Influence of Bacillus subtilis and Trichoderma harzianum on Penthiopyrad Degradation under Laboratory and Field Studies.

In plant protection, biological preparations are used alternately with chemical pesticides. The applied microorganism can influence the concentration of chemical substances. Laboratory and field studies were conducted to assess the influence of Bacillus subtilis and Trichoderma harzianum on the penthiopyrad concentration. In laboratory studies, the effectiveness of penthiopyrad degradation by B. subtilis was approximately 5% during 14 days of the experiment. For penthiopyrad treated with T. harzianum strains, the degradation effectiveness ranged from 34.2% on Day 3 to 56.9% on Day 14. In experiments testing the effects of mixed culture of microorganisms, the effectiveness of penthiopyrad degradation ranged from 23.7% on Day 3 to 29.1% on Day 14. After treatment of apple trees of Gala and Golden Delicious varieties with a biological preparation, a maximum degradation of penthiopyrad of 20% was found in both varieties. Samples of apples were prepared by the quick, easy, cheap, effective, rugged and safe (QuEChERS) method, and penthiopyrad was analyzed by gas chromatography with a mass detector. A determined value of the chronic exposure to penthiopirad was 1.02% of the acceptable daily intake, both for children and for adults. The acute exposure amounted to 7.2% and 1.9% of the acute reference dose for children and adults, respectively. These values were considered to be acceptable and not threatening to health.