Julie Dionne

Current and potential use of pathogens in the management of turfgrass insects as affected by new pesticide regulations in North America

New legislation by governments and municipal authorities for the application of synthetic pesticides, including insecticides on turfgrass is currently changing the management of insect pests. Since the late 1990s, societal concerns over perceived health risks and environmental hazards of pesticides have led to tighter restrictions on insecticide use. In Canada, two provinces have banned the use of pesticides for cosmetic purposes and more than 152 municipalities have adopted some form of bylaw restricting or banning the use of landscape pesticides. Turfgrass managers are facing increasing constraints regarding the use of synthetic pesticides and only a few effective biological control agents are currently available on the markets to control turfgrass insects. Here we review the different pathogens that show potential for control and commercial use against turfgrass insect pests in North America. Even though numerous studies have shown the virulence of various pathogens against turfgrass insect pests, few of these pathogens are widely used. Limiting factors for their adoption include a narrow host range and, compared to synthetic insecticides, lower consistency, higher costs, and/or shorter shelf-life. However, new pesticide regulations, particularly in Canada, should lead to better opportunities for the biological control industry in turfgrass markets.

Cold-induced responses in annual bluegrass genotypes with differential resistance to pink snow mold (Microdochium nivale)

Greens-type annual bluegrass (Poa annua L.) is susceptible to winter stresses including subfreezing temperatures and pink snow mold (SM). To better understand the mechanisms of SM resistance in annual bluegrass, four SM-resistant and four SM-sensitive genotypes were incubated at low temperature with Microdochium nivale (Fries) Samuels & Hallett, the causal agent of pink snow mold. We assessed the impact of a 6-week incubation period with SM at 2 °C under high humidity (≥ 98%) on the accumulation of cold-induced metabolites and on freezing tolerance. Incubation of annual bluegrass inoculated with SM lead to a major decrease in concentration of cryoprotective sugars such as sucrose and HDP (high degree of polymerization) fructans. Conversely, major amino acids linked to stress resistance such as glutamine and arginine increased in crowns of annual bluegrass in response to SM inoculation. One of the major differences between resistant and sensitive genotypes was found in the concentration of HDP fructans, which remained higher in SM-resistant genotypes throughout the incubation period. HDP fructans were also more abundant in freeze-tolerant genotypes, reinforcing their positive impact on winter survival of annual bluegrass. The identification of genotypes that are resistant to both SM and freezing shows the possibility of being able to improve both traits concomitantly.

Virulence of entomopathogenic nematodes (Rhabditida: Steinernematidae, Heterorhabditidae) against Tipula paludosa (Diptera: Tipulidae), a turfgrass pest on golf courses

Abstract The European crane fly (ECF), Tipula paludosa Meigen feeds on leaves, crowns, and roots of cool-season turfgrasses causing damage to residential lawns and golf courses. A laboratory study was conducted to determine the susceptibility of ECF larvae to four commercial entomopathogenic nematode (EPN) species (Heterorhabditis marelatus, H. megidis, Steinernema carpocapsae and S. feltiae). The virulence of four S. feltiae isolates recovered from golf courses in Quebec and Ontario were also compared to a commercial strain. LC50 values of EPN against late instar ECF larvae were 152, 562, 763, and 3584 for S. feltiae, H. megidis, H. marelatus and S. carpocapsae, respectively. When non-feeding (without grass seedling), ECF larvae mortalities decreased for all nematode species and concentrations tested. At 25°C, LC50 values for the two most virulent indigenous S. feltiae were 129 and 187 nematodes/larva, not different from the commercial strain. At 5°C, the commercial S. feltiae was more effective than both BIC14A and RE6A isolates against ECF larvae. However, at 15°C, BIC14A was the most virulent at the low concentration of 200 IJs/larva.

Natural occurrence of entomopathogenic nematodes (Rhabditida: Steinernematidae) on golf courses in eastern Canada

A survey of entomopathogenic nematodes from 38 golf courses was conducted in different climatic areas of Ontario and Quebec provinces, Canada, during autumn 2002 and 2003. Soil samples were collected on golf course greens, fairways and roughs. Entomopathogenic nematodes were isolated from soil using wax moth (Galleria mellonella) and carrot weevil (Listronotus oregonensis) larvae as bait. Of the 436 samples (218 sites), 11 contained entomopathogenic nematodes for this study. All entomopathogenic nematode-positive samples were isolated from roughs. Isolates were characterised using DNA satellite probes and 28S rDNA sequence data. Both methods confirmed the identities of nematode isolates as Steinernema carpocapsae, S. feltiae and S. kraussei.