Lethal and sublethal effects of the biopesticide Kingbo (oxymatrine 0.2 % + psoralen 0.4 %) on the two-spotted spider mite (Tetranychus urticae Koch) were investigated in laboratory bioassays. The biopesticide was applied to bean leaf discs or primary leaves by using a Potter spray tower. Acute toxicity tests showed no significant ovicidal action: toxic effect (LC50 = 55.49 μl/l) was the result of a residual activity against larvae that hatched from the treated eggs. Preovipositional females and female teleiochrysales showed similar susceptibility (LC50 = 52.68 and 59.03 μl/l, respectively), whereas larvae, protonymphs and female deutonymphs were the most susceptible stages (LC50 = 6.88, 13.03, and 8.80 μl/l, respectively). In a choice test, females preferred the untreated halves of leaves over the halves treated with 2,000, 1,000, and 500 μl/l in the first 24 h, and their oviposition in those treatments was significantly greater on the untreated halves after 24 and 48 h, as well as the summed oviposition over 72 h. Viability and reproduction of survivors, as well as population growth, were strongly affected after the treatments of preovipositional females and female teleiochrysales with 100, 50 and 25 μl/l. On the other hand, sublethal effects on the females that survived treatment at the egg stage or reached adulthood from the eggs laid on the treated surface (treatments with 50 and 25 μl/l) were significantly weaker. Acaricidal and sublethal effects of the biopesticide Kingbo were discussed as a starting point for further research aimed to improve management of T. urticae populations. Regulatory issues and safety concerns regarding further commercialization of this biopesticide are addressed as well.
SuMMARYThe effects of five tomato genotypes (cv. Narvik and hybrids NS-6, Tamaris, Alliance and Marko) on the survival, reproduction, development and population growth of the greenhouse whitefly Trialeurodes vaporariorum were examined. A laboratory population of T. vaporariorum had been reared on tobacco plants for three years before the study. Females that laid eggs on the genotype Marko lived significantly longer and their offspring needed significantly shorter periods to develop than females on the genotype Narvik. The highest gross and net fecundity rates were found in females on the genotype Marko (36.74 eggs/ female and 27.93 eggs/female, respectively) and they differed significantly from the corresponding rates of females living on the genotype NS-6 (18.55 eggs/female and 15.33 eggs/ female), who had the lowest fecundity rates. The highest gross and net fertility rates were also found in females on the genotype Marko (31.24 adults/female and 23.73 adults/female), and they were significantly higher than those of females living on NS-6 (14.85 adults/female and 12.53 adults/female). Besides, net fertility rate of the females living on the genotype Narvik (13.80 adults/female) was also significantly lower than the rate of females on Marko. The instantaneous rates of increase showed no significant difference over a 10-day interval following the start of oviposition, while the increase rate was significantly higher on the genotype Marko after 12, 14 and 16 days, compared to the genotype NS-6. Eighteen, 20 and 22 days after the beginning of oviposition, the instantaneous rate of increase on the genotype Marko was significantly higher than it was on NS-6 and Narvik. Our data provide a basis for further research aiming to improve programs of integrated management of greenhouse whitefly.
Acaricidal and sublethal effects of the biopesticide RequiemEC (containing an essential oil extract of Chenopodium ambrosioides near ambrosioides) on the two-spotted spider mite, Tetranychus urticae Koch, were evaluated in laboratory bioassays. The biopesticide was applied to bean leaves or leaf discs using a Potter spray tower. Acaricidal activity against eggs and immatures was evaluated in successive acute toxicity bioassays. Concentration-mortality data were subjected to probit analysis and the following LC values (ml/l) were calculated: 2.47 (eggs), 0.71 (larvae), 1.13 (protonymphs), 2.23 (female deutonymphs), and 6.02 (female teleiochrysalises). In adult bioassay, in which pre-ovipositional females were treated with a series of concentrations (0.31-10 ml/l), a run-off effect ranging 4-80% (after 24 h) and 8-93% (after 72 h) was observed. In two-choice bioassay, T. urticae females preferred the untreated halves of leaves over the halves treated with 1.25-10 ml/l biopesticide and they laid significantly more eggs on the untreated halves in the first 24 h and summed over 72 h. The indices of repellency and oviposition deterence ranged 11.2-77.3 and 14.8-87.9%, respectively. In age-stage two-sex life table bioassay, the females that hatched from eggs treated with 2.5 ml/l biopesticide and reached adulthood on treated leaf surface showed a significantly reduced the intrinsic rate of increase (r = 0.222), compared to the control (r = 0.317). The reduction of population growth was mainly due to a reduced preadult survival rate (0.42 ± 0.04) and extended juvenile developmental time (9.27 ± 0.11 days), compared to the control (0.93 ± 0.03 and 7.70 ± 0.06 days, respectively).
SUMMARYThe mycopesticide Naturalis (based on Beauveria bassiana strain ATCC 74040) and botanical pesticide Kingbo (based on oxymatrine, an alkaloid from Sophora flavescens, a traditional Chinese herb) were tested against the two-spotted spider mite (Tetranychus urticae) on greenhouse vegetables and the European red mite (Panonychus ulmi) on apples. These biopesticide products were applied twice at 5-day interval and concentrations of 0.1% and 0.2%, and their effectiveness was compared to abamectin-based products and the synthetic acaricides acrinathrin and spirodiclofen, applied once at their recommended rates. The mycopesticide Naturalis, applied at 0.1% concentration against T. urticae on cucumber, reduced mite population density by 85-86%, achieving 91-93% efficacy. In a trial on tomato, efficacy reached some 96%, while population density was reduced by 93%. In a field trial on apple, Naturalis demonstrated an increasing and long-lasting effectiveness against the summer population of P. ulmi of nearly 100%, and population reduction was achieved in assessments 30 days after the first treatment. Naturalis applied at a double rate achieved a somewhat better effect but only in the first trial. The botanical pesticide Kingbo, applied at 0.1% concentration, demonstrated very high control efficacy (≥98%) and population density reduction (≥96%) of T. urticae in both trials. A high and long-lasting effectiveness of this bioacaricide was also achieved in a trial on P. ulmi. Its concentration of 0.2% achieved similar effect. The results in these trials indicate that applications of the mycopesticide Naturalis and the botanical pesticide Kingbo can provide effective control of T. urticae on cucumber and tomato grown in greenhouses, as well as P. ulmi on apple.
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