Summer annuals like prostrate knotweed and crabgrass are turning orange and dying, leaving behind bare soil on fields.
Prostrate knotweed (Polygonum aviculare L.) is a mat-forming weed that is one of the first summer annuals to germinate in the spring but it goes orange and dies out in October in Ohio. It is an indicator of soil compaction, so is often found in high traffic areas between hash marks (see picture left)or in goal mouths.
The only way to approach this problem right now is to watch it die and to get as much perennial ryegrass germination in those bare soil areas as possible. Applying a starter fertilizer at 1 lb nitrogen per 1,000 sq.ft and keeping the seed moist during the germination period will significantly improve the seed establishment rate.
In early spring 2008 there are several strategies to prevent & control reinfestation of this weed:
1. Put together a soil improvement program for 2008. This should include regular coring, deep tining, or vertidraining at least 1 x per growing month (6-8 times per year).
2. Apply a preemergence herbicide, taking into consideration that most preemergence herbicides have a re-entry period, so bare soil areas cannot be seeded with desirable grasses for several weeks following the herbicide application.
3. Seed desirable grasses into bare areas and apply mesotrione (Tenacity) to control emerging weeds.
4. Apply a selective postemergence herbicide, once the weed is present. Combinations that have shown efficacy in trials include MCPP and dicamba. Please note that there is also a several week re-entry period for postemergence products.
5. If the field is not going to be used until fall, apply a non-selective postemergence herbicide and seed or sod. Sod offers a great opportunity to bring in a 100% Kentucky bluegrass turf and also prevents weeds from emerging. It is very difficult to establish new turf from seed in spring as pressure from crabgrass and knotweed is high, so sod takes some of that pressure away. Authors: Pam Sherratt & Dave Gardner
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