Farm Ireland

Wednesday 21 March 2018

Leaf emergence is faster than ever as high temperatures push growth rates

Pat Minnock

Pat Minnock

The heavy rain of the last week has been very welcome for autumn-sown cereals. Crops have been drilled in excellent conditions and with high soil temperatures, emergence has been even and rapid.

Crops have never looked as well for this time of the year and contrasts dramatically with the last few autumns. Leaf emergence and tiller numbers are driven by temperature, with a leaf emerging every 12 days when temperatures are 10C.

Each extra leaf can be expected to produce a tiller bud. The recent weather has been well above 10C.

The excellent seed quality of the 2013 harvest is an added bonus. Seed bed conditions have seldom been as good and growers are amazed at the speed of emergence of crops sown. The downside of this is obviously possibly greater problems with aphids leading to yellow dwarf virus and higher levels of take all, greater disease pressure in the autumn and higher lodging pressure.

Advanced crops of barley wheat or oats should have already received an aphicide. Any early winter barley treated with Redigo Deter will require an aphicide towards the end of October/early November.

Warm, moist soil conditions facilitate aphid movement through soils. 'Green bridge' transmission is most likely in early-drilled crops and in mild damp autumns. Aphids transfer directly from weedy stubble to new cereal crops. The ITCA aphid traps show very high aphid levels.

While it appears that there is currently a relatively low level of pyrethroid resistance in the grain aphid, it is important to remember that this is becoming an issue and should be monitored carefully. If aphid activity remains high after spraying, there should be a follow-up treatment.


Also Read

All crops should be sprayed at the two-three leaf stage. Generally for crops sown from mid-October onwards, one application at the two leaf stage should suffice. Crops sown after the middle of November will only require an aphid spray if weather conditions remain mild and aphid counts remain high.

Some of the very early winter barley crops show large amounts of spring barley volunteers and will suffer from early disease pressure.

Early winter wheat sown in high take-all situations will need particular care next spring. A delayed first split of spring nitrogen and extra plant growth regulator (PGR) applications may also be required. Most winter barley has been sown at this stage, with levels up 40-50pc on last year. If sowing from now on a minimum of 260kg/ha (17st/ac) should be used for the two-row variety Cassia to achieve 450+ seeds per square meter, assuming 70pc establishment.

For wheat sown from now on, 400-500 seeds per square metre should be targeted, assuming a 60-70pc establishment and based on the thousand grain weights (TGW).

Winter oats sowing appears to be significantly up on usual, with Barra and Huskey the main varieties. The target plant stand for oats should be 350 plants per square metre. This will require approximately 540 seeds per square meter sown from now on.

It is also time for autumn weed control for barley and wheat. The most popular treatment will be varying rates of DFF plus IPU. While this treatment is good in low weed situations this mix is poor on Cleavers, Fumitory and Poppies.

Oilseed rape looks particularly good this autumn, with few bare patches. However, diseases such as Phoma and Light Leaf Spot are apparent and require treatment. A Triazole such as Punch C, Folicur or Proline should be considered.

Volunteers should also be treated with a half rate graminicide and trace elements, particularly boron applied at the same time.

Pat Minnock is a Carlow-based agricultural consultant and a member of the ACA and the ITCA.

Irish Independent