Thatch Thickness Research Articles

Investigating the spatial associations between thatch and white grub populations in imidacloprid‐treated turfgrass

AbstractField surveys were conducted on golf courses reporting the inability of imidacloprid to control white grubs (Coleoptera: Scarabaeidae) when applied preventively. Surveys of five sites with significant past imidacloprid use (>10 years) revealed significantly greater white grub populations in rough‐mown turf following imidacloprid treatment than that of adjacent short‐mown fairways. Additionally, spatial analysis by distance indicEs (SADIE) analyses demonstrated a positive correlation between white grub and thatch spatial patterns. To investigate the impact of thatch on imidacloprid efficacy and translocation throughout the turfgrass plant, greenhouse experiments were conducted using turf with differing thatch levels. Imidacloprid concentrations in soil and plant tissues were measured with high‐performance liquid chromatography (HPLC) and compared to values obtained through an enzyme‐linked immunosorbent assay (ELISA) kit to determine if the latter could be a cost‐effective alternative in future studies. ELISA provided reliable estimates of concentrations of imidacloprid compared to HPLC, with only minor discrepancies noted across different types of treatments and assessment timings. Despite finding higher imidacloprid levels in leaf tissues compared to roots and some differences in concentration across thatch treatments, there was no clear pattern showing that thatch thickness significantly affects imidacloprid penetration or accumulation in plant tissues or soil over time. These findings suggest that factors other than thatch thickness may contribute to the observed field failures of imidacloprid in controlling white grubs. Further research is necessary to identify these factors and optimize the use of imidacloprid in turfgrass pest management strategies.

Influence of Turfgrass Parameters on the Abundance of Arthropods in Sod Farms.

Sod farms, where turfgrass is commercially produced, have a unique system, in which sod is harvested within 2 yr after planting. Understanding the turfgrass factors that influence the abundance of predators, herbivores, detritivores, and parasitoids that inhabit turfgrass paves the foundation for developing effective pest management programs. However, little is known about those factors in sod farms. The objective of the study was to determine the influence of turfgrass height, density, and thatch thickness on abundance of arthropod taxa in sod farms. The study was conducted at 18 and 10 sod field sites in 2019 and 2020, respectively. Four pitfall traps were deployed at each site. In 2019, each site was sampled in May, June, and July, whereas in 2020, each site was sampled in June and August. In 2019, the numbers of predatory heteropterans were two times greater in bermudagrass (Cynodon dactylon L.) than in zoysiagrass (Zoysia spp.). The numbers of predatory mirids, Spanogonicus albofasciatus (Reuter), and carabids significantly decreased with increases in turfgrass height. In 2020, the abundance of staphylinids increased as the thatch thickness increased. The abundance of Sphenophorus spp. adults were significantly greater in bermudagrass than in zoysiagrass in 2020 and were more abundant in the denser turfgrasses in both years. The predatory arthropods were positively correlated with increased densities of cicadellids, whereas predatory mirids were positively associated with cicadellids, delphacids, and chrysomelids. These results have implications on management of arthropod pests in sod farms as abundance of beneficial arthropods are influenced by turfgrass factors.

Evaluating biological thatch control on Zoysia matrella (L.) Merr. golf greens

AbstractThatch is a layer of living and dead plant material (stems and roots) between turfgrass leaf tissue and the soil surface. If excessive, thatch can decrease turf playability, increase scalping and disease pressure, reduce pesticide efficacy and water infiltration, and harbor insects. In golf putting greens, disruptive mechanical practices such as vertical mowing, core cultivation, grooming, and topdressing are traditional agronomic methods for managing thatch/organic matter. Non‐disruptive biological thatch reducers have been used as an alternative. Field studies were conducted to evaluate two commercial biostimulant products, a liquid vermicompost extract marketed as Worm Power® Turf and a liquid humate derivative marketed as EarthMAX, and their ability to reduce thatch on a Zoysia matrella (L.) Merr. ‘Diamond’ putting green; rooting depth and weight were also evaluated. EarthMAX® was applied at two rates/frequencies, EarthMAX (1) and EarthMAX (2). In addition, two industry standards were included: blackstrap molasses and sand topdressing. In Year 2, untreated resulted in ≥42% thicker thatch than EarthMAX (2) and blackstrap molasses, no other treatment was statistically different to untreated for both years. All treatments provided lower (≥48%) thatch thickness than the industry standard sand topdressing for both years. No treatment performed differently to the untreated for thatch weight. Blackstrap molasses provided greatest root weight for both years (≥133% and ≥184% than all other treatments); however, it also provided amongst the lowest root length. Inconsistent results make it difficult to recommend biostimulants for thatch reduction. Improvements amongst some treatments over untreated and sand topdressing indicate potential benefits of their use.

Carbon accumulation of cool season sports turfgrass species in distinctive soil layers

AbstractCarbon sequestered by turfgrasses may contribute to reducing atmospheric CO2 levels, to improved soil health, and to increased turfgrass quality. The objective of this study is to compare the amount of soil C accumulated by nine cool season turfgrass monocultures and 12 mixtures of turfgrass species during the first 3 yr of establishment. Thatch, mat, and other soil layers were sampled and thickness of these layers was quantified in a field study conducted in the Netherlands. From these samples, dry matter, C and N concentrations, and C/N ratio were measured. Festuca rubra spp. and Poa pratensis had a thicker thatch layer than Lolium perenne, Festuca arundinacea, Festuca ovina, and Agrostis stolonifera. Lolium perenne had a thicker mat than Festuca rubra spp. Mixtures of turfgrass species and subspecies seemed to vary more in thatch and mat thickness, as well in the total thickness of both layers combined, than did monocultures. Thatch thickness but not mat thickness correlated to C accumulation in the soil, and this accumulation in the top soil till 20‐cm deep was species dependent. The highest amount of C accumulated in Festuca rubra spp. monocultures, whereas the smallest amount was found in soils with Lolium perenne. Thatch of Festuca rubra spp. showed high C accumulation with high C and N concentrations, whereas in Lolium perenne and Poa pratensis monocultures low C accumulation was related to low C and N concentrations. Only for Festuca rubra spp. and Poa pratensis, C/N ratios partly explained variation of C accumulation with soil depth.

Documenting Changes in USGA Specification Rootzone Properties in Ultradwarf Bermudagrass Greens

The United States Golf Association (USGA) Green Section has specifications for putting green construction to provide uniform playability and performance throughout the golfing season. However, it is recognized that chemical and physical rootzone properties of these greens change over time. To monitor and characterize these changes, thatch, organic matter (OM) accumulation, and saturated hydraulic conductivity (Ksat) of two ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] greens on four southern Florida golf courses (i.e., eight greens total) were measured over an 8‐yr period from 2006 through 2013. Over time, thatch thickness stabilized at 2.5 cm or less, whereas the OM stained layer increased in thickness to nearly 10 cm. The OM content fluctuated during the year in response to summer cultivation programs (i.e., verticutting and hollow‐core aerification), but OM content was typically greater in spring than in fall. The Ksat was typically lower in spring and higher in fall, which could be attributed to summer cultivation practices and OM content. Golf course superintendents who routinely monitor thatch, OM, and Ksat on their ultradrawf bermudagrass USGA‐specification sand‐based greens can potentially use that information to illustrate to their stakeholders why summer cultivations are necessary, and what has been achieved from a summer cultivation program.

Association between Blissus insularis Densities and St. Augustinegrass Lawn Parameters in Florida

Core Ideas Cultural control of southern chinch bug in St. Augustinegrass by following recommended guidelines for mowing heights based on turfgrass cultivar, and practicing thatch management may reduce insecticide use and nontarget impacts. Turf parameters (turf height and thatch thickness) were closely associated to southern chinch bug densities observed in St. Augustinegrass residential lawns. Best management practices recommended for growing St. Augustinegrass in Florida may help to maintain a balance between turf health and pest pressure. Turf characteristics in conjunction with environmental factors influence the microclimate suitability for insect pest survival in grasses. In this study, we sought to find the association between southern chinch bug (Blissus insularis) densities, St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] health characteristics (weed abundance, turf density and height, turf color, chlorophyll content, total Kjeldahl nitrogen concentration, and thatch thickness), and abiotic factors (soil pH, soil and air temperature, soil moisture, and light intensity) by sampling residential lawns in Alachua and Marion counties, Florida. A 2‐year study was conducted: approximately 90 St. Augustinegrass lawns were selected for monthly sampling in May and June 2011. This was followed by weekly sampling in 17 selected lawns in July and August 2011 and 13 lawns in June to August 2012, respectively. Results from lawn surveys indicated that light intensity (r = 0.30, P = 0.0034), and thatch thickness (r = 0.22, P = 0.0390) were positively associated with B. insularis densities. The inverse relationship between turf color and B. insularis densities indicated the impact of insect feeding damage. A significant positive association of insect abundance with grass height and thatch thickness identified the need for turf management practices (mowing at recommended cut height and verticutting/thatch removal) to reduce habitat suitability for insect pest survival.

Small Mammal Habitat Preferences in a Patchwork of Adjacent Reconstructed Grasslands Subject to Semiannual Burns

This study used small mammal capture-recapture methods within a mosaic of side-by-side prairie reconstructions to evaluate the relationship between floristic diversity, the effect of prescribed burns, and habitat use. This unique 10.4 ha study of opportunity consisted of multiple plots of three habitat types: low floristic diversity exotic cool-season grasses (CSG), low floristic diversity grass plantings dominated by native warm-season grasses (WSG), and floristically diverse, mixed prairie (MP) plantings with 45 species of forbs. Data for calculating small mammal abundances (new captures/trap effort) were determined by trapping in August following spring burns in 2002 and 2004, and unburned years in 2003 and 2005. Fire-positive species (meadow jumping mice, Peromyscus spp.) preferred fields with a more open understory (MP plantings), and a reduced thatch thickness and leaf litter layer (burned fields). Fire-negative species (meadow voles, northern short-tailed shrews) populated all restorations (CSG, WSG, MP plantings) but only during the unburned years when the fields provided a high density of vegetative cover. Even though the distinct floristic diversity found within the three reconstruction types influenced small mammal foraging preferences, the effect of semiannual burns on floristic structures had a noteworthy impact on their distributions. The results of this study demonstrate an important take home message for restoration practitioners: techniques that promote differences in structural characteristics are just as important as creating plantings with high floristic diversity.

Effects of Surface Conditions on Baseball Playing Surface Pace

Abstract The speed at which a baseball travels after impact with a playing surface has been referred to as playing surface pace. Little information is available regarding the effects of varying construction and maintenance practices on the pace of baseball playing surfaces. Research was conducted to evaluate the effects of construction and maintenance practices on a non-turfed basepath, Kentucky bluegrass (Poa pratensis L.) turf, and six synthetic turf surfaces. Factors evaluated on the non-turfed basepath included soil compaction at installation, surface scarification, and topdressing with a soil conditioner (calcined clay). The effects of cutting height and thatch thickness were evaluated on Kentucky bluegrass, while the effects of simulated traffic and grooming were evaluated on synthetic turf. On the non-turfed basepath, increasing soil compaction yielded increases in surface pace. Calcined clay topdressing and increasing scarification depth did not affect surface pace. On Kentucky bluegrass, varying cutting height and thatch thickness levels had no effect on surface pace. On synthetic turf, increases in simulated traffic resulted in slight increases in pace. Surface pace measurements on synthetic turf were less variable than those made on natural turfgrass. The results indicate that the pace of commonly used baseball playing surfaces is not easily altered with minimally invasive maintenance procedures and should be addressed at construction or during aggressive renovations.

Cool-Season Turfgrass Species and Cultivars: Response to Simulated Traffic in Central Italy

Turfgrass species differ greatly in their ability to withstand the abrasion and compaction of traffic. Wear tolerance of turfgrass species and cultivars has been evaluated abroad by many researchers, while only few and partial studies have been conducted in Italy. Field experiment was carried out in Viterbo in 2001, 2002 and 2003 to evaluate the effect of the simulated traffic on 110 varieties belonging to four turfgrass cool-season species: tall fescue (Festuca arundinacea Schreb.), fine fescues (Festuca rubra L. ssp. rubra Gaud., ssp. commutata Gaud., ssp. tricophylla Gaud.), perennial ryegrass (Lolium perenne L.) and Kentucky bluegrass (Poa pratensis L.). Shoot density, visual turfgrass quality and thatch thickness were the major characters recorded to estimate wear tolerance. Traffic was simulated using a device containing three rollers pulled by a small tractor. The traffic simulator weighed 564 kg and applied a pressure of about 3 MPa. Results indicated that perennial ryegrass and tall fescue had high wear tolerance and low statistical variation among cultivars. Kentucky bluegrass showed an average wear tolerance owing to its shoot density and good recovery potential. In spite of their high shoot density, fine fescues exhibited poor wear tolerance because of their scarce resistance to high temperatures which are typical of the Mediterranean climate in late spring and summer. This study enabled a preliminary selection of the most suitable cool-season grasses and cultivars for trafficked and non-trafficked areas in Central Italy and highlighted that different turfgrass species have different wear tolerance mechanisms.

Control of nest water losses through building behavior in leaf-cutting ants (Acromyrmex heyeri)

Like many ants inhabiting temperate regions, leaf-cutting ant colonies of a number of Acromyrmex species build thatched nests that achieve more stable temperatures than those of the environment. Workers are expected to counteract short-term variations in nest microclimate by modifying the thatch structure, for instance by reducing thatch thickness or by permeating the thatch with openings so as to favor heat exchanges with the outside. Such thermoregulatory responses may compromise the control of nest humidity because of the concomitant water losses resulting from the escape of humid air to the environment. We asked whether water losses through the thatch trigger deposition of nest material as a regulatory response for humidity control. In a laboratory colony of A. heyeri, we defined four equidistant spots on the nest thatch through which losses of air with different humidities were experimentally simulated. The deposition of building material on the spot was recorded as indicative building response. Results showed that material deposition occurred significantly more frequently with higher humidity content of the air leaving the spot. Dry air leaving the nest hardly triggered material deposition. The observation of a continuous turnover of thatch material indicates that the building of a nest thatch is a permanent process, and that short-term responses for the control of nest climate, as the deposition of building material to suppress an outflow of humid air, are guided by specific cues such as the humidity content of the air stream.

Differential Tree Colonization of Old Fields in a Temperate Rain Forest

Abstract Most old fields in the Queets Valley of Olympic National Park, USA, remain dominated by exotic herbs 60 y after abandonment although the fields are surrounded by temperate rain forest. However, areas of some fields have been invaded by Picea sitchensis, one of three dominant forest species (with Alnus rubra and Tsuga heterophylla). This provided an opportunity to examine local variation of factors (competition, facilitation, cervid herbivory, soils) that influence tree colonization within a set of old fields, an approach rare in previous studies. Picea sapling invasion of field edges was negatively correlated with percent cover of Agrostis gigantea and positively correlated with Anthoxanthum odoratum. Potential indicators of competition (sod thickness, thatch thickness, percent ground cover) were correlated with Agrostis cover. Picea edge invasion was also correlated with soil organic matter. In experiments, seedlings of Picea and Tsuga emerged as readily in Agrostis as in Anthoxanthum or Pteridi...

Extractable Soil Phosphorus Concentrations and Creeping Bentgrass Response on Sand Greens

Few studies have directly related turfgrass growth and quality responses to extractable soil P concentrations in sand greens. A 3‐yr field experiment was conducted on a sand‐based putting green to determine creeping bentgrass (Agrostis stolonifera L.) growth and quality responses to extractable soil P. Extractable soil P concentrations were obtained by using the modified‐Morgan, Mehlich‐1, and Bray‐1 extractants. Critical extractable P concentrations (above which there is a low probability of response to increasing soil P concentrations) for shoot counts, thatch thickness, relative clipping yields, quality ratings, P deficiency ratings, tissue P concentrations, and root weights were determined using Cate‐Nelson (CN) and quadratic response and plateau (QRP) models. Both models fit the data relatively well in most cases (R2 values from 0.12 to 0.89), and critical concentrations for the QRP models were always greater than the CN models. Critical extractable P concentrations were lowest for the modified‐Morgan extractant (1.4 to 12.0 mg kg−1) and greatest for the Mehlich‐1 extractant (14.1 to 63.6 mg kg−1). Application of estimated critical extractable P concentrations in this study could be used to substantiate observed responses or explain lack of responses in other previously reported creeping bentgrass P studies. We found better model fits with modified‐Morgan extractable P for bentgrass quality ratings, deficiency ratings, and tissue P concentrations than with P extracted by the Mehlich or Bray methods. This suggests that the modified‐Morgan extractant may have advantages over stronger‐acid extractants when used on sand‐based media. The results can be used to revise or update existing P fertilization recommendations for bentgrass grown on sand‐based media.

Lawn Parameters Influencing Abundance and Distribution of the Hairy Chinch Bug (Hemiptera: Lygaeidae)

Management of lawns that promotes conditions detrimental to the development of insect pests may represent a valuable environmentally benign turfgrass management strategy. In the cool-humid region of Quebec, Canada, we investigated 45 lawns infested with hairy chinch bug, Blissus leucopterus hirtus Montandon, to identify lawn parameters related to its distribution and abundance. Kentucky bluegrass, creeping bentgrass, and perennial ryegrass, respectively, accounted for 55.8, 19.6, and 9.3% of the grass species. Chinch bug population density was associated positively with abundance of perennial ryegrass, whereas it was marginally negatively related with the abundance of creeping bentgrass. An index of the severity of chinch bug infestation was obtained for each lawn by combining estimates of number of infested patches per lawn, average size of the patches, and chinch bug number per patch. The index was associated positively with abundance of Kentucky bluegrass and perennial ryegrass. There was evidence that abundance of creeping bentgrass was associated negatively with the number of infested patches per lawn, area of the patches, and number of chinch bugs within those patches. The number of infested patches increased, whereas patch area and chinch bug number per patch tended to decrease, when broad-leaf weeds were more abundant on a lawn. No significant relationship was found between thatch thickness and patterns of chinch bug abundance and distribution. These results suggest that management of lawns to respectively increase and decrease abundance of creeping bentgrass and perennial ryegrass could facilitate control of hairy chinch bug populations in cool-humid regions.

Dollar Spot Severity as Influenced by Trinexapac‐ethyl, Creeping Bentgrass Cultivar, and Nitrogen Fertility

AbstractDollar spot (Sclerotinia homoeocarpa F.T. Bennett) is a widely distributed and destructive pathogen of turfgrass in the United States. A 2‐yr field study was conducted at Columbus, OH, to determine the influence of a plant growth regulator, creeping bentgrass (Agrostis stolonifera L.) cultivars, and N fertility on dollar spot severity. ‘Crenshaw’ creeping bentgrass was seeded alone or in a 50:50 blend by weight with ‘Penncross’ creeping bentgrass. Plots were fertilized at 0, 24.4, or 48.8 kg N ha−1 per application. One‐half of each plot received trinexapac‐ethyl (TE) [4‐(cyclopropyl‐α‐hydroxymethylene)‐3,5‐dioxo‐cyclohexanecarboxylic acid methyl ester] at 0.8 L ha−1. The TE and fertilizer treatments were initiated in May 1995 and 1996 with four subsequent applications made at 30‐d intervals. Initially, the cultivar blend reduced the rate of dollar spot development compared with Crenshaw alone; however, neither the blend nor Crenshaw provided commercially acceptable dollar spot suppression throughout the study. Both TE and N fertilization significantly (P ≤ 0.05) reduced dollar spot severity over the 2‐yr period. Trinexapacethyl applied alone effectively suppressed dollar spot activity, but efficacy increased with increasing N rates. Dollar spot symptoms decreased and thatch thickness increased at elevated N levels. During this 2‐yr study, interactions between TE and N fertility resulted in a significant (P ≤ 0.05) reduction in dollar spot severity. Thus, on golf course fairways where dollar spot may be severe, incorporation of these two treatments into a turfgrass management program will enhance dollar spot suppression and reduce fungicide inputs.

Control of Japanese Beetle Larvae on Golf Course Fairway, WV, 1995

Abstract Treatments were applied 27 Jul to plots 8 X 8 ft arranged in a RCBD, replicated 4 times. Granular materials were applied with a shaker jar. Liquid treatments were applied in 1 liter of water per plot with a sprinkling can. The plot area was irrigated after the last treatment had been applied with about ¼inch water using the golf course system. Water pH to apply was 6.85; to irrigate, about 8.0. Environmental conditions at start (8:30 am) and finish (9:35 am) of treatment applications were, respectively: air temperature, 23° C and 31.5° C; RH, 84% and 60%; overcast (fog) and clear (calm); soil temperatures (surface) 26° C and 32° C, (1 inch) 25.5° C and 29.5° C; soil moist from regular irrigation; soil type, loam; soil particle analysis, 40.7% sand, 46.6% silt, 12.7% clay; organic matter, 11.7%, pH 5.35; CEC, 23.81 meg/100 g; 1/3 bar, 31.29%. Thatch thickness ranged from 0.24 to 0.38 inches for 28 samples over plot area. Grub population was 100% Japanese beetle (pre- and post-treatment); avg no. grubs at treatment was 34.5/ft2 (59.4% mid to late 1st instar, 40.6% early 2nd instar). Efficacy was evaluated at 53 DAT using a cup changer to extract 4 plugs near the center of each plot to a depth of 2-3 inches and counting live larvae in each sample. The no. larvae for the 4 plugs from each plot was averaged to produce a mean for each replicate for statistical analysis.

Soil and Thatch Microbial Populations in an 80% Sand : 20% Peat Creeping Bentgrass Putting Green

This study examined the numbers of specific soil and thatch microbial populations in a U.S. Golf Association (USGA) specification sand-peat putting green of creeping bentgrass (Agrostis palustris Huds.) over 17 months. Changes caused by adding a water-soluble or bio-organic (water-insoluble, contains microbial inoculum) N source were examined. Thatch was found to contain 40 to 1600 times as many bacteria as the soil, 500 to 600 times as many fungi, and up to 100 times as many actinomycetes. Soil populations of nitrate- and nitrite-reducing anaerobes were similar and ranged from 103 to 105 per gram of dry soil. Adding the bio-organic N source increased soil fungal counts and thatch thickness when compared with the control (no N applied), but not as much as the water-soluble N source. The amendments had no effect on soil respiration, total organic carbon. or total N content.

Association of Thatch with Populations of Hairy Chinch Bug (Hemiptera: Lygaeidae) in Turf

Hairy chinch bug, Blissus leucopterus hirlus Montandon, population density increased in plots where a thick thatch layer was induced by applications of the fungicide mancozeb. However, the rate of chinch bug development was similar in plots treated with mancozeb and in untreated plots. Hairy chinch bugs released into thatched and dethatched plots at the Hancock Turfgrass Research Center of Michigan State University had a short-term habitat preference for thatchy turf. The mean number of hairy chinch bugs per sample 24 h after release was 6.9 in thatched plots compared with 2.1 in dethatched plots. In a survey of 108 randomly selected home lawns in the Lansing, Mich., area, thatch thickness was greater in infested lawns (7.8 mm) compared with uninfested lawns (5.1 mm). In a 12-mo period from August 1986 to August 1987, thatch thickness in survey lawns significantly increased from 6.5 to 10.0 mm in infested lawns but not in uninfested lawns.

Relationship of Hairy Chinch Bug (Hemiptera: Lygaeidae) Presence and Abundance to Parameters of the Turf Environment

Relationships between hairy chinch bug, Blissus leucopterus hirtus Montandon, infestation and parameters of the turfgrass environment were examined in a survey of 108 home lawns in the Lansing area of Michigan. Variables examined were thatch thickness, dry weight of grass clippings, chlorophyll content, and grass species. Chinch bugs and predaceous arthropods were counted with a transect sampling method. Thatch thickness was positively correlated with chinch bug abundance and was the only variable that was significantly correlated with chinch bug abundance in all 3 yr. More fine fescue ( Festuca rubra ) and less Kentucky bluegrass ( Poa pratensis ) were present in infested lawns compared with uninfested lawns. A linear discriminant function with percentage Kentucky bluegrass and thatch thickness variables correctly predicted chinch bug presence in lawns 63-81% of the time.

Kentucky Bluegrass Thatch Characteristics Following Application of Bio-organic Materials

Three bio-organic materials were evaluated at four application rates, based on N contents, for their potential to degrade Kentucky bluegrass (Poa pratensis L.) thatch in a field experiment. Treated thatch was reduced in thickness and had increased earthworm (Lumbricus spp. Hoff.) populations when compared to untreated thatch. Thatch thickness was negatively correlated with level of N (r = –0.91), thatch lignin content (r = –0.94), and earthworm population in the thatch (r = –0.64), and positively correlated with thatch cellulose content (r = 0.62).

White Grub Control, 1988

Abstract The experiment was conducted in a golf course fairway in Apple Valley, Calif. Experimental design was a randomized complete block with 4 replicates. Plot size was 5 by 20 ft2 and granular formulations were shaken manually from a glass jar over the plots. Liquids were applied with a Solo backpack sprayer with a hollow-cone nozzle at 32 psi and a spray rate of 6 gal/1,000 ft2. Immediately after application, treatments were watered in with one-half inch of water. Pretreatment grub density was determined on 25 Apr by cutting 5 1-ft by 1-ft by 3-in. randomly selected sections in the sod in each plot and counting the number of grubs. Insecticide treatments were applied the same date. Posttreatment grub density was determined in the same manner on 25 May. Average thatch thickness was one-half inch; water pH was 7.2. The course was irrigated daily with one-quarter in. as normal.