ISHS Acta Horticulturae 698: VI International Symposium on Chemical and non-Chemical Soil and Substrate Disinfestation - SD2004
BEHAVIOR OF FUMIGANTS IN SOIL |
| Author: | A. Gamliel |
| Keywords: | metam-sodium, Formalin, Dazomet, soil disinfestation, soilborne diseases, methyl bromide |
| Abstract:
Few fumigants [e.g. metam sodium (MS), dazomet, chloropicrin, 1,3-dichloropropene, and formalin] are potential alternatives after the phase-out of methyl bromide, and are characterized by a narrower range of controlled pests. Most of these fumigants are also characterized by a high boiling point and low vapor pressure. Thus, effective control of soilborne pests requires application under optimal soil conditions (soil preparation, moisture and temperature) and efficient and uniform delivery of the fumigants along and across the soil profile. Traditionally, soil fumigants are shank injected into the soil. However, in recent years these fumigants are also applied through the irrigation system. Effective application of fumigants through water depends upon maintaining the appropriate chemical concentration at all soil depths. This requires that fumigant dosage will be adjusted according to the desired soil depth to which fumigation is aimed. Application of fumigants through drip irrigation is often done under plastic tarp, in order to maintain higher soil temperatures and prevent the escape of the fumigant vapors. Such application requires dense drip line system for uniform delivery of the fumigant solution on the soil surface. Activity of MITC generators (metam sodium, dazomet) depends upon the soil temperature. At higher soil temperatures maximal MITC peak is higher, and its dissipation is also faster enabling shorter time between fumigation and planting. The effect of soil temperatures on MITC generation is reflected in fungal toxicity. Different dissipation curves were obtained for different soils in Israel ranging from fast dissipation (24 hours) to slow and long dissipation, leading to high concentration of MITC in soil. The diversity of MITC dissipation curves among the tested soils can explain failures in pest control in certain fields following MS application for disease management. Combination of fumigants with different spectra of target pests can extend the spectrum of control of these fumigants. In addition, combination of these fumigants enables significant reduction of dosage of the individual fumigants. The mixture of fumigants also enables delivery of the fumigants to deeper soil layers. The combination of fumigants with solarization can further improve disease control and enable reduction of fumigant dosage, minimizing environmental hazards. | |
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