Poa Annua Control Update And Specticle Herbicide Application

Poa Annua is a difficult to control weed in warm season turf for several reasons. There is widespread resistance to many herbicide mode of action groups, perennial biotypes are becoming more common and, in some areas, Poa germination is occurring all year not just the traditional autumn period. Herbicide application strategies must be tailored to these different situations;

• In Poa free situations with a traditional peak of germination in the autumn, the normal pre-emergent herbicide application timing in late summer/early autumn is an appropriate strategy. If any escapes become evident in the weeks or months following the pre-emergent application, these should be controlled, ideally before the plants go to seed, by an application of a tank mix of post-emergent herbicides with different modes of action.
• Where Poa plants are already present, control should be made with a tank mix of post-emergent herbicides with different modes of action. Even if using non-selective herbicides these should be mixed with at least one other post-emergent herbicide. The tank mix to be used will vary between facilities and different combinations should be trialed before embarking on broadcare spraying. The tank mixes used should be changed from one application to the next so that the same group of modes of action is not being continually used. Pre-emergent herbicides should also be applied in these situations to optimise control and reduce pressure on post-emergent chemistry.
• A recent strategy which has been demonstrated to be effective in research from several universities in the USA is to delay the traditional early autumn pre-emergent herbicide application until late autumn when the peak of Poa germination and emergence has occurred. A mix of a long residual pre-emergent herbicide with two post-emergent herbicides with different modes of action is made at this timing. At this time the new Poa plants are still young and easier to control and the pre-emergent component(s) will provide residual control through winter.

Envu is continuing to invest in local testing to investigate alternative timing and tank mixes in Australian conditions to optimize control and also mitigate against further resistance development.

Specticle^®Herbicide is a pre-emergent herbicide shown to be very effective for the control on Poa in warm season turf. To optimise Specticle Herbicide performance for Poa control;

• Apply prior to Poa germination commencing. A cool wet summer may mean Poa germination starts earlier than it has previously and earlier application than normal may be warranted.
• Lightly irrigate after application (3mm is adequate in most situations)
• Do not apply to waterlogged soils. The majority of Poa seed are in the thatch and upper part of the soil profile. We want the herbicide to be in the same place and drier soil conditions at the time of application will ensure this.
• Do not apply if heavy rainfall in forecast in the next few days. Going by the past few wet autumns encountered in eastern regions of Australia it may mean applying well before germination or delaying application until after emergence and combining Specticle Herbicide with at least two different post-emergent herbicides. The long residual control that Specticle Herbicide provides gives you flexibility to time your application to when conditions are most suitable, even if this is well in advance of peak germination.