Toxicity of thiacloprid as single and mixture with wood vinegar against Leptinotarsa decemlineata (Say)

عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most destructive pest of potatoes in the world. Synthetic chemical insecticides are commonly used in the pest control. However, there is a considerable problem in the use of these chemicals due to their residual toxicity in the post-harvest products and occurrence of insecticide resistant. Wood vinegar is a by-product from charcoal production. It is a liquid generated from the gas and combustion of fresh wood burning in an airless condition. Wood vinegar contains 80-90% water and 10-20% organic compounds including more than 200 chemical components with mainly acetic acid. It also contains various kinds of phenol, carbonyl and alcohol compounds. In the aspect of plant protection, the wood vinegar has been used for antibacterial, antifungal, termiticidal and insecticidal properties. The larvae and adults of Colorado potato beetle were collected from potato fields in Ardabil province and were reared at 25±3°C, 70±5 relative humidity and 16:8 (L: D) in the laboratory. The adults obtained from laboratory cultures were stored in separate insect cages with appropriate amounts of potato leaves. To determine the toxicity of single chemicals, concentrations of thiacloprid (100 and 200 μL) and wood vinegar (100 and 200 μL) were tested on adults. The mixture of thiacloprid and wood vinegar were prepared as follows: half-recommended doses (50 and 100 μL) of thiacloprid were mixed with half-recommended doses (50 and 100 μL) of wood vinegar. The adults put on Petri dishes and were covered with a lid and transferred into incubator and then kept under 25±3C, 70±5 relative humidity and 16:8 (L: D) photoperiod. The exposure times of 48 and 72 h were used in all treatments. Each experiment was replicated 4 times at each dose. Results showed that the mean mortality for mixture of thiacloprid and wood vinegar (56.58±4.62, 91.66±3.40) was significantly higher than thiacloprid (38.88±5.22, 65.46±3.90) as single at 72 h exposure time. Wood vinegar (8.22±5.66, 13.45±2.42) as single did not show insecticidal activity at 72 h exposure time. In conclusion, mixture of thiacloprid and wood vinegar was effective than thiacloprid and wood vinegar as single. As results, mixture of thiacloprid and wood vinegar recommend for control of pest. Our study suggests that wood vinegar enhances the activity of insecticide when applied together. Semi-field and field studies that assess efficacy of the combined use of these chemicals still needed to better understand the applicable conditions for the field.

Leptinotarsa decemlineata؛ wood vinegar؛ thiacloprid؛ mixture؛ toxicity