Benjamin A. McGraw

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is arguably the most destructive turfgrass insect pest of golf courses and tennis courts in eastern North America, threatening high-value playing surfaces. The ABW was first detected on golf courses in Long Island, New York, in the late 1950s, and has since spread throughout the northeastern United States and eastern Canada. Its accelerated spread over the past 30 yr is likely related to the transport of infested sod, leading to its establishment in the southeastern and midwestern United States. Concomitantly, it has increasingly infested less favorable hosts, such as creeping bentgrass, especially in regions where its preferred host, Poa annua L., is scarce. With few viable alternatives for ABW management, insecticides remain integral to maintaining the aesthetic and functional characteristics of managed turfgrass playing surfaces. Insecticide applications are often made sequentially throughout the season due to the relatively small size of ABW, its cryptic life stages, and the potential for damage to high-value turf. This overreliance on chemical control has fueled widespread resistance to pyrethroids, with some highly resistant populations exhibiting decreased sensitivity to unrelated compounds (i.e., multiple resistance), disrupting ABW control and threatening the long-term sustainability of management programs. Understanding ABW ecology and targeting key vulnerabilities can help design management programs that disrupt its life cycle and minimize turfgrass damage. Here, we review over 50 yr of research on ABW ecology, biology, and management, highlighting key discoveries, persistent and emerging challenges, and potential opportunities for more sustainable control strategies.

The development of pyrethroid resistance within annual bluegrass weevil (ABW), Listronotus maculicollis (Kirby), a severe pest of golf course turfgrass in eastern North America, has created a dire need for alternatives to conventional insecticides. This study assessed the efficacy of novaluron, a recently registered benzoylphenyl urea insect growth regulator which inhibits chitin synthesis in developing larvae, as an alternative to conventional neurotoxic insecticides. Field trial treatments were designed to assess the effect of application timing in relation to population development stages, including peak overwintering adult emergence and early‐instar (stem‐boring) and late‐instar (soil‐dwelling) larvae. Novaluron was effective at all timings, even when larvae were not yet present (overwintering adult peak). In laboratory assays, novaluron topically applied to adults reduced the recovery of first‐instar larvae by 91%–98% and 0%–43% in 2020 and 2021, respectively. Significant ovicidal activity was also observed with reductions of 67%–85% and 35%–68% in 2020 and 2021 trials, respectively. Females treated with 9.3 L ha⁻¹ novaluron experienced reduced fecundity over 8 weeks (52%), though weekly reductions were only significantly different from controls in the first week after exposure. Novaluron‐treated adults resumed oviposition after being transferred to untreated turf, suggesting potential recovery from exposure. These studies demonstrate novaluron's effectiveness against a wide range of larval instars which should facilitate flexible application timing in field settings. However, the transient effects observed on adults in laboratory studies may reduce novaluron's reliability as an adulticide.

The annual bluegrass weevil (Listronotus maculicollis Kirby) is a devastating insect pest of annual bluegrass (Poa annua L.) and, to a lesser extent, creeping bentgrass (Agrostis stolonifera L.) on golf courses. Listronotus maculicollis-reared A. stolonifera, a comparatively tolerant host, incurs fitness costs, including longer developmental periods and reduced larval survivorship. This study sought to characterize microbiota diversity in L. maculicollis adults and larvae reared on P. annua and A. stolonifera cultivars (Penncross & A4) to explore whether intrinsic factors, such as microbial community composition, vary across host plants and developmental stages, potentially influencing host suitability. Alpha diversity analyses showed adults feeding on A4 exhibited higher bacterial species richness than their offspring reared on the same cultivar. Beta diversity analysis revealed significant dissimilarities between L. maculicollis adults and offspring regardless of host. Pseudomonas sp. was consistently abundant in larvae across all turfgrasses, indicating a potential association with larval development. Elevated levels of Wolbachia sp., known for insect reproductive manipulation, were observed in adults, but appear to be unrelated to host plant effects. The most prevalent bacterium detected was Candidatus Nardonella, a conserved endosymbiont essential for cuticular hardening in weevils. Given the role of cuticular integrity in insecticide resistance, further investigations into insect–microbe–plant interactions could guide the development of targeted pest management strategies, reducing resistance and improving control measures for L. maculicollis.

This study investigates the efficacy of surfactants as a means to manage the annual bluegrass weevil, Listronotus maculicollis , particularly in populations demonstrating resistance to pyrethroids. Laboratory assays evaluated L. maculicollis adult mortality when exposed to 13 unique turfgrass surfactant classes alone and in combination with a low rate of bifenthrin. Results from dose–response assays suggest that the alkylpolyglucoside (Alypso), organosilicone (Silwet), anionic blend (Pervade), and the anionic + nonionic blend (Duplex) surfactants were acutely toxic to adults. When combined with low rates of pyrethroid, additive effects were seen with each of these classes plus the block copolymer + alkylpolyglucoside (Dispatch), which was non‐toxic in the absence of pyrethroids. The top four surfactant classes were further examined for their ability to depress cytochrome P450 enzyme activity, an enzyme family suspected to confer resistance within L. maculicollis . Only the block copolymer + alkylpolyglucoside blend showed a notable decrease in P450 activity, suggesting a potential mechanism for overcoming insecticide resistance in populations where enhanced enzymatic activity is responsible for pyrethroid resistance. However, the enzyme activity in the tested population of moderately resistant weevils did not show a significant increase, indicating that resistance to pyrethroids in L. maculicollis involves mechanisms other than enhanced enzymatic detoxification. Further research is needed to elucidate additional mechanisms of resistance as well as confirm the benefits of incorporating surfactants into L. maculicollis management strategies in the field.

Insecticide resistance is a pressing issue in urban pest management. The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is a highly destructive turfgrass pest in northeastern North America. The overuse of pyrethroids has led to resistance in some ABW populations in the northeastern United States. Understanding ABW resistance mechanisms is pivotal for sustaining turf quality and minimizing environmental impact. This study investigated the potential for enzymatic detoxification, a common resistance mechanism in insects, to be the mechanism behind ABW tolerance to pyrethroids. Different ABW populations’ resistance levels to bifenthrin were determined through dose–response Petri dish assays. Cytochrome P450 activity and protein concentrations were measured following bifenthrin exposure. Results indicated golf course‐specific effects on enzyme and protein levels but found no direct correlation between these levels and bifenthrin dosage. P450 activity varied among different golf course populations, showing no dependence on bifenthrin dosage. These findings question prior studies suggesting P450 involvement in bifenthrin detoxification in populations of all resistance levels. This study establishes a foundation for comprehending ABW resistance mechanisms and devising effective management strategies. However, further research is needed to investigate additional detoxification enzymes and other resistance mechanisms.

Field 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.

The annual bluegrass weevil, Listronotus maculicollis Kirby, is considered the most destructive insect pest of short‐mown turfgrasses in northeastern North America. Poa annua L. is the preferred host plant, though the weevil can develop in other cool‐season (C3) turfgrasses such as bentgrasses ( Agrostis spp . L.) and perennial ryegrass ( Lolium perenne L.). Recently, damaging populations have been reported in midwestern and southeastern United States, where cool‐ and warm‐season (C4) turfgrasses are grown. However, it is unknown whether L. maculicollis can establish and develop within common warm‐season turfgrasses such as zoysiagrasses ( Zoysia matrella L.) and hybrid bermudagrasses ( Cynodon dactylon Pers. × transvaalensis Davy). Larvae reared on Agrostis stolonifera ‘Penncross’, an older cultivar, experienced a significant reduction in survivorship and longer development periods compared to a newer cultivar (Penn‐A4) and P. annua . Agrostis stolonifera ‘Penncross’ possessed significantly greater quantities of carotenoids and flavonoid content, which may explain differences in host suitability among C3 turfgrasses. No larvae were recovered from C4 hosts in no‐choice ovipositional assays, suggesting Z. matrella and C. dactylon × transvaalensis are nonviable hosts of L. maculicollis . Further investigation into the morphological and physiological defense mechanisms in Z. matrella and C. dactylon × transvaalensis may broaden our understanding of tolerance mechanisms not observed in C3 cool‐season turfgrasses and provide guidance for future breeding efforts.

The annual bluegrass weevil (Listronotus maculicollis) is the most damaging insect pest of short-mown turfgrass on golf courses in eastern North America. Listronotus maculicollis larvae cause limited visible damage as stem-borers (L1-3), compared to the crown-feeding (L4-5) developmental instars. Prolonged larval feeding results in discoloration and formation of irregular patches of dead turf, exposing soil on high-value playing surfaces (fairways, collars, tee boxes, and putting greens). Annual bluegrass (Poa annua) is highly susceptible to L. maculicollis compared to a tolerant alternate host plant, creeping bentgrass (Agrostis stolonifera). This study explored whether defense signaling phytohormones contribute to A. stolonifera tolerance in response to L. maculicollis. Concentrations (ng/g) of salicylic acid (SA), jasmonic acid (JA), jasmonic-isoleucine (JA-Ile), 12-oxophytodienoic acid (OPDA), and abscisic acid (ABA) were extracted from turfgrass (leaf, stem, and root) tissue samples as mean larval age reached 2nd (L2), 3rd (L3), and 4th (L4) instar. Poa annua infested with L. maculicollis larvae (L2-4) possessed significantly greater SA in above-ground tissues than A. stolonifera. Levels of constitutive JA, JA-Ile, OPDA, and ABA were significantly higher within non-infested A. stolonifera aboveground tissues compared to P. annua. Inducible defense phytohormones may play a role in P. annua susceptibility to L. maculicollis but are unlikely to provide tolerance in A. stolonifera. Additional studies in turfgrass breeding, particularly focusing on cultivar selection for increased constitutive JA content, could provide a non-chemical alternative management strategy for L. maculicollis for turfgrass managers.

The annual bluegrass weevil (ABW), Listronotus maculicollis (Kirby), is a severe pest of golf course turf in eastern North America. The development of pyrethroid- and multiple-resistant populations has created a dire need for novel tactics to control adults. We examined the insecticidal properties of a petroleum-derived spray oil (PDSO; Civitas Turf Defense™.) and an organosilicone, nonionic soil surfactant (Silwet L-77^®) in laboratory and greenhouse bioassays. Civitas and Silwet killed > 75% of ABW adults in multiple assays. The level of control was positively affected by increased rate, spray application volume, and soil moisture levels. Dissections of weevils treated with Civitas revealed material entering the insect’s hemocoel after 15–30 min, though most mortality occurred between the 3 and 24 h observation periods. Reducing rates while increasing carrier volume or soil moisture levels through irrigation applied prior to or after application also provided excellent control of adults in the same observation periods. Silwet provided comparable, yet less consistent levels of control in the laboratory studies but was excluded from further tests after treated plants demonstrated phytotoxicity in greenhouse studies. Neither Silwet nor Civitas efficacy was affected by pyrethroid resistance levels in the ABW populations tested.