Cleavers (Gallium aparine) is a dicotyledonous, or broad-leaved, annual species. At the early seedling stage cleavers produce distinct, large cotyledons with a characteristic notch at the tip. Until the first whorls begin to appear, these seedlings can be confused with those of ivy-leaved speedwell. The adult plant has a very characteristic appearance because of the way its leaves are arranged in whorls running up the stem and the size of the plant as it scrambles across the field using the crop for support. In summer, typically June, numerous tiny white flowers produce pairs of seeds covered in hooked hairs that can attach themselves to clothing or animal fur. Partly because of the size the adult plant can reach, and its ability to climb over the top of the maturing crop, cleavers infestations have the potential to cause very considerable crop losses.
There are two priorities for selecting a cleavers control product: final level of control and speed of control. To prevent yield loss and minimise seed return products need to deliver a consistent 95 – 98% control, whatever the time of year, whatever the climatic conditions. After crop GS30-32, in addition to the level of control, speed of control is essential to prevent cleavers smothering the crop and competing for light. Most damage to yield and profitability is done after this stage.
The longer the control of cleavers is left after GS32 the lower will be the return. Late emerging cleavers, i.e. those that appear around GS32, have less impact on final yield. They are more likely to be the source of seed return.
To maximise profitability from the control of cleavers applications should be made at or around crop GS32. Apply a cleavers herbicide with the T1 fungicide program. For products to deliver the required control at the appropriate time of the season they need to have certain key attributes.