background image
MARCH 2018
Tillage Focus
MARCH 2018
Tillage Focus
conditions. This is most notable when they are applied as solo
products and when applied curatively. It is, therefore, essential to
ensure they are used in mixtures, as protectantly as is possible and
in combination with multi-site chlorothalonil (eg. Bravo). Careful
consideration should be given to both the timing of application
and rates applied to ensure the weaknesses that now exist do not
unduly impact control. Where rates or timings are compromised,
particularly earlier in the season, the application of a multisite such
as chlorothalonil when leaf two is fully emerged may be warranted.
Joe Mulhare, Teagasc, presented a paper on `Assessing weather-
based forecasting for Ramularia', which is a seed and wind-borne
pathogen of barley. Ramularia has become a significant threat on
both winter and spring barley crops throughout Europe over the
past two decades, as this disease reduces both the quality and
quantity of harvested grains. Yield losses in spring barley can be 0.5
In 2015, harvested grain samples from both winter and spring
crops, from four representative regions of Ireland, were analysed
for the presence of Ramularia. Ramularia was found in 82 per
cent of 229 samples tested, although at low levels. This was in
spite of a relatively low Ramularia pressure season. Previous work
in Scotland found disease development to be directly related to
leaf wetness between growth stage (GS)25 and GS32 (for spring
barley), indicating scope to use this as a decision support (DSS)
tool for disease forecasting. If the crop is deemed to be at high
risk (minutes of leaf surface wetness [LSW] >7,500, which equates
to leaves being wet at high relative humidity [>90 per cent] for
roughly one-third of the total time in this period), fungicide
mixtures with known efficacy against the pathogen can be
deployed at the GS45 application.
This research aims to assess whether the DSS tool is relevant to
Irish field conditions. Field trials were conducted in 2016 and
2017 at Oak Park, Carlow (considered a medium-disease-pressure
environment) and in Kildalton, Co Kilkenny (a high-disease-
pressure environment), using four different spring varieties from
the recommended list (Propino, Irina, Olympus and Planet).
Plots received five different disease control treatments at GS45:
(i) a `standard' of prothioconazole (Proline) and chlorothalonil
(Bravo) applied at 50 per cent of the recommended rate; (ii)
`QoI' pyraclostrobin (Modem) to let Ramularia develop but not
other major barley pathogens; (iii) `DSS product' of chlorothalonil
(Bravo), bixafen and prothioconazole (Siltra Xpro) selected due to
high levels of leaf wetness at the start of stem extension; (iv) `DSS
rate' with increased rates (75 per cent) of the standard treatment
also due to high forecasted risk; and (v) an `untreated' control.
At GS75, the percentage of Ramularia and green leaf area (GLA)
were visually assessed on leaf two of 10 main tillers per plot. There
were significant differences between varieties for disease control
and yield in both years. In 2016, Kildalton was considered a high-
risk site and Oak Park a low-risk site, according to the DSS tool.
While analysis found that both DSS programmes provided the
best control, neither was significantly different, in either control
or yield, to the standard programme. In 2017, both sites were
considered high-risk and, again, there was no significant difference
between both DSS programmes and the standard programme. This
may be due to the superior activity provided by chlorothalonil
against Ramularia.
Joe concluded that, in a high-risk season, such as 2017, the
standard programme provides adequate control while, in a low-risk
season, such as 2016, it can be reduced with confidence while still
providing control.
Robert Beattie, Teagasc, indicated that winter barley has become
increasingly popular due to improved yield potential as a result of
genetic improvement and improved agronomy. The introduction of
hybrid six-row varieties have performed very well in recommended
list trials, consistently producing higher yields than conventional
two-row varieties.
To investigate if the crop protection strategy needs to be altered
depending on ear morphology, a field trial to study fungicide
application timing in a two-row (KWS Tower) and six-row
(Volume) winter barley variety was carried out for three years
(2014/2015, 2015/2016 and 2016/2017) at two sites: Scotland's Rural College
(SRUC), Edinburgh, Scotland; and Teagasc, Oak Park, Carlow,
Ireland. The fungicide applications were applied as part of
programmes, consisting of a control, a single application (GS31/32),
a two-spray (GS31/32, GS49), a three-spray (GS25-30, GS31/32, GS49)
and four-spray programme (three-spray plus GS65). The results
showed that, despite the dramatically different yield components
of each variety, there was no significant interaction between variety
and fungicide application, suggesting that disease management
does not need to be tailored to ear type.
To investigate if a six-row variety has a greater requirement for
plant growth regulator (PGR) treatment compared to a two-row
variety, in the same field trial as mentioned above, additional
treatments of the three-spray and four-spray programmes
without PGR treatment were investigated. The treatments were
independent applications at GS30 and GS37. The products used
were: 1L/ha of CeCeCe 750 plus 0.2kg/ha of Medax Max at the GS30
timing; and 0.4kg/ha of Medax Max at the GS37 timing. The results
indicated that each variety responded differently to PGR treatment,
with the six-row variety displaying a significant yield reduction in
the absence of PGR, while there was no significant effect on the
A report by Lael Walsh of Teagasc concluded that the grain aphid
can also detoxify pyrethroids an additional resistance mechanism
to knockdown resistance (kdr). This increases the challenge for
growers with limited alternative chemical control. Growers must
adopt cultural control options such as sowing date changes, use of
varietal resistance etc. to reduce the pressure on insecticides.
There are a number of mechanisms by which insects may become
resistant to insecticides, including reduced insecticide penetration,
metabolic de-activation and alteration of the insect's target site, all
of which reduce susceptibility to the insecticide's mode of action.