Forage Quality of Alfalfa as Affected by Potato Leafhopper Feeding
- Scott H. Hutchins ,
- Dwayne R. Buxton and
- Larry P. Pedigo
The potato leafhopper (PLH), Empoasca fabae (Harris), is a major pest of alfalfa, Medicago sativa L., in the north central USA, yet little information exists regarding its effects on forage quality. Three field trials were conducted in 1984 and 1985 to determine the consequence of PLH feeding on chemical composition and nutritional quality of alfalfa stem and leaf components. A factorial arrangement of four densities of PLH adults (0, 50, 100, and 200 m−2) and two infestation periods (1 and 14 d after first harvest) was replicated four times in a randomized complete-block design. Weekly plant samples were collected for assays of in vitro digestibility, neutral-detergent fiber (NDF), and crude protein. Total herbage digestibility did not differ among plots. Digestibility of the stem component was actually enhanced (up to 3.0% change) by severe PLH feeding. The leaf component also was slightly higher in digestibility (up to 2.2% change) under extreme PLH-induced stress. Total herbage NDF concentration was largely unaffected at harvest by levels of PLH-induced injury. Leaf protein concentration was reduced (about 8.2% change) in most infested plots but stem protein concentration was maintained or enhanced (up to 9.1% change) with increasing levels of PLH-induced injury. Comparisons of chlorotic vs. nonchlorotic leaves suggested that visible symptoms of PLH feeding did not necessarily indicate differences in chemical composition of the herbage. The small effects of PLH feeding on total herbage forage quality indicate that PLH control programs should be based primarily on the likelihood of reductions in biomass or nutrient yield, rather than the likelihood of reduced forage quality.
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