title: Agrichemical impact on growth and survival of non-target apple phyllosphere microorganisms.
abstract: The impact of conventional agrichemicals commonly used in New Zealand apple production on non-target, culturable phyllosphere microbial populations was studied in the laboratory (agar, leaf, and seedling assays) and field (apple orchard). Morphologically distinct bacteria (three), yeasts (five), and filamentous microfungi (two) were used as indicator species. The agar assay showed that agrichemical toxicity to microorganisms was dependent on product type, product rate, and organism studied. While the fungicides metiram and captan stopped or severely reduced growth of nearly all microorganisms studied, the insecticides tebufenozide and lufenuron and the fungicide nitrothal-isopropyl showed the least amount of microbial toxicity, each affecting 2 of the 10 indicator organisms studied. In the leaf assay a single agrichemical application at field rate either reduced or increased microbial population counts, again depending on product and microorganism. Repeated agrichemical applications, however, reduced microbial population numbers from 10- to 10,000-fold in planta. Further field research validated these findings, although differences in microbial numbers before and after agrichemical applications were less dramatic. In the orchard, total organism numbers recovered within 2-6 days, but species richness (sum of recognizable taxonomic units) declined. Agrichemicals clearly affected non-target, culturable surface microorganisms. The importance of diversity and stability of microbial populations for disease control still needs to be established.
authors.affiliation: Horticulture and Food Research Institute of New Zealand Ltd., Lincoln. mwalter@hortresearch.co.nz
authors.forename: Monika
authors.initials: M
authors.lastname: Walter
authors.forename: Christopher Miles
authors.initials: CM
authors.lastname: Frampton
authors.forename: Kirsty Sarah Helen
authors.initials: KS
authors.lastname: Boyd-Wilson
authors.forename: Patricia
authors.initials: P
authors.lastname: Harris-Virgin
authors.forename: Nicholas William
authors.initials: NW
authors.lastname: Waipara
mesh_terms: D016573:Agrochemicals / Q000009:adverse effects*; D001407:Bacillus / Q000187:drug effects; D044822:Biodiversity; D015169:Colony Count, Microbial; D017753:Ecosystem; D005658:Fungi / Q000187:drug effects; D016946:Gram-Negative Aerobic Rods and Cocci / Q000187:drug effects; D027845:Malus / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010575:Pesticides / Q000009:adverse effects*; D018515:Plant Leaves / Q000382:microbiology*; D014197:Trees / Q000382:microbiology*
chemical_list: D016573:Agrochemicals; D010575:Pesticides