The Farmers Mart Apr-May 2019 - Issue 62 | Page 51

ARABLE 51
• APR/MAY 2019
Trial plots point to better Ramularia
reduction from earlier fungicide spray
NEW results from trials suggest barley
growers looking to boost control of the
growing problem of Ramularia spotting
could do so by shifting a key fungicide used
against the disease to an earlier timing in
the spray programme.
According to Syngenta field technical
manager, Iain Hamilton, Ramularia col-
lo-cygni, which can cause devastating
losses in barley green leaf area and yield
losses of up to 10%, was traditionally mainly
a problem in Scotland. However, over the
last five years, its grip has spread from the
north of the UK to the south.
Infection starts from the seed, he says,
though can also come from crop debris,
with the disease then entering a dormant
phase, only to be triggered later when the
crop is put under stress, when it results in
spotting symptoms on upper leaves.
“With no effective seed treatments
against Ramularia, and variety resistance
ratings not currently available, the mul-
ti-site fungicide Bravo (chlorothalonil) has
become a mainstay for tackling it,” says Mr
Hamilton, “especially following the reduced
performance or resistance seen with other
fungicide groups.
“Historically, Bravo has been applied as
part of the conventional T2 fungicide spray
at the awns emerging to ears emerged
timing (GS49-59).
“However, new results from last season,
where Bravo was used in winter barley
with the SDHI-based fungicide, Elatus Era,
showed a much greater Ramularia reduc-
tion was achieved on the top three leaves
by spraying earlier than this – either at the
flag leaf emerged timing (GS39) or when
flag leaf sheaths were swollen (GS45).
“More significantly, these results were
echoed by improvements in green leaf area
by spraying at these earlier timings and,
more importantly, by increases in yield.”
Based on the new findings, Mr Hamilton
says growers should consider these earlier
spray timings in winter and spring barley –
either by applying Bravo at GS39 followed
by Elatus Era as ears emerge at GS55-59;
or by applying a tank mixture of Bravo and
Elatus Era at GS39-45. The former approach
may suit situations where late brown rust is
expected, he notes.
“Bringing the Bravo spray forward from
the traditional T2 timing fits with what we
know about Ramularia,” says Mr Hamilton,
“in that it is important to treat it before
symptoms appear, since Bravo is a protect-
ant fungicide it needs to be used preventa-
tively.
“Usefully, applying Bravo at GS39 isn’t
necessarily an extra spraying operation.
An ethephon based plant growth regula-
tor is often sprayed on barley at this time
anyway.
“Other trials have also shown better net
blotch control, better green leaf retention,
better yield and better margin over fungi-
cide cost with the GS39-45 Bravo plus Elatus
Era timing.”
www.syngenta.co.uk
EMERGING THREAT FROM
NEW TOMATO VIRUS
UK growers are being urged to look out for symptoms of a potential new
virus that could be devastating to UK crops of tomatoes and peppers.
FIRST identified in Israel in 2014, tomato
brown rugose fruit virus (ToBRFV) has now
been confirmed in Germany, posing a po-
tential risk to UK production.
The virus results in unmarketable fruit
and can affect up to 100 per cent of stock,
which could have substantial economic im-
‘ It’s important growers
are aware of hygiene
protocols to minimise
the risk of infection
’
pact – the home production market value
of UK tomatoes was £104.9m in 2017.
AHDB has issued information to help
growers, glasshouse and packhouse staff
to identify the symptoms in anticipation of
its arrival in the UK. Recommendations on
preventing infection and spread through
hygiene measures are also available.
Nathalie Key, knowledge exchange man-
ager at AHDB, said: “While the virus isn’t yet
in the UK, we are mobilising resource to
make sure that the industry is aware of the
possible symptoms. It’s important growers
are aware of hygiene protocols to minimise
the risk of infection.”
Symptoms
The virus is related to Tobacco mosaic
virus and Tomato mosaic virus, however
varieties with resistance to those viruses
will be susceptible to ToBRFV.
Tomato is the major host of ToBRFV but
trials have demonstrated that sweet pepper
can act as a minor host, showing slight
symptoms.
Symptoms to look out for include:
• Mosaic staining of the leaves
• Discoloured fruit with yellow spots
• Deformation of fruits
Suspected outbreaks should be report-
ed to the relevant authority. For England
‘ the virus results in
unmarketable fruit
and can affect up to
100 per cent of stock
’
and Wales, contact APHA Plant Health. For
Scotland, contact the Scottish Govern-
ment’s Horticulture and Marketing Unit. For
Northern Ireland, contact the DAERA Plant
Health Inspection Branch.
ahdb.org.uk/knowledge-library/tomato-
brown-rugose-fruit-virus