Population management
Potatoes
Nematicides are an essential means of slowing the rate of population increase after harvest. Without a nematicide, the population, as measured in eggs per gram of soil, would be many times that recorded before the crop is planted. Using a nematicide has the potential to see land brought back into production earlier than might otherwise be achievable.
The effectiveness of a nematicide in limiting the rate of increase in population is measured by the ratio of final population (Pf) to the initial population (Pi).
Across 18 PCN trials conducted between 2015 and 2021, the average yield of crops treated with Velum Prime was 38.7t/ha, an increase of 6.0t/ha over the untreated. In the same trials, the yield protection afforded by Nemathorin 10G (fosthiazate) at 30 kg/ha was 7.9 t/ha.
The population management achieved by Velum Prime was broadly similar to that of Nemathorin 10G. In 17 trails between 2015 and 2021, Velum Prime achieved a 34% reduction in the population compared with the untreated and close to the 38% reduction achieved by Nemathorin 10G at 30 kg/ha.
The trials had an average Pi value of 37.6 eggs/gm of soil and the reduction achieved by Velum Prime is an average of results where it was applied either in-furrow at planting or as a broadcast spray ahead of planting.
The benefit of nematicides in managing PCN populations

Yield protection
It is for the grower to decide what level of yield protection is needed and how this may be best achieved in practice. In higher pressure situations, this may be best achieved by the use of Velum Prime in sequence with a granular nematicide. In lower pressure situations and as part of an integrated approach, Velum Prime applied alone may provide sufficient protection. Wherever possible, measures should be integrated with the use of resistant varieties and crops shown to reduce nematode multiplication.
Higher pressure PCN situations
The yield protection delivered by Velum Prime when applied alone and in sequence with Nemathorin 10G on sites selected specifically for their PCN higher pressure.
Velum Prime alone delivered an average yield increase over the untreated of 2.71 t/ha. When applied in sequence with Nemathorin 10G at half and full rate, the yield gain increased by 2.74 t/ha and 3.04 t/ha over Nemathorin 10G-alone respectively.

The positive population management achieved by Velum Prime in sequence with Nemathorin 10G also exceeded that achieved by Nemathorin 10G when applied alone.
The yield protection delivered by Velum Prime used alone is an average of that seen when applied by the in-furrow and broadcast spray methods. Where Velum Prime is applied in sequence with a granule, it is applied in-furrow at the time of planting.

From left to right: Untreated, Velum Prime (in-furrow), Velum Prime + Nemathorin 10G
Lower pressure PCN situations
Pressure is often a subjective term. It will depend on field history, soil type, resistant status of the variety to be planted.

Across, 11 trials between 2013 and 2020 where pre-crop soil testing revealed a PCN population of 5 eggs per gram of soil or less, Velum Prime delivered an increase in the yield over untreated of 2t/ha.
Free-living nematodes (in potato)
Velum Prime can be used for the reduction in spraing symptoms caused by tobacco rattle virus vectored by certain species of free-living nematodes (FLN). Potato mop top virus, the other source of spraing infection is linked to the powdery scab fungus, Spongospora subterranea, will not be controlled.
There is a chance that treated crops may still express symptoms of spraing. As with PCN, Velum Prime should only be used against FLN as part of an integrated programme of measures. The reduction in spraing symptoms from the use of Velum Prime is broadly similar when applied as either a broadcast spray ahead of cultivations or in-furrow at the time of planting.

In trials Velum Prime has given a greater reduction in spraing than other nematicides
The FLN pressure in the five trials between 2015 and 2017 can be considered as ‘high’. The average number of Trichodorus species found in trials was 2279 per litre of soil. The soil types involved were sandy/silt loams and involved susceptible varieties, Lady Claire (1), Maris Piper (1) and Pentland Dell (3).
Carrots
In carrots, as in potatoes, the use of nematicides is often essential to protecting yields in the face of pressure from parasitic nematodes. In carrots, the application of Velum Prime resulted in yields significantly higher than the untreated crops.
Yield protection

Carrot crops treated with Velum Prime produced greater marketable yields than if treated with other nematicides
Across the same trials, crops treated with Velum Prime also had a lower incidence of fanging and other associated FLN symptoms.

Carrot crops treated with Velum Prime were found to suffer a lower incidence of fanging than those treated with other nematicides
Incidental control of Sclerotinia
The use of Velum Prime in carrots was also observed to make an incidental contribution to the control of Sclerotinia.
In 10 UK trials the average post-harvest incidence of Sclerotinia was 55.7%. A soil application of Velum Prime for yield protection in the presence of parasitic nematodes, reduced the incidence of Sclerotinia by 32%.
In comparison, a conventional four-spray programme based on Signum (boscalid + pyraclostrobin) achieved a reduction of 52% relative to the untreated.
Velum Prime applications in carrots must not target Sclerotinia but any contribution to reduced sclerotinia incidence is to be welcomed. Where Velum Prime is applied it counts towards the total foliar SDHI fungicides applied to the crop which means the first foliar spray must belong to another mode of action group.