Binomial sequential sampling plans were developed to forecast weevil Listronotus maculicollis Kirby (Coleoptera: Curculionidae), larval damage to golf course turfgrass and aid in the development of integrated pest management programs for the weevil. Populations of emerging overwintered adults were sampled over a 2-yr period to determine the relationship between adult counts, larval density, and turfgrass damage. Larval density and composition of preferred host plants (Poa annua L.) significantly affected the expression of turfgrass damage. Multiple regression indicates that damage may occur in moderately mixed P. annua stands with as few as 10 larvae per 0.09 m2. However, > 150 larvae were required before damage became apparent in pure Agrostis stolonifera L. plots. Adult counts during peaks in emergence as well as cumulative counts across the emergence period were significantly correlated to future densities of larvae. Eight binomial sequential sampling plans based on two tally thresholds for classifying infestation (T = 1 and two adults) and four adult density thresholds (0.5, 0.85, 1.15, and 1.35 per 3.34 m2) were developed to forecast the likelihood of turfgrass damage by using adult counts during peak emergence. Resampling for validation of sample plans software was used to validate sampling plans with field-collected data sets. All sampling plans were found to deliver accurate classifications (correct decisions were made between 84.4 and 96.8%) in a practical timeframe (average sampling cost < 22.7 min).
We characterized the spatio‐temporal distribution of emerging overwintered adult Listronotus maculicollis populations colonizing golf course fairways with Spatial Analyses by Distance IndicEs (SADIE) with the goal to better target management tactics and to test assumptions for weevil preference for annual bluegrass (Poa annua). Adults randomly colonized and moved throughout fairways. However, cumulative captures were significantly aggregated along fairway edges closest to overwintering sites demonstrating progressive movement through the edges. Spatial association analyses suggest that the spatial patterns of cumulative captures of adults rather than weekly patterns were strongly associated with larvae, indicating that the adults enter fairways from the edges and deposit eggs over the course of several weeks. We did not observe an effect of host species on the distribution of either adult or larval L. maculicollis which leads us to question traditional assumptions of host preference for short mown P. annua. Instead, we propose that the aggregated distribution of larvae is generated by a low encounter rate of short mown hosts, rather than preference for species or cultivar. This study indicates that caution need to be applied when using preference‐performance criteria in host preference studies. Future behavioural studies need to address the contributions of encounter rate and host species on L. maculicollis host selection and oviposition.
Listronotus maculicollis Kirby is a highly destructive pest of low mown, cool-season turfgrasses in the northeastern United States and Canada. Behavioral and electrophysiological assays were conducted to identify compounds that may be useful in developing novel monitoring techniques. In Y-tube assays, males and females responded differently to volatiles from intact and clipped annual bluegrass (Poa annua L.). Females were signiÞcantly attracted to intact P. annua but repelled from clippings; males did not respond signiÞcantly to either treatment. Electroantennogram (EAG) recordings from both sexes showed a signiÞcant response to volatiles from both treatments. Gas chromatography mass spectrometry (GC-MS) identiÞed 12 volatile compounds from P. annua of which nine were common to both intact plants and clippings. On average, seven-fold higher quantities of volatiles were collected from clippings than from intact plants (24.3 versus 3.4 ng/g of tissue/h). Eight compounds were released in signiÞcantly greater quantities from clippings of which 50% were the n-C 6 compounds hexanal, (E)-2-hexenal, and (Z)-3-hexenyl acetate, commonly referred to as "green leaf volatiles" (GLVs). Only octanal was emitted in greater amounts from intact plants than clippings. These nine compounds were tested individually against male and female antennae. Both sexes displayed greatest sensitivity to nonanal, octanal, and (E)-2-hexenal, but a signiÞcant doseÐ response relationship was observed with all compounds tested. These studies indicate that both sexes respond physiologically and that L. maculicollis females exhibit behavioral responses to host-plant volatiles. Future studies will need to assess the effects of individual compounds and component mixtures on L. maculicollis behavior in the Þeld.
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