Evaluation of selected nonfumigant nematicides on inoculation densities of Meloidogyne incognita on cucumber

Authors: HAJIHASSANI, ABOLFAZL - University Of Georgia; Davis, Richard; Timper, Patricia - Patty

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2019
Publication Date: 9/23/2019
Citation: Hajihassani, A., Davis, R.F., Timper, P. 2019. Evaluation of selected nonfumigant nematicides on inoculation densities of Meloidogyne incognita on cucumber. Plant Disease. 103:3161-3165. https://doi.org/10.1094/PDIS-04-19-0836-RE.
DOI: https://doi.org/10.1094/PDIS-04-19-0836-RE

Interpretive Summary: All commercial cucumber cultivars are highly susceptible to the southern root-knot nematode (RKN), which causes great economic damage to the crop in the US. The most economically beneficial management option for RKN in cucumber has been the use of nematicides, which are widely used by growers. However, it is not known to what extent nematicide effectiveness is influenced by the level of nematodes in the field. Additionally, it is not known how new nematicidal compounds compare to currently available chemicals. This research was conducted to compare the effectiveness of several nematicides in cucumber and to determine whether the relative nematicide effectiveness was influenced by the initial number of nematodes present prior to nematicide application. Two microplot experiments were conducted in which four nonfumigant nematicides were examined for their efficacy in reducing gall severity and soil nematode numbers and improving growth and yield of cucumber in plots with increasing population levels (1000, 5000, 10000, and 20000 per plot) of RKN. Nematicides were applied one day prior to transplanting cucumber seedlings, except fluensulfone, which was applied 7 days before transplanting. At harvest, root gall index and nematode population levels differed significantly among nematicides. All four nematicides were effective in reducing the root gall index when compared with the untreated control at each M. incognita population level. At the lowest nematode population level, no significant difference in gall index or final population level was observed among nematicides, however, gall index increased with increasing nematode population levels in nematicide-treated plots. Correlations between gall index and initial population levels clearly showed that soil treatment with fluensulfone or fluazaindolizine was more effective than treatment with oxamyl or fluopyram in reducing gall severity. Regression analysis also indicated no significant effect of nematode population levels on yield of cucumber treated with these nematicides. Results of this study will provide guidance for improving nematicide efficiencies in soil with varying population levels of RKN.

Technical Abstract: The southern root-knot nematode (RKN) Meloidogyne incognita is particularly difficult to manage because of high susceptibility of all commercial cucumber (Cucumis sativus L.) cultivars to the nematode. Growers have conventionally relied on nematicide applications to control RKN. Two microplot experiments were conducted in which four nonfumigant nematicides were examined for their efficacy in reducing gall severity and soil nematode numbers in plots with increasing population levels (1000, 5000, 10000, and 20000 per plot) of M. incognita and improving growth and yield of cucumber. Nematicides were applied one day prior to transplanting cucumber seedlings, except fluensulfone, which was applied 7 days before transplanting. At harvest, root gall index and nematode population levels differed significantly (P < 0.0001) among nematicides. All four nematicides were effective in reducing the root gall index when compared with the untreated control at each M. incognita population level. At the lowest population level, no significant difference in gall index or final population level was observed among nematicides, however, gall index increased with increasing nematode population levels in nematicide-treated plots. Correlations between gall index and initial population levels clearly showed that soil treatment with fluensulfone or fluazaindolizine was more effective than treatment with oxamyl or fluopyram in reducing gall severity. Regression analysis also indicated no significant effect of nematode population levels on yield of cucumber treated with these nematicides. Results of this study will provide guidance for improving nematicide efficiencies in soil with varying population levels of RKN.