Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Wildland Resources

Department name when degree awarded

Range Science

Committee Chair(s)

Jerry R. Cox


Jerry R. Cox


Diana G. Alston


Roger E. Banner


G. Allen Rasmussen


Christopher A. Call


I conducted field studies during 1984-1988 to determine how (1) precipitation amount and distribution affect buffelgrass [Cenchrus ciliaris L. (Link) l productivity, (2) summer rainfall amount and distribution and temperature influenced the spittlebug (Aeneolamia albofasciata Lalleman) life cycle, and (3) summer burning affects spittlebug densities and buffelgrass productivity.

Experiment I was conducted from 1985 through 1988. Forage samples collected at 15-day intervals were separated into live, recent-dead standing, old-dead standing, and litter. There was a positive relationship between the summer precipitation and the live biomass. Recent-dead standing and old-dead standing decomposed during the summer, fall, or spring.

Experiment II was conducted during summers of 1984, 1985, and 1986. studied climatic effects on spittlebug life cycle and monitored nymph and adult populations. Egg hatch occurred after accumulative summer precipitation exceeded 50 mm. Five nymphal stages were completed in an average of 27 days and the life cycle averaged 43 days.

Experiment III was conducted during the summer of 1985 and 1986. Four burning treatments were applied at different stages within the spittlebug life cycle. Burning should be conducted as buffelgrass initiates summer growth, and between the second and third nymphal stages. Burns conducted before plant growth and during rapid growth damaged the plant, and insect control was inconsistent.

My studies will help ranchers in northwestern Mexico, south Texas, and northeast Mexico effectively manage buffelgrass pastures. Forage accumulation and decomposition cycles can be used to adjust stocking rates, and knowledge of the insect life cycle and plant productivity can be used to maximize insect control and minimize adverse effect on plant productivity.