Application of fertilizer and insecticide can reduce Antonina graminis (Hemiptera: Pseudococcidae) and improve the quality of golf course putting greens.

BACKGROUND: Rhodesgrass mealybug, Antonina graminis, is a serious pest of ultradwarf hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) on golf course putting greens. A. graminis feeding damage appears as extensive yellowing of turfgrass blades and heavy thinning from mid-to-late summer into fall. Putting greens are intensively managed areas of the golf course where fertilizers are routinely applied to maintain and enhance turfgrass quality, playability and aesthetics. We hypothesize that A. graminis populations can be minimized by reducing nitrogen (N) fertilizer and then effectively managed using systemic insecticides. The objective of this study was to determine the effects of various levels of N fertilizer and flupyradifurone on the A. graminis population and turfgrass quality on the golf course putting green. The treatments were low, medium, and high N fertilizer rates with and without insecticide (flupyradifurone). RESULTS: Applying a high dose of N fertilizer improved turfgrass quality without increasing A. graminis densities on the golf course green. Although flupyradifurone application reduced A. graminis densities regardless of N fertilizer treatments, suppression of A. graminis densities improved at the high fertilizer dose with flupyradifurone. Additionally, the turfgrass quality on the putting green improved with high N fertilizer alone, regardless of flupyradifurone application. CONCLUSION: A. graminis populations can be managed using moderate to high levels of N fertilizer and applying a systemic insecticide. The low nitrogen fertilizer did not effectively reduce the A. graminis densities on the putting green. © 2024 Society of Chemical Industry.

Phenology and sampling crawlers of rhodesgrass mealybug (Hemiptera: Pseudococcidae) in Georgia golf course putting greens.

Rhodesgrass mealybug, Antonina graminis Maskell (Hemiptera: Pseudococcidae), is an emerging pest of turfgrass in Georgia golf course putting greens. Because the feeding damage of A. graminis severely affects the aesthetics of the putting surface, it is necessary to understand the phenology of A. graminis on putting greens. To develop management strategies, the temporal emergence of crawlers is determined; however, a sampling tool for A. graminis crawlers on putting greens has not been developed. Thus, the objectives were to determine (i) the phenology of A. graminis and turfgrass quality and (ii) the best trap types for sampling crawlers on the putting greens in Georgia. From 2019 to 2022, 10-20 turfgrass plugs were sampled from the putting greens at biweekly intervals from the spring to fall. The numbers of crawlers, sessile nymphs, and adults of A. graminis were quantified from these plug samples. To determine the best trap types for sampling crawlers, 6 trap types were evaluated on the putting greens in 2021 and 2022. In the spring, the A. graminis densities remained low until June or July, then all stages of A. graminis increased. In the late fall and winter, A. graminis densities declined and remained low. The turfgrass quality improved temporally from April to June but progressively declined from the mid-to-late summer to fall. Significantly greater numbers of crawlers were sampled in the paper-folded sticky card method than in the turfgrass plug method. Thus, sticky traps could be used to sample crawlers for pest management decision.

Exploring risk factors for insect borer attack in Georgia's (USA) urban landscapes.

Urban trees are at risk of stress due to heat island effects and the increased proportion of impervious areas surrounding them. Among pests of trees, insect borers such as bark beetles (Coleoptera: Curculionidae) and flatheaded borers (Coleoptera: Buprestidae) are some of the most devastating, frequently colonizing stressed trees. The objective of this study was to explore the effects of biotic and abiotic risk factors on borer attacks on trees in urban areas. In the summer of 2021 and 2022, this study was conducted in 50 urban sites in Atlanta and Augusta, Georgia (USA). Specific factors explored include overall tree health, differentially warmer maximum and minimum temperatures of sites compared to surrounding areas, tree species, and the percentage of impervious surface surrounding trees. Generalized linear models and zero-inflated models explored how these factors were related to damage from these borers. The number of borer attacks on trees increased with higher percentage impervious area. As the two most commonly encountered trees, Acer rubrum was found to be significantly more susceptible to attack from borers than Ulmus parvifolia. Unhealthy trees were more likely to experience more frequent and more severe borer attack. Trees with increased impervious cover around them as well as those with differentially warmer daily maximum and minimum temperatures relative to surrounding were more likely to be attacked.

Residual activity of insecticides against adult Systena frontalis (Coleoptera: Chrysomelidae) under semi-field conditions.

Systena frontalis (Fabricius) (Coleoptera: Chrysomelidae) is a serious insect pest in nursery production. Insecticides are an important control tactic for S. frontalis adults to reduce economic losses associated with its injury. Because densities and activity of S. frontalis adults are influenced by many biotic (e.g., adult emergence timing) and abiotic (e.g., fluctuating temperatures) factors in the nurseries, it is challenging to reliably determine the efficacy and residual activity of insecticides under field conditions. Thus, the objective was to determine the residual activity of common and alternative insecticides on adult S. frontalis under semi-field conditions. Field-collected S. frontalis adults were exposed to 0-, 7-, 14-, and 21-d-old, field-aged residue of 13 insecticides applied on panicled hydrangea (Hydrangea paniculata Siebold) shoots and maintained in the field. The fresh residues of tetraniliprole, cyclaniliprole, and sulfoxaflor + spinetoram were the most effective against S. frontalis adults, whereas only tetraniliprole and cyclaniliprole elicited evidence of efficacy when their residues were aged for a week. Fourteen- and 21-d-old residues of tetraniliprole were still effective on S. frontalis adults and reduced the injury. Based on the results, tetraniliprole, cyclaniliprole, and sulfoxaflor + spinetoram were effective for immediate management, cyclaniliprole can provide short-term efficacy, and tetraniliprole provides longer-term efficacy.

Growing media is the major source of damaging population of Systena frontalis (Coleoptera: Chrysomelidae) in ornamental plant nurseries.

Systena frontalis (F.) (Coleoptera: Chrysomelidae) is a serious pest of ornamental shrubs in containerized ornamental plant nurseries in the central and eastern United States. Adult S. frontalis cause numerous shot holes on foliage, rendering ornamental plants unmarketable. Growing media in plant containers is an overwintering site of S. frontalis, but the extent to which adults emerging from the growing media can damage the plants is unclear. Experiments were conducted on panicled hydrangea (Hydrangea paniculata Siebold) in Georgia, North Carolina, and Virginia nurseries in the spring of 2021 and 2022 to answer this question. The treatments were (i) canopy caged, (ii) whole-plant caged, and (iii) noncaged hydrangea plants. In all 3 states, beetle abundance and feeding damage found on caged (whole plant) and noncaged plants were significantly greater than those on plants where only the canopy was caged. In most sites and years, beetle abundance and feeding damage were not significantly different between the noncaged plants and those where the canopy and containers were caged, suggesting that the majority of S. frontalis emerged from the growing media and the majority of damage suffered by the hydrangea plants were caused by beetles emerging from the containers. Because growing media contributed to a significant proportion of the S. frontalis population in a nursery, treatment targeting larvae in the growing media should be a critical component of a holistic management plan against S. frontalis.

Effects of permethrin on ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in ornamental nurseries.

Exotic ambrosia beetles (Coleoptera: Curculionidae: Scolytinae), such as Xylosandrus crassiusculus (Motschulsky), Xylosandrus germanus (Blandford), and Xylosandrus compactus (Eichoff) are serious pests in southeastern ornamental nurseries. Preventative pyrethroid trunk sprays effectively reduce boring damage. However, it is unclear how pyrethroids such as permethrin prevent attack. Thus, the objective was to determine how permethrin-treated bolts interact with invading ambrosia beetles. In 2022, a study with 2 independent trials was conducted in a nursery on red maple (Acer rubrum L.), bolts during March and April, respectively. The treatments were (i) nonbaited, nontreated bolt, (ii) ethanol baited bolt, (iii) nonbaited bolt + glue [painted on bolt], (iv) ethanol baited bolt + glue, (v) ethanol baited bolt + glue + permethrin, (vi) ethanol baited bolt + glue + permethrin + verbenone, and (vii) ethanol baited bolt + glue + verbenone. Ambrosia beetles trapped on glue, beetles which fell into the pail with soap solution under the bolts, and entry holes on bolts were quantified. Permethrin prevented beetle attacks but did not reduce the number of ambrosia beetles landing on the treated bolts. Verbenone reduced ambrosia beetles from landing on the bolts but did not prevent boring into bolts. The numbers of ambrosia beetles in soapy water were not significantly different among treatments. Ambrosia beetles are landing on permethrin-treated bolts but not boring into the bolts, implying that fresh permethrin residues may not be necessary for ambrosia beetle management.

Relative Susceptibility of Brassicas to Cabbage Maggot (Diptera: Anthomyiidae) Infestation.

Cabbage maggot, Delia radicum (L.) (Diptera: Anthomyiidae) is a serious pest of Brassica such as broccoli (Brassica oleracea var. italica Plenck) and cauliflower (B. oleracea L. var. botrytis) in California's Central Coast. Since there are limited non-chemical options available for growers to manage D. radicum, there is an urgent need to develop alternative tactics. The objective of this study was to determine the effects of side-by-side plantings of turnip (Brassica rapa var. rapa L.), lettuce (Lactuca sativa L.), cauliflower, and cabbage (B. oleracea L. var. capitata) with broccoli on D. radicum infestation. In 2013 and 2014, the experiments were conducted in Salinas, California. Significantly greater numbers of eggs and larval feeding damage were found on turnip compared with broccoli. Lettuce (Asteraceae), a non-Brassica crop, was compared with broccoli; however, lettuce did not reduce oviposition or larval feeding damage on broccoli. The larval feeding damage on cauliflower was significantly lower than on broccoli when planted side-by-side. The effects on cabbage were not significantly different from broccoli in terms of oviposition and larval feeding damage. This new information generated from the Central Coast of California will be further utilized to develop a trap crop to effectively tackle the D. radicum problem in Brassica fields.

Vertical Distribution of Arthropod Interactions Within Turfgrass.

Arthropod predators are abundant in turfgrass systems, and they play an important role in managing pests. Understanding the vertical distribution of predation is critical to developing cultural strategies that enhance and conserve predatory services. However, little is known on how the predation is vertically distributed within the turfgrass canopy. Thus, the objective of this study was to determine the vertical distribution of predation within the turfgrass canopy. Clay models were used to emulate the general appearance of Noctuidae caterpillars, to estimate the predatory activity. The choice and no-choice experiments were conducted by placing clay models at 2.54, 5.08, and 7.62 cm from the thatch surface and denoted as lower, intermediate, and upper levels, respectively, within turfgrass canopy. The predator-mediated impressions, paired mark, scratch, deep cut mark, deep distortion, prick, dent, stacked surface impression, scooped mark, granulation, and U-shaped mark, were identified on clay models. The incidence and severity of impressions were significantly greater on clay models placed at the lower canopy level than on those placed at the intermediate and upper canopy levels in the choice and no-choice experiments (P < 0.05). Thus, predators are more likely to find their prey at the soil level. This information can be used to refine management strategies, such as mowing height and insecticide use for effectively managing soil-borne and foliar-feeding arthropod pests and beneficial arthropods.

Evaluating invasion risk and population dynamics of the brown marmorated stink bug across the contiguous United States.

BACKGROUND: Invasive species threaten the productivity and stability of natural and managed ecosystems. Predicting the spread of invaders, which can aid in early mitigation efforts, is a major challenge, especially in the face of climate change. While ecological niche models are effective tools to assess habitat suitability for invaders, such models have rarely been created for invasive pest species with rapidly expanding ranges. Here, we leveraged a national monitoring effort from 543 sites over 3 years to assess factors mediating the occurrence and abundance of brown marmorated stink bug (BMSB, Halyomorpha halys), an invasive insect pest that has readily established throughout much of the United States. RESULTS: We used maximum entropy models to estimate the suitable habitat of BMSB under several climate scenarios, and generalized boosted models to assess environmental factors that regulated BMSB abundance. Our models captured BMSB distribution and abundance with high accuracy, and predicted a 70% increase in suitable habitat under future climate scenarios. However, environmental factors that mediated the geographical distribution of BMSB were different from those driving abundance. While BMSB occurrence was most affected by winter precipitation and proximity to populated areas, BMSB abundance was influenced most strongly by evapotranspiration and solar photoperiod. CONCLUSION: Our results suggest that linking models of establishment (occurrence) and population dynamics (abundance) offers a more effective way to forecast the spread and impact of BMSB and other invasive species than simply occurrence-based models, allowing for targeted mitigation efforts. Implications of distribution shifts under climate change are discussed. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ambrosia Beetle Occurrence and Phenology of Xylosandrus spp. (Coleoptera: Curculionidae: Scolytinae) in Ornamental Nurseries, Tree Fruit, and Pecan Orchards in Georgia.

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae, Platypodinae) in the genus Xylosandrus are problematic in ornamental nurseries and are emerging as serious pests in orchard crops. An updated survey of ambrosia beetles focusing on these damaging species, and their corresponding phenology was conducted in Georgia to aid in refining management practices for these beetles. Ambrosia beetles were monitored across nine sites in 2019 and seven sites 2020 at ornamental nurseries, tree fruit, and pecan orchards in Georgia. At each site, six ethanol-baited bottle traps were deployed; with three traps along the edge of a wood-line and three traps placed 30 m from the edge of the nurseries and orchards. Traps were deployed from mid-January through July or August depending on site and year. All captured ambrosia beetles were counted and identified. Captures of X. crassiusculus, X. germanus, and X. compactus, were analyzed further to investigate spatial distribution and seasonal flight activity. At high population sites, more beetles were captured along adjacent wood lines than in the orchard or nursery interior. At most sites, flight activity began in February and March continued until the termination of the study in July or August. At most sites, sustained flight activities with multiple peaks were observed in March, April, and May, corresponding to average weekly temperatures reaching ≥15.5°C. These results have important implications on temporally and spatially precise management for these beetles across three important agricultural production systems in the southeastern US.

Temporal Incidence of Eriophyid Mites on Rose Rosette Disease-Symptomatic and -Asymptomatic Roses in Central Georgia, USA.

Phyllocoptes fructiphilus Keifer (Acari: Eriophyidae) is the vector of rose rosette virus (RRV), which causes rose rosette disease (RRD) in North America. The RRD symptoms, such as witches' broom, flower, and leaf deformation, disrupt the aesthetic appearance of plants and cause plant mortality. Because there is no cure for RRV, it is critical to manage the vector and reduce the spread of the virus. The information on the phenology of P. fructiphilus on rose plants is essential to develop management strategies and reduce its spread. Thus, the objectives of the study were to determine 1) the phenology of eriophyid mites (including P. fructiphilus) in central Georgia due to its widespread occurrence in the state and 2) the incidence of eriophyid mites on closed and opened flower buds and other plant parts. In central Georgia, eriophyid mites, including P. fructiphilus were active on both symptomatic and asymptomatic plants from April to December. The mite densities were greater during July and August than during the remaining months on asymptomatic plants. The mites were more abundant on the RRD-symptomatic than on the asymptomatic plants. Similar numbers of eriophyid mites were observed on closed and opened flower buds. Eriophyid mite densities were greater on sepals and leaf bases than on other plant parts.

Insect growth regulators elicit transovarial effects on Teleonemia scrupulosa (Hemiptera: Tingidae).

BACKGROUND: Lantana lace bug, Teleonemia scrupulosa Stål (Hemiptera: Tingidae), is an important insect pest of lantana (Lantana camara L.). The adults and nymphs feed on the leaves, gradually deteriorating the quality of leaf tissue, as the affected leaves appear brown and desiccated. Infestations of T. scrupulosa reduce the market value of container plants in nurseries and the aesthetic value of ornamental landscapes. Because T. scrupulosa typically is managed using neonicotinoids and concerns related to the nontargeted effects of neonicotinoids on pollinators are mounting, practitioners are seeking alternative options to manage T. scrupulosa infestations. Insect growth regulators (IGRs) elicit transovarial activity, where adults exposed to IGRs produce nonviable eggs, but this effect has not been documented for T. scrupulosa. RESULTS: A significantly lower number of T. scrupulosa nymphs was produced when adults were sprayed topically with novaluron and pyriproxyfen than nontreated adults. The number of T. scrupulosa nymphs produced was not significantly different when adults were exposed to a lower dose (0.125×) and a maximum dose (1.0×) of novaluron. CONCLUSION: Novaluron and pyriproxyfen elicited transovarial effects on T. scrupulosa when adults were exposed to these IGRs. Evidence of transovarial effects was demonstrated when T. scrupulosa adults were exposed to lower doses (≤0.125×) than the maximum label dose, as densities of nymphs were similar between the lower doses and the maximum label dose of novaluron.

Influence of Abiotic Factors on Walking Behavior of Hunting Billbugs (Coleoptera: Curculionidae).

The hunting billbug, Sphenophorus venatus vestitus Chittenden, is an important insect pest of warm-season turfgrass. Larvae and adult S. venatus vestitus feed on turfgrass and affect normal grass growth and development. In sod farms and golf courses, management sprays are typically confined to affected areas because of the high insecticide and application costs. Understanding the walking behavior of S. venatus vestitus adults would help us to refine management tactics. Thus, the objective of this study was to determine the influence of abiotic factors on the walking behavior of adult S. venatus vestitus. A series of laboratory, semifield, and field assays were conducted in 2019 and 2020. For the laboratory assays, field-collected S. venatus vestitus adults were acclimated at 15, 18, 21, 28, and 32°C for 24 h, and the distances walked by these pre-acclimated adults were measured on sand and filter paper substrates using Noldus EthoVision XT software. For the semifield assays, the total and net distances walked by pre-acclimated adults were measured on a paved indoor surface. Sphenophorus venatus vestitus males and females moved farther when the temperature increased from 15 to 28°C in the laboratory and semifield assays. For the field assays, field-collected S. venatus vestitus adults were not acclimated. The total and net distances walked by the adults were documented on a paved surface. Increases in temperature and relative humidity did not affect the distance moved by adults, but an increase in wind speed reduced the distance moved.

Sub-Lethal Effects of Bifenthrin and Imidacloprid on Megacephala carolina carolina L. (Coleoptera: Carabidae) in Turfgrass.

The tiger beetle, Megacephala carolina carolina L. (Coleoptera: Carabidae), is a common predator in turfgrass and ornamental landscapes in Georgia, USA. Among insecticides used in turfgrass to control foliar and root-feeding insect pests, bifenthrin and imidacloprid are routinely used. It was unclear whether sub-lethal doses of bifenthrin and imidacloprid could cause nontarget effects on larvae and M. carolina carolina adults. Thus, the objective was to determine the sub-lethal effects of bifenthrin and imidacloprid on larvae and M. carolina carolina adults. The results show that M. carolina carolina larvae actively hunt for passing prey by waiting at the hole of the tunnel during the day and nighttime. This larval behavior was affected by sub-lethal doses (up to 25% of full label rate) of bifenthrin but not of imidacloprid. The walking behavior of adult M. carolina carolina was also altered when exposed to sub-lethal doses of bifenthrin as they traveled further distances at greater velocities than the nontreated control. The results imply that turfgrass managers should avoid treating lawns where tiger beetles have actively colonized.

Influence of the Color, Shape, and Size of the Clay Model on Arthropod Interactions in Turfgrass.

Many predatory arthropods occur naturally in turfgrass, and they provide adequate control of lepidopteran pests, such as fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), and black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae). Recording predation is challenging under field conditions because predators rarely leave any evidence. Clay models were successfully employed for studying predation, and this technique is underutilized in turfgrass. Little is known about whether the characteristics of clay models, such as color, shape, and size, influence arthropod interactions in turfgrass. To improve the utility of clay models in turfgrass, the influence of the color, shape, and size of clay models on arthropod interactions was studied by exposing clay models during daytime and nighttime in a turfgrass field. The results showed that arthropods interacted with clay models, and various types of impressions were recorded, including paired marks, scratches, cuts, and pricks. Although the color of the clay model had no significant effects on arthropod interactions during the night, significantly greater numbers of impressions were noticed on the blue and green models than on the yellow models during the daytime. The caterpillar-shaped models captured significantly greater densities of impressions than the beetle-shaped models. Additionally, the number of impressions significantly increased with an increase in the size of the model regardless of shape.

Could Broccoli and Cauliflower Influence the Dispersal Dynamics of Western Flower Thrips (Thysanoptera: Thripidae) to Lettuce in the Salinas Valley of California?

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an important, worldwide vector of two tospoviruses (Family Bunyaviridae; Genus Tospovirus), Impatiens necrotic spot virus (INSV) and Tomato spotted wilt virus (TSWV). In the Salinas Valley of California, INSV causes severe necrosis, stunting, and crop losses to lettuce (Lactuca sativa L.). Because broccoli (Brassica oleracea var. italica L.) and cauliflower (Brassica oleracea var. botrytis L.) are major rotation crops with lettuce in the Salinas Valley, it is critical to understand if these Brassicas influence the dispersal dynamics of F. occidentalis. In 2013 and 2014, surveys were conducted evaluating yellow sticky cards and plant samples in lettuce, broccoli, and cauliflower fields in three regions of the Salinas Valley. F. occidentalis were collected on sticky cards from April to November and on foliage in all three regions. Two-choice oviposition assays as well as no-choice and two-choice feeding assays were conducted where F. occidentalis adults were exposed to leaves of lettuce, broccoli, and cauliflower. A significantly greater number of eggs was found on lettuce than on broccoli or cauliflower leaves in the choice assay, whereas for the broccoli and cauliflower choice assay, the number of eggs retrieved was low and not significantly different between hosts. The number of F. occidentalis feeding spots and leaf area injury ratings were similar on broccoli and lettuce leaves but were significantly lower on cauliflower than on lettuce and broccoli leaves. The implications of these results on thrips and plant virus management are discussed.

Effects of Trap, and Ethanol Lure Type and Age on Attraction of Ambrosia Beetles (Coleoptera: Curculionidae).

Ambrosia beetles (Xylosandrus spp.) are pests of woody ornamental nurseries and tree nut orchards. Growers use ethanol-infused bolts and ethanol-mediated bottle traps for monitoring ambrosia beetles in the spring. To refine these monitoring tools, we investigated the 1) sensitivity of the commercially available ethanol pouches placed on bolts compared with that of ethanol-infused bolts for ambrosia beetle attacks; and 2) the effect of aging of ethanol pouches on ambrosia beetle captures in bottle traps. Experiments were conducted in ornamental nurseries and pecan orchards in 2019 and 2020. For objective 1, the treatments included a bolt infused with locally purchased ethanol, an ethanol pouch attached to a bolt, and a control (bolt without ethanol). For objective 2, ethanol pouches were initially field-aged for 0, 1, 2, 3, and 4 wk and ambrosia beetle captures were documented weekly for 4 wk. Ethanol pouches older than 5 wk were replaced with fresh pouches at the pecan sites while ethanol pouches at nursery sites were aged up to 8 wk. The ethanol-pouch comparison study showed that the number of ambrosia beetle attacks was significantly greater on ethanol-infused bolt traps than with the ethanol pouches on bolts at the nursery and pecan sites in both years. The age of the ethanol pouches did not affect captures of Xylosandrus crassiusculus (Motschulsky) and X. germanus (Blandford) in bottle traps within 8 wk of deployment. Results provide practical implications into the sensitivity of the different ethanol lure types in association with bolt traps and the longevity of the ethanol pouches for grower use.

Spatial Distribution of Hunting Billbugs (Coleoptera: Curculionidae) in Sod Farms.

The hunting billbug, Sphenophorus venatus vestitus Chittenden (Coleoptera: Curculionidae), is an important turfgrass pest, especially in sod farms. S. venatus vestitus larvae feed on the stems and roots of turfgrass. Damaged turfgrass is loosely held together and poses a challenge for machine harvesting. Additionally, the normal growth of turfgrass is affected, especially after winter dormancy. Because S. venatus vestitus larvae are hidden inside the stems or under the soil, larval management is challenging. To improve sampling and management, the spatial distribution patterns of S. venatus vestitus larvae and adults were assessed at four sod farm sites with a history of S. venatus vestitus infestation in central Georgia (USA). The larvae were sampled by soil cores using a hole cutter, whereas adults were collected using pitfall traps for 7 d. The spatial distributions of larvae and adults was analyzed using SADIE and variograms. The SADIE and variogram analyses revealed a significant aggregation pattern for adults, whereas aggregated distributions were detected for larvae with variogram analyses. The average ranges of spatial dependence for larval and adult samples were 3.9 m and 5.4 m, respectively. Interpolated distribution maps were created to visually depict S. venatus vestitus infestation hotspots within the sod farms.

Surface Movement of Billbugs (Coleoptera: Curculionidae) in Harvested and Nonharvested Sod.

The billbug complex, Sphenophorus spp. (Coleoptera: Curculionidae), is an important pest on the sod farms of Georgia. The feeding damage of larvae within stolons and on roots delays the sod harvest and makes it difficult to conduct machine harvests. To develop an effective management strategy, the timing of insecticide applications is critical. The activity of billbugs, especially soon after sod harvest, has not been documented, as newly emerging adults could reinfest the harvested area or adjacent nonharvested sod fields. In 2019 and 2020, adult billbugs were sampled from harvested and nonharvested areas of sod farms by using linear pitfall traps. Although a significantly greater number of billbug adults were captured from the nonharvested sod, the data showed that adults were present in the harvested sod area. To understand the direction of billbug movement in harvested and nonharvested sod, a square area was selected, and the sod inside the square was removed. Linear pitfall traps were deployed along the perimeter of square areas to collect adults from outside and inside the square. In 2020, a significantly greater number of billbug adults were collected in the traps from the nonharvested areas outside the square than from harvested area inside the square, whereas in 2019, adult captures were similar from both areas. The data documented the activity of billbugs in the areas where sod was harvested, posing a risk of infestation for both strips of nonharvested grass in the harvested area and the adjacent, nonharvested sod fields that were near harvest.

Seasonal Occurrence and Abundance of Billbugs (Coleoptera: Curculionidae) in Georgia Sod Farms.

The billbug, Sphenophorus spp. (Coleoptera: Curculionidae), is an important pest complex in sod farms in Georgia. Larval feeding within stolons and on roots affects spring recovery of slow-growing zoysiagrass and poses a serious challenge to machine harvesting, as the damaged turfgrass rarely holds together. Little is known about major billbug species and their seasonal occurrence and abundance in Georgia sod farms, as most previous research was conducted in golf courses in the region. In 2018 and 2019, adult billbugs were sampled from five zoysiagrass sod field sites in central Georgia. Four linear pitfall traps were used per site from February to December each year, and the traps were checked at weekly intervals. The data show that >98% of the sampled billbugs were the hunting billbug, Sphenophorus venatus vestitus Chittenden, whereas the nutgrass billbug, Sphenophorus cariosus Olivier; uneven billbug, Sphenophorus inaequalis Say; and vegetable weevil, Listroderes difficilis Germain were the minor species. Seasonal billbug capture was influenced by turfgrass phenology (e.g., early-growth-stage, late-growth-stage or fully grown turfgrass). The numbers of Sphenophorus spp. collected were significantly greater in the fully grown turfgrass than in the early- or late-growth-stage turfgrasses. Significantly greater densities of billbug were found in Zoysia matrella (L.) Merrill ('Zeon') and the Z. matrella × Zoysia pacifica (Goudswaard) M. Hotta & S. Kuroki hybrid ('Emerald') than in the Zoysia japonica (Steudel) cultivars 'El Toro' and 'Zenith'. Similar numbers of male and female billbugs were collected from the sod field sites.