The annual bluegrass weevil [Listronotus maculicollis (Kirby)] is a severe pest of golf course turf in North America. Most turf managers attempt to minimize larval damage by targeting adults with insecticides upon emergence from overwintering habitats in spring. Fluctuations in weather often create asynchronous emergence patterns that lead to inefficacious applications. We sought to describe L. maculicollis reproductive phenology to determine when mating and oviposition occur to better time insecticide applications. Dissections were performed on adults collected weekly from golf course fairways and tees between adult emergence and the end of the first generation over a 3‐yr period. Most females emerged with well‐developed reproductive systems, though <40% were mated. Fewer than 20% of males were mature upon emergence and required 5–8 wk after first emergence before all captures displayed mature reproductive systems. Few adults were found to have fed between emergence and adult peak, suggesting that systemic insecticides applied during the migration are not likely to be ingested. In caged oviposition studies, females survived up to 15 wk, with oviposition occurring as late as 14 wk. Average total fecundity ranged between 60 and 90 eggs per female with most oviposition occurring between the start of the experiment and 5 (2013) or 8 wk (2012). A strong correlation between growing degree days per week and eggs per female per week was detected over this period. Our findings suggest that insecticide applications targeting adults to reduce asynchronous larval development and damage should not be applied prior to peak emergence.
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 trinexapacethyl.
This chapter addresses the advances in turfgrass insect pest management. It starts by first reviewing the recent studies of major turfgrass insect pests, such as annual bluegrass weevil, bill bugs, white grubs and fall armyworm. The chapter then moves on to discuss recent studies on emerging turfgrass pests, focusing specifically on European crane flies and Chaetocnema minuta. A section on integrated pest management practices is also provided, drawing attention to methods such as pest detection and monitoring, chemical control, insecticide resistance and non-target issues with chemical insectides. The chapter also discusses biological control, cultural control, host plant tolerance and resistance to pests and the use of plant growth promoting rhizobacteria.
White grubs, or the larvae of scarab beetles, are widespread destructive pests of turfgrass systems around the world. We sought to determine if turfgrass cultivation machinery could reliably manage white grubs in turfgrass systems. Hollow-tine aeration provided greater reductions in grub densities than solid-vibratory tine and air/solid injection cultivation in field trials. In following studies, low to moderate reductions (0-53%) were observed with single hollow-tine applications, though low grub densities encountered within field plots hindered the ability to detect statistical differences between cultivation treatments including tine diameter and tine spacing. Increasing aerification frequency on plots from one to two or more passes produced statistically significant reductions (>80% control) in both years of trials. To eliminate the variability observed in the field, a simulation model was constructed to determine the expected outcome of varying tine patterns have on increasing grub densities. Models suggests that expected mortality is likely to be minimal (<10%) in one-time aerification events. In-field simulations using templates overlaid on natural populations demonstrated two-fold greater control than theoretical simulations. Differences in control between field studies and model simulation are likely caused by an over-estimation of mortality when performing presence-absence counts in field studies when grub densities are low. Although multiple aerification events will likely improve control, current cultivation practices are unlikely to achieve the level of control expected by turfgrass managers in intensely managed landscapes.
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