Cereals 2024 Weed Control Part 2 Herbicide Use and Pesticide Resistance

• 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)

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- availiable under a range of brandnames - Arelon, Fieldguard, Tolkan, but mostly used in a product which is a formulation with other a.i.’s 4- In UK IPU had big problems with leaching into waterways and was banned 15 years ago 5- In Ireland and EU - banned from 2017 onwards

1- Is a residual soil-acting herbicide with good activity on broad-leaved weeds and useful grass weed activity 2- Diflufenican goes into tank mix combinations 3- end-Sept. to early-March 4- fumitory is resistant (also resistant to Ally) 5- new high activity products alternatives are Firebird & Alister

Firebird Alister

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

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

IMPT Correct spraying technique is very important - Boom height

• Product choice / Formulation Important but ….. • Sprayer in good working order and properly calibrated • Nozzle Choice • Reducing water volumes can improve timing • Boom Height 50cm above target for 110 fan nozzles • Forward Speed determined by keeping boom level

7 years seed

1-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- good spectrum on other weeds – wild oats, ryegrass 7- Weak on AMG (need pendimethalin mix)

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

99%

• chickweed • speedwell • mayweed • cleavers • red deadnettle • fumitory • field pansy

• chickweed • speedwell • fat hen • red shank • knotgrass • corn marigold

– ‘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 2- key ‘different’ weeds are the polygonum weeds

typical cost is Euro 25-35/ha

sulphonyl urea’s

typically applied before the end of tillering (GS 30)

• excellent spectrum • good performance where rates are reduced to 50- 75% of R.Rate • excellent activity on previously difficult annual and perennial B/L weeds • low dose rates 15-30 g/ha • granule and tablet formulations • wide window of appl. up to flag leaf on all cereals • very compatible with other crop protection products • low mammalian toxicity

• sprayer contamination • sensitivity of brassicae crops to 1/70 of rate • recent emergence of resistant weeds - chickweed, marigold

More focussed spectrum targeting the control of blackgrass, annual meadow grass, sterile brome, cleavers etc • Issues with resistance management strategies • Key products – Atlantis (UK) for blackgrass – Alistar/Pacifica/Hussar for AMG / wild oats – Pacifica and M for sterile brome control – Eagle for cleavers control

– Healthy plants beside dead plants of the same species – Poor control of one susceptible species when other species are well-controlled – Discrete weed patches – Gradual decline in control over several years

Herbicide resistance is an inherited trait and with repeated selection resistant plants survive, multiply and dominate the weed population