Olga S. Kostromytska

Entomopathogenic Nematodes in Turfgrass: Ecology and Management of Important Insect Pests in North America

Several genera of grasses are capable of forming a mat of intertwined plants to form a solid ground cover with an extensive root mass. They can also regenerate from the crown after defoliation. The about 50 grass species amenable to use in turfgrass systems are further on able to form a high shoot density under the continuous mowing regimes characteristic for turfgrass systems (Christians, 1998). These properties allow turfgrasses to provide a hard–wearing permanent or semi–permanent ground cover that can be used for various recreational spaces in urban and suburban environments including lawns, parks, golf courses, and athletic fields. Other areas in which turfgrasses are grown include cemeteries, roadsides and sod farms. In the USA, turfgrass areas cover about 20 million ha and the size of the turfgrass industry is estimated at

Ovipositional preferences and larval survival of annual bluegrass weevil, Listronotus maculicollis, on Poa annua and selected bentgrasses (Agrostis spp.)

40,000 million per year (National Turfgrass Federation, 2009). Besides their recreational uses, turfgrasses control soil erosion, capture and clean run–off water from urban areas, provide soil improvement and restoration, moderate temperature, reduce glare and noise, reduce pests, pollen and human disease exposure, create good wildlife habitats, and improve physical and mental health of urban populations (Beard & Green, 1994).

Synergistic Combinations of a Pyrethroid Insecticide and an Emulsifiable Oil Formulation of Beauveria bassiana to Overcome Insecticide Resistance in Listronotus maculicollis (Coleoptera: Curculionidae)

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.

Chilling effect on termination of reproductive diapause in Listronotus maculicollis (Coleoptera: Curculionidae)

The annual bluegrass weevil, Listronotus maculicollis (Kirby), is a major pest of golf course turf in eastern North America and has become particularly problematic owing to widespread development of insecticide resistance. As an alternative option to manage resistant adult L. maculicollis, we explored combinations of the pyrethroid insecticide bifenthrin with an emulsifiable oil formulation of the entomopathogenic fungus Beauveria bassiana strain GHA (Bb ES). Combinations synergistically enhanced mortality in both insecticide-susceptible and insecticide-resistant L. maculicollis adults in the laboratory when bifenthrin was used at LC50s for each population. To determine the component behind the synergism, technical spores of B. bassiana GHA and the emulsifiable oil carrier in the fungal formulation were tested separately or in combination with bifenthrin. In both separate and combined applications, the emulsifiable oil carrier was responsible for high mortality within 3 d after treatment and interacted synergistically with bifenthrin, whereas fungus-induced mortality started later. Strong synergism was also observed in three field experiments with a relatively resistant L. maculicollis population. Combinations of Bb ES and bifenthrin hold promise as an effective L. maculicollis management tool, particularly of pyrethroid-resistant populations.

Seasonal Phenology and Management of Tomarus subtropicus (Coleoptera: Scarabaeidae) in St. Augustinegrass

Diapausing adults of the annual bluegrass weevil, Listronotus maculicollis, were collected from their hibernating sites at different times in autumn and winter, and subjected to different conditions to observe diapause termination by dissecting and measuring the reproductive organs. When diapausing weevils were maintained under laboratory cold conditions (10 h light at 6 °C:14 h dark at 4 °C) from early December to late March, the sizes of reproductive organs of both sexes increased or fluctuated slightly, and very few females had developing oocytes, suggesting that most adults did not resume development during the chilling period. When diapausing weevils (chilled for 40-83 days) were transferred to warm conditions (LD 14:10 and 21 °C) for different lengths of time, reproductive organ sizes in both sexes increased as chilling period prolonged, implying that chilling played an important role in diapause termination. Under field conditions, an apparent peak of reproductive development was observed on January 07 when 80% of males and 53% of females had resumed growth of reproductive organs. Diapausing weevils collected in September without chilling did not develop successfully despite exposure to warm conditions. In contrast, 87% of males and 93% of females collected from the field on January 21 had initiated reproductive development after 5 days of exposure to warm conditions, indicating the necessity of chilling for diapause termination. Male and female reproductive organ sizes increased faster and to a greater final size the longer the preceding chilling period was. The prolonged chilling period in the field resulted in more synchronized and advanced development in L. maculicollis when exposed to warm conditions.

Cross-resistance Patterns to Insecticides of Several Chemical Classes Among Listronotus maculicollis (Coleoptera: Curculionidae) Populations With Different Levels of Resistance to Pyrethroids

Abstract The grub Tomarus subtropicus Blatchley (Coleoptera: Scarabaeidae) is one of the most destructive pests of turfgrass and sugarcane (Saccharum spp.) in southern Florida, but its life cycle has only been described in sugarcane production. Preventive insecticides applied against T. subtropicus in turfgrass when adult activity and oviposition were expected in sugarcane have necessitated subsequent curative treatments. Thus, the seasonal activity of T. subtropicus was monitored using UV blacklight traps and by sampling soil in infested St. Augustinegrass lawns in Cape Coral and Punta Gorda, FL, during 2005–2006. Several preventive and curative insecticides and entomopathogenic nematode species were evaluated in laboratory, greenhouse and field tests. T. subtropicus is univoltine in both sugarcane and St. Augustinegrass, but adult flight peaked ≈1 mo later in St. Augustinegrass than in sugarcane. Halofenozide, clothianidin, and imidacloprid were effective preventive control products, and carbaryl and trichlorfon were satisfactory curative insecticides. The nematodes Steinernema scarabei (Stock & Koppenhöfer), S. glaseri (Steiner), and Heterorhabditis bacteriophora (Poinar) were most effective against T. subtropicus grubs, and second instars were more susceptible compared with third instars. Improved knowledge of the biology and effectiveness of different management options for T. subtropicus will help minimize excessive pesticide use, especially in coastal areas of Florida.

Types and Functions of Mole Cricket (Orthoptera: Gryllotalpidae) Antennal and Palpal Sensilla

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.

Tomarus Subtropicus (Coleoptera: Scarabaeidae) Larval Feeding Habits

Abstract Invasive mole crickets (Orthoptera: Gryllotalpidae: Scapteriscus spp.) are destructive subterranean pests that cause significant economic losses for the turfgrass, sod and pasture industries. Their behavior suggests that they may sense insecticides applied to the soil, so we sought to examine and describe the antennal and palpal structures of S. vicinis Scudder, S. borellii Giglio-Tos, S. abbreviatus Scudder, and the native mole cricket, Neocurtilla hexadactyla Perty, by scanning and transmission electron micrography. The most abundant sensilla were antennal sensilla chaetica with mechanoreceptory and contact chemoreceptory functions. Each segment had olfactory sensilla basioconica and sensilla trichodea, sensilla coeloconica (with olfactory and thermo-hydroreceptory functions), and sensilla campaniformia (proprioreceptor). Sensilla on the mole cricket palps were non-pore or tip-pore, which suggests mechanoreceptory and contact chemoreceptory functions. Similar to other hemimetaboulous insects, mole cricket nymphs and adults have the same sensilla types. However, the number and size of antennomeres increased with each molt, allowing the antennae to accommodate more sensory sensilla as insects matured.

Behavioral Responses of Pest Mole Crickets, Neoscapteriscus SPP. (Orthoptera: Gryllotalpidae), to Selected Insecticides

ABSTRACT The importance of soil organic matter for Tomaras subtropicus Blatchley larval development and survival, the amount of damage larvae could cause on turfgrasses, and potential larval host range were investigated in greenhouse experiments. First instars were reared individually in seedling trays containing sand or peat, with or without St. Augustinegrass. Survival, developmental stage, and final weight were recorded 1 month after introduction. First instars died in the pots with peat but no grass, so it appears that grass roots were critical for larval growth and development. Soil organic matter did not significantly affect grub weight gain and development, but more root loss occurred with grass grown in sand. In host range tests (2005 and 2006), first and third instars were reared on 6 species of warm season grasses and ryegrass. Grub weight gain, development, survival and grass root reduction were determined 2 months after introduction. Larval survival ranged from 62–93% if grubs were reared on warm season grasses to only 40% if reared on ryegrass. Grubs reared on warm season grasses gained weight and successfully developed into third instars, indicating that all of the tested warm season turfgrasses were suitable for larval T. subtropicus growth and development. Grub feeding caused significant root reduction of all grasses in our study, which ranged from 36 to 87% and differed among grass species. As result, quality ratings and clipping yields decreased for most of the turfgrasses after 5 weeks of infestation, but bahiagrass and seashore paspalum were less affected by T. subtropicus root feeding, compared to the other grass species.

Pyrethroid-Resistance Level Affects Performance of Larvicides and Adulticides From Different Insecticide Classes in Populations of Listronotus maculicollis (Coleoptera: Curculionidae)

BACKGROUND Mole crickets (Neoscapteriscus spp.) consume turfgrasses and pasture grasses and uproot plants by their tunneling, which is detrimental to turf aesthetics and decreases forage quantity and quality. Insecticides are frequently used to prevent damage. In typical field trials, damage symptoms, not percent mortality or achieved level of control, are used to assess treatment efficacy. Here, however, laboratory tests assessed the direct effect of key insecticides on Neoscapteriscus mole cricket behavior. RESULTS Mole crickets, Neoscapteriscus spp., were able to detect and avoid areas treated with fipronil [formulated product (FP)] and imidacloprid (FP). They tunneled less in sand treated with fipronil and avoided sand treated with fipronil and imidacloprid if given a choice. Mole crickets escaped areas treated with acephate, bifenthrin and fipronil. Bifenthrin and acephate caused increased tunneling during the first 90 min of observation. Fipronil and imidacloprid significantly reduced overall tunneling on treated areas. CONCLUSION Tested insecticides elicited two types of behavioral changes in Neoscapteriscus mole crickets: increased locomotory activity and tunneling [acephate (organophosphate) and bifenthrin (pyrethroid)] and reduced spatial movement [fipronil (phenylpyrazole) and imidacloprid (neonicotinoid)]. These behavioral responses resulted mainly from contact chemoreception and inherent neurotoxicity of the chemicals on Neoscapteriscus mole crickets.