JOHN NEYLAN JOHN NEYLAN
Effects of pre-emergent herbicides on a couch sportsfield at 18 weeks after treatment. All pre-emergent herbicides were very effective compared to the untreated control
Controlling
the enemy ATM columnist John Neylan presents the
findings of a recent research project he and David Nickson (Grand Prix Turf) conducted with funding from Sports Turf Association (Victoria). The project assessed the efficacy of various pre-emergent herbicides to control Poa annua in couchgrass and kikuyu.
I
n November 2016 a discussion was held among course superintendents regarding the challenges of controlling Poa annua in couch. This discussion arose at the same time that the results of the Poa annua in warm-season grasses survey was published (see previous column in ATM Volume 18.6, pages 42-46). The common theme has been the increasing difficulties in controlling Poa annua in warm-season grasses and the increasing reality that we are dealing with herbicide-tolerant and resistant Poa annua types. Following these discussions I felt that it was timely to revisit some research work recently undertaken with the Sports Turf Association (Victoria). During 2014/15 a series of trials were undertaken to assess the efficacy of various pre- and post-emergent herbicides to control Poa annua in couch (Cynodon sp.) and kikuyu (Pennisetum clandestinum). One of the key reasons was to determine whether the herbicides met the level of expectation promoted
in the advertising literature. This article details the outcomes of the pre-emergent herbicide trials and the seed bank studies.
PRE-EMERGENT TRIAL The pre-emergent trials were established on a couch field with a sandy rootzone and in an open position, while the kikuyu site had a loam-clay loam rootzone soil and was affected by shade. Both sites were in the southern suburbs of Melbourne (South Frankston and Seaford). The herbicides were applied on 27/2/14 and the conditions were calm, warm (24oC) and dry. The soil temperature was 24oC and the plots were irrigated after the herbicides were applied. The herbicides used in the trial are detailed in Table 1. Following the herbicide applications there was a significant rainfall event on the 1/3/15 (18mm), however, the rainfall totals were below the monthly averages for March, April, May and June. The low rainfall totals resulted in the late germination of Poa annua at both sites. Within one week following the application of the herbicides there was a very slight discolouration of the kikuyu plots where oxadiazon had been applied. This did not occur on any of the couch plots.
TABLE 1: PRE-EMERGENT HERBICIDES Treatment Herbicides Product T1 Oryzalin Embargo™ T2 Pendimethalin Stomp 330™ T3 Prodiamine Barricade™ T4 Oxadiazon Ronstar Turf and Ornamental Herbicide™ T5 Dithiopyr Dimension EW™ T6 Untreated Control -
Application Rate Expected Life (Product/Ha) (Approximate)* 5L/ha About 100 days 4.2L/ha About 70 days 2L/ha Up to 150 days *** 200kg/ha About 70 days 3.5L/ha -
About 120 days ** -
* Information drawn from the label or other company documentation. Always check the label. ** Information drawn from general literature. *** In high infestations the label recommends repeat applications in 3-4 months.
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AUSTRALIAN TURFGRASS MANAGEMENT 19.1