Don't forget reseeding spray
Tuesday September 06 2005
Annual weeds such as Redshank or Fat Hen are not a problem; the first grazing will eliminate them. However, perennial weeds are an altogether different matter. Grazing or topping has no effect on them whatever. Chemical control is essential.
Despite all warnings about the necessity of applying a post-emergence spray, every year I walk farms where the reseeds are not receiving such a spray.
Believe it or not, in certain areas there is no history of applying a post-emergence spray to a reseed.
The thinking here is that since a spray was initially used to kill off the existing vegetation, this spray took care of the weeds in the subsequent reseed. This thinking is about as useful as an ashtray on a motorbike.
Seedling docks are very easy to control relative to mature docks.
This is an ideal opportunity to break the cycle and prevent seedlings from developing a large root reserve that is very difficult and expensive to control.
Five to six weeks after reseeding you will see seedling docks in the reseed, but you will have to look for them and you may have to go down on your knees to find them; the seedling will have a leaf area about the size of your thumbnail.
At this stage, they are very susceptible to chemicals.
Controlling weeds in a new reseed is complicated by the fact that in almost all cases one is trying to protect clover as well.
Clover and sprays do not go hand-in-hand and many a farmer has managed to eliminate the clover problem with a clover-"friendly" spray.
If clover is unimportant, you can use any chemical containing CMPP.
The best-known products here are Duplosan, Optica. Products containing CMPP are cheap and the cost of the spray in such situations is €10-12/ac.
However, where clover is important, I would use either Legumex DB or Alistell. The first one costs approximately €17-18/ac when applied at 7 litres/ha rate. However, the Alistell will set you back about €30/ac.
Care is needed when you are using clover-friendly sprays. The clover has to be given time to establish, otherwise the clover-friendly sprays may inhibit or even kill clover.
A window of opportunity exists and it is about 2-3 weeks in duration, i.e. 5-8 weeks after sowing. In very good growing conditions, the ideal spraying time would be closer to 5-6 weeks. Generally, the clover must have one trifoliate leaf before it can be safe to spray.
Chickweed is a perennial weed which has been causing problems for the past few years. I have seen severe damage done to reseeds where it is left unchecked. Of the clover-friendly sprays mentioned, only Alistell will kill it, simply because it contains the chemical Linuron (30g/litre).
Linuron can be purchased separately and added to products like Legumex DB. Linuron (370g/litre) can be purchased on its own and if applied at a rate of 0.3 litres/ha (0.21 pt/ac) it will control chickweed.
Linuron is a cheap product and if it is applied at the rate mentioned above, it would cost you about €2/ac.
So there you have it. At your peril don't miss out on the post-emergence spray. Spray on a good dry day and allow 10 days before calves are sent in to graze the reseed.
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Dairy
