Nematicide treatment application set for greater accuracy

New developments in application technology will help with the accuracy of nematicide treatments this year, providing machinery is serviced and checked throughout the process, according to machinery specialist Graham Basil of GSBtec.

GPS systems have been the breakthrough required for monitoring the area treated and comparing it with the amount of product used, he says.

But field checks remain vital, he urges, as soil conditions and ambient moisture can make a difference to application rates in practice. “Machinery set-up and calibration in the workshop is great, but things can be very different out in the field.

“If you do the first calculation after one hour of operation, then repeat it at the end of the morning, you can pick up any changes in application rate and make the necessary adjustments. It’s important to always work out the area covered and the amount of nematicide used, just in case there’s been a change.”

Graham Basil 

Graham Basil tells growers to watch out for wear.

The same can be done on tractors without GPS through the use of a handheld device, such as the Garmin Dakota 20, he added. “They cost around £150. Driving around the perimeter of the treated area will give you a precise area in sq m.”

The arrival of simple one piece cartridge units has also been a significant step forwards in both reliability and accuracy, he explained. “They’ve replaced the rotor metering mechanisms and can be fitted to rotate in either direction.”

This means that the complete set of cartridges can be reversed when they start to show signs of wear, he adds. “You should get at least 20ha per cartridge outlet in one direction, and then a further 15ha per outlet once they’ve been reversed.”

But the whole cartridge set must be reversed in one go and the machine recalibrated, he says.

Inspecting cartridges for wear involves turning them at least one full revolution, so that each flute can be assessed, continues Mr Basil.

“If there’s any damage to any single cartridge, the entire set must be changed. One of the most common causes of damage is where the nematicide kegs haven’t been fitted carefully over the hoppers and bits of plastic or tags have broken off and fallen into the hopper. “

Why was 2011 a bad year?

The dry weather definitely played a part in the higher number of samples which were found to be above the accepted residue limit for Nemathorin last year, says Pat Haydock of Harper Adams University College.

“With all nematicides, adequate soil moisture is needed for two reasons,” he explains. “Firstly, it allows the diffusion of the active ingredient from the granule and secondly, it enables the PCN hatching process to occur.”

Another possibility is that nematicide breakdown is delayed, or slowed, in very dry soils. “Irrigation after application could help to prevent this, but it should only be necessary in exceptional circumstances.”

The balance for growers is to get the required persistence for the extended hatching period of PCN, while avoiding any residues in harvested tubers, says Dr Haydock.

“That means observing harvest intervals, especially where more than one product is being used, as they do vary. Granules must be incorporated in the top 15-20cm of soil and they shouldn’t be applied if it’s very wet.”


Where growers need to switch between different cartridges during the season, the cartridge set must be reinstalled to all run in the same direction.

“If you go from using Nemathorin (fosthiazate), to Mocap (ethoprophos), and then back, for example, mark the cartridges with a direction arrow using a waterproof pen as you take them out.”

Watching out for wear is Mr Basil’s key tip for operators this season. “If you’re putting on too little nematicide, or mixing the granules in too much soil, the effect will be diluted.

“And if you’re over applying, there’s a financial penalty and a risk to the crop and the environment.”

Nemathorin granules need to be mixed evenly to an appropriate depth, so that they are in the zone where roots and tubers are developing. “This is usually the top 15 to 20cm. A common mistake is to take too much soil when incorporating granules on a deep tiller or bed former, especially in light soils.

“Think about the soil you will be lifting at harvest to collect tubers. That’s the area you should be treating at planting.”

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