Tough season highlights seed treatment value

Challenges from take-all, BYDV, foliar disease and black-grass over the past season have underlined the importance of cereal seed treatments, says a leading agronomist.

If for no other reason, seed treatments have value because application is independent of the difficult weather conditions which have seriously interfered with the timing and effectiveness of so many autumn and spring spraying programmes this season.

Agrii crop protection technical manager Chris Bean says seed treatment continues to be the only technical opportunity to target many seed-borne diseases such as bunt, smuts and fusarium seedling blight, and key pests such as wireworm and wheat bulb fly.

However, it has developed far beyond these traditional uses to offer much wider agronomic value. These include early take-all, BYDV and foliar disease control, together with greater black-grass competitiveness and resistance to environmental stresses, he says.

"In recent years, we’ve come to appreciate the value of using a take-all active seed dressing like silthiofam (Latitude) or fluquinconazole (Galmano) as routine for most, if not all, second wheats.

Monitoring

"The national monitoring with which we’ve been involved shows record levels of take-all infection - and potential inoculum carryover - this season. So, robust autumn treatment will be vital to restrict disease development in the face of both earlier sowing and generally milder winters.”

Seed treatment also has an essential role to play in addressing the serious BYDV concerns which have come to the fore for many in the past year. Widespread wheat and barley infections have underlined the critical importance of early vector control.

As well as protecting wheat and barley from the early attentions of BYDV-carrying aphids, clothianidin is valuable in restricting damage from wireworms and seed hollowing by slugs, especially when combined with the seed-borne disease control benefits of Redigo in wheat or Raxil Star in barley.

Aphid activity

The exceptionally mild conditions of the past winter meant the UK saw aphid activity well into January in many areas, says Chris Bean. Under these conditions, nothing but the most intensive treatment programme would have fully protected crops in high BYDV risk areas.

Where seed was treated against aphids, levels of BYDV infection have been significantly lower than where pyrethroids alone were used.

"Under these circumstances, we strongly recommend clothianidin (Deter) or imidacloprid (Tripod-Plus) are employed in all areas where aphid vectors are a problem,” says Mr Bean.

Controlling early insect activity becomes even more important given the extra risk posed by grain aphids (sitobion avenae) which appear to have developed resistance to pyrethroids in some areas.

"Equally, with more emphasis on pre/peri emergence weed control even in non-black-grass situations, seed treatment is invaluable in relieving pressure on autumn aphicide timings.

Agrii trials highlight the value of reduced rate fluquinconazole (Galmano Silver) seed treatment in suppressing yellow rust inoculum, in particular, through to spring in first and second wheats, giving more leeway to control one of the biggest threats to such a popular range of wheat varieties.

Its value was especially apparent this spring where high levels of early disease infection in untreated crops led many growers to bring forward T0 treatment. Weather delayed T1s, then led to a gap of five weeks or more between treatments, allowing septoria to get an early hold on leaf 2.

"In contrast, the seed treatment held yellow rust infections back well for a better-timed T0 which enabled far better T1 timing whenever the April weather permitted,” says Mr Bean. “In turn, this enabled more optimal T2 and T3 control.”

Three years of trials at Agrii’s main black-grass management site at Stow Longa have shown fluquinconaozole treatment also gives clear improvements in root and leaf area development on shy tillering varieties.

Early-drilled Torch, Robigus, Alchemy, Oakley, Battalion and Sahara were the most responsive, averaging a 0.5t/ha (0.2t/acre) yield response, but 0.8-1.0t/ha where black-grass was a problem - as a result of greater crop competitiveness.

Pressure

"This extra seed treatment benefit has been very valuable in the past season too,” says Mr Bean.

"Good drilling conditions and generally dry soils in September meant limited pre-planting glyphosate. On top of this, autumn and early winter conditions were far from ideal for pre-em control. All of this piled the pressure on increasingly vulnerable post-ems, leading to serious black-grass problems for many and reinforcing the need for the greatest possible contribution from cultural controls.”

Improvements in emergence and root mass have been secured from treating cereals with the root stimulating seed dressing.

Take-Off. By improving root development, it increases winter hardiness and drought tolerance. It works synergistically with take-all active seed treatments, as does a new manganese seed dressing. This is proving particularly valuable in second and third wheats and on low pH, high organic matter or other soils with low manganese availability.

In addition to the non-weather dependent protection seed treatments provide, Mr Bean sees their relatively low rates of highly targeted active ingredient representing value for money and environmental value.

"Seed treatments have become more and more valuable in recent years. In our experience, they offer some of the best and most cost-effective agronomic risk insurance you can buy.”

Seed treatment challenge

The real challenge in making the best use of seed treatments, however, lies in the sheer range of different treatment and variety combinations possible, says Chris Bean. This is added to by the complexity involved in matching individual needs to the limitations of local seed processing within the short time between seed crop harvesting and autumn drilling.

"This makes it more vital than ever for growers to work closely with their agronomists to identify individual variety needs and the most appropriate treatments for each particular circumstance. It is important to do so as early as they can to make sure they secure specific seed packages they require ahead of their target drilling window,” he says.