HGCA fungicide performance trials suggest that BASF’s Adexar is the strongest of the new SDHI fungicides against septoria, particularly at lower doses.

It is also excellent against rusts and challenges Siltra Xpro for best all-round barley fungicide.

The trials are a severe test of product efficacy, using single applications at either T1 or T2 on disease-susceptible varieties at high-risk sites. Three years of trials are used for the analysis with, in the case of septoria, 13 eradicant and 17 protectant trials series used to differentiate between products.

Presenting the results at the HGCA Agronomist Conference, Jonathan Blake said Adexar separated itself from Aviator Xpro at the lower doses in both eradicant and protectant septoria conditions. At full doses Adexar had the edge, but the differences were small.

Both products had separated themselves from the third SDHI fungicide, Seguris, particularly in eradicant situations, where the additional isopyrazam in Seguris had not added much to epoxiconazole, Mr Blake said.

There was less difference between products in protective septoria situations, which is typically the conditions growers would apply the products, he suggested. “When we get the products out in programmes the differences could be less than what we see here.”

All three products are an improvement over the two most commonly used triazole fungicides, epoxiconazole and prothioconazole. However, the highly-loaded triazole fungicide, Brutus, has similar performance to Aviator Xpro in eradicant circumstances – better than Seguris – and similar performance where protection was tested.

Yields from those trials followed a similar pattern, with Adexar and Aviator Xpro strongest. Adexar had the edge at lower doses, with Seguris and Brutus similar and above that of epoxiconazole and prothioconazole.

In three additional trials, where two half doses of each product were sprayed at T1 and T2, Adexar was the top-yielding treatment, with all the new SDHIs giving a yield boost over single triazole fungicide treatments. “On average it amounted to about 0.7t/ha, which is a significant improvement,” Dr Blake said.

Against yellow rust, Adexar and Seguris were the strongest products in a 2011 trial at Terrington, while Aviator Xpro lagged behind, although an assessment after three weeks showed only minimal differences between products where at least half rates had been applied. “However, later in the season we did see differences in persistence, which came through to yield. Adexar and Seguris held on well later in the season, while Aviator wasn’t quite so strong and that showed in the yields.”

The relative yellow rust weakness of Aviator Xpro, and particularly prothioconazole, was shown in the T1 + T2 yellow rust trial at the site, Dr Blake added. “Aviator was better than Proline, but still not quite as strong as the other SDHIs.”

Against brown rust, the trials information dated from 2009, and all three SDHI fungicides were strong against the disease, Dr Blake said.

Barley disease comparison

Adexar and Siltra Xpro were difficult to separate across seven barley trials comparing performance for rhynchosporium eradication, although both products were clearly superior to Proline and Bontima.

In a protectant situation Siltra Xpro had started to separate from Adexar, Dr Blake said.

Most products did a good job against net blotch, with little to choose between any once half dose had been reached.

But Siltra Xpro and Adexar again had a clear advantage over Bontima against ramularia, with Proline and Bravo a further step behind.

Active ingredients

Adexar – fluxapyroxad + epoxiconazole

Aviator Xpro – bixafen + prothioconazole

Bontima – isopyrazam + cyprodinil

Bravo – chlorothalonil

Brutus – epoxiconazole + metconazole

Proline – prothioconazole

Seguris – isopyrazam + epoxiconazole

Siltra Xpro – bixafen + prothioconazole

For more from the HGCA’s Agronomist Conference see our dedicated page.