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During the spring of 1973, white grubs, PhyZZophugu crinita (Burm.)‘, at a density of 46.3/m2, reduced cover of perennial grasses by 88% in localized areas of a shortgrass community in Scurry County, Texas. Forbs and broom snakeweed were not affected. Chlordane applied to the soil surface at 3.36 kg/ha did not control white grubs. Chlordane, nitrogen fertilization (112 kg/ha of N), and a combination of the insecticide-fertilization treatments did not appreciably enhance rehabilitation of white grub-denuded rangeland. Seeding with introduced grasses was not successful because of inadequate precipitation, heavy grazing by lagomorphs on the small areas, and competitive effects of buffalograss. Forbs and broom snakeweed were not important in the early seral stages of secondary succession on the study site, but common broomweed and common sunflower were dominants on other denuded sites in the area. Most plant species had recovered by the end of the second growing season without fencing to control livestock grazing. White grubs (Coleoptera: Scarabaeidae), the larvae of June beetles, are among the most destructive of soil-dwelling insects (Hewitt et al. 1974). However, no quantitative evaluations of their effects on rangeland vegetation have been published. The adult June beetles feed on foliage of broadleaf and coniferous trees and cause little damage, but the larvae feed largely on the roots of grasses. Large acreages of rangeland in the northwestern Texas panhandle, northeastern New Mexico, Colorado, Kansas, and Nebraska have been severely damaged by white grubs (Saylor 1940; Schumacher 1959; Daniels 1966; Anon. 197 1 a; Anon. 197 1 b). Moderate damage by white grubs is often attributed to drought or low levels of soil fertility. The author is associate professor, Department of Range and Wildlife Management, Texas Tech University, Lubbock. His present address is Texas A&M University 7&t A ‘cultural Research and Extension Center, Route 2, Box 950, San Angelo, Texas This study is approved as Texas Tech University, College of Agricultural Sciences Publication No. T-9-200. The author expresses appreciation to Dr. R.D. Gordon, Systematic Entomology Laboratory, U.S.D.A.S.E.A., Beltsville, Maryland, for taxonomic determination of insect specimens. Manuscript received August 23, 1979. ’ Coleoptera: Scarabaeidae. However, high population densities of white grubs can kill rangeland vegetation, crops, pastures, and lawns (Anon. 1959; Randolph and Garner 196 1). Feeding by white grubs can also provide a mode of entry for disease organisms which can eventually kill infected plants (Drake 1964). Graber et al. (193 1) reported that liberal fertilization and favorable growing conditions reduced the degree of injury by white grubs to Kentucky bluegrass (Pea prutensis L.) pastures. Most species of white grubs have a 3-year life cycle, and most of the damage to plant roots occurs during the 2nd year. White grubs may cause damage every year if several broods co-occupy the same area, but usually the severe injury occurs in 3-year cycles (Anon. 1959). A localized die-off of range vegetation in the southwestern Rolling Plains resource area of Texas during the spring of 1973 was attributed to severe root-feeding by the white grub Phyllophaga crinitu (Burm.). This study was initiated to quantify white grub damage to rangeland vegetation and to evaluate fertilization, insecticide treatment, and seeding for rehabilitation of rangeland severely damaged by white grubs. Methods and Materials This study was initiated in May, 1973, and continued through September, 1975, on the Lefors Ranch, 3 km west of Dermott in Scurry County, Texas. Average annual precipitation of the area is 48 cm. About 70% of the annual precipitation falls during the April to September growing season. Soils are of the Mansker and Potter series and textures are loams to clay loams. Topography is rolling with 1 to 5% slopes. The major grasses in this shortgrass community include buffalograss (Buchloe ductyloides Nutt.), red threeawn (Aristidu longisetu Steud.), and hairy tridens [Erioneuron pilosum (Buckl.) Nash]. Major forbs include common broomweed [Xunthocephalum drucunculoides (D.C.) Shinners] and leatherweed croton [Crotonpottsii (Klotzsch) Meull. Arg.]. Broom snakeweed [Xunthocephulum surothrue (Pursh) Shinners] is a common half-shrub or shrublet. Localized honey mesquite (Prosopis glundulosu Ton-. var. glundulosu) occurs on deeper soils. On May 22, 1973, the following treatments were applied to grubdenuded plots: (a) 3.36 kg active ingredient (a.i.)/ha of chlordane JOURNAL OF RANGE MANAGEMENT32(6), November 1979 445 (octachloro-4,7-methano tetrahydroindane); (b) 112 kg/ha of nitrogen as ammonium sulfate; (c) 3.36 kg a.i./ha chlordane + 112 kg/ha nitrogen as ammonium sulfate. Untreated check plots were established on a grub-denuded and adjacent undisturbed rangeland. Each treatment was replicated three times in a randomized complete block design. Plot size was 6.1 by 13.4 m. The insecticide was applied to experimental plots with a 203-cm boom, with nozzles on 50-cm centers, mounted on bicycle wheels. Fertilizer was applied with a whirl-wind type hand spreader. The experimental plots were not fenced and were grazed continuously during the study at a moderate stocking rate with a cow-calf herd. Population density of P. crinitu was determined before application of treatments and on June 6,1973, May 2 1,1974, and June 19,1975, by excavating soil in ten, 30.5 by 30.5cm quadrats to 20 cm deep. Soil was sieved over 0.5-cm mesh hardware cloth to facilitate counting of larvae, pupae, and adults. Below ground plant biomass was determined on May 10, 1973, by extracting roots from ten randomly selected soil cores (8 1.07 cm2 by 30.5 cm) taken from grub-denuded rangeland and from ten similar cores taken from adjacent undisturbed rangeland. Each soil core was washed over a soil sieve (0.42-mm mesh) to separate the soil and roots. Root samples were oven-dried, weighed, and ashed to determine an ash-free weight for each sample. Foliar cover was determined on May 24, 1973, and subsequently on October 18, 1973, October 25, 1974, and September 25,1975, by the point-frame technique (Levy and Madden 1933). One hundred points were observed in each plot on each sampling date. Readings were taken at ten equidistantly spaced intervals along a permanent line transect across the diagonal of each plot. Any above-ground plant part hit by the pin point was recorded as a hit. Differences between treatments in foliar cover for major plant species and vegetation categories were determined by analyses of variance of total hits per plot. An auxiliary study was conducted to evaluate seeding with introduced grasses for rehabilitating white grub-denuded rangeland. Plots 6. lby 13.4-m were tilled to 8 cm deep on May 23, 1973, on white-grub denuded rangeland. Kleingrass (Panicurn colorutum L.) and Ermelo weeping lovegrass [Erugrostis curvula (Schrad.) Nees var. Ermelo] were seeded in single plots at 3.4 kg P. L. S./ha and 3.1 kg P.L.S./ha, respectively, in rows on 50-cm spacings. Seeded plots were fenced to exclude livestock. Results and Discussion Initial Impact on Plant Community White grub-infested areas were localized and did not constitute a major range management problem in Scurry County, although ranchmen who had patches of dead grass were concerned that infestations might spread and become a major problem. Most white grub-denuded areas were 0.1 ha or less in area, but some covered 1 ha or more. In early May, 1973, all grass plants in infested areas appeared to be dead. Grass roots had been completely severed at 2 or 3 cm below the soil surface, and most grass plants had fallen to a horizontal position, exposing the severed roots. Foliar cover of perennial grasses had been reduced 88% compared to adjacent undisturbed rangeland, while cover of all live herbaceous plants was reduced 83% (Table 1). Litter cover increased 63 % on white grub-denuded areas compared to adjacent undisturbed rangeland, because of the deposition of dead perennial grasses. Bare soil increased 20%. Cover of forbs and half-shrubs was not affected by the white grubs (Table 1). Below-ground plant biomass in the upper 30.5 cm of soil in white grub-denuded areas was reduced to 3,478 kg/ha compared to 6,143 kg/ha on adjacent undisturbed rangeland (43% reduction). In late May, 1973, the mean population density of P. crinitu was 46.3/m2 in the upper 20 cm in white grub-denuded areas. No larvae, pupae, or adults were found at depths greater than 20 Table 1. Cover (%) of vegetation, litter, and bare soil on white-grub infested rangeland and adjacent undisturbed rangeland in Scurry County, Texas on May 24, 1973.

Impact of a White Grub (Phyllophaga crinita) on a Shortgrass Community and Evaluation of Selected Rehabilitation Practices