In past work, dichloropropene + 17% Pic (1,3-D + Pic) at 327 L·ha–1 plus pebulate provided good control of nematode, soil fungi, and nutsedge in mulched tomato (Lycopersicon esculentum Mill.) and is considered the best alternative for methyl bromide (MBr) + chloropicrin (Pic), which is scheduled for phase-out in the United States by Jan. 2001. Metam-sodium did not provide acceptable pest control. In the present study, metam-Na (295 L·ha–1 combined with Pic (168 kg·ha–1) + 4.5 kg·ha–1 pebulate, and 1,3-D + 35% Pic at 168 and 225 L·ha–1 + pebulate were compared to MBr-Pic (98-2% at 345 kg·ha–1 and 67-33% at 505 kg·ha–1). Fumigants were injected into the bed except metam-Na and pebulate were surface-applied and incorporated and drip tubing and mulch were applied. Marketable yields with MBr-Pic, 225 L·ha–1 1,3-D + Pic, and metam-Na + Pic were higher than with the check. Yields with metam-Na alone or with additional water before transplanting were similar to the check. Nutsedge was controlled with MBr-Pic and all treatments with pebulate. Nematode root-gall ratings were high on tomato grown without fumigants (8.9 rating on a scale of 0 to 10 with 0 = no galling), low with MBr-Pic (0.33), and intermediate with all other treatments (2.2 to 5.5) except with 168 L·ha–1 1-3-D + Pic (8.3). This study indicates that metam-Na + Pic + pebulate also is a possible alternative to MBr-Pic for tomato.
Two methods for the preparation of high molecular weight [3H]hyaluronic acid were investigated. In the first one, hydrogen atoms in the molecule were replaced by tritium. This isotopic substitution was performed in aqueous solution using Pd/CaCO3 as the catalyst. In the second method, the high molecular weight hyaluronic acid was alkylated with [3H]methyl bromide in liquid ammonia at a temperature of -33.5 °C. High-performance gel permeation chromatographic separation method was used for the isolation and characterization of the high molecular weight [3H]hyaluronic acid. Molecular weight parameters for the labelled biopolymers were Mw = 128 kDa, Mw/Mn = 1.88 (first method) and Mw = 268 kDa, Mw/Mn = 1.55 (second method). The high molecular weight [3H]hyaluronic acid having Mw = 268 kDa was degraded further by specific hyaluronidase. Products of the enzymatic depolymerization were observed to be identical for both, labelled and cold biopolymer. This finding indicates that the described labelling procedure using [3H]methyl bromide does not induce any major structural rearrangements in the molecule.
In a field experiment with strawberries, pre-plant treatments with broad-spectrum fumigants methyl bromide-chloropicrin (450 kg/ha) or methyl isothiocyanate-dichloropropene (500 l/ha) (and 300 l/ha) controlled wilt caused by Verticillium dahliae Kleb and resulted in increased yields. Soil fumigation with the nematicide ethylene dibromidz (105 l/ha) also improved yields. It controlled the root-knot nematode (Meloidogyne hapla Chitwood), delayed the onset of wilt symptoms and reduced the severity of disease. This indicated a nematode-fungus interaction and is the first report of a Meloidogyne-Verticillium interaction in strawberry.