Recent rainfall throughout much of the country is likely to cause a flush of weeds, particularly where pre-ems could not be applied because it was either too wet or too dry.
This is according to Lynn Tatnell, research scientist in weed biology at ADAS.
She says: “I am finding particularly in the East, because it has been so dry things were not emerging and the weeds were quite slow, but after all this rain things are going to accelerate because it is warm.
“Now we have had the moisture, we have really got to think about the correct post-em. Decisions need to be made quickly based on what growers know is going to emerge, or what they can see emerging and get their post-em dose correct for those weeds because it is going to be quite a short window of opportunity.”
In autumn sown crops, wild oats are particularly one to watch, Ms Tatnell says.
“They are up and really accelerating. There are options to still spray them, but it needs to be done imminently because they will get big very soon. If you are still worried about wild oats in a few weeks’ time, hand rogueing remains a good option for control.
“We are also getting a good flush of broad-leaf weeds and there are lots of herbicide options available. People may be caught out thinking it was too dry and they did not need anything, but now with this moisture and warmth they will be taking off too.”
With many crops not receiving a pre-em or conditions being too dry for it to take effect, all of the pressure will be on a post-em, meaning applying the treatment while weeds are still small is all the more key.
Ms Tatnell says: “If you already have resistant black-grass, that makes it even more difficult. Growers should be targeting them right now. I have seen reports of black-grass in head already in some fallow land.
“Weeds are now actively growing and we do not want them to get too big,” she adds. “Quite often people think their grass-weeds are resistant but a lot of the time they have just been sprayed at the wrong time. If you have let them get too big, you cannot expect the chemical to still do the same job.
"On the plus side, the crops will start to get away now and get more competitive.”