Browsing Journal of Range Management, Volume 51, Number 4 (July 1998) by Subjects
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Effect of hand defoliation on herbicide efficacy in honey mesquiteGreenhouse and field experiments were conducted to evaluate the effect of hand defoliation of honey mesquite (Prosopis glandulosa Torr) before herbicide application on herbicide efficacy. In the greenhouse, the monoethanolamine salt of clopyralid, the butoxyethyl ester of triclopyr, and 1:1 mixtures of clopyralid plus triclopyr were applied as foliar sprays at 140 g ha-1 each on 2-year-old single-stemmed plants averaging 50 cm tall. In the field, the same herbicides were applied as broadcast sprays at rates of 280 g ha-1 on multistemmed trees 1 to 2 m tall. Plants were defoliated prior to herbicide application at 0, 25, and 50% of original foliage. Defoliation at 25 or 50% did not reduce herbicide efficacy compared to nondefoliated plants in the greenhouse or field. The clopyralid:triclopyr mixture was sometimes synergistic in controlling honey mesquite in the greenhouse and field.
Temperature effects on regrowth of 3 rough fescue speciesThree species of rough fescue, alpine rough fescue (Festuca altaica Trin.), mountain rough fescue (F. campestris Rydb.), and plains rough fescue (F. hallii (Vasey) Piper) were grown for 12 weeks under 5 temperature regimes — 7:3, 12:8, 17:13, 22:18, and 27:23 degrees C — and defoliated 3 times to 3.5 cm at 4-weekly intervals in a growth cabinet study. Final plant dry mass and harvestable biomass production were greatest at 17:13 degrees C for alpine rough fescue and plains rough fescue, and at 12:8 degrees C for mountain rough fescue. Harvestable biomass plateaued or declined at the final harvest in all species for temperatures above 12:8 degrees C. Tiller numbers increased at successive harvests. Biomass per tiller declined markedly at the final harvest of alpine rough fescue at all temperatures. Regrowth in alpine rough fescue was markedly reduced at temperatures either above or below the optimum. The results indicate that mountain rough fescue and plains rough fescue are better able to regrow following defoliation at temperatures below or equal to their optima, than at temperatures above their optima. This provides greater understanding of field responses in both species where frequent defoliations are more deleterious after the April/May period when temperatures are above optimal.