Degradation of the nematicide oxamyl under field and laboratory conditions

Abstract

The persistence of nematicides such as oxamyl can vary greatly in field conditions. The objectives of the present studies were: i) to compare oxamyl degradation in soils with different properties; ii) to quantify and examine the influence of various abiotic factors on oxamyl degradation; iii) to establish the validity of using simulated models to predict the degradation in the field; and iv) to examine if a second application of oxamyl to the same soil 13 or 26 weeks after the first application enhances degradation. The first two studies included field measurements of oxamyl concentration and parallel laboratory incubations. For the field measurements, soils were collected from each of ten potato (Solanum tuberosum) fields in Shropshire, UK, immediately after application of oxamyl on the day of planting and then at weekly intervals for the duration of the two experiments. After each collection, oxamyl was extracted and its concentration determined. For the laboratory incubations, soils were collected from the same ten sites immediately prior to field application and received one application of oxamyl in the laboratory at the same day (day 0). The PERSIST model was then used to predict oxamyl degradation in the field (modelled degradation). Modelled degradation was then compared with the measured degradation up to 91 days (study 1) or 56 days (study 2) after application. In study 3, an extra application of oxamyl to that in the field at day 0 was made in the laboratory at 13 or 26 weeks after application. There were wide variations in the persistence of oxamyl between the ten sites, with the field half-life ranging from 10 to 24 days. Degradation in the field was significantly greater at site 4, where it could not be detected 28 days after application. At other sites, the chemical persisted for 42-63 days and was still detectable at two sites 91 days following application. Soil temperatures had a greater impact on oxamyl degradation than rainfall accounting for up to a maximum of 79% of the variation. The short persistence at site 4 was attributed to the combination of warm and moist conditions in a higher pH soil. The PERSIST model predicted the same rate of decline of oxamyl as actually occurred in the field at only four (sites 5, 6, 7 and 8) sites. At the other sites, degradation in the field occurred at more rapid rates than predicted. This could be as a result of the model not allowing for the movement of nematicide by leaching, or because enhanced degradation of nematicides occurred at these latter sites, or due to a combination of these factors. The wide variation in half-lives and the behaviour of soils after subsequent additions of oxamyl in study 3 were suggestive of complex microbial dynamics even under controlled conditions. Further studies would be required to establish the influence of soil microflora together with that of abiotic parameters on oxamyl degradation. as a whole in the region of €300M (Deliopoulos et al., 2007).Nearly 180 t of granular nematicides were applied on approximately 40 000 ha...

Observations on the life cycle of potato cyst nematodes, Globodera rostochiensis and G. pallida, on early potato cultivars

“…This might be attributed to the long hatching period of G. pallida compared with that of G. rostochiensis contributing to its presence in the soil over a long period, extending the time when most of the active substance of oxamyl has been degraded. It was shown that after incorporation, the con centration of granular nematicides, e.g., oxamyl, will de crease due to degradation of the nematicide, which could be influenced by the environment (e.g., temperature), soil properties and microbial activities in the soil (Smelt et al, 1987;Haydock et al, 2012). This chemical could persist in the soil for 28-91 days after application (Haydock et al, 2012).…”

Accelerated Microbial Degradation of Nematicides in Vineyard and Orchard Soils

“…The frequency of pesticide applications is also an important factor that can affect such degradation (Harrison, 1990). Nevertheless, the degradation of xenobiotic compounds by members of the soil microflora is an important means by which said compounds Smelt et al (1987); Haydock et al (2012) * Currently not available, and prohibited from January 2014 ** Trade name of generic products *** Plums excluded are removed from the environment, and thus prevented from becoming pollution-related problems (Karns et al, 1986). The involvement of microorganisms in the degradation of fenamiphos was proven in a study conducted by Stirling et al (1992).…”

Effect of Application Timing of Oxamyl in Nonbearing Raspberry for Pratylenchus penetrans Management

“…Therefore, whereas oxamyl concentrations in soil were likely higher in April than May or June, potentially this difference was not as large due soil temperatures being .108C at all application dates. Soil type is another factor that can impact oxamyl degradation and absorption (Barmilow et al, 1980;Haydock et al, 2012). Our trials encompassed several different soil types (loam, sandy loam, silt loam) and we did not observe any noticeable differences in oxamyl efficacy across these soil type.…”