Varieties and virus were major topics at CROPS FORUM

Last week’s Teagasc Crops Forum provided valuable information for tillage farmers. The update on varieties alone is very useful, but it also covered other topics such as BYDV, CAP changes and the environment.

The regular winter variety update slot was presented by John Joe Byrne from the Department’s variety evaluation centre in Backweston.

While these are only one-year results, they do provide a guide to growers and challenge field performances at times. But the recommended list provides a more robust assessment of relative performance.

Winter Wheat

Interestingly, Torp came out on top of the recommended varieties in 2019, followed by Bennington at 102 (Table 1).

Graham was the best of the candidate varieties at 105, while the newer SY Insitor also looks impressive. Cellule did not have a good year and its collapse to septoria may not have helped.

The tightness of a variety’s performance provides some measure of its dependability across sites and seasons. Table 1 shows variety performance in 2019 and its yield range across sites. In general, the recommended varieties tend to have a tight range and the candidate variety Graham also looks good, as does SY Insitor. LG Skyscraper yielded well but it has weaker straw and a problem with septoria.

Some new varieties had lower performance in 2019 than in 2018, so they may fall of out of the testing process.

On septoria, Password shows good resistance while Graham is moderate.

On yellow rust, Costello is the most resistant, while Torp, Bennington, Diego and Garrus are amongst the most susceptible, but to different stages of the disease.

Costello and Conros are regarded as most resistant to lodging. Costello, Cellule and KWS Conros are regarded as being best against sprouting with LG Skyscraper, Bennington, Password, KWS Scimitar and Garrus most susceptible in that order.

Winter barley

Winter barley performance was much more variable across the country this harvest and the same can be said of performance across trial sites (Table 2). The trials show considerable benefit from the six-rows this season, with the average benefit somewhere around 20% over the recommended two-rows.

They still showed considerable variability across trial sites. There was not much difference between KWS Kosmos, Quadra, Belfry and Bazooka, but Pixel was a step behind due to its performance at one site in particular – possibly a ramularia issue.

The last six varieties in Table 2 are candidate varieties for recommendation this year. Libra and Orbit are six-rows. Libra seems to have very high specific weight, while Orbit is poor, but the latter is very good against ramularia. Carneval, Casting, Valerie and the NOS variety are all two-row types and the latter three show some potential for yield improvement.

Belfry, NOS911.015-60, Cassia, Bazooka, Quadra and Libra are amongst the best against ramularia, with Pixel, Orbit and Valerie faring worst. Cassia is poorest on rhyncho, but the new varieties and the six-rows are good. On mildew, Orbit, Kosmos and KWS Higgins are the best, while Cassia, Infinity, Carneval and Libra are poorest.

On net blotch, most varieties are good but Tower now shows little resistance to the spot form. Cassia, Libra, Valerie, Bazooka and Quadra are best on KPH while Infinity, Tower, Pixel and Orbit are poorest.

Winter oats

Variety performance in 2019 was along traditional lines. Keely had a good year in trials which will help its average, while Husky and Barra showed their usual yield difference, but with very tight inter-site performance (Table 3).

The provisionally recommended Delfin and RGT Southwark, and the candidate variety WPB Isabel, all had a particularly good year too, but all three showed much higher inter-site variability (Table 3).

On specific weight, Barra is joined by Isabel at the top, with Husky and Keely coming in joint second. On crown rust, Southwark is the most resistant, followed by Isabel and Keely, while Husky, Barra and Delfin have the poorest resistance. Mildew resistance tells a different story, with Delfin faring best, followed by Husky and Isabel and the three others being quite susceptible.

With regards to straw strength, Isabel and Delfin are strongest, Husky is regarded as medium while Keely, Southwark and Barra are the weakest.

The loss of Redigo Deter for aphid control introduces a new set of challenges, especially for early drilling. This is exacerbated by concerns over the efficacy of pyrethroid insecticides, with the widespread presence of knock-down resistance (kdr).

Steve Foster from Rothamsted in the UK reaffirmed that kdr represents reduced efficacy from pyrethroid insecticides, but said they will still work at full rates where no other resistance type is present.

He said research studying kdr populations seems to show a decline after a population reaches the 50% level. He also said insecticides seem to exhibit a deterrent affect on the susceptible types.

Foster points to the benefit of knowing if aphids on the move are carrying virus or not. Knowing this would enable more targeted insecticide use.

He said science has developed a molecular assay which can test for the two main virus types in plants or aphids.

This is now being used in conjunction with sampling inflight aphids to improve risk guidance.

While plant breeders are working on BYDV tolerance, we will still have to rely on a combination of husbandry, integrated pest management and sensible use of insecticides to control this disease, said Ciaran Collins of Teagasc.

He said risk is greatest with early planting so that must be our main change to help control this problem. But it needs to be balanced against individual field challenges.

As well as early sowing, mild winters play a part in the risk factor, as do specific sites, the presence of a green bridge, weather and rotation.

While there are many seasonal variations, infection risk is said to be eight and a half times higher when planting cereals after cereals.

While research here is also looking towards forecasting tools, Ciaran said we must aim to minimise insecticide use by acting to reduce the risk factors we can control. This is important because the risk of other types of resistance increases each time we use an insecticide.

While later planting must form part of the control process, Ciaran said that an early sown crop for a region will need two insecticides, one at the two- to three-leaf stage and a second in early November.

An October sown crop should be sprayed in early November and a November emerging crop may only occasionally benefit from an insecticide. A January insecticide can also be beneficial in a mild winter.