Annual bluegrass weevil, paclobutrazol, and overseeding for annual bluegrass control in bentgrass fairways
Creators: name: Diehl, Katherine Helen Dupont
Publisher: name: No Publisher Supplied
Year: 2020

description: The annual bluegrass weevil (ABW; Listronotus maculicollis) is a common pest of annual bluegrass (Poa annua) in cool season turf. Larvae can cause substantial plant injury in highly managed turf areas, and golf course managers often apply insecticides preventatively for ABW control. Although its host specificity for annual bluegrass is well documented, little is known about how ABW management influences long-term annual bluegrass cover. The objective of this research was to compare the effects of threshold-based and industry-standard insecticide programs on annual bluegrass populations on golf course fairways alone and in combination with herbicide and overseeding programs.The first experiment was conducted over a two-year period at two locations in New Jersey to evaluate the effects of three ABW insecticide programs (preventative, threshold, and no-insecticide), monthly paclobutrazol applications, and creeping bentgrass (Agrostis stolonifera L.) overseeding on annual bluegrass control. The preventative insecticide program was an industry standard program designed to prevent ABW damage to annual bluegrass. The threshold program was designed to allow ABW larvae damage to occur only until turfgrass quality was compromised. The no-insecticide program was included for comparison. Overseeding did not affect annual bluegrass cover at either location. Insecticide program only affected annual bluegrass cover on one site. At this site, the no-insecticides program provided more annual bluegrass control than the other insecticide programs in the absence of paclobutrazol. When paclobutrazol was applied, annual bluegrass was completely controlled at the conclusion of the two-year experiment, regardless of insecticide program. Lower paclobutrazol rates (210, 105, 70, or 0 g ha-1) were evaluated in combination with the aforementioned insecticide programs in a second experiment. Research was conducted from 2018 to 2019 on adjacent sites at Rutgers Horticulture Farm No. 2 in North Brunswick, NJ on a simulated creeping bentgrass fairway. At the conclusion of the 2018 experiment, annual bluegrass control varied by insecticide program for the 105 and 0 g ha-1 paclobutrazol rates. The preventative program resulted in the greatest annual bluegrass cover (33% and 83%, for the 105 and 0 g ha-1 paclobutrazol rates, respectively) compared to the threshold and no-insecticide programs (8 and 13% and 56 and 68% for the 105 and 0 g ha-1 paclobutrazol rates, respectively). At the conclusion of the 2019 experiment, the preventative program resulted in more annual bluegrass cover (56%) at 105, 70, and 0 g ha-1 paclobutrazol rates than the threshold and no-insecticide programs (36% and 26%, respectively). Insecticide programs did not affect annual bluegrass control at highest paclobutrazol rate in either year.These findings indicate that threshold-based insecticide control of ABW can reduce annual bluegrass cover compared to industry-standard preventative insecticide program. In North Brunswick, NJ, the ABW offered similar selective annual bluegrass control as one year’s worth of monthly paclobutrazol applications (70 and 105 g ha-1).