Seed dressings are an important crop input

Seed dressings are the single input that farmers take for granted, generally because they are not involved in choosing them. That does not mean they are not important. Seed dressings help to keep our seed stock free of the potentially serious diseases that most farmers, thankfully, know little or nothing about. These diseases were covered in this equivalent Focus last year in the Irish Farmers Journal dated 10 August.

Some are choices

One of the few choices that farmers have to make has been the addition of Latitude for Take-All control in wheat and sometimes in barley.

Following the discontinuation of Lindane many years ago, most of the seed dressings used now are solely for disease control using fungicides. The most recent exception, of course, was the addition of Deter, a neonicotinoid insecticide, to Redigo, but this is also gone now.

This year also saw the loss of mesurol, an important seed dressing on maize. This has long been used on maize as a bird repellent. The impact of its loss was certainly seen by some growers this spring when birds destroyed several crops sown in the open.

Many of the crops we sow no longer have dressings applied. This does not mean that there are no potential serious seed disease issues. It means that seed stocks must be kept clean during seed multiplication by whatever means. So, in general, crops such as beans and oilseed rape are not dressed but, so far at least, there are still lots of options for use on cereals.

Change continues in the cereal seed dressing arena too. Last year brought the loss of thiram as a cheap active that has given long service on cereals. Many of the actives now used are also in fungicides.

Actives such as difenoconazole (Score), prochloraz (Sportak), fluxapyroxad (Imtrex), tebuconazole (Folicur), and prothioconazole (Proline) form the mainstay of the actives used for seed protection. These are supplemented by other specific actives also.

The dressings

The main seed dressings in the Irish market are shown in Table 1. This is largely the same as the list we published last year, in that there are no new products.

The loss of thiram means that Anchor is no longer an option and this had served us well for many years. It also offered some level of deterrent against bird damage, albeit limited.

Barley growers will be aware of the presence of a low level of loose smut in some crops. This is always an underlying threat which could become serious if it were allowed to go through a generation without treatment. All seed diseases are serious and can multiply rapidly if they get a foothold in a crop to be used for seed.

Regardless of the seed source that one is using, it is always important to have a germination and pathology test completed ahead of the decision to plant. This is generally looked after by others in the case of certified seed but for home-saved seed it is up to the grower to have this done. And while a rough germination test can be done at home, pathology tests and disease risks are best assessed by the experts at the Seed Testing Station at Backweston.

Details of the services available and the costs of different tests can be found at this link: https://www.agriculture.gov.ie/.

Virtually all seed lots are dressed for seedling blights caused by fusarium and Microdochium species. These can affect germination and establishment as they sap energy from the emerging seedling. These diseases are almost ubiquitous and can even impact on germination tests.

The presence of other diseases adds to the complexity of the seed dressing required. As most products contain some systemic actives, they have a level of activity on diseases such as loose smut. This can be seen in the dressings listed in Table 1.

One other important consideration for a seed dressing is its likely effect on the speed of germination. This becomes a more important issue as we move to later drilling dates in an effort to reduce BYDV and grassweed pressure. Seed dressings tend to be neutral or mildly negative in this regard.

Last year Syngenta introduced its two Vibrance seed dressings – Duo and Star. Duo is to be used on winter cereals only, excluding barley, but it is also cleared for spring oats.

The addition of triticonazole to the Duo’s fludioxonil and Sedaxane in Vibrance Star adds a number of additional diseases. One of the claimed characteristics of these two products is the softness of the products on the emerging seedlings – useful with late planting.

Activity ratings

One of the big challenges with seed dressing is to get a handle on their relative control of different target diseases. There are no independent rankings of actives and little is provided as to the contribution of individual actives against specific diseases.

It is of interest to note that the French research organisation, Arvalis, provides disease ratings for a range of the products in its market on each of the specific cereals. The information in Table 2 is for products that seem common to the Irish and French markets and this provides some specific product comparisons.

Some of the product names are different in the French market and I have included the name of the equivalent Irish product beside the French name in Table 2.

It is also interesting that they include a disease of wheat and rye called “Caire Commune”, which appears to be what we call bunt or covered smut.

It is obvious from Table 2 that most products common to both markets are highly effective against fusarium and microdochium, which are our main problems on any cereal.

It is also obvious that none of the dressings are rated as having worthwhile activity against ergot but Bayer suggest that Redigo Pro can provide some reduction.

Some of the French products are recommended on crops for which they are not cleared for use here.

While Celest Power is the equivalent of Vibrance Duo it is of interest to note that Vibrance Star is not used in France. They use a product called Vibrance Gold, which is similar to Vibrance Star, but this uses difenconazole rather than triticonazole and double the concentration of Sedaxane.

This reinforces that fact that actives are chosen to target the major diseases in specific markets. While we may share common diseases, their prevalence and threat can differ considerably in different countries.