Inatreq - great promise that needs careful minding

The arrival of Inatreq to the market is opportune on many levels. It is the first big product into the fungicide market from Corteva, the company that is the amalgam of DuPont, Dow AgriSciences and Pioneer.

Its arrival also brings a new active to a market at a time when most previous modes of action are being challenged by continuing mutations in a number of different fungi.

Inatreq brings a new family of chemistry to the fungicide market.

As well as this, it also brings a welcome new mode of action.

In some ways, it is similar to the strobilurins but it is a different active which works close to the site where the strobilurins work, but it is still distinctly different.

Inatreq is to be sold under three separate brand names in 2021, Questar, Peacoq and Aquino.

The first two will be co-packs with a mix of prothioconazole and tebuconazole while the latter will be a co-pack with Turret, which is metconazole.

Inatreq is the trademark for the new active fenpicoxamid, and all the products contain 50g/l of the straight active.

With a maximum rate of 2.0l/ha, these products apply a relatively low amount of active per hectare, which is one of the ways the company is attempting to reduce the risk of resistance development.

Fenpicoxamid, or Inatreq, is not just a new active. It belongs to a new family of actives called the picolinamides and targets a new site in the fungus.

This family is new to the cereal fungicide market but other actives from this family are used for late blight control in potatoes.

Inatreq is quite effective against ascomycete and basidiomycete fungi.

Originally developed by Dow, it is now part of the Corteva stable. It is quite a unique active in that it is a natural secretion from a streptomyces bacterium that can break down in sunlight.

So, there was some unique juggling needed to make it workable and this was done through the development of its unique i-Q4™ formulation technology.

The discovery of Inatreq

Inatreq is the trademark for the new chemical fenpicoxamid. When it was discovered many years ago as an extract from a bacterium, it was identified as a product coded UK-2A.

While this was very active in the laboratory against a range of diseases, its success on plant leaves was more questionable. This was because UK-2A was found to be photosensitive, ie it was broken down by UV light.

At the launch of Inatreq, Greg Kemmitt, who is global biology leader for Corteva, explained how the photosensitivity issue was resolved by adding a tail to the molecule which protects it from light during the application stage. The molecule is then converted back to UK-2A once it is taken up by the plant.

This conversion from fenpicoxamid back to UK-2A is done by a relatively ubiquitous carboxylase enzyme. This conversion can take place either in the leaf tissue or within the cells of the fungus.

Formulation challenges and i-Q4 technology

While this initial challenge was overcome, the active still had many other obstacles to its being a successful fungicide. Its lack of ability to move within the plant leaf was a concern and a potential limitation to its usefulness.

Formulation scientist, Derek Hopkins, explained that it is critical to understand the physical and chemical properties of any active to develop a formulation that will deliver it to the crop. He explained that Inatreq is naturally a white powder with very low mobility.

After many failed attempts at trying conventional formulation technologies, the scientists eventually created a new and unique formulation, which is now called i-Q4™ technology, and aspects of this are being patented.

The formulation is said to deliver much improved retention of spray droplets, combined with excellent adherence to the leaf surface. This gives the potential to deliver a more dilute concentration of active because of the much-improved coverage on the leaf surface.

Another unique characteristic of the i-Q4™ formulation provides increased ability to move the active around the surface of the plant.

The ability to get high leaf coverage, plus rapid entry through the wax layer on the leaf, makes the product rainfast in as little as one hour

This movement capacity is impressive and it can continue for some time after application, transferring the active on to new plant growth. This surface movement also enables the spray to be moved on to the lower surface of leaves, to move down the leaf to the leaf base, and to move on to new emerging leaves.

Penetration is also a feature of this new formulation.

The ability to get high leaf coverage, plus rapid entry through the wax layer on the leaf, makes the product rainfast in as little as one hour. Indeed, it is possibly much faster than that in practice. This rapid uptake helps to deliver its curative activity within the plant, while the ability to distribute the active around the surface of the plant adds to its protectant activity. And there is no issue with hard water for application.

These combined characteristics enable greater flexibility in water rate and droplet size.

Bigger drops will be better retained on the leaf surface and the mobility characteristics of i-Q4™ will still provide excellent leaf coverage. All these things combine to deliver high disease control efficacy from low rates of active with good yield response.

Single site activity

Persistence is one thing, safety is another. Inatreq is a single-site respiration inhibitor, like many other actives from other families. Inatreq acts to disrupt energy production in the fungus and without energy the fungus will die.

However, the fact that it is a single site mode of action means that a fungus need only make one small change to become resistant.

Like the strobilurins before it, Inatreq binds at the Complex III site in the mitochondria of fungal cells. But it binds on the inside, while the strobilurins bound on the outside. Both families work by disrupting quinone production and the strobilurins were known as quinone outside inhibitors or QoIs, while Inatreq is a quinone inside inhibitor or a QiI.

The SDHIs bind at Complex II, a different binding site and there is no known cross resistance.

Protection against resistance development is important. Greg Kemmitt said that this should involve a three-pronged approach based on:

Inatreq has no known cross resistance to any of the septoria mutants that are known to currently challenge other actives from other fungicide families. Corteva has established the baseline sensitivity of septoria populations to Inatreq and this will be monitored into the future.

Field flexibility

While it is only cleared for use on wheat and triticale for now, the combination of its different characteristics gives Inatreq great flexibility for field use.

It works well at low water volume, is suited to low-drift nozzles and it enables high forward speed during spraying.

Speaking at the launch, Stuart Jackson, Corteva’s technical lead for Inatreq, said that these characteristics combine to make Inatreq very flexible on many fronts.

Products such as Questar can be used at either T1 or T2 timing to provide excellent curative and protectant activity of the main target diseases in wheat. Its ability to control septoria and yellow rust is excellent and Stuart said that it brings very persistent control over a longer period compared to its competitors. This adds to green-leaf retention and photosynthetic capability for grain fill.

While it is a strong active, Stuart acknowledged that a tank mix partner adds to the performance of Inatreq alone. While the maximum individual dose is 2.0l/ha, Stuart sees field rates being closer to 1.5l/ha for those targeting septoria and 1.25l/ha where yellow rust is the major target.

However, he and other speakers stated that disease control and yield performance are consistently better from higher application rates.

Stuart emphasised that the objective must always be to apply the minimum dose required to do a specific job in order to minimise the pressure to select for resistance. But lower than optimum rates may reduce disease control and yield response.

Favourable Irish trial results

Speaking at the launch, both Steven Kildea of Teagasc and Tom McCabe of UCD acknowledged the strong performance of Inatreq in trials in Ireland and elsewhere, and in particular its longevity of protection. Steven commented that the SDHIs are weakening, so its introduction is timely.

Both speakers commented that the use of good mixtures is very important to help fend off resistance, with only one application per crop per season. Also, a multisite like folpet should always be used with Inatreq.

While yield benefits will always vary with season, results to date would indicate that Inatreq, sensibly used in good mixtures, provides both good disease control and yield benefit over good competitors.

I-Q4 FORMULATION BENEFITS IN THE FIELD

i-Q4™ is the patented formulation empowering Inatreq active. It helps spray:

Together these enable the use of:

These characteristics can benefit significantly, especially where coverage is challenged.