| Abstrakt: |
Large populations of black grass bugs, Labops hesperiusUhler (Hemiptera:Miridae), have been observed on extensive hectares of range lands. These bugs cause severe damage to range grasses, lowering their palatability and productivity. Perusal of the literature indicated a correlation between trichome size and density and plant resitance to insect damage. This study was to determine whether morphological differences among breeding lines of grass species or synthetics could be correlated with the feeding behavior of black grass bugs. If so, plant breeders should be able to develop resistant cultivars. To explore this possibility, bug densities per treatment chamber of 10, 20 or 40 for Instars‐ II and ‐IIl and 10 or 20 for Instars‐IV and ‐V were grazed on quackgrass, Elytrigia repens(L.) Nevski, bluebunch wheatgrass, Pseudoroegneria spicata(Pursh) Löve, standard crested wheat‐grass, Agropyron desertorium(Fisch. ex Link) Schult., fairway crested wheatgrass, A. cristatum(L.) Gaertn., quackgrass ✕ standard crested wheatgrass, E. repens✕ A. desertorium, RD hybrid, quackgrass ✕ bluegrass wheatgrass, E. repens✕ P. spicata, RS hybrid, quackgrass ✕ fairway crested wheatgrass, E. repens✕ A. cristatum, RC hybrid, Kentucky bluegrass, Poa pratensisL., orchardgrass, Dactylis glomerataL., and reed canarygrass, Phalaris arundinaceaL. A scanning electron microscope (SEM) was used to compare and relate trichome size and density on range grass plants with the level of black grassbug preference or nonpreference. Based on leaf area damaged by feeding insect, orchardgrass and reed canarygrass were the least preferred. Kentucky bluegrass, quackgrass, standard and fairway crested wheatgrass, RS, and RC hybrids were most preferred. Older nymphs preferred the RD hybrid over the RC hybrid. Bluebunch wheatgrass and the RD hybrid were less preferred by the nymphs. Quackgrass, Kentucky bluegrass, orchardgrass and reed canary‐grass had relatively smooth surfaces with very short trichomes, if any, on either side of the leaf. Trichomes on the leaf surface of the RS hybrid were similar to those of the quackgrass parent, whereas the trichomes on the RC and RD hybrids were similar and intermediate between that of their parents. Field grown grasses had denser trichomes and more surface waxes, and the trichomes appeared more rigid than on.grasses grown in the green house. Given the relatively large size of the trichomes (194.5 μm) on some grasses, e.g., fairway crested wheatgrass, comparison to the small size of the early nymphal stages of the black grass bug, selecting clones of wheatgrasses with large trichomes should offer some resistance to this troublesome pest. |
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