Nematode pest anxiety tempered by effective biocontrol

Nathan Whitehouse, Certis Belchim marketing manager

Soil-dwelling plant-parasitic nematodes are the nemeses of many crops.

Patchy, sporadic, and in some cases hard to accurately quantify, a handful of species can have a devastating impact on yield and quality in crops like carrots, parsnips, and sugar beet, to name but a few.

In carrots and parsnips, it’s estimated that about 70% of the UK’s 14,000ha (2022 Defra crop statistics) is affected by various free-living nematodes and/or root knot nematode (distribution of the latter is much sparser).

In the past, growers had plenty of tools at their disposal, including total fumigants like Telone (1,3-dichloropropene) and metam sodium to sterilise soils ahead of planting high-value vegetable crops.

More recently, granular carbamate nematicides like Temik (aldicarb) and then Vydate (oxamyl) were industry standards for negating damage caused by free-living and root knot nematodes early in seedling development.

However, the toxicity of these conventional products – for both humans and the wider environment – led to a search for more operationally and environmentally benign products to target these tricky pests.

One company integral to that search was UK-based ECOspray, set up in 1997 by its technical director Murree Groom and funded by two Norfolk farming families with an interest in crop protection.

Its focus was the potential of garlic extract and the exploration of how biologically active substances found within the Allium plant species might affect bacteria, fungi, and pests, including nematodes.

These substances include highly toxic sulphur compounds known as polysulfides, which are generated when garlic cloves are subject to certain conditions, such as being chopped, crushed, or attacked by microbes.

When this occurs, the sulphur-containing amino acids in the garlic are hydrolysed – the process of breaking the amino acids into one or more chemical compounds – and produce an unstable substance known as allicin.

When allicin decomposes or is heated, it produces many sulphur compounds and ECOspray research work revealed that diallyltrisulfide (DATS) and diallyltretrasulfide (DATTS) have the highest levels of activity.

The next step was to develop an effective product that farmers could use in practical nematode control programmes.

Early iterations produced inconsistent results and ECOspray refined and perfected the garlic extraction process.

Combining granulation technology that initially mixed the food grade extract with wood flour and biodegradable binders, then more recently diatomaceous earth, led to the granular nematicide product NEMGuard DE of today.

After more than 10 years of hard work, the garlic extract was included on the European Union’s Annex 1 list of pesticide active ingredients in 2008 and in late 2014 NEMGuard DE gained full UK approval for use in carrots and parsnips.

By this point, growers only had Vydate for control of nematode pests and given its robust, consistent performance over many years, shifting farms to a biological alternative would be no mean feat.

Like any biological plant protection product, it was initially met with some degree of scepticism.

Certis Belchim began applying marketing and technical expertise to this challenge in 2015 and soon after, the door into the market was left ajar by an explosion at Dow AgroSciences’ US-based Vydate production facility.

The resulting shortages in 2015 and 2016 meant growers had to take a leap of faith and try NEMGuard DE, which can be applied through the same applicators.

When supplies of Vydate resumed, not all farms switched back to the product on 100% of their crop.

This indicated that growers believed its mode of action worked and benefits were comparable to conventional chemistry in reducing the fanging symptoms so damaging to carrot and parsnip marketable yield.

With a degree of market penetration and the impending withdrawal of Vydate by a final use-up date of December 31, 2020, Certis Belchim set about building a dataset of its efficacy at reducing fanging symptoms.

Working with root crop specialist Howard Hinds and key carrot growers, trials were set up and over three years, results showed a 20% increase in total yield and an 85% reduction in fanging relative to untreated plots.

Commercially, reports also indicated that NEMGuard was maintaining fanging incidence within the range expected when using Vydate on the same land.

Certis Belchim engaged with the industry through the British Carrot Growers Association (BCGA), sharing this positive news and intelligence on how to get the most out of the product and achieve the results seen in trials.

Firstly, NEMGuard DE needs adequate soil moisture to soak the granules and release and distribute the nematocidal polysulfides through the rooting zone, where it comes into contact with the target pests.

Rainfall at the right time helps, but is not guaranteed, so where irrigation is available it can be used early in seedling development to maximise product efficacy.

As with any biological product, application is critical in getting the best from the active substance and working with application specialist Richard Lapage of RWL Services, Certis Belchim provided best practice guidance to drill operators.

Whilst the same applicator can be used, NEMGuard DE is applied at a higher rate than Vydate, so a change of metering rotors and cassettes and a recalibration was required.

Another key message relates to the product’s hydroscopic nature, meaning it absorbs water like a sponge. While this is crucial for activating the active substance in the soil, it means operators have to take extra care when handling the product during the drilling period.

Working with ECOspray, Certis Belchim has improved the product packaging by moving from paper bags to foil bags much less prone to taking on moisture and has stressed the importance of not leaving granules in hoppers overnight. Lumps can occur and block applicators when up and running the next day.

Sugar beet growers had access to Vydate for a season longer than other root crop growers via an emergency approval requested by the British Beet Research Organisation ahead of 2021 drillings to control Docking disorder, caused by FLN.

However, it was a one off and to fill the gap BBRO worked with manufacturer ECOspray and Certis Belchim to collect the necessary data and gain full approval of NEMGuard DE for 2022.

Trials that year showed that the product significantly reduced fanging symptoms and its availability was announced ahead of drills moving in 2022.

All the knowledge and experience Certis Belchim gained in carrots and parsnips, and ongoing BBRO work to build a multi season picture of the product’s efficacy against Docking disorder, has paved the way for a smooth introduction of NEMGuard into the sugar beet sector.

NEMGuard DE is another great example of how a biological product – with the right development, marketing, and industry engagement – can stand up to technical scrutiny and be a worthy replacement for conventional chemistry.

Given the broad-spectrum nature of previous nematicides, it is also a win for the environment, as NEMGuard DE is very target specific and has little negative impact on the wider soil microbiome.

What is not to like?

To learn more about the NEMGuard DE product click here!