THE EFFECT OF THE HERBICIDE MECOPROP ON HELISCUS-LUGDUNENSIS AND ITS INFLUENCE ON THE PREFERENTIAL FEEDING OF GAMMARUS-PSEUDOLIMNAEUS

Exposure of the aquatic hyphomycete Heliscus lugdunensis to the herbic ide Mecoprop did not significantly affect production of the antigen re cognized by the specific monoclonal antibody NG-CF10. Therefore, an EL ISA method, developed in a previous study, could be used to quantify t he biomass of H. lugdunensis colonizing leaves exposed to this herbici de. Exposure to Mecoprop significantly reduced the mycelial biomass as sociated with alder leaves. This was shown to be a threshold response rather than a dose response, with higher biomass recorded on control l eaves. No significant differences were found over the range of Mecopro p concentrations used. In laboratory experiments, Gammarus pseudolimna eus was offered a choice of alder leaves exposed to a range of Mecopro p concentrations. The animals were able to discriminate between the ex posed and control leaves, and between inoculated and sterile leaves. P resence of the fungus resulted in increased leaf consumption, but no i nteraction between the Mecoprop concentrations and fungal colonization was observed. The major factor affecting food choice was the concentr ation of Mecoprop that the leaves were exposed to-not the Mecoprop-med iated effects on fungal biomass.