The application of
fenamiphos either alone or in combination with soil fumigants is a common practice in greenhouses and potato-cultivation areas in Greece. However, repeated applications of
fenamiphos in the same field for a number of years can lead to the development of enhanced biodegradation of the nematicide. Studies in previously treated greenhouse sites and potato field sites in Greece were employed in order to investigate the development of enhanced biodegradation of
fenamiphos and the respective effect of soil fumigants on the development of the phenomenon. Enhanced biodegradation of
fenamiphos in a soil from a previously treated greenhouse site from the area of Aggelohori in Northern Greece was observed using both incubation and bioassay studies with nematodes. Fumigation of the enhanced soil with
methyl bromide (MeBr) only temporarily inhibited degradation of
fenamiphos unlike
metham sodium (MS) whose application significantly reduced microbial degradation of
fenamiphos. Similarly, enhanced biodegradation of
fenamiphos was evident in soil from potato fields that had a history of previous exposure to
fenamiphos. The slow rates of
fenamiphos degradation observed in
soils from the previously treated sites after sterilization with broad-spectrum
antibiotics and also in
soils from previously untreated sites suggested that soil microorganisms were responsible for its rapid degradation. The inhibition of enhanced biodegradation of
fenamiphos in soil from the previously treated greenhouse site caused by the
antibiotic penicillin probably indicates that Gram+ or other bacteria sensitive to
penicillin are responsible for the rapid degradation of
fenamiphos in this soil. No cross-adaptation was observed between
fenamiphos and other nematicides registered in Greece for the control of root-knot and potato
cyst nematodes, including
cadusafos,
ethoprophos, and
oxamyl. According to our results, applications of MS followed by
fenamiphos or in rotation with other registered nematicides are the most promising means for minimizing the risk of development of enhanced biodegradation of
fenamiphos in
soils.