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

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 interactionsbetween pathogens and insects. Elucidation of factors which modulate insectimmune responses could be a significant part of investigations in this area. In thisstudy, adults of Eurygaster integriceps, as the destructive pest of wheat, were keptat different temperatures in addition to injection with different concentrations ofCa2+ to find the effect on cellular immune reactions against Beauveria bassiana.Results showed that total and differentiate hemocyte numbers, nodule formationand phenoloxidase activity increased with elevation of temperature so that thehigher values were obtained at 30 and 40°C at various intervals. Higher concentrationsof Ca2+ ion (5 mM) caused an increase in plasmatocyte length and widthespecially after 60 min. Similar results were observed for nodule formation andphenoloxidase activity of E. integriceps adults after injection by B. bassiana sporesand phenoloxidase activity. It is clear from the current study that thermoregulationand Ca2+ ion can positively affect the hemocyte numbers especially plasmatocytesand granulocytes, nodule formation and phenoloxidase activity in E. integriceps.The understanding of modulators of the insect immune response may directlyinfluence novel approaches to obtain safe and effective biological control agents

Interaction between Bt-transgenic cotton and the whitefly’s parasitoid, Encarsia formosa (Hymenoptera: Aphelinidae)

Transgenic Bt cotton developed against lepidopteran pests may not be compatible with parasitoid of secondary pests such as Bemisia tabaci which attack many plants such as cotton. In this study, the effects of Bt cotton on the demographic parameters of Encarsia formosa, parasitoid of B. tabaci were assessed. The data were analysed using the age specific, two-sex life table parameters. The results indicated that pre-adult developmental time, the total preoviposition period (TPOP) and the adult preoviposition period (APOP) in the Bt cotton were significantly longer than in the non-Bt cotton. Also, fecundity and body size in both lines were significantly different. The fecundity was 23.64±0.73 and 43.75±0.89 eggs/females in the Bt and non-Bt cotton, respectively. All the population parameters were affected by the Bt cotton. The intrinsic rate of increase (r) was 0.15 day-1 in the non-Bt cotton but it was 0.10 day-1 in the Bt cotton. The finite rate of increase (λ) was 1.11 day-1 in the non-Bt cotton whilst it was 1.08 in the Bt cotton. The net reproductive rate (R0) in the non-Bt cotton was 36.75 but in the Bt cotton these parameters showed 19.62 offspring/individual. Also, the mean generation time (T ) in the non-Bt and Bt cotton was 22.69 and 27.79 days, respectively. The results illustrated, that although transgenic crops are effective tools for management of the target pests, they can adversely affect, either directly or indirectly, the natural enemies dependent on these plants