Some Physiological Effects of Nanofertilizers on Wheat-Aphid Interactions

The increasing use of nanofertilizers in modern agriculture and their impact on crop yield and pest management require further research. In this study, the effects of nano-Fe, -Zn, and -Cu (which are synthesized based on nanochelating technology), and urea (N) fertilizers on the antioxidant activities of wheat plants (cv. Chamran), and the wheat green aphid Schizaphis graminum (Rondani) are investigated. The authors observed the highest levels of phenolics in non-infested nano-Zn-treated plants (26% higher compared with control). The highest H2O2 levels are in the infested and non-infested nano-Zn-treated and infested nano-Fe-treated plants (in infested nano-Zn and nano-Fe treated plants, 18% and non-infested nano-Zn-treated plants, 28% higher compared with control). The highest peroxidase (POX) activity is observed in the infested and non-infested N-treated and non-infested water-treated plants (almost 14%, 37%, and 46% higher than control, respectively). The lowest activity is in the infested plants’ nano-Zn and -Fe treatments (almost 7 and 5 folds lower compared to the control, respectively). The highest and lowest catalase (CAT) activity are in the infested N-treated plants (almost 42% higher than control) and water-treated plants, respectively. The infested nano-Zn, -Fe, -Cu and Hoagland-treated plants showed the highest superoxide dismutase (SOD) activity. Regarding the antioxidant enzyme activities of S. graminum, the highest POX activity is in the nano-Cu treatment (more than two folds higher compared with control); the highest CAT and SOD activities are in the nano-Cu and -Zn treatments. It can be concluded that the application of nanofertilizers caused increasing effects on the wheat plant’s antioxidant system and its resistance to S. graminum

Toxicity of some biorational and conventional insecticides to cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae) and its ectoparasitoid, Habrobracon hebetor (Hymenoptera: Braconidae)

Insect growth regulators and spinosyns which are physiologically and ecologically selective, respectively, have been investigated as replacements or complements to non-selective conventional insecticides. The effects of diflubenzuron, hexaflumuron, profenofos, spinosad and thiodicarb were assessed on the 1st instars of cotton bollworm, Helicoverpa armigera (Hübner) using dietary and leaf disc bioassay methods. Based on modes of action of the insecticides tested, the mortalities were recorded after 24 h in profenofos, thiodicarb and spinosad experiments and after 120 h in hexaflumuron and diflubenzuron treatments. The LC50 values for diflubenzuron, hexaflumuron, profenofos, spinosad and thiodicarb in dietary method were 595.05, 0.31, 3.69, 0.13 and 11.2 mg ai/L; and in leaf disc method, they were >2000, 0.46, 9.55, 0.2 and 15.52 mg ai/L, respectively. The effects of these insecticides on adult Habrobracon hebetor Say, an ectoparasitoid of cotton bollworm were tested using residual method. The mortalities were recorded after 24 h in all treatments. The LC50 values for diflubenzuron, hexaflumuron, profenofos, spinosad and thiodicarb for females were >2000, >2000, 12.44, 15.64 and 81.04 mg ai/L, respectively and for males, they were >2000, >2000, 6.91, 11.73 and 40.39 mg ai/L, respectively. In this study spinosad and hexaflumuron seemed to be more useful than the other insecticides due to their higher toxicity to H. armigera and lower toxicity to H. hebetor

Lethal and sublethal effects of dinotefuran and thiamethoxam on the population growth parameters of the green lacewing, Chrysoperla carnea (Neu.: Chrysopidae), under laboratory conditions

The green lacewing, Chrysoperla carnea (Stephens), is a common natural enemy of various agricultural pestsand widely used as a biocontrol agent in integrated pest management (IPM) programs. The lethal and sublethal effects of the insecticides dinotefuran and thiamethoxam on the first instar larvae of C. carnea was assessed in the laboratory conditions at 25 ± 1°C, 60 ± 5% RH and a photoperiod of 16: 8 (L: D). The LC50 values for dinotefuran and thiamethoxam were 19.382 and 9.880 mg ai/l, respectively, that showed the high toxicity of thiamethoxam on the first instar larvae of C. carnea. To assess the sublethal effects, the first instar larvae were treated with the LC30 for dinotefuran and thiamethoxam at 3.532 and 1.692 mg ai/l, respectively. The estimated rm values in the control, dinotefuran and thiamethoxam were 0.185, 0.186 and 0.143 day-1, respectively. Finite rate of increase (λ) in the control, dinotefuran and thiamethoxam were 1.204, 1.204 and 1.154 day-1. Generation time and doubling time values in the control, dinotefuran and thiamethoxam were 30.77, 30.46 and 35.14 as well as 3.73, 3.72 and 4.82 days, respectively. The gross and net reproductive rates in the control, dinotefuran and thiamethoxam were 459.89, 439.08 and 309.42, and also 298.01, 278.45 and 155.03 (female/female/generation), respectively. Dinotefuran caused no significant adverse effects on the population growth parameters of C. carnea. If similar results are obtained for dinotefuran in the field, it might be an insecticide with low toxicity to C. carnea by using the reduced doses of the insecticide in IPM context. Studies under the laboratory conditions can help us to select some insecticides for additional studies under more natural conditions and for application of suitable insecticides along with natural enemies in pest management