1 March 2002

Kill cleavers early to avoid yield loss

Cleavers control is the

subject of our latest

baseline advice series.

Getting it right at least

cost is the aim

GROWERS have a wider choice of cleavers killers than ever this spring. Which one to use will depend on the scale of the problem, autumn herbicide use, the range of other broad-leaved weeds involved and desired spray timing.

"Early removal has been gaining in popularity because it is easier to incorporate the cleavers spray with other treatments then," says Bob Bulmer of Dalgety Arable.

In any case, cleavers need controlling by GS32. "Otherwise you get yield loss. After then, it might still be worth spraying to prevent seed return, but the yield damage is already done."

Dr Bulmer believes there will be two cleavers scenarios this spring. "Some farms will have vigorous cleavers coming into the spring, while others will only have late germinators, or very low populations, due to the success of autumn herbicides."

"Pico Pro and Stomp have had a good effect on cleavers. So growers who used them will be wondering whether they need to over-spray."

Normally product choice is between an early or late herbicide, but a new product launch extends timing opportunities this year. "An early spray always carries the risk of missing the late germinators and their subsequent seed return," says Dr Bulmer.

Products

Early season products that can be used from early February include Eagle (amidosulfuron), Boxer (florasulam), Platform S (carfentrazone-ethyl+ mecoprop) and Lotus (cinidon-ethyl).

"Platform S has an advantage because it is not based on SU chemistry, so there are no restrictions if Lexus has been used in the autumn," says Dr Bulmer. "It is a contact herbicide and works quickly, but you must get good coverage."

Boxer also has a broad-spectrum and is good on mayweed, chickweed and groundsel, as well as cleavers. "There is dose flexibility with Boxer, it works well and can be applied up until mid-April. It is classed as an ALS inhibitor, so can be used after Lexus, provided no other SUs will be needed in that crop."

Eagle has a narrower spectrum. "It does a good job on cleavers, but the plants must not be too big. And it cant be used after Lexus."

Late season products include Starane and Dalgetys GEX353. "Both of these are temperature dependent, so they come into their own in April. As they contain fluroxypyr, the effect on cleavers is very good.

"GEX353 also contains two SUs, so it will control a wider range of weeds as well."

A new option on the market this spring is Starane XL (fluroxypyr + florasulam). Manufacturer Dow AgroSciences claims its Starane version is less timing dependent. "It can be used from the beginning of March onwards and takes away any concerns about missing your spray timing," says Dr Bulmer. "It will be a useful addition to the armoury."

Cost

Depending on product, a cleavers spray will add £7-16/ha to the herbicides bill, with the newer products at the top end of the range, calculates Dr Bulmer. "Where you know theres a problem, it will cost around £15/ha to get the desired level of control."

One way to reduce the cost is patch spraying. "Its tricky to get right and you must be certain of where the cleavers are, and the weed is generally on the increase," says Dr Bulmer. &#42

1Control timing Remove cleavers by GS32 to prevent yield loss.

2Other weeds Other broad-leaved weeds that may need controlling include mayweed, chickweed and groundsel.

3Autumn residuals Some have activity on cleavers. Stomp and Pico Pro have worked well this season.

4Populations Zero tolerance, a "must do" in cereals.

5Cleavers size Bigger plants need higher doses and good spray coverage.

6Early season products Use Eagle, Boxer, Platform S and Lotus from early February.

7Late season products Use Starane 2 and Dalgetys GEX353 in April.

8New product Starane XL (fluroxypyr + florasulam) is less dependent on timing and can be used from early March.

9Cost Adds £7-15/ha to weed control budget.

10 Cultural factors Heavy, moisture retentive soils worst affected, min-till also seems to favour cleavers.

Uncontrolled cleavers patches can soon add to the seed bank and lead to wider field infestations.