Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 15, 2010
Publication Date: January 14, 2011
Citation: Cabrera, A., Wang, D., Schneider, S.M., Hanson, B. 2011. Effect of potential methyl bromide alternatives on plant parasitic nematodes and grape yield under vineyard replant conditions. American Journal of Enology and Viticulture. 62(1):42-48. Interpretive Summary: Plant parasitic nematodes are widely distributed in grape production worldwide. In California, Meloidogyne and Tylenchulus species commonly parasitize grapevines. For decades soil fumigants have been used for the preplant control of plant parasitic nematodes in California vineyards. Among soil fumigants, methyl bromide (MB) has been widely preferred due to its broad pest-control spectrum and high nematode control efficacy. Alternative fumigant and non-fumigant management strategies for controlling parasitic nematodes in vineyard replant situations are a high research priority. It was determined that 1,3-dichloropropene plus chloropicrin (1,3-D/Cp or Inline), iodomethane plus chloropicrin (Im/Cp or Midas), and propargyl bromide (PBr) can provide root-knot and citrus nematode control in grape replant situations comparable to MB for up to eight years. These alternative pesticides enhanced grape yield similar to MB, however, this was obtained only with one grape rootstock combination (Merlot on 1103P). These potential MB alternatives may be very useful where no resistant rootstocks are available for the mixed nematode community infesting the field or where there is a history of new nematode pathogenicity that can break down partially tolerant rootstocks. Wherever possible the use of root-knot nematode-resistant rootstocks is encouraged. However, the use of pre-plant fumigant pesticides is still required in replant vineyards where the citrus nematode is known to be present for a long-term control.
Technical Abstract: Root-knot (Meloidogyne spp.) and citrus (Tylenchulus semipenetrans) nematodes are often present in vineyards affected by “replant problems” of grapes in California. Methyl bromide (MB) has been used to control these nematodes and other soil borne pathogens prior to replanting new vineyards, but, except for critical use exemptions, its use has been banned under the Montreal Protocol and the U.S. Clean Air Act. Efficacy of treatments with alternative fumigants was tested following removal of an 85-year old raisin vineyard near Parlier, California. Two months after fumigation, own-rooted ‘Thompson Seedless’, ‘Merlot’ on ‘1103P’ and ‘Thompson Seedless’ on ‘Freedom’ rootstock grape nursery stock was planted. The study revealed that 1,3-dichloropropene plus chloropicrin (1,3-D/Cp) (InLine, 578 kg/ha shank-injected), iodomethane plus chloropicrin (Im/Cp) (Midas, 515 kg/ha shank-injected or 448 kg/ha chemigated through drip tape) and propargyl bromide (PBr) (221 kg/ha shank-injected or 207 kg/ha chemigated through drip tape) generally controlled root-knot and citrus nematodes as well as MB (507 kg/ha shank-injected) over an 8-year evaluation period. Sodium azide (Agrizide) (336 kg/ha chemigated through drip tape followed with either a water cap or tarp), and chloropicrin alone (449 kg/ha chemigated through drip tape) were less effective. Application of 1,3-D/Cp, Im/Cp drip and PBr shank gave similar grape yields as MB in one grape type combination (Merlot on 1103P rootstock). In general, the effect of the fumigants on nematode control was very evident in the own-rooted “Thompson Seedless”. The “1103 Paulsen” rootstock was partially tolerant to root-knot and citrus nematodes for the first 3 to 4 years, respectively. In contrast, the rootstock Freedom proved to be a highly root-knot nematode resistant cultivar and kept nematode numbers in soil relatively low regardless of fumigant treatment during the course of this experiment. However, pre-plant fumigation is still required where citrus nematodes are present.