Potato planting©Tim Scrivener

A toxic chemical leak at US manufacturer DuPont’s La Porte factory near Houston, Texas, which killed four factory workers, could lead to the shortage of a key pesticide.

Production and supply of Vydate – a nematicide for root crops – has been suspended since the incident in November while US government authorities and DuPont carry out an accident investigation and ensure the facility is safe to restart operations.

In a statement to growers, DuPont said that there was likely to be a shortfall in 2015 and it was making every effort to minimise the effect on farmers’ businesses.

See also: Act now to save spud seed industry from ‘PCN creep’


  • Mocap – ethoprophos
  • Nemathorin – fosthiozate
  • Vydate – oxamyl

Vydate, which contains the active ingredient oxamyl, is one of just two fully approved nematicides now available for use in the UK.

Spud Agronomy potato specialist John Sarup said Vydate is a hugely important product for potato growers, helping to control potato cyst nematodes (PCN) and free living nematodes (FLN) where the pests are a problem.

Alternatives include Nemathorin, which has full label approval for PCN, but only offers a reduction in FLN. Mocap controls wireworm, but offers only a reduction in both PCN and FLN.

Secure supplies

Mr Sarup advised growers to secure Vydate supplies as soon as possible, particularly those growing first and second early crops or varieties susceptible to spraing – a tuber disorder caused by tobacco rattle virus (TRV) transmitted by FLN.

“If you have early ware crops with a shorter growing season, Vydate is the product of choice for PCN control as it has a shorter harvest interval than Nemathorin (80 days compared with 119 days).

“It is also crucial for free living nematode control as it is approved for in-furrow application at planting and can protect tubers from direct feeding,” he explained.

Mr Sarup added that while maincrop growers would be less concerned about the longer harvest interval when using Nemathorin to control PCN, Vydate is the more viable option for free-living nematode control.

Nemathorin only offers a suppression of FLN, with a typical cost of £440/ha, however, Vydate can be used at lower rates when only targeting FLN feeding and spraing reduction, which could save growers about £200/ha if they can secure supplies.

Not all potato varieties are susceptible to spraing, but where growers are planting susceptible varieties and Vydate can’t be sourced, Mr Sarup said they should reconsider where they are growing those crops.

“Where harvest interval isn’t a problem use Nemathorin as it is certainly better than nothing to suppress free-living nematodes.

“But for early crops planted on irrigated light land sites where they are typically more of a problem, if you can’t get hold of Vydate and the variety is susceptible to spraing, you should reconsider your field selection,” he added.

Sugar beet

Growers of sugar beet on light, sandy land also rely on Vydate to control free-living nematodes, with a seed-bed application ahead of drilling protecting the crop up to the six true-leaf stage.

Two species – trichodorus and longidorus – can particularly be a problem in a wet spring when a rising water table brings the pest up the soil profile to feed on young roots.

British beet research organisation (BBRO) lead scientist Mark Stevens explained that the damage caused to root tissue in the spring and early summer causes docking disorder, resulting in patches of stunted plants.

However, it is often not detected until crop lifting when beet can be seen with fanging and small tap roots, causing breakage and yield losses.

“Vydate is very important as it is the only control option for the two species, but it must be put into context as only about 5% of the beet area would be at risk.

“Those growers on light, sandy land need to think about getting hold of some product, otherwise the problem will take some careful managing,” said Dr Stevens.

The management of nematodes for carrot and parsnip growers could also prove more difficult where growers can’t secure supplies of Vydate.

However, alternative natural product Nemguard from Agrochemical company Certis – based on garlic extract – could assist in suppressing nematodes in both crops.

Steve Bennett, who manages the product supply chain at Agrii, said the company is aware of the shortfall, but it is too early to predict the final amount available to growers.

“Our technical staff are feeding back what their requirements may be and we will ensure that there are alternative products available for farms to use.

“The positive things is that it is not last-minute, so there is still time to make alternative plans,” he said.


 Nematode control options in potatoes 




Harvest interval



55kg/ha applied overall

80 days


Vydate (in-furrow)

FLN spraing reduction

210g/100m row (23kg/ha)

80 days

Vydate (in-furrow)

FLN feeding damage reduction

140g/100m row (15kg/ha)

80 days


PCN and reduction of FLN

30kg/ha applied overall

119 days

Mocap 15G


+ PCN/FLN reduction

40kg/ha applied overall

80 days