Three contenders for an early assault
CMPP CAN no longer be regarded as a true cleavers herbicide, says Chris Bean, technical director at UAP.
"It does not work well at low temperatures, and by the time the weather warms up enough you are often close to the GS32 cut-off stage."
"We had Lotus in small plot UAP trials for two years before its launch. But it was less reliable as a cleavers killer than other developments such as Boxer. Another problem is its potential to interfere with the activity of sulfonylureas, such as Ally."
In Mr Beans opinion there are three serious contenders for the early timing.
"Platform S tends to be chosen where we need rapid burn down of cleavers. They are generally cooked within seven days, whereas Eagle and Boxer can take a month to work. And of the three only Platform offers high levels of control of both types of speedwell. That can be important after autumn IPU, Hawk or Puma X which dont offer much control of either." The choice between Eagle and Boxer depends partly on relative cost-effectiveness based on what other weeds are present, says Mr Bean.
"In our trials 100ml/ha of Boxer, the minimum dose for cleavers, gave similar results to 30-40g/ha of Eagle.
"The big advantage of Boxer is that it deals with groundsel which is becoming more persistent after IPU/Stomp and IPU/DFF mixtures. There is also a lot more resistant groundsel about in crops after vegetables."
Mayweed and chickweed seem set to be more troublesome this season after the use of certain autumn products, he adds. "Hawk and Amazon do not touch them, and much of the IPU used will have leached out, so it will give less control. Eagle does not control them, but Boxer does along with some tricky upstarts like shepherds needle."
Even with the newer materials, soil temperature plays a part. "All application rates can be reduced, but you have to take seasonal variations into account to avoid regrowth. Actively growing cleavers are much more herbicide susceptible."
In the relatively mild 1999 February, Eagle gave very good cleavers control at 20g/ha (half dose), he notes. "We even had some good results at that stage with Starane. But that was not the case the previous season when it was colder.
"Starane is probably the best choice from mid-April, but we have had good results from Boxer in April. The reliability curves cross around the middle of the month."
Depending on season up to 10% of cleavers emerge after early spraying. "You can leave them but they do make a mess and contribute to seed return."
Boxer has a 5m buffer zone restriction, but there is none for Eagle, Platform S, Starane or CMPP.
"That may help some growers with their decisions.
"Whatever the line of attack, good spray coverage of cleavers is essential," Mr Bean advises. "Keep the water volume up and avoid too high a pressure, which leads to spray drift rather than penetration." *
This seasons choice of cleavers-specific weapons has been extended with recent approval of Boxer (florasulam). Other options include Lotus (cinidon-methyl) launched last year, Eagle (amidosulfuron), Platform S (carfentrazone + mecoprop), well established Starane (fluroxypyr) and a range of mecoprop-only products such as CMPP.
Options would have been wider but for a delay in getting Monsantos MON 375 (sulfosulfuron) approved, notes Mr Neale. Now it is unlikely to be available until 2001. "But it is very promising."