Cereals 2024 Weed Control Part 2 Herbicide Use and Pesticide Resistance Flashcards
Choice of Herbicides (4)
- select products which are safe on the crop
- select products usable at the relevant GS’s
- select a product to best control the most
difficult weed problems - look at alternatives to the product chosen in the
light of :
– cost/ha, toxicity, nature of use
Key active ingredients in widely used herbicides:(9)
- Mesosulfon-methyl (Alister / Pacifica)
- Diflufenican (DFF / Alister / Firebird )
- Iodosulfuron-methyl (Hussar/Alister / Pacifica)
- Pedimethalin (PDM / Flight (Crystal )
- Sulphonyl-Urea’s (SU) many of
- Hormonal (CMPP / MCPA)
- Fluroxypyr (Starane / Hurler / Reaper,
- Ioxynil, bromoxynil (HBN’s)
- Isoproturon (IPU)
History of Isoproturon (IPU) use in winter cereal crops:
1-What sort of acting herbicide is it?
2- grass weed control was based on the use of…
3- What are used widely nowadays?
1* a residual soil-acting herbicide with activity on grass weeds and broad-
leaved weeds
2– grass weed control was based on the use of IPU before tillering of
the grass / some b/l weeds, historically was useful for wild oats
control
3* cheap generic herbicide (off patent) and widely used from 1980s
to recent times
* availiable under a range of brandnames - Arelon, Fieldguard,
Tolkan, but mostly used in a product which is a formulation
with other a.i.’s
* In UK IPU had big problems with leaching into waterways and
was banned 15 years ago
* In Ireland and EU - banned from 2017 onwards
What is DFF?
is a residual soil-acting herbicide with
good activity on broad-leaved weeds and useful
grass weed activity
– diflufenican goes into tank mix combinations – pre- and post-emergence on winter wheat and
barley ; end-Sept. to early-March – very wide spectrum of weeds controlled– good suppression of cleavers but unreliable control– fumitory is resistant (also resistant to Ally
new high activity products alternatives are
Firebird & Alister
Current options for weed control in winter cereals: (2)
1* Firebird is a residual soil-acting herbicide with
activity on grass weeds and broad-leaved weeds– DFF + flufenacet (400+200 g/l) with a recommended
rate of 0.3 l/ha– Early post-emergence on winter wheat and barley– Very good on annual meadowgrass (AMG)– Weakness on cleavers, charlock
2 * Alister is a post-emergence herbicide for GS 13 to 30
and is broadspectrum with strength on AMG– DFF + mesosulfuron + iodosulfuron with a rate of 0.75
1.0 l/ha
Small Grass Weeds!–
Good spraying technique is IMPT
Correct spraying technique is very important , what’s the correct height?
- Boom height
One years weed is =
seven years seed
What will seed before harvest?
What happens to the large seed bank?
1-Many weeds like wild
oats and sterile brome
will seed before
harvest
2-* the large seed bank
then returned to the
soil become weeds for
many future years
Sterile Brome Control Options:
1- Whats it a widespread problem in?
2- Whats their problems with?
3- What is a granule formulation?
4- What sort of action?
5- When is an ideal time to spray?
6- What is it weak on?
1 * Widespread problem in min-till system
2 * Problems with achieving high level of control 99%
3 * Broadway Star (pyroxsulam + florasulam)
in a granule
formulation
4* Contact only action so only works on weeds present so
use medium to fine nozzles and an adjuvant
5 * Early-autumn use is ideal but also in spring – up to GS
32 (less efficacy)
6- Weak on AMG (need pendimethalin mix)
1- What is a big problem?
2- Fast or slow at multiplying?
3- Is it competitive?
4- Is it cheap or expensive to control?
5- What do you need to ensure is in place?
6- Whats it a good example of?
1-Wild oats are a very important
weed in cereal crops
2- Weed can multiply very fast x
100+ in two years
3- it is a very competitive weed
with the crop - reduces yield
and quality
4- expensive to control with
herbicides – Axial Pro at rates
from 0.6 – 0.85 l/ha
5- Need good spray placement
and spraying practice
6-It’s a good example of a
‘niche’ herbicide , another is
Starane for cleavers control
Wild oats, what are they difficult to get?
Whats the target with them?
– difficult to get wetting / product uptake
– especially in a dense crop canopy
Target is 99% plus control
Common weeds in winter and spring cereals
Winter Cereals :(7)
- chickweed
- speedwell
- mayweed
- cleavers
- red deadnettle
- fumitory
- field pansy
Common weeds in winter and spring cereals
Spring Cereals :(6)
- chickweed
- speedwell
- fat hen
- red shank
- knotgrass
- corn marigold
Spring weed control in spring cereal crops:
What should weed control be?
Key ‘different’ weeds are?
- weed control should be relatively simple– ‘soft’ weeds in good growing conditions with wider
‘window of opportunity’ to spray in suitable
weather conditions– opportunities to reduce herbicide rates alone and in
mixture : typical cost is Euro 15-30/ha - key ‘different’ weeds are the polygonum weeds
