Reproductive phenology and feeding patterns of Listronotus maculicollis during spring emergence: Implications for spring management

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AbstractThe 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.