Måling af bioaerosoler under udbringning af mikrobiologiske bekæmpelsesmidler og ved efterfølgende arbejdsprocesser i potteplanter

Measurement of Biological Pest Control Agents in the Air during Application and Subsequent Working Processes

Summary and conclusions

The aim of the project was to quantify the concentration of viable spores of two microbiological pest control agents in the air during and after application. The two microbiological control agents contained the fungi Verticillium lecanii and Trichoderma harzianum as active ingredients, respectively. Further, the aim was to investigate whether viable spores were released during working processes taking place after the application. Furthermore, seven commercial microbiological control agents were analysed for purity and concentration. Measurement of viable spores in the air was carried out using a self-made impact air sampler, collecting the spores on a fungus-growing medium.

The investigation of the seven microbiological control agents showed that all products contained the declared microorganism in pure form. In three of the products the concentration of the microorganism was up to 10³ times higher than declared on the label.

The results of the measurements of the concentration of spores of V. lecanii in the air during different working processes showed that the number of colony forming units (CFU) per m³ calculated as time weighted average during weighing of the product in two trials were 4,4 x 10⁴ and 4,8 x 10⁴. During application by spraying, values from 9,4 x 10³ to 5,4 x 10⁴ were recorded. These concentrations of spores are of an order that provokes eye and nose irritation (2 x 10⁴- 5 x 10⁵ spores pr. m³) according to Eduard et al. (2001), and the concentrations are approximately of the order of 5 x 10⁴ CFU/m³spores that Gorny & Dutkiewicz (2002) propose as occupational limit for industrial installations. However, the exposure of the glasshouse workers depends on the period of time they are exposed to high concentrations of spores.

Registrations of spores in the air immediately after mixing T. harzianum into peat moss showed a very quick drop of the concentration, and the results of registration of spores in the air after repeated applications showed highly variable concentrations. In conclusion the results show that the exposure of the glasshouse workers varies greatly.

Viable spores were registered in the air during all working processes besides weighing of the product and spraying. These working processes comprised removal of plastic cover from a table with plants, transport of plants to another glasshouse, spacing of plants, cutting and wrapping up the final product. During these working processes only very low concentrations of airborne spores were registered, but the presence of viable spores up to ten weeks after application indicates that V. lecanii is able to establish and retain itself in a plant culture. However, it was not possible to determine whether the spores were released to the air from the plants during the working processes or whether they originated from former applications in the nursery.