As carrot and parsnips crops are drilled, Free Living Nematode (FLN) control will be a key concern for many. We investigate current pressure levels and potential solutions for managing the yield robbing pest.
One of the biggest influences on crop damage by FLN is the weather, explains Independent carrot and parsnip agronomist, Howard Hinds.
“FLN pressure was moderate last year due to dry conditions in the early part of the season, but in recent years when conditions were wetter in April and May we’ve seen higher levels of damage.
“Rainfall makes it easier for the pest to move around the soil profile, increasing feeding activity on smaller roots and causing significant damage. However, it can also make FLN sampling less accurate.”
Howard explains that as tests for FLN usually occur once a year, in the autumn or early spring, FLN will be more active and mobile depending on if the weather is wet or dry, what time of day it is and even what week the test is taken on. This means that results can differ widely.
“FLN sampling should be an integral part of any root crop planning process, but the data can be hard to interpret,” he explains.
“Quite often the figures that the farmer gets back don’t always relate to the damage they will then find in the field.”
Having provided advice to the carrot sector for over 20 years, Howard adds that little is known about the pest at a practical level, in particular which species are most damaging.
“We know that Root-Knot Nematode can cause severe damage to carrot and parsnip crops and that numbers have increased in recent years. Perhaps due to warmer soils, and the shrinking land base that we have to grow these crops.
“However, to grow our knowledge base and make more informed decisions on how to tackle this threat, we need to get smarter with sampling, which might mean increasing the frequency of testing,” he says.
“At present we have little historical data, so are unable to monitor trends, but widening the sampling areas and increasing the number of tests could influence better land choice decisions and also help to reduce nematicide usage.”
He adds that increased sampling will have a cost implication, but as nematicides are the second biggest pesticide cost for carrot and parsnip crops the potential savings are huge.
“We’ve learnt to accept that 5-6% crop loss from FLN is the ‘norm’, but ultimately this is not acceptable. The UK produces 700,000 tonnes of carrots a year, so the value of this loss soon adds up.”
James Bramley, vegetable manager at MH Poskitt, is responsible for their carrot and parsnip crops in the Yorkshire and North Lincolnshire area, and has experienced high incidences of FLN in the past.
“FLN and incidental fanging can be a big problem for us with the percentage of affected crop being anything up to 10% across our cropping area,” he says.
“Last year we experienced average pressure with fanging levels of around 5% across the board, however, we anticipate an increase in pest pressure this year.
“As we’re constantly striving to grow the best quality crop we can, management of risk is key and as such we implement an integrated approach which starts with a good rotation,” says James.
“We try to maintain clean stubble over the winter by controlling weed volunteers. We’ve found that certain weeds, such as shepherds purse and Field Pansies, can host FLN over the colder months, so we’ve made a proactive effort to break the cycle where we can.”
However, James adds that like many root crop growers, most of the land is rented, meaning this isn’t always an option.
“In these situations, we have no control over the preceding crop or previous inputs. And as our crops can sometimes follow turf, we’ve found the amount of FLN is often higher.
“Working alongside Howard we are increasing our sampling to get the most accurate picture of the pest pressure we’ll have to manage.
“We’ve also been using alternative nematicides in our root vegetable crops and have had good results with a garlic based biorational nematicide, NEMguard DE, which we have used on all of our parsnip crops. I think it’s important not to rely solely upon one mode of action,” he says.
Howard explains that research into alternative methods of FLN control is an ongoing priority in Europe.
“Cover crops combined with black fallow periods are being trialled in Europe and have seen promising results,” he says.
Although these control methods are mainly being used in organic systems, as they have much more control over their rotations, he explains that this is something he plans to implement on organic farms in the UK.
“The James Hutton Institute has also been looking at a molecular test for FLN – an advancement on the present visual method. This is still in development, but is promising for the future of FLN control.
“As soon as a carrot crop is drilled it’s open to an unbelievable level of risk, be it through FLN or cavity spot, so it’s important to do everything possible to ensure damage to the crop is minimised from day one.”
With this in mind, Selchuk Kurtev IPM Manager at Certis adds how they have also invested in carrot and parsnip trials, to provide a better understanding on how to get the best out of biorationals such as, NEMguard DE.
“We‘ve already seen incidental activity on cavity spot in a recent trial, which is an exciting development for the sector,” he says.