Constitutive and induced resistance of Brachiaria spp. to Collaria oleosa (Hemiptera: Miridae)

The objective of this study was to evaluate the effects of silicon application on the constitutive resistance of Brachiaria spp. and on the induced resistance of these grasses to attack by the mirid bug Collaria oleosa by examining the mechanisms of antibiosis and tolerance. Silicon application did not significantly affect the length of development or the survival of the insect pest. The genotypes CNPGLBR39, CNPGLBR43, CNPGLBR97, and CNPGLBR100 and B. brizantha were selected because they show constitutive resistance to mirid bug. In the second trial, CNPGLBR7 and B. brizantha (resistant) and CNPGLBR100 (susceptible), selected based on the results of the first test, were treated with silicon. Ten days after silicon application, these plants were attacked by mirid bugs at different densities. Silicon had no significant effect on the loss of forage dry mass and chlorophyll content; however, plants responded to silicon with reduced insect damage and less functional loss. In Brachiaria attacked by eight C. oleosa adults, chlorophyll was reduced, and the functional loss, damage score and number of injured leaves increased.