Biology, ecology, and management of the annual bluegrass weevil (Coleoptera: Curculionidae) in turfgrass

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is an economically important pest of short-cut turfgrass in Eastern North America. Wide spread insecticide resistance warrants the development of alternative management strategies for this pest. ABW damage typically occurs in areas with a high percentage of annual bluegrass, Poa annua L., the preferred ABW host. Damage to bentgrasses, Agrostis spp., is much rarer and usually less severe. To aid the implementation of host plant resistance as an alternative ABW management strategy we investigated the tolerance of three bentgrass species to ABW feeding. Responses of P. annua, creeping bentgrass, Agrostis stolonifera L., colonial bentgrass, Agrostis capillaris L., and velvet bentgrass, Agrostis canina L., to adult and larval feeding were compared in greenhouse experiments. Grass responses were measured as visual damage, dry weight of the grass stems and leaves, color, density and overall grass quality. To determine possible mechanisms of grass tolerance constitutive fiber and silicon content were also determined. The three bentgrass species tolerated 2-3 times higher numbers of ABW adults and larvae than P. annua before displaying any significant quality decrease. Creeping bentgrass had the lowest damage ratings. ABW infestation caused higher plant yield reduction in P. annua (up to 42%) than in bentgrasses. Observed differences among the grass species in fiber and silicon content in the plant tissue are unlikely to play a role in the resistance of bentgrasses to ABW. Our findings clearly show that A. stolonifera is the best grass species for the implementation of host plant resistance in ABW management.

For insects that develop on few hosts and/or have immobile immature stages, optimal oviposition theory suggests that females should seek high-quality hosts that maximize larval development and reduce competition from conspecifics. However, there is a growing amount of evidence that suggests female choice may often be at odds with their offspring's development. Listronotus maculicollis (Kirby) (Coleoptera: Curculionidae) is a serious pest of golf course turfgrass in eastern North America. The weevil develops on few hosts and demonstrates improved fitness traits when developing on Poa annua L. (Poaceae). However, previous population studies observed either weak or no correlations between the spatial dispersion of larval populations and P. annua in the field. In this study, populations on three golf course fairways were monitored over a 4-year period (2009–2012) to determine whether the lack of spatial associations between preferred hosts and immatures was a result of spatial scale or the density and distribution of conspecifics. Spatial Analysis by Distance IndicEs (SADIE) was used to characterize the spatial dispersion of populations of individual stages (larvae and pupae), P. annua, and turfgrass damage. Life stages were aggregated in each observation, independent of population density or the spatial dispersion of hosts. The distribution of consecutive and non-consecutive immature stages was found to be correlated in all years, suggesting that females do not avoid patches already occupied by conspecific eggs. Surprisingly, significant spatial associations were not found between larvae and P. annua when the host plant was relatively abundant. Hence, multiple mechanisms may drive L. maculicollis oviposition site-selection behavior, and a flexible strategy may allow the weevil to persist in areas where P. annua is not the dominant species. Future studies are required to determine what other factors (e.g., natural enemy-free space, egg or time limitations) influence oviposition behavior.

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby (Coleoptera: Curculionidae), is a serious and expanding pest of short‐cut turfgrass on golf courses in eastern North America. Increasing problems with the development of insecticide resistance in this pest highlights the need for more sustainable management approaches. Plant resistance is one of the most promising alternative strategies. Bentgrasses are the dominant grass species on golf course fairways, tees, and putting greens in the areas affected by ABW. But Poa annua L. (Poaceae), a highly invasive weed, often constitutes a large percentage of turf stands in short‐mown golf courses and is thought to be particularly susceptible to ABW. We studied resistance to ABW in four cultivars of creeping bentgrass, Agrostis stolonifera L., and two cultivars each of colonial bentgrass, Agrostis capillaris L., and velvet bentgrass, Agrostis canina L. (Poaceae), in comparison with P. annua by addressing the three major components of resistance: antixenosis (adult ovipositional and feeding preferences), antibiosis (larval survival and growth), and grass tolerance (grass damage). Our findings suggest that antixenosis/non‐preference is at least partially involved in bentgrass resistance to ABW. Even though oviposition was observed in all tested grasses, females laid significantly fewer eggs in Agrostis spp. than in P. annua. Compared to P. annua, Agrostis spp. were also less suitable for larval development with lower numbers of ABW immatures recovered and larvae weighing less and being less advanced in development. Resistance levels to ABW larvae varied significantly among Agrostis spp. and cultivars. Agrostis canina was least preferred by females for oviposition and A. stolonifera was the least suitable for larval survival and development. Agrostis spp., especially A. stolonifera, were more tolerant to ABW feeding than P. annua. Our findings suggest that reduction in P. annua and replacement with Agrostis spp., especially A. stolonifera, wherever feasible should be integral to more sustainable approaches to ABW management.

The annual bluegrass weevil, Listronotus maculicollis Kirby (Coleoptera: Curculionidae), has emerged as a serious pest of Poa annua L. (Poales: Poaceae) (annual bluegrass), in the Northeastern US. In 2007, topical application bioassays of bifenthrin and λ-cyhalothrin conducted on field-collected populations of L. maculicollis Kirby from eight southern New England golf courses resulted in LD50 ranges of 1.80-244.67 ng/insect and 0.52-159.53 ng/insect for bifenthrin and λ-cyhalothrin respectively. These results revealed low to high levels of resistance to bifenthrin (6.1-135.9 fold) and λ-cyhalothrin (28.7-306.8 fold), possibly due to insecticide overuse. In 2008, topical application bioassays with bifenthrin and bifenthrin plus synergists affecting three detoxification systems were conducted on four field-collected adult populations of L. maculicollis to determine if resistance was metabolically mediated. In the population with the lowest resistance only detoxification by cytochrome P450 monooxgenases (P450s) was significant. Detoxification in the population with the second highest level of resistance involved both P450s and glutathione S-transferases (GSTs), and detoxification in the population with the highest level of resistance involved P450s, GSTs and carboxyl-esterases (COEs). Since P450s are inhibited by demethylation inhibitor fungicides (DMI-Fs) and gibberellin inhibitor plant growth regulators (GI-PGRs), both of which are commonly used on golf courses, we tested these compounds using topical application bioassays and simulated field trials for synergistic activity with bifenthin against a pyrethroid resistant population of L. maculicollis . The LD50 for bifenthrin (120 ng/insect) was significantly higher than the LD50s for bifenthrin plus the fungicides fenarimol, fenpropimorph, prochloraz, propiconazole, pyrifenox and plus the plant growth regulators, flurprimidol, paclobutrazol and trinexapac-ethyl (range of 8-36 ng/insect). The means of mortality for Talstar® (bifenthrin) in combination with each of the following, BannerMAXX® (propiconizole), Rubigan® (fenarimol), Cutless® (flurprimidol) and PrimoMAXX® (trinexapac-ethyl) ranged from 9.8 to 14 and were significantly higher than an untreated control (0.3) and Talstar ® (5.0) alone. We also studied the effects of liquid and granular formulations of Metarhizium anisopliae (Metschnikoff) Sorokin strain F52 against L. maculicollis larvae under field conditions. The liquid formulation provided 31-46% control of L. maculicollis larvae, but the granular formulation provided no control.

The annual bluegrass weevil (ABW; Listronotus maculicollis Kirby) host preference for annual bluegrass (Poa annua L.) is well documented, but ABW efficacy for annual bluegrass control in mixed turfgrass stands has not been researched. This study evaluated threshold‐based insecticide ABW control for annual bluegrass control in mixed‐species golf course fairway turfgrass. To investigate integrated pest management programs for annual bluegrass control in fairways, the effects of creeping bentgrass (Agrostis stolonifera L.) overseeding, three insecticide programs (preventative, threshold‐based, and no insecticide), and the plant growth regulator paclobutrazol (280 g ha–1, applied monthly) were evaluated for annual bluegrass control in field experiments conducted over 2 yr on golf fairways in North Brunswick and Bloomfield, NJ. Treatments were replicated four times and arranged in a split‐split‐plot randomized block design. Overseeding (whole‐plot factor) did not affect annual bluegrass cover at either location. Paclobutrazol (split‐plot factor) reduced annual bluegrass cover each year at both locations. At the North Brunswick site, paclobutrazol resulted in 0% annual bluegrass cover, compared with 37% in the nontreated control at the conclusion of the 2‐yr experiment. Insecticide program (split‐split‐plot factor) only affected annual bluegrass cover at the North Brunswick site. In the absence of paclobutrazol, the no insecticide program had lower annual bluegrass cover (23%) than the threshold (37%) and preventative (44%) programs at the conclusion of the experiment. These findings show that monthly paclobutrazol applications during the growing season can reduce or eliminate annual bluegrass after 2 yr. This is the first study to show that omitting ABW insecticidal control can also reduce annual bluegrass, although efficacy was site specific.

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is an economically important pest of short cut turfgrass. Annual bluegrass, Poa annua L., is the most preferred and suitable host for ABW oviposition, larval survival and development. We investigated the involvement of grass volatiles in ABW host plant preference under laboratory and field conditions. First, ovipositional and feeding preferences of ABW adults were studied in a sensory deprivation experiment. Clear evidence of involvement of olfaction in host recognition by ABW was demonstrated. Poa annua was preferred for oviposition over three bentgrasses, Agrostis spp., but weevils with blocked antennae did not exhibit significant preferences. ABW behavioral responses to volatiles emitted by Agrostis spp. and P. annua were examined in Y-tube olfactometer assays. Poa annua was attractive to ABW females and preferred to Agrostis spp. cultivars in Y-tube assays. Headspace volatiles emitted by P. annua and four cultivars of Agrostis stolonifera L. and two each of A. capillaris L. and A. canina L. were extracted, identified and compared. No P. annua specific volatiles were found, but Agrostis spp. tended to have larger quantities of terpenoids than P. annua. (Z)-3-hexenyl acetate, phenyl ethyl alcohol and their combination were the most attractive compounds to ABW females in laboratory Y-tube assays. The combination of these compounds as a trap bait in field experiments attracted adults during the spring migration, but was ineffective once the adults were on the short-mown turfgrass. Hence, their usefulness for monitoring weevil populations needs further investigation.

Simple SummaryThe annual bluegrass weevil (ABW), the most severe insect pest of short-mown turfgrass in eastern North America. Control programs traditionally target overwintering adults in spring (prior to egg laying) with broad-spectrum insecticides. However, the development of pyrethroid- and multiple-resistant populations has created the need for novel approaches. We investigated the insecticidal activity of a petroleum-derived spray oil and a surfactant on adults in laboratory and greenhouse trials. Both products caused rapid mortality, though were affected by carrier volumes, irrigation volume, and soil/substrate moisture. Neither products’ efficacy was affected by ABW pyrethroid resistance levels.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.

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 (Listronotus maculicollis), is the most destructive insect pest of fine turf found on golf courses in eastern North America. Although considerable densities of adults may be found on putting greens in spring following emergence from overwintering, larval damage in these areas is rare. Annual bluegrass (Poa annua L.) putting surfaces are frequently treated with nitrogen and plant growth regulators during this time. We assessed whether these inputs alone and in combination influenced L. maculicollis oviposition site selection, larval fitness, or survival. Significantly more females were found in high‐nitrogen (39 kg N ha–1 mo–1) treatments in laboratory preference assays, though significantly more eggs were found in the moderate concentration treatments (19.5 kg N ha–1 mo–1). Choice and no‐choice assays demonstrated an ovipositional preference for the moderate nitrogen rate as well, though no fitness advantage was observed. Given that most P. annua greens management programs include plant growth regulation, field experiments were conducted to assess ovipositional preference in P annua treated with various nitrogen concentrations (4.88, 19.5 and 39 kg N ha–1 mo–1) in combination with a gibberellic acid inhibitor (trinexapac‐ethyl) and/or a seedhead suppressor (ethephon). Significantly fewer larvae were found in trinexapac‐ethyl treatments in two of the three years of study, with significantly higher counts in the other year. No differences were detected in larval survival or fitness related to nitrogen in any year. Taken together, these findings suggest that fertility regimes are not likely to influence L. maculicollis development, though further studies are needed to assess the effects of trinexapac‐ethyl.

Entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) are generalist obligate pathogens present in the soil of most ecosystems. They have the potential to infect a broad host range, yet the potential for endemic entomopathogenic nematodes to regulate soil-dwelling insect populations has received limited attention. I investigated the population dynamics of endemic entomopathogenic nematodes to determine their ability to regulate annual bluegrass weevil (Listronotus maculicollis) (Coleoptera: Curculionidae) populations, a major pest of turfgrass in the northeastern United States. Weekly sampling of nematode and L. maculicollis populations was conducted in untreated fairway transects on three golf courses in New Jersey between April and October of 2006 and 2007. Steinernema carpocapsae Weiser and Heterorhabditis bacteriophora Poinar were found infecting all weevil stages from third instar to teneral adults. Both nematode species exhibited a distinct seasonality, appearing in high densities in the weeks immediately following high densities of first generation weevils in the soil. A positive temporal relationship was

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby (Coleoptera: Curculionidae), is the most damaging golf course insect pest in eastern North America. Heavy reliance on synthetic insecticides against this pest has led to widespread problems in controlling ABW with pyrethroid resistance already reported from populations in southern New England. This study evaluated the degree and scope of ABW resistance, determined existing cross-resistance patterns, and confirmed laboratory findings under greenhouse conditions. The susceptibility of 10 ABW populations to insecticides of different chemical classes was assessed in topical, feeding, and greenhouse assays. The level of susceptibility to pyrethroids varied significantly among populations (LD50s ranging 2.4-819.1 ng per insect for bifenthrin and 1.1-362.7 ng for λ-cyhalothrin in the topical assay). Three populations were relatively susceptible to pyrethroids, and seven populations had moderate to high resistance levels (RR50 for bifenthrin ranging 30.5-343.1). The toxicity of chlorpyrifos (RR50s ranging 3.3-15.3), spinosad (RR50s 2.4-7.7), clothianidin (RR50s 4.2-9.7), and indoxacarb (RR50s 2.8-9.7) was decreased for the pyrethroid-resistant populations. Toxicity data for bifenthrin and chlorpyrifos obtained under more realistic greenhouse conditions confirmed laboratory observations, indicating that the topical assay is an accurate method of detection and measurement of resistance level. The current study expanded the previously known geographic range of ABW pyrethroid resistance to include the New York metropolitan area, New Jersey, and eastern Pennsylvania and provided clear evidence of cross-resistance not only within the pyrethroid class but also to several other chemical classes.

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.

The “annual bluegrass weevil” (Listronotus maculicollis) became resistant to synthetic pyrethroid insecticides (bifenthrin and cyhalothrin) in several adult weevil populations from Connecticut, Rhode Island, and Massachusetts in 2007-09, and management of this insect has become increasingly complex. Annual bluegrass weevil continues to be a serious pest of Poa annua L. (Poaceae) and bentgrasses (Agrostis spp) on many golf courses in mid-Atlantic and northeastern United States and eastern Canada. Adults chew notches on grass blades and at the juncture of leaves and stems. However, adult feeding has little effect on plant vitality. Early instars feed inside plant stems and late instars on plant crowns. The first generation larvae, which usually become apparent in late May or early June, typically cause the most severe damage. During July and August damage caused by second generation larvae is usually less extensive, especially if good control of the overwintering generation was obtained. In most cases, adequate control of the insect has been achieved through the use of pyrethroid applications targeting adult weevils as they emerge from overwintering sites and before they begin to lay eggs. However, if a population is resistant to pyrethroids, alternative controls are required to prevent damage. My research objectives were to evaluate the entomopathogenic fungus Beauveria bassiana for control of L. maculicollis and how neonicotinoid insecticides can best be used to manage this increasingly serious pest. While pyrethroids remain the preferred choice of many golf course superintendents for managing this species, resistance has forced some superintendents to incorporate other strategies. Some of the new strategies include: (1) the use of a pyrethroid or chlorpyrifos early against overwintering adults; (2) neonicotinoid/pyrethroid combinations (Aloft, Allectus) during peak adult emergence to control adults and first generation larvae; (3) primarily preventative larvicidal compounds (chlorantraniliprole (Acelepryn), neonicotinoids) for early instars; and (4) curative larvicidal compounds (trichlorfon (Dylox), spinosad (Conserve), indoxacarb (Provaunt), chlorpyrifos, pyrethroids) for control of fourth and fifth instars. Some locations may need to use one or more of these strategies to prevent turf damage and resistance development. It is imperative that the timing of treatments coincide with various life stages (adults, early or late instar larvae) to maximize chemical efficacy. This is particularly important for the systemic compounds (neonicotinoids/chlorantraniliprole) to insure there is sufficient chemical in the xylem for maximum effectiveness. If treatment strategies 1-3 are not effective, a curative larvicidal compound may need to be applied to prevent damage. Finally, since all subsequent

The annual bluegrass weevil (ABW) is a pest of fine turfgrass, but recent research has found that withholding insecticides for ABW control can reduce annual bluegrass cover. The objective of this research was to evaluate threshold-based insecticide and paclobutrazol programs for annual bluegrass control. The effect of three insecticide programs (preventive, threshold, and no insecticide) and four rates of paclobutrazol (0, 70, 105, or 210 g ha−1 applied monthly) were evaluated. Replicate experiments were conducted from April to November in both 2018 and 2019 on a mixed creeping bentgrass and annual bluegrass fairway in North Brunswick, NJ. By the conclusion of both experiments, all paclobutrazol programs exhibited reduced annual bluegrass cover compared with the nontreated plots. In threshold and no-insecticide programs, reduction in annual bluegrass cover was enhanced by paclobutrazol applied at 105 g ha−1 in both years, and at 70 g ha−1 in the 2019 experiment. Paclobutrazol at 210 g ha−1 resulted in annual bluegrass cover of <20% regardless of insecticide program. In 2019, threshold-based ABW control without paclobutrazol provided similar annual bluegrass control as monthly applications of paclobutrazol at 70 and 105 g ha−1 with the preventive insecticide program. A reduction in turfgrass quality from threshold-based insecticide programs persisted for a shorter duration than the no-insecticide program, regardless of paclobutrazol treatment. Threshold-based ABW insecticide programs that allow ABW feeding damage to occur can result in reduced annual bluegrass cover. These reductions were further enhanced by paclobutrazol applications. The combination of threshold-level insecticide with moderate rates of paclobutrazol (70 to 105 g ha−1) provided reductions in annual bluegrass cover that were similar to the highest rate of paclobutrazol (210 g ha−1) without ABW damage. Turfgrass managers who integrate the threshold-level insecticide approach and monthly paclobutrazol applications may achieve greater annual bluegrass control than either strategy alone if temporary reductions in turf quality can be tolerated.

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.