BIOLOGICAL WEAPONS AGAINST BLACK GRASS!

Black Grass Biology Group

2024 progress report

On-farm trials

This year we partnered with 16 farms to run commercial-scale trials to assess the potential for applying fungal spores to help with the control of black grass. Most of the trials were 50-150 hectares in size. Below is a summary of our findings so far this year:

• 32% of the farms running trials reported observing either an effect on black grass numbers by June, or symptoms of disease amongst the black grass population.

• The remaining 68% did not observe an effect at the time we enquired in June.

• The unprecedented wet spring meant that the spores could not be applied as early as we planned in any of the farm trials.The delays lasted for up to 6-8 weeks on some farms.

• The delay to the date of application had three major consequences on the trial:

1. The black grass plants were larger when the spores got to them.
2. The air temperature was higher when they were applied.
3. The spores were eventually applied very close to an application of a fungicide (either just before or just after). This was probably the most damaging consequence because any fungicide applied to the crop would also assist the black grass in fighting off infection from our applied fungi.

• One of the farm trials was at Agrovista’s Lamport AgX site. This was fully independent and run by their technical staff, not Eutrema. This trial is showing a clear difference in black grass numbers between untreated and treated.
• In addition to a very positive result from this project, the Lamport trial also demonstrated another key finding = where an application of Avadex was missing from the treated field there was no difference between treated and untreated sections in black grass plant numbers. This demonstrates that our biological technology is an additional weapon against black grass, but not a replacement for conventional herbicides.

Interesting findings from our laboratory experiments

• In our grow room trials it was found that the optimum temperature for the growth of the fungal pathogens was 16°C or below. This is very different to what is the optimum for black grass growth (>25°C). This further reinforces our belief that the optimum time for spore application is early spring.

• We have learnt a lot about spore production in the Eutrema lab this year. We have even learned how to kill off all the fungus (accidentally!). So with more time for creating the spores than we had last year, combined with an improved production process, we should have far more spores to get out to the trials this year. This means even more spores per hectare, and an increased chance of success.

• It was repeatedly observed in the grow rooms that once the black grass plants were successfully infected the leaves changed from being extremely hydrophobic (water repellent) to being extremely hydrophilic (water holding). This change is due to the formation of fungal lesions on the leaf surface breaking through the leaf’s waxy cuticle layer. This may seem like a minor finding with no consequence, but it could have massive implications as it means we could go from a situation where most of the droplets of a foliar herbicide (e.g. Centurion Max) fall off the black grass, to a situation where the vast majority attach. If this were indeed the case, then it vastly increases the dose of herbicide taken in by each weed plant! By increasing the delivery of herbicide into the weed, we might be able to turn ineffective herbicides into super-effective herbicides, and/or allow farmers to reduce dose rates in future. In order to test this, we will be running a further experiment where we will be spraying a set of infected and a set of uninfected black grass plants with Centurion Max (clethodim). The dose rate will be set at 50% of the field applied dose rate to maximise the chances of observing a difference in the grow room. Standard dose rate being 1 L / ha in 200-400L of water. We will then monitor both the number of spray droplets that attach to each plant, plus the subsequent effect on black grass health or death!

• We also tested a range of compounds that are purported to increase the severity of fungal infections on crops when applied. You will often hear reports of certain conditions that promote the growth of foliar fungal pathogens, especially powdery mildew; such as spraying foliar nitrogen or molasses. However, we have tested all these reported compounds and attempted to increase infection rates on black grass plants in the grow room by applying them. Unfortunately, none of these compounds increased infection rates. In fact, all it did was spread the spores around and make them germinate on the leaf surface.

Plan going forward with farm trials

• Owing to the inability to get the spores onto the fields due to the wet conditions this spring, we will be repeating all the current on-farm field trials in 2025. This will be at no cost to the farms involved. Hopefully we will have better conditions for early spring applications if weather is better than 2024 (I cannot see how it could be any worse!).

• We will also be providing an autumn application free of charge. The rationale for this extra application is three-fold:

1. A BYVD insecticide is applied at this time of year, so no extra pass over the crop is required.
2. No fungicide is applied at this time of year, thus we do not have to worry about fungicides killing the black grass pathogens.
3. If successfully infected, black grass plants could have reduced resilience through harsh winter conditions. However, there are also counter arguments to be made for this, so we need the trials to see if this happens in reality.

• 2025 field trials will also receive higher dose rates due to the improvements in our production process.

• We might have opportunities to expand to other farms who are interested in signing up for trials. However this will be dependent upon how spore production proceeds in the second half of 2024.

Finally, we now have 174 farms signed up to receive more information on the project, and to receive early updates once the sign up page goes live on our website again. Clearly there are more than 174 farms affected by black grass in the UK, so if you know of somebody who is suffering then please pass on our details so they can sign up too.

Best regards

Dr Russell Sharp

eutrema.co.uk