2 March 2001

TIMING KEY TO OPTIMUM FUNGICIDE USE

TIMING is everything when it comes to applying fungicides, says ADAS pathologist Bill Clark.

"It is the key to profitability and the effect can easily be as big as that from product choice and dose."

With more than half the response of a three-spray strobilurin/triazole programme on wheat coming from the flag leaf timing, a delay of just 10 days can cut 0.75t/ha (0.3t/acre) from the yield of a septoria-susceptible variety such as Consort, he notes.

The extra yield from accurate T1 spray timing can be as good as that from switching from triazoles to strobilurins, adds Mr Clark. "People forget that you can get it just by correct timing."

A two-spray fungicide programme will be appropriate in most seasons, says Mr Clark. "I am always struck by how different the UK is compared with France and Germany. Most Germans cannot believe we sometimes apply four sprays. It is very rare for them to use three. "If you are using more than four here you are doing something wrong."

Match the number of treatments to variety, advises Mr Clark. Disease-prone types merit more. There is no justification for straying beyond the benchmark doses, he maintains. "But there are always people well outside the range."

Be sure to use fungicides most active against the target diseases, advises Mr Clark. Growers using the benchmark project are guided to a helpful star-ratings chart in the HGCAs wheat disease management guide, where detailed response curves are also available.

Water volume and spray quality have little impact on fungicide performance, so it is worth considering dropping the amount applied, he says. "It is a very simple thing which you can do to improve timings and still get good disease control." &#42

Yield penalties from 14-day flag leaf spray delay

Consort, Riband 1.3t/ha (= 0.09t/ha/day)

Equinox, Savannah 1t/ha (= 0.07t/ha/day)

Yield penalties from 10-day T1 spray delivery

Consort 0.7t/ha (= 0.07t/ha/day)

Equinox, Savannah 0.25t/ha (= 0.025t/ha/day)

Claire, Shamrock Nil

Number of fungicide sprays

Benchmark Acceptable range

2 1-4

Fungicide timing benchmarks

Benchmark Acceptable range

GS32 GS30-32

GS39 GS37-45

GS59 GS59-65

Yield penalty from single-v three-spray programme

Consort 1.9t/ha

Equinox, Savannah 1.1t/ha

Claire, Shamrock 0.7t/ha

Fungicide dose split

Benchmark Acceptable

range

T1 0.5 0.25-0.75

T2 0.75 0.5-1

T3 0.25 0-0.5

Note: of total units supplied.

Spray volume

Benchmark Acceptable range

100 litres/ha 50-200 litres/ha