A few years ago, it looked like the cupboard was bare which held the potential new solutions for tillage crops. Now, a few years later, that cupboard appears to be relatively well-stocked with fungicides, or it is about to be if all of the actives now known to be in the pipeline make it to the market. This is important because I note approximately 50 products with stated use-by dates across the various inputs in our fungicide, herbicide, growth regulator and insecticide tables.

The major change this year is the introduction of Revysol and its two commercial products, Revystar XE and Lentyma. Both are Revysol plus Xemium mixes with different mix proportions in each. They will be a very welcome addition to the toolkit for septoria control in wheat, but they also give some hope for ramularia control in barley.

Last year, we had hoped to also have access to Inatreq from Corteva but it is met with delays in the registration process. However, just as I was writing this piece, I got clarification that it is now registered. The unfortunate thing is that a registration this late in the year means that it will not be commercially available in 2020.

QiI

In his article on pages 10 to 13, Steven Kildea referred to the pending introduction of a new active from a different family of chemistry, the QiIs. This might sound familiar in that the strobilurins were called QoIs, which stands for quinone outside inhibitor, an abbreviation of where the active worked.

Well, if you haven’t figured it out already, QiI stands for quinone inside inhibitor. It is also a respiration inhibitor but is active at a different site to the strobilurins and the SDHIs.

So, it is a new mode of action targeting a different site to the strobilurins, but we must assume that it carries a similar fragility in terms of resistance risk. But that may be something we can live with more easily when we have a crop of effective actives arriving to the market at the same time. Having actives with near-equal strengths against individual disease is a luxury we did not have up to now.

Fenpicoxamid or Inatreq

Containing the active fenpicoxamid, Inatreq belongs to the picolinamide family. That family is new to cereal fungicides but it is used in some blight products. It has no known cross resistance to any other fungicide family, so it starts its life with a clean sheet.

It is a very interesting active in that it is a natural secretion from a streptomyces bacterium, which is known as UK-2A, and this is the actual fungicide active. So it is a naturally occurring active. Interestingly, this natural active is not photo-stable so it is broken down by natural light.

In theory, this is not something that lends itself to application on leaves in an open field and it presented the formulation chemists with a real challenge.

The first was to physically make the active in sufficient quantities. This has been done and it is now manufactured through fermentation. But the challenge of making it photo-stable also had to be overcome. The formulation chemists managed to be successful here by adding a hydroxyl element to the molecule. This tweaking turned UK-2A into Inatreq, which is stable in the open and there the journey begins.

On the leaf

Once sprayed on to a leaf, the Inatreq active very quickly binds to the wax on the leaf surface where much of it remains for some time.

It is the photo-stable bit that stays here and when this moves into and through the leaf surface, it loses the hydroxyl element and reverts back to the highly active UK-2A. This process happens both in the leaf, as well as in the fungus.

After application, the active spreads across the leaf surface in the leaf wax. It binds strongly and remains here for weeks, offering external preventative activity against diseases. In this regard, it is seen as an active with long legs for durability. But some of the product moves through the leaf surface where it is converted back into the UK-2A active to provide a level of curative activity within the leaf.

The active can get into the leaf tissue within a few hours of spraying, according to Corteva. The company suggests that most of the distribution happens across the leaf surface and, from there, it penetrates into the leaf from the wax.

In the environment

The environmental fate of an active is now a hugely important factor in its acceptability for use as a commercial product. This necessitates a huge amount of testing to ensure that an active does not negatively affect any aspect of the environment.

It is also very important that an active does not hang around too long in the environment after application.

The fact that Inatreq is a naturally occurring active means that nature has already developed a process of disposing of it in the soil. This means that soil residues, etc, are not an issue with this active. Indeed, Corteva says that Inatreq has a half-life of only four days in the soil. It was also shown that it has no effect on soil organisms.

i-Q4™ formulation

Other aspects of the formulation of Inatreq form part of its performance potential. This patented formulation technology helps the spray droplets to spread across the leaf surface while at the same time binding them tightly to the wax. It has been developed specifically for Inatreq.

The i-Q4™ technology is a critical element of the product, enabling it to spread almost instantaneously across the leaf surface.

This also makes the product somewhat indifferent to water quantity at spraying and it is recommended at between 100l/ha and 300l/ha.

Evaluation research showed that the overall coverage of the leaf with the active post spraying was extremely good. And while relatively little may go into the leaf from the surface, the impact of the fungicide is enhanced as the active is penetrating almost the entire leaf surface.

It is also likely to be a significant factor in the consistent performance being seen from the product in field trials. Its overall combination of characteristics makes it a good fungicide but its greatest strength seems to come from its persistence.

Looking at trials testing the product in the UK last year, it would have been difficult to point to any major beneficial difference after four weeks following treatment and it was after that that Inatreq began to stand out.

All reports suggest that Inatreq offers significant curative activity within a seven- to 10-day window. While this would normally be a concern with a single-site active, the presence of other highly active molecules in the market may directly and indirectly help to minimise this risk in the short to medium term.

Questar™

Inatreq was registered for use in early April but there will not be product available commercially in 2020. Still, confirmation of its availability thereafter adds significantly to the strength of our chemical toolbox.

The first product to come to market here is to be called Questar. It had already been registered in France and, more recently, in New Zealand making Ireland the third registration for the product globally. It is significant in that it is the first new active in many years, which provides a new mode of action against septoria.

Corteva is pursuing registrations for an Inatreq plus prothioconazole co-formulation and straight Inatreq. Currently, only the straight formulation, branded Questar, has been registered. However, it is certainly not meant to be used on its own and the product to be sold will come as a co-pack – Questar plus another fungicide to be used with it in the tank mix.

The intention is still to bring the co-formulation with prothioconazole to the market when it is approved.

We do not have information on application rates at the time of writing, but the belief is that the original registration will apply for wheat only, with barley still a few years away.

What we do know is that the label recommendation will be for a single-use application only on a crop in the same season, allowing use at either of the two main septoria control timings.

Diseases

Inatreq offers outstanding biological performance against septoria and it gives farmers a new tool to help them to manage this menacing disease. Its unique target site for septoria, giving it a new mode of action, shows no cross-resistance to existing cereal fungicide chemistries. However, resistance development is a definite potential risk, as with the strobilurins and the SDHIs, because it is single-site activity.

While its obvious strength is in septoria control, it also offers control of many other diseases and is quite broad-spectrum. On the assumption that it will be sold in conjunction with prothioconazole (this may not be the case), Corteva says that the mix will offer control of all strains of septoria, yellow rust, brown rust, fusarium ear blight, tan spot, powdery mildew and eyespot. It is also good on rhyncho and net blotch, when it is cleared for use on barley.

While prothioconazole is likely to be an important element in some of these claims, Inatreq has intrinsic activity against many of these diseases also, providing additional strength to the combination, while acting to help protect prothioconazole.

Corteva says that while the active is useful on rust diseases, it is not as good as Solatenol where rust is the main target disease, but is roughly equal to all others against these diseases.

Based on all the available information to date from disease control trials, Corteva indicates that the combination of its strengths brings an additional 0.6t/ha yield benefit over the best of the current SDHI combinations.

This is an important benefit and we must hope that it will hold true for commercial practice in time.