CROP CRACK - 23.03.07
By WENDY FEARON
Clarendon Agricare
SERIOUS THREAT FROM LEATHERJACKETS!
I will begin by apologizing for the crop crack on 10th
March which was a copy of crop crack 10th February and
was accidentally sent to Farming Life by mistake. I hope the
information this week will make more sense!
The dreadful weather over last week has
certainly halted all fieldwork. The cooler conditions will have
slowed down feeding activity by leatherjackets.
According to samples taken over the last couple
of months to access leather jacket numbers, populations are
extremely high. Despite the predictions of a serious grub threat,
blanket insurance spraying is not recommended. Experience has shown
that grub populations can be extremely variable, not only from area
to area but also within an area and from field to field on the same
farm. Consequently, even in years of high predicted risk, there
will always be some fields where conditions are less favourable for
leatherjacket survival and which therefore contain lower levels of
infestation. Hence even where past history of problems may suggest
that fields may be at risk from leatherjacket attack, it is
essential that some form of assessment of leatherjacket infestation
is conducted prior to deciding whether any insecticide application
is necessary. Conducting such assessments in early spring helps
identify those fields at risk before any damage has occurred.
If infestations are proved to be high, either
in grass to remain as herbage or in leys to be ploughed, a spray
should be applied as soon as ground conditions permit.
Pre-ploughing treatments are more effective than those applied once
damage is under way in the replacement crop. However, where grub
densities prior to arable crops are marginal for treatment, current
advice is not to take preventative action against the grub straight
away but to wait and monitor the brairding crops and treat only if
necessary.
The population threshold for treating permanent
pasture is one million leatherjackets per hectare (100/m2).
The threshold in spring crops is 0.5 million leatherjackets per
hectare (50/m2).
Fields with a history of leatherjacket damage
should be monitored for large numbers of rooks and crows feeding on
the larvae. Risk assessments and testing for the presence of
leatherjacket larvae will provide a good indication of fields that
are most likely to need treatment.
If treatment is justified use
Dursban* WG at 1.0 kg per hectare applied in 200 to 1000 litres
of water. Control will be reduced if temperatures are below 5oC
as the larvae will move deeper into the soil profile.
Winter Barley
Crops range from early tillering up to
pseudostem erect stage. Rhynchsporium and net blotch are the most
common disease on winter barley at present, although in more forward
crops mildew is also present. A fungicide should be applied as soon
as ground conditions allow. The other thing to consider at this time
is the use of Adjust to increase root development and help boost
tillers.
Winter Wheat
Winter wheat crops have turned very yellow over
the last week and consideration is now turning to fertilizer. It is
essential to achieve healthy plant establishment as critical spray
timings may be delayed due to crops being under stress.
Due to the milder conditions over winter foliar
disease is present on most crops especially in crops of Robigus
where Septoria tritici is very apparent. Winter wheat should receive
a T0 fungicide application now followed by T1 at GS31-32.Adjust will
benefit crops which have a poor root system and few tillers.
Oilseed Rape
Most rape crops achieved good establishment
over the autumn and winter, but bare patches are now appearing in
some crops due to clubroot.Wet soils coupled with the mild autumn
are the reasons for this outbreak. Light leaf spot is now appearing
in some crops and it is advisable to apply a fungicide now rather
than stem extension, especially to crops which did not receive an
autumn treatment.
Sprayer Calibration
I would like to remind you again the importance of
maintaining all farm machinery especially sprayers. All too often
serious problems arise due to very simple errors with the sprayer.
Calibration is important as a properly calibrated machine can save
money and improve efficacy. For a certain category of pesticides
which are applied using a ground crop sprayer to land near to a
watercourse, there is a legal obligation to carry out and record the
results of a Local Environment Risk Assessment for Pesticides, LERAP.
By carrying out a LERAP the size of the buffer zone may be reduced. |
