12 December 1998

cleavers KNOCKED FOR six

A new competitor is joining the field in the battle for cleaver control. Lucy Stephenson sizes it up.

LOTUS – a new cleavers killer in cereals from BASF – comes on sale this January. What does it offer growers that other cleavers killers dont? In summary a new group of chemistry (cinidon ethyl) and quick knock-down, which gives greater flexibility in spray timing.

Its the second cleavers killer from BASF this year, coming hot on the heels of quinmeric-based Katamaran for use in oilseed rape. Lotus is likely to compete with sulfonylurea Eagle for market share – since it has a long application window and contact activity.

Libby Powell, of the Morley Research Centre which trialled Lotus for BASF, says that it kills cleavers in about seven days, and its effect is "very visual". Rival products Eagle (amidosulfuron) and the old favourite Starane (fluroxypyr) rapidly stop cleavers growth, but the plants appear almost unaffected many days later, and take a few weeks to die, she says.

The best time to control cleavers is by no means clear-cut because there may be a trade off between the long germination period of cleavers and the potential risk of seed return.

Compared with other weeds, cleavers grow later in the year and have a longer emergence period. The weed emerges in two distinct flushes, a larger one with soil disturbance on sowing, and a smaller one in the spring.

Peter Lutman, of IACR Rothamsted, says theres some evidence that only about 10% of the total cleavers population is spring emerging, and these are very much less vigorous than those that emerge with the crop. Whats yet to be discovered is how much seed these spring cleavers leave behind.

Later drilling this autumn means fewer spray opportunities but also fewer weeds. Weeds are more susceptible when theyre small, but theres no need to hit twice when one later control will be sufficient, says Jim Orson, director of the Morley Research Centre. Later germinators shouldnt affect yield, but falling down on weed control could put your rotation at risk, he says. His advice is to look for cleavers in February, when cleavers begin to pose more of a challenge.

Dr Lutman says that in most years leaving cleavers control until April is unlikely to affect crop growth or yield, which is very late compared with weeds such as blackgrass.

Lance Middleton, technical services officer with BASF, says Lotus should be used in late winter or early spring, when the majority of cleavers have germinated, but before they have begun to compete strongly.

David Ellerton of ProCam sees Lotus being used to knock cleavers on the head in the autumn, and also in cold weather which wouldnt suit Starane, where cleavers are beginning to compete with the crop.

Killing speed

Small cleavers grow slowly in shade, waiting until the crop opens up before taking off. Andrew Jones, herbicides product manager for BASF, says: "If application is delayed, the speed of kill is important – this is where Lotus fits in after GS31, because cleavers are competing with the crop for light and so must be taken out quickly."

Lotus has approval from GS2 to GS33. "Spraying up to GS31 prevents yield loss in winter cereals even where high populations are present," says Mr Orson. Lotus and Duplosan gives 98% control, which is on a par with Starane.

Lotus can be used alone on cleavers before the two-whorl stage, says Mr Middleton, and can be applied with New 5C Cycocel early in the season. Its not a standalone product though, and does need to be mixed with Duplosan (CMPP) for wide spectrum control.

Lotus can also lead to some necrotic spotting of the crop – more unsightly than damaging, says Dr Ellerton. Nor should it be mixed with sulphonylurea products, because of the possibility of antagonism which would affect cleavers control. But Miss Powell says she certainly wouldnt be afraid to give a Lotus-Diplosan mix a go, especially with high cleavers populations.

Lotus

Cinidon ethyl

Emulsifiable concentrate, 200g/litre in 1 litre containers

Winter and spring barley, winter wheat and winter rye, also durum wheat. Approved for wholecrop cereals grown for stockfeed

Contact activity only. Rainfast in 1-2 hours if applied to a dry leaf. Works at cool temperatures

Maximum individual dose and maximum total dose 0.25 litres/ha. One dose at maximum rate recommended for reliable control.

Growth stages 12 -32, except spring barley at growth stages 12-30.

Yet to be finalised, but manufacturer says it will be competitive with Eagle.