Efficacy and crop tolerance of 1,3-dichloropropene applied at low rates in established vineyards for the control of plant-parasitic nematodes

Abstract

Plant-parasitic nematodes are the most important group of root pathogens affecting vineyards for fresh fruit and wine production in Chile. Due to the low efficacy of presently available nematicides and their high variability of control, new alternatives were evaluated in order to obtain a faster and more reliable control. The aim of this work was to assess the use of the soil fumigant Cordon (R), containing 81.4% of 1,3-dichloropropene (1,3-D) plus emulsifiers that allow 1,3-D to be mixed with water and applied at low rate via drip irrigation systems over established vines for the control of Xiphinema index, the main nematode species associated with grapevine injury in the country. During the first year of studies, one trial was performed in a group of ungrafted vines cv Chardonnay, applying the treatments twice, one in autumn, and the second one in the next spring, with three Cordon (R) concentrations, 100, 200 and 400 ppm, equivalent to 3.7, 7.4 and 14.8 L ha(-1) according to the irrigation system water flow. A second trial was performed the following year to determine limits of crop safety by applying 200, 400 and 800 ppm, equivalent to 12, 24 and 48 L ha(-1) in two established vineyards, cv Thompson Seedless and Cabernet Sauvignon. Results showed that 200 ppm, equivalent to 7.4 or 12 L ha(-1) depending of the field, achieved good results considering efficacy and phytotoxicity, with a 93.2% control and no crop damage. Two non-fumigant nematicides, Nemacur (R) 240 CS (24% Fenamiphos) and Rugby (R) 200 CS (20% Cadusaphos), used as chemical controls, did not show differences in X index populations when compared to the untreated plants. At rates over 400 ppm of 1,3-D, although no visible foliar injury was observed, the pruning weight of treated plants was reduced, indicating a growth reduction.