyte and adipohaemocyte. In general, haemocytes in G. pyloalis were smaller than those of H. cunea. This difference were quiet obvious in prohaemocytes and spherulocytes. Differential haemocyte counts showed the granulocytes and plasmatocytes to be the most abundant haemocytes and were recorded 27 and 23 percent for G. pyloalis, and also 28 and 36 percent for H. cunea, respectively. Total haemocyte count were also worked out that was 1800 ± 0.081 cells/mm3 for G. pyloalis and 3013.3 ± 413 cells/mm3 for H. cunea. While bringing about major structural changes to important cell types i.e. plasmatocytes and granulocytes, the juvenile hormone I (JH I) in 0.004 μL/Larva on topical application induced significant changes in total and differential counts compared to controls

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