Oat, wheat, and barley resistance to white grubs of Phyllophaga congrua (Coleoptera: Scarabaeidae)

Field and greenhouse tests of selected small grain cultivars disclosed large differences in their resistance to Phyllophaga congrua (LeConte) white grubs. Resistance was evidenced first in a field plot test of four cultivars each of wheat (Triticum aestivum L.), oats (Avena sativa L.), and barley (Hordeum vulgare L.) (Poaceae). P. congrua white grubs that were present at planting caused high rates of seedling mortality and reduced the yields of some varieties. The most resistant cultivars of each species ('Nora' oats, 'Adder' wheat, and 'Tambar 401' barley [1, 10, and 43% seedling mortality, respectively]) and the least resistant ones ('Florida 501' oats, 'Wysor' barley, and 'Collin' wheat [10, 65, and 68% seedling mortality, respectively]) were tested further in the greenhouse. When the six cultivars were planted intermingled in the greenhouse, 22.8 times as many 'Collin' seedlings and 19.4 times as many 'Tambar 401' seedlings were destroyed by P. congrua third instars as were seedlings of 'Florida 501'. Two no-choice feeding experiments (each greenhouse plot contained only one cultivar) confirmed the trends for resistance shown in the choice experiments. Overall rates of grub-induced seedling mortality in the three greenhouse experiments were 8.5% ('Florida 501'), 10.9% ('Nora'), 25.8% ('Adder'), 35.7% ('Wysor'), 41.4% ('Collin'), and 42.3% ('Tambar 401'). The resistance apparently is due to the nonpreference