RESUMEN
Silicon (Si) has been reported to effectively manage some pests and diseases of plants. This study was conducted to determine the effect of Si concentration, mode, and frequency of application in managing Meloidogyne incognita in cucumber. A susceptible cultivar of cucumber (cv. Cyclone) was planted in pots containing heat-sterilized soil. Three weeks after planting, the plants were inoculated with 1,000 juveniles/ pot. Uninoculated plants were provided to serve as control. Three concentrations of Si in the form of sodium metasilicate was applied on the leaves and roots alone and also on both the leaves and roots. Application was done once during the growing period and weekly until seven days before harvest. Leaf and root application of Si was found to significantly increase (p = 0.0029) the fresh top weight of inoculated and uninoculated plants. On the other hand, inoculation of root-knot nematode significantly increased the fresh root weight of cucumber which could be due to enlargement of roots or formation of galls. Interestingly, the inoculated plants gave significantly higher marketable yield than uninoculated ones. Application of Si at the rate of 200 ppm significantly increased the marketable yield compared to the higher rate of Si (400 ppm). At 200 ppm, one application of Si both on the leaves and roots significantly reduced the number of galls in inoculated plants. This was comparable to the same concentration applied continuously on the roots and at higher concentration (400 ppm) applied continuously on the leaves and on the roots. On the other hand, single root application of Si at the rate of 400 ppm gave the lowest number of eggmasses, however, it was comparable to the same Si concentration applied singly on the leaves and applied continuously both on the leaves and roots. These treatments, however, were at par with continuous application of the lower rate of Si (200 ppm) on the leaves and both leaves and roots.