Differential Reaction of Clones of Phalaris arundinacea to Oscinella frit12

Abstract

The mean number of frit fly, Oscinella frit (L.), infested stems in field plantings of reed canarygrass, Phalaris arundinacea L., ranged from 11.1 to 39.9% for 16 clones at one site and from 9.7 to 31.2% for 25 clones at another site. The mean number of stems/9.3 dm2 ranged from 31.0 to 101.1 at site 1 and from 56.7 to 148.2 at site 2. Alkaloid contents ranged from 0.075 to 0.617% (d.w.) at site 1 and 0.072 to 0.532% at site 2. Mean percentages of infested stems were negatively correlated with both mean number of stems/9.3 dm2 (r = −0.865) and with total basic alkaloid concentration (r = −0.544). Alkaloid content was positively correlated (r = 0.661) with number of stems/clone. There was a weak negative correlation (r = −0.478) between number of immature frit fly (larvae + pupae)/stem and alkaloids. The mechanism of resistance to the frit fly in reed canarygrass could be nonpreference controlled by stem density or antibiosis controlled by toxic alkaloids, or a combination of both factors. The great variability in frit fly infestation among these clones suggests that selection for resistance to frit fly should be productive.