This study assessed the long-term effects of three ABW insecticide programs on annual bluegrass control and fairway turfgrass quality, both alone and in combination with different paclobutrazol programs and creeping bentgrass control. We hypothesized that applying threshold level insecticides to control ABW over time would reduce annual bluegrass cover in creeping bentgrass fairways and that monthly applications of paclobutrazol would further enhance control.
Over time, two field experiments were conducted and repeated. Experiment 1 was a two-year field experiment conducted from 2017 to 2019 at two sites with a history of ABW. This study examined three insecticide programs, creeping bentgrass management, and monthly applications of paclobutrazol (Trimmit 2SC, Syngenta) at 0.25 lb active ingredient per acre (16 fl oz product per acre; 280 g ai per hectare) from seed annual bluegrass. . Crush before October for annual bluegrass control.
Research was conducted in 2017 and 2018 on a simulated golf course at Loggershot 2 Farm (North Brunswick, NJ) with an estimated annual bluegrass cover of 85% at the start of the experiment. The experiment was repeated in 2018 and 2019 on golf courses at Forest Hills Course Club (Bloomfield Hills, NJ), where visual cover was assessed at 15% creeping bentgrass and 10% perennial black wheat (Lolium perenne L.). In the experiment, 75% was Poa annua.
The seeding treatment consisted of planting creeping bentgrass 007 at a rate of 1 pound of clean live seed per 1,000 square feet (50 kilograms per hectare) one week after the start of the pesticide threshold program (see pesticide program details below). Treatments were repeated four times and arranged as a 2 × 3 × 2 factorial in a randomized complete block with split plots. Seeding as full site ratio, insecticide program as subplot, paclobutrazol as subplot, 3 x 6 ft (0.9 m x 1.8 m).
This prevention program is designed to prevent the damage to bluegrass that occurs each year during the season. It consists of the systemic insecticide cyantraniliprole (Ference, Syngenta) applied at a dose of approximately 200 GDD50 (80 GDD10) during the late flowering period of dogwood (Cornus florida L.) to control early spring generation ABW larvae before using indoxacarb (Provaunt). was applied at approximately 350 GDD50 (160 GDD10) when the Catawbiense Michx hybrid was in flower to control any surviving spring generation larvae, and Spinosad (Conserve, Dow AgroSciences) was used to control first generation larvae in the summer.
Threshold programs suspend the use of insecticides to control ABW until turf quality in untreated areas reaches a deterioration threshold of
To objectively determine turfgrass species composition, two 36 x 36 in (91 x 91 cm) square grids with 100 evenly spaced intersection points were placed in each plot. Identify the species present at each intersection between June and October. Annual bluegrass cover was visually assessed monthly during the annual growing season on a scale from 0% (no cover) to 100% (full cover). The quality of lawn grass is assessed visually on a scale of 1 to 9, with 6 considered acceptable. To evaluate the effectiveness of the ABW insecticide program, larval densities were assessed using salt extraction in early June before new adults began to emerge.
All data were subjected to analysis of variance using the GLIMMIX procedure in SAS (v9.4, SAS Institute) with random-effects replication. The first experiment was analyzed using a split-plot design, and the second experiment was analyzed using a randomized 2 × 4 factorial split-plot design. When necessary, Fisher’s Protected LSD test was used to separate means (p=0.05). Sites were analyzed separately because interactions with sites occurred on different dates and site characteristics varied.
ABW can selectively reduce annual bluegrass cover in creeping bentgrass, but only if severe damage to annual bluegrass is allowed. In these experiments, overall turf quality was only temporarily reduced by ABW damage to levels considered unacceptable by some golfers. This may be due to the fact that the majority (60–80%) of turfgrass is annual bluegrass. Damage to creeping bentgrass ABW was never observed using the threshold method. We suspect that in order for a threshold-based ABW insecticide program to effectively control annual bluegrass without a PGR program, we suspect that initial annual bluegrass coverage would need to be lower to allow ABW to cause significant annual damage to bluegrass without affecting general quality of the lawn. If only minor damage is allowed before insecticide spraying, these results suggest that long-term annual bluegrass control will be negligible.
Threshold insecticide strategies are most practical and effective when combined with plant growth management programs. We used paclobutrazol in this study, but fluoropyrimidine may produce similar results. If a threshold-based ABW plan is used without a PGR plan, annual bluegrass suppression may not be consistent or significant because annual bluegrass can quickly recover from damage in late spring. The best strategy is to begin monthly applications of paclobutrazol in the spring after the seed heads have ruptured, let ABW do the damage until it can no longer be tolerated (managers or others), and then apply larvicides at the maximum label doses to control ABW. A plan that combines these two strategies provides more effective annual bluegrass control than either strategy alone and provides high-quality playing fields for all but one to two weeks of the growing season.
Post time: Oct-25-2024