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Large populations o+ black grass bugs, Labops hesperius Uhler, have been observed on extensive acreages o+ range lands. These bugs cause severe damage to the range grasses, lowering their palatability and productivity. This study was to determine whether morphological differences among breeding lines o+ grass species or interspecific hybrids could be correlated with the feeding behavior o+ black grass bugs. I+ so, plant breeders should be able to develop resistant cultivars. To explore this possibility, cultivars and synthetics o+ range grasses, representing the genera, Agropyron, Dactylis, Phalaris and Poa, were exposed to di++erent instar stages was examined under a scanning electron microscope. Leaf pubescence (trichomes) varied in density and size and appeared to be associated with resistance of plants in the genera, Agropyron, to the Labops nymphs (instar stages II and III> but had no relation with the feeding behavior of adult black grass bugs. Plant leaves of the general, Dactylis and Phalaris, were smooth (few and small if any trichomes> and were the least preferred of any of the grasses by all stages of the bugs. Trichomes on leaves of other genera were varied in density and size. Based on percent damage, preference by the nymphs was for the species with intermediate sized trichomes. The adult bugs showed no discrimination in their feeding behavior. Field grown plants developed more trichomes per unit leaf area and appeared to have thicker surface waxes than the same species grown in the greenhouse. For this reason, nymph feeding habits may be different in the field than in the greenhouse. Future studies should perhaps investigate (1) first stage nymph activity on field plants and (2) palatability and/or chemical differences of the grasses. |
