Several EU-funded projects have investigated methods of improving soil management practices and creating viable and sustainable alternatives to peat as a soilless substrate. The data and outcomes of one of these projects ‘EXCALIBUR’ will now be exploited by transforming agri-food by-products either into soil fertilising products or sustainable alternatives to peat substrates.

Within the project, Niab is working with ReCoir Ltd to recycle and repurpose spent coir for fruit and vegetable production. 

Spin-Fert website

Partners

A total of 19 other partners from EU countries will collaborate with Niab

Funding

Horizon Europe

Duration

June 2024 to November 2027

Title: New sustainable solution to save healthy fruit from spotted wing drosophila: STOP-SPOT
Funder: Innovate UK
Industry partners: Big Sis (Lead), Berry Gardens Growers Ltd
Term: October 2021 to March 2023

Since the arrival of SWD in the UK in 2012, commercial soft and stone fruit growers have been heavily dependent on the use of conventional plant protection products to control the pest. Early research helped us to understand how best to monitor for the pest and manage its control but lately, Niab has been engaged in developing novel management and control techniques that rely less on conventional chemical control. In this project, Niab collaborated with BigSis, a start-up company, and Berry Gardens Growers Ltd, to exploit a new approach called the Sterile Insect Technique (SIT).

Sterile males are produced and introduced regularly by BigSis staff, to the semi-natural areas surrounding crops and within the crops themselves. These sterile males compete with wild males to mate with wild female SWD, which subsequently fail to produce any offspring. Such an approach is sustainable, non-toxic as the sterile males can’t establish in the environment, and is species specific, so has no effect on beneficial insects or other fauna.  As native wild SWD are used to create the sterile males, there are no barriers to introducing the control system in the UK once the technique has been proven to be effective.

The project

Early trials on strawberry, now published, showed very encouraging results with SWD levels remaining very low throughout the season compared to the SWD populations in adjacent crops with no SIT release which received plant protection products only. Further studies in 2022 assessed the SIT technique in the laboratory, in further field trials, and in ‘semi-field’ trials. The laboratory work has been testing, for example, how well the sterile males compete with wild female SWD and what ratios of sterile males to wild females are required for effective control.

Results

The research found that small plot experiments are vulnerable to border effects, where wild males can migrate across adjacent fields, so future commercial experiments need to be done on a minimum field size of 7 ha. Work on blackberry provided season-long suppression compared to an untreated control. However, different crops have different dynamics and this has implications for release rates and tactics to control wild populations. It has also been found that if no or low releases are made for one to two weeks or more, wild populations increase rapidly and it is impossible to regain control using SIT.

In small scale cage studies to assess the optimum ratio of sterile males to wild males, a ratio of 5:1 was efficacious; however, in commercial practice, BigSis is aiming for a ratio of 10:1. In the early stages of this work, BigSis were rearing sterile males by hand, but this is time consuming and cannot produce sufficient numbers to provide a commercially reliable service to growers. BigSis has since been developing a fully automated system for rearing larger numbers of SWD males using several micro-production units. They plan to produce millions of sterile males per week, which will be released in commercial soft fruit crops over very large areas. Producing such high numbers will avoid the problem of having insufficient numbers to release for a week or two in the middle of the season, which can lead to loss of control.

Title: Exploitation of interspecific signals to deter oviposition by spotted wing drosophila
Funder: Biotechnology and Biology Science Research Council
Industry partners: University of Greenwich (Lead), Berry Gardens Growers Ltd, University of Southampton 
Term: January 2019 to June 2022

Previous research by Niab discovered that Drosophila suzuki (Spotted Wing Drosophila - SWD) lays fewer eggs on media previously visited by Drosophila melanogaster, the common fruit fly, which only tends to lay its eggs on ripe and overripe fruits, unlike SWD, which also lays eggs on under-ripe fruits. The project hypothesis was to try and identify what exactly is deterring SWD from laying eggs after D. melanogaster has visited, so that this compound might be employed as a control strategy in commercial crops.

The project

The aim of this project was to understand SWD egg laying behaviour and to investigate how interactions with other Drosophila species affect SWD egg laying (oviposition). The work was carried out in the laboratory by a researcher, Trisna Tungadi, at East Malling. Trisna exposed D. melanogaster adults (male and female) to egg laying media before exposing the same media to SWD adults alongside a fresh media plate for comparison.

Results

The first experiment confirmed previous research, with fewer eggs laid by SWD on the plate that had previously been exposed to D. melanogaster. The next question was to find out which life stage and what D. melanogaster had left on those plates to deter SWD from laying its eggs. Further work discovered that the presence of live D. melanogaster larvae always resulted in fewer eggs being laid by SWD, rather than the presence of adult D. melanogaster.

Biochemical research was done to assess cuticular hydrocarbons found in the larvae of both D. melanogaster and SWD. Both species shared some compounds but also species specific cuticular hydrocarbons were identified. A synthetic blend of the D. melanogaster cuticular hydrocarbons was made and spread on egg laying media, but unfortunately this did not deter SWD laying eggs. Further work has been investigating whether other compounds left by D. melanogaster larvae deter SWD from laying eggs.

Title: Second Life: Development of sustainable recycled growing media
Funders: Overland Ltd, Growing Kent and Medway and The East Malling Trust
Term: April 2023 to March 2025

There has been a major shift in soft fruit production in the UK out of field soils and into soilless substrates, and with government policies aiming to reduce reliance upon peat, the majority of production is now in coconut coir. However, the increasing price of coir, limited availability and volatile shipping expenses have resulted in increased costs for growers. The carbon footprint associated with shipping substrate from Asia is also a concern, whilst additional labour costs are incurred in replacing and disposing of waste coir.

There has been much interest in re-using, composting or recycling coir although growers have so far been reluctant to use at scale due to concerns over pest, disease and weed build-up reducing both yields and the quality of the fruit produced. An early EU funded research project carried out by Niab identified that Junebearer strawberry can be replanted in used coir bags with little effect on yield as long as no disease was observed in the first year. Everbearers on the other hand suffer around 7% year on year yield decline when grown in reused coir bags.  

Overland has developed an automated process to recycle coir from strawberry bags which includes automated, low labour removal of bags from the tunnels, followed by the removal of plastic, plant leaves, roots and crowns, to leave clean coir. The coir is then treated to reduce the risk of pests and diseases, before making it available for growers.

Overland partnered with Niab to do further work to assess how the cycles of both growing and recycling change coir properties over time. We found that the water holding capacity increases while the air filled porosity (AFP) decreases in recycled compared to virgin coir. The extent of this change varied with different coir manufacturers. Recycled material also has slightly lower pH, higher electrical conductivity and higher nutrient content compared to virgin coir.  Levels of crown rot (Phytophthora cactorum) tend to increase in directly re-used and composted coir compared to virgin, but this has not been evident in the fully recycled coir that Overland is producing.

The project

Overland and Niab secured further funds from Growing Kent and Medway to accelerate this research and bring sustainable recycled coir media into commercial strawberry production. The aims of the project were to 1) develop energy efficient and robust procedures to eliminate pest, pathogen and weed risks in recycled material; 2) to demonstrate the use of recycled media on a commercial scale and develop wrap around agronomy advice; 3) compare lifecycle analysis of the virgin and recycled coir to measure any economic and environmental gains from using recycled media.  

Results

In work to eliminate pest, pathogen and weed risks from recycled coir, a heating process was developed and refined which successfully inactivated pest, pathogen and weed seeds from the substrate. Further work was done to study and compare the microbiome (community of microorganisms) within both virgin and recycled coir. We investigated fungal, bacterial and oomycete organisms in each coir type collected from a commercial scale trial during peak harvest.

A greater biodiversity of fungi was found in virgin coir compared to recycled and within these, we recorded more potential fungal pathogens on the roots of strawberry plants grown in virgin coir compared to recycled. These pathogens included species of Ilyonectria, Neopestalotiopsis, Verticillium, Mucor, Macrophomina and Fusarium. We also found more Colletotrichum and Penicillium species in virgin coir but not all of these are considered pathogenic. In assessing beneficial fungi, we found more Trichoderma (both commercial biocontrol species and others), Metharizhium and Serendipita in virgin coir. In contrast we found more Rhizophagus species (beneficial arbuscular mycorrhizal fungi) in recycled coir.

Bacteria were more diverse in recycled coir, but some were more prevalent in recycled and others in virgin coir. Potentially pathogenic groups were again found to be more abundant in virgin coir. 

Of the oomycetes (pathogens such as Pythium and Phytopthora species), very similar levels were recorded in virgin and recycled coir. There was a very slight increase in Phytophthora cactorum in recycled coir.

It is worth noting that no disease symptoms were observed on plants grown in virgin or recycled coir.

In work to demonstrate the use of recycled media on a commercial scale, the everbearer variety Katrina was planted in virgin Legro bags, directly reused Legro bags and Overland’s recycled Legro bags at a commercial site (Kelsey Farms) in 2023. Each coir type was used in nine commercial tunnels (over 3,000 bags per coir type) with an independent irrigation schedule. Sadly, during harvest the virgin and re-used coir were mistakenly picked and recorded together, so the recycled coir was compared to both virgin and directly replanted coir together.

The yields were similar (around 1.3 kg per plant) and no differences were found in pests (thrips, aphids, weevils), weeds or root rot pressure between coir types, but there were visual differences in plant growth. In the recycled coir, plants appeared to be stronger and cropped 7-10 days earlier than the virgin coir bags. The plants grown in recycled media also used 12 % less fertigation over the season. This reduction in water and fertiliser use in recycled material was especially prominent during hot days.

The grower was very happy with the performance of the recycled media, and has since expanded its use to over 200,000 pots of raspberry. A similar trial was repeated in 2024 at a Summer Berry Company site in Chichester, where 1.45 kg of fruit per plant (variety Favori) was produced in both recycled and virgin coir with 8% water and fertiliser saved in recycled media. The trial was done in troughs where roots could be inspected fortnightly. More uniform and higher density roots were observed in recycled material.

At Niab’s East Malling site in 2023, the everbearer variety Malling Supreme was planted in a small trial with both virgin and recycled Legro and Cocogreen coir in troughs rather than bags. Separate irrigation rigs were used for recycled and virgin media but not for each coir brand. The two recycled coir samples used 4% less water than virgin. Reduced need for wetting up and maintaining moisture in recycled material at the start of the season was the primary reason although reduced water use on the hot days due to the higher water holding capacity of the recycled coir also contributed.

The total yield from recycled coir was slightly lower comparing Legro recycled and virgin coir. This was due to the fact that virgin materials of both brands were fairly comparable in terms of water demand, but recycled materials with different previous growing histories were not. Namely, recycled Legro material had much higher water holding capacity compared to recycled Cocogreen. This meant that recycled Legro coir was over irrigated and recycled Cocogreen underirrigated resulting in a slight yield reduction. This highlights the need for the of use different irrigation/fertigation regimes with different coir types, or at least to use separate valves to manage coir moisture adequately.

In 2024, low grade, single crown, bare rooted Malling Centenary plants were planted in virgin and recycled material as a worst case scenario experiment. Yields were very low in both coir types (75-95 g per plant), but the plants yielded significantly more fruit in recycled material.

In an exercise to compare the carbon footprint of using recycled versus virgin coir, Niab and Overland calculated that removal-recycling-delivery of recycled coir emitted around 40% less CO2 than sourcing virgin coir shipped from Sri Lanka.

In summary, to date we have demonstrated that recycling coir offers much better potential than either re-using or composting coir. Recycled material can achieve strawberry yields and quality that is comparable to virgin material. Recycled coir poses no greater pest, disease or weed threat than virgin coir and there were fewer pathogenic fungi recorded in recycled coir compared to virgin, although there was a very slight increase in the oomycete P. cactorum in recycled coir. The rate and level of physical and chemical degradation does vary depending on the coir type, manufacturer and growing history but we believe that cost effective coir recycling is possible with little yield reduction.

However, it is important that the irrigation and fertigation of crops grown in recycled coir are managed separately from virgin coir, to adjust for the lower AFP in the recycled product, otherwise over-watering can occur leading to root death and reduced yield and quality.

Title: Reducing the risk of oomycete pathogens, thrips and weevils for sustainable, coir based soft fruit production
Funder: Biotechnology and Biological Sciences Research Council 
Industry partner: Overland Ltd
Term: March 2023 to November 2023
 

The UK soft fruit industry has moved almost entirely from soil based production into virgin coir substrate which is normally used for a single growing season. By growing in a clean substrate, the incidence of soil borne pests and diseases has decreased, but a number of  pests and pathogens continue to adversely affect fruit yields and quality, requiring management interventions. Recently, recycling of spent coir media has been investigated as a more economic and sustainable approach. Recycled material however is associated with a much higher risk of pests and pathogens. A sustainable approach to prevent or reduce the risk of pests and pathogens in virgin and recycled coir media has been urgently needed.

The project

This project studied the biology of pests, pathogens and biocontrol agents in both virgin and recycled coir.  The research aimed to investigate the diversity and function of the microbiome in recycled and virgin coir substrate, and in particular survival and efficacy of biological control agents in virgin and recycled material. We expect recycled material to have a higher diversity of both pathogenic and beneficial microorganisms and also to enable better establishment of added biocontrol agents. The work was done on strawberry crops and to complement Growing Kent & Medway funded work with Overland Ltd on recycling optimisation and practical implementation into growing practice.

Results

The early work aimed to eliminate pest, pathogen and weed risks from recycled coir and a heating process was developed and refined which successfully inactivated pest, pathogen and weed seeds from the substrate. Further work was done to study and compare the microbiome (community of microorganisms) within both virgin and recycled coir. We investigated fungal, bacterial and oomycete organisms in each coir type collected from a commercial scale trial during peak harvest.

A greater biodiversity of fungi was found in virgin coir compared to recycled and within these, we recorded more potential fungal pathogens on the roots of strawberry plants grown in virgin coir compared to recycled. These pathogens included species of Ilyonectria, Neopestalotiopsis, Verticillium, Mucor, Macrophomina and Fusarium. We also found more Colletotrichum and Penicillium species in virgin coir but not all of these are considered pathogenic. In assessing beneficial fungi, we found more Trichoderma (both commercial biocontrol species and others), Metharizhium and Serendipita in virgin coir. In contrast we found more Rhizophagus species (beneficial arbuscular mycorrhizal fungi) in recycled coir.

Bacteria were more diverse in recycled coir, but some were more prevalent in recycled and others in virgin coir. Potentially pathogenic groups were again found to be more abundant in virgin coir.

Of the oomycetes (pathogens such as Pythium and Phytopthora species), very similar levels were recorded in virgin and recycled coir. There was a very slight increase in Phytophthora cactorum in recycled coir.
It is worth noting that no disease symptoms were observed on plants grown in virgin or recycled coir.

Title: A phenology-perceptive integrated biocontrol programme for Large raspberry aphid (Amphorophora idaei) control: PHENCONTROL
Funder: Growing Kent & Medway and Innovate UK
Industry partners: Asplins PO, Biobest, Rumwood Green Farm
Term: May 2023 to May 2025
 

Control of aphids on raspberry was relatively simple in the past, with a wide selection of aphicides available to UK growers. However a progressive withdrawal of control products over the past decade or more has left raspberry growers with few effective options. Early season population increases of the large raspberry aphid have become particularly common in glasshouse and protected crops and despite relying on biological control options, levels of control have been inadequate, in part because their deployment has not aligned with seasonal variations in aphid populations and crop growth. Previous genetic resistance bred into raspberry varieties is also absent in modern cultivars. Improved forms of management and control are urgently needed.

The project

Niab aimed to develop an integrated biocontrol programme for raspberry that provides adequate protection against aphid herbivory and damage across all stages of aphid and raspberry phenology. We chose three routes to achieve this, firstly by trying to identify an optimal parasitoid species mix which will spread uniformly across the plantation. We also set out to  investigate novel ways of spreading Chrysoperla carnea (green lacewing) eggs across plantations to control hot-spot outbreaks of aphids whilst testing a strategy to deploy Micromus angulatus (brown lacewing) for predation of aphid eggs and spring hatching female aphids, when temperatures are still low.  

Results

In the early parasitoid work, the scientists worked with growers to monitor and identify the most prevalent naturally occurring parasitoids found in their crops over the course of the growing season. Between April and June, the parasitic wasp Aphidius ervi was most commonly recorded. Interestingly, other parasitoid species in the Aphidius genus, currently not in the parasitoid mixes were also found, especially later in the season. In later work when the Niab team assessed an integrated biological control approach, these Aphidius species appeared to dominate the total number of species identified. These findings will be used by industry partner Biobest when refining the mix of parasitoids they offer to their commercial customers.

In the work on Chrysoperla carnea (green lacewing), the strategy was to develop a method of applying eggs to areas of the crop where ‘hot-spots’ of large raspberry aphids are found. The challenge was to find a method of applying the eggs to the crop in a way that ensured that they would land and stick to the affected leaves. Different adjuvants carrying the eggs were compared to a water control. A highly diluted solution of food grade Xanthan gum provided the best suspension of the eggs in solution and level of adherence to the leaves and better than the other products tested and the water control. Importantly, the percentage rate of egg hatch on the raspberry leaves of eggs deployed in this manner was comparable to the control group proving that this method would not compromise biocontrol.

In the Micromus angulatus (brown lacewing) work, the hope was to find a way of controlling eggs and spring-hatching female aphids very early in the season before populations of large raspberry aphid began to rise. In this work the Niab team applied aphid eggs to a commercial crop of Malling Bella early in the season to establish early aphid colonies, then made weekly introductions of Micromus angulatus starting on 21st March. The aphid colonies were tagged before introductions began and monitored over the duration of the trial.

Concurrent assessments of both pests and predators were made. A reduction in aphid numbers began to take place by mid-April compared to the untreated control indicating that the brown lacewings were having a positive effect. The investigation also identified that Micromus angulatus will start to predate aphid eggs and adults at 12^oC and above. The numbers of naturally occurring insects were monitored alongside the aphids and brown lacewings. This provided valuable insights into the pest and predator dynamics that occur in early spring-time.

Further work was carried out in the autumns of 2023 and 2024 where aphids and natural enemies in both the crop and neighbouring hedgerow habitats were sampled until leaf fall, with the intention of identifying species which might endure the winter seasons thereby offering an early level of control the following spring. Higher numbers of aphids were recorded in 2023 than in 2024, but numbers of lacewings and parasitoids were also higher in that year, suggesting that the predator and parasitoid numbers reflected the pest populations.

In a final piece of work, Niab linked up with Rumwood Green Farm to deploy and evaluate a fully integrated biological control (IBC) programme for the large raspberry aphid. The team recorded the release of commercially available aphid parasitoids and other biocontrol products and sampled crops for aphids at each chosen site on nine occasions during the spring and summer of 2024. Mixes of commercially available parasitoids were released fortnightly, while green lacewing eggs were applied to aphid hotspots at a release rate of 30-50 eggs per square metre.

Unfortunately, very low numbers of aphids were recorded in 2024 during this trial period, so the results were inconclusive and an additional season would be required to confirm any major findings. However, the growers involved in the work are of the view that despite an IBC programme being more expensive, they would expect that long-term establishment and persistence of parasitoids and other natural enemies should offer incremental yield and cost benefits to growers over successive seasons.

While further work would be valuable to demonstrate the cost-effectiveness of these approaches in commercial raspberry production, this project has yielded important, actionable findings for growers, industry, and researchers alike. A key scientific outcome is the identification of parasitoid species present within raspberry plantations, offering potential to enhance control of the large raspberry aphid. This warrants further investigation, enabling Biobest to refine its commercial biological control products for raspberry growers. In addition, the project has developed a promising method for applying green lacewing eggs, which could reduce labour requirements.

Rather than relying on manual application to aphid ‘hot-spots’, prophylactic spraying of lacewing eggs may suffice; the eggs would adhere to raspberry foliage, hatch, and provide more uniform aphid control across the crop. Products using this methodology are already authorised in the USA, and were the UK to resolve the current regulatory barriers, such an approach would represent a valuable addition to the tools available for aphid management.

Finally, the finding that brown lacewings will prey on large raspberry aphid at temperatures as low as 12°C adds further value. This insight is particularly relevant for early-season aphid control and is likely to be of particular interest to organic growers. Together, these findings provide a practical foundation for improving aphid control in raspberry crops, with immediate relevance for growers and scope for future innovation.

Title: Exploring the links between soil microbiome and carbon sequestration in a cross-section of agricultural soils (arable, pastural, orchards)
Funder: Growing Kent & Medway Business Innovation Voucher
Industry partner: Verdant Carbon
Term: June 2023 to May 2024

Soils provide a natural sink for carbon dioxide but we need to improve our understanding of how the soil microbiome can be manipulated to improve soil carbon storage capability.

The project

Niab worked with Verdant Carbon in this Growing Kent & Medway project to understand the links between soil microbial abundance/diversity and the volume of carbon sequestered in different agricultural crops. They aimed to identify any correlations between levels of specific soil microbes and soil carbon content across the soil profile (10-60 cm) and between soil management practices (regenerative and conventional).

Results

In the project, soils were sampled at two depths (15-30 cm and 45-60 cm). Total soil organic/residual/inorganic carbon and soil nitrogen was determined at Verdant Carbon using the internationally recognised Dumas Combustion analysis method. Microbial analysis was done using Microbiometer and Soil Food web assessments at Verdant carbon, and state-of-the-art molecular tools (qPCR, amplicon sequencing) at Niab to determine the diversity and abundance of the bacterial and fungal species in the soil. The data was collected from both arable soils and pasture soils.

A comparison of fungal to bacteria ratio (F:B) obtained with different microbial analysis methods was done to determine if methods at Verdant Carbon agree with methods at Niab. The effect of farming type (arable or pasture), sampling depth and total organic content (TOC) on microbial abundance and diversity was measured to find potential associations between the quantity of carbon and microbial populations.

The ratio of fungi to bacteria (F:B) measured with Microbiometer and Soil Food Web analysis did not correlate with molecular measurement (qPCR), which was the only method that produced results in line with the literature.

There were greater numbers of bacterial and fungal communities found in the top soil (15-30 cm) compared to subsoil (45-60 cm). This effect was more pronounced in arable fields than pasture. Fungal communities were found to be richer in arable fields compared to pasture while there were few differences between bacterial communities on both farm types. The relative abundance of bacterial and fungal organisms was not affected by soil nitrogen levels.

The microbiome in arable fields was largely unaffected by various levels of TOC. In contrast the microbiome in grasslands was more affected by TOC with many fungal and bacterial species either increasing or decreasing in response to TOC. Among the species that significantly increased their relative abundance with increased soil TOC were potentially beneficial microbes (eg. nitrogen fixing and mycorrhizal fungi), but also some known pathogens such as Ilyonectria robusta, so it seems that increasing soil TOC levels could therefore have both plant growth promoting and disease promoting consequences.

This collaboration led to further IUK/Defra funded work where Niab and Verdant Carbon aim to develop a holistic soil biological health assessment.

Title: Novel approaches to pest and disease control in apples and pears
Funder: British Apples and Pears Ltd
Term: April 2023 to March 2024
Project leader: Michelle Fountain

British Apples and Pears Ltd funded Niab to investigate new approaches to controlling a range of pests and diseases. In 2023, we worked on apple canker and apple scab control whilst reviewing IPM techniques for codling moth and brown marmorated stink bug control. In addition, precision monitoring, semiochemical and biological manipulation was investigated to control pests such as apple blossom weevil, capsids and sawfly.

The final part of the work sought to develop natural control methods for woolly apple aphid (WAA), currently one of the most challenging pests for apple growers to manage. The pest used to be successfully controlled by broad-spectrum spray products, but the most effective of these have been withdrawn.

Batavia (spirotetramat) currently has an EAMU authorisation to control woolly apple aphid, but weather conditions and application timing are not always optimum for effective control. Rootstock resistance also used to contribute to control, but recent research by a Niab PhD study demonstrated that WAA has at least partially overcome such genetic resistance in some rootstocks. Alternative natural and biological control methods need to be assessed.

The project

Earwigs (Forficula auricularia) are important generalist predators in both apple and pear, of many pest species including aphids. In pear, previous Defra funded research demonstrated that earwigs contribute significantly to the predation of pear sucker. Wignests were developed in an Innovate UK project and offer shelter for earwigs, spiders, anthocorids and other predators, and where earwigs have been present in such wignests in apple orchards, a reduction in incidence of pest damage caused by codling moth and aphids has been recorded. The wignests are commercially available through Russell IPM. This project set about assessing if earwigs housed in wignests and deployed in apple trees hosting WAA, could reduce WAA colonies and colony size.

Results

Large numbers of earwigs were harvested from other habitats in May and June 2023, housed within wignests and then deployed in apple trees in three different WAA affected orchards. Plots both with and without wignests were compared for WAA numbers in July and August.

Overall, placing wignests containing 5 earwigs each in apple tree canopies did not significantly reduce the numbers of WAA in apple trees in one season. However, a trend was seen, especially on one of the sites, which demonstrated an overall reduction in the numbers of WAA on shoot leaf nodes, especially in the middle of the growing season (July and August) following the deployment of earwig loaded wignests at the end of June.

These results are encouraging, so it has been suggested that this work might be continued to examine the long-term impacts of relocating earwigs to apple orchards both to assess if earwigs return to the wignests in subsequent years, and also to test if re-inoculating the refuges with earwigs in a second year might reduce the WAA numbers further.

Further research might also seek to develop methods of harvesting and redeploying earwigs which are less reliant on labour. Additional research might address recent reports of fewer earwigs in orchards which might have been brought about by changing cultural practices such as less frequent mowing and the incorporation of cover crops. 
 

Title: Innovative push-pull control of spotted wing drosophila, an invasive pest of fruit crops
Funder: Innovate UK
Industry partners: Russell IPM, Rumwood Green Farm, University of Greenwich (NRI), WB Chambers
Term: April 2023 to March 2025
 

Previous research carried out by PhD student Christina Conroy as part of the CTP for Fruit Crop Research studentship scheme, identified a chemical repellent that causes a reduction in egg laying in strawberries up to six metres away from the sachet containing the repellent. Other research has demonstrated how precision monitoring traps can be used to reduce overwintering populations in habitats such as woodland adjacent to fruit crops in the winter.

The project

Working with industry partners, Niab set out to combine these findings into a push-pull approach to improve management and control of the pest. They set out to test the repellent compound in raspberry crops then carried out further trials in a commercial strawberry crop, combining the repellent inside the crop (to push the pest out of the crop), with a lure around the perimeter of the crop (to pull the pest away from the crop). Further work was done to optimise existing repellents and attractants for use by commercial growers.

Results

Disappointingly, in testing the repellent compound in 12m long mini-tunnels planted with raspberry, no clear reduction in SWD egg laying was recorded, despite increasing the dose of the compound.

In the push-pull experiment in a commercial strawberry crop over two years, no reduction in egg laying was recorded. Further testing was done using double the number of repellent dispensers, sampling fruit close to dispensers, deploying dispensers in the crop from planting onwards, and including Russell IPM’s commercially available MagiPal.

The MagiPal product, demonstrated to attract natural enemies into crops, was also shown by Christina Conroy in the laboratory to be repellent to SWD. However, despite making these adjustments, no further egg reductions were observed. These results were disappointing and demonstrate how difficult it is to control SWD in a commercial setting even though laboratory and small field tests can initially look promising. It is likely that other factors in commercial crops prevent the repellent working. For example the size of the fields and how the fly perceives the cropping area through vision, detection of fruit and yeast volatiles, and climatic conditions.

In seeking to optimise attractants (the pull component), the Niab team had an idea of a component that might be blended into the liquid products developed by Russell IPM to improve attraction. Liquid baits were compared to standard commercially available liquid baits in field trials. Encouragingly, the newly developed Russell IPM blend was as attractive as the standard Gasser bait which is no longer available. This was an encouraging result, showing that a UK produced bait can be substituted for a bait produced overseas, thereby reducing transport costs and carbon footprint.

Niab is extremely grateful to the commercial growers who hosted this research, without whom the work would not have been possible.

Previous work by Niab has shown that practising winter precision monitoring year after year can help to reduce local numbers of SWD on farms over time and particularly in crops in the spring. Traps should be positioned in hedgerows and woodland, especially in areas of bramble, elder and ivy.

Title: BEESPOKE
Funder: European Regional Development Fund
Industry partners: Policy makers, research institutes and agronomists from seven different north sea region countries including UK, Belgium Netherlands, Germany, Denmark, Norway and Sweden
Term: April 2019 to March 2023
Project leader: Michelle Fountain, Niab

Niab was a partner of BEESPOKE, an EU funded project which sought to increase the number of pollinators and crop pollination on a local and landscape scale by providing expertise, tools and financial knowledge to support growers across the North Sea region. Flower rich semi-natural grassland is the main habitat that supports pollinators, but by 1984, in lowland England and Wales, the area had declined by 97% compared to the previous 50 years, with only 7,500 hectares remaining by 2010. Fruit crops benefit from wildflower rich habitats, not only in the provision of pollinators to maximise yields, but also for the provision of beneficial insects which help to regulate populations of insect pests. Fruit farms therefore will benefit from the establishment of flower rich habitats, which can help to replace at least some of the semi-natural grassland area that has been lost.

The project

One of the aims of the project was to develop a range of seed mixes for planting on farms to help reverse the decline in pollinators. These have been targeted at the types of pollinators needed by each crop type. Some were sown at demonstration centres such as Niab’s East Malling site to evaluate how effective they are by increasing not only the levels and types of pollinators visiting the strips, but also whether they increase numbers in the crops, and whether this has a subsequent impact on crop yield and quality.

Results

Impact of wildflowers on fruit crops

Niab assessed and recorded the impact of wildflower strips at East Malling over the life of the BEESPOKE project. Early data suggested that wildflowers outside tunnel-grown soft fruit crops did not compete with flowering crops for visits by commercially installed bumblebees inside the tunnels. Indeed the fluorescent tracer marked  bumblebees visited the crop flowers far more than the adjacent wildflowers. In raspberry crops, adjacent wildflowers enhanced the number of insect pollinator visits to the crop. This would dispel any concerns commercial growers might have about wildflowers competing with their crop for pollinators.

Research in apple orchards demonstrated how over three seasons, with alleyway sowings of knapweed, yarrow, oxeye daisy, bird’s foot trefoil, self-heal, red campion and red clover, tree populations of predatory spiders, hoverflies, anthocorids and lacewings increased, while numbers of codling moth decreased. Early season aphids, such as rosy apple aphid, decreased in some years but not others, while rust mite increased in one season. Niab also identified adult thrips in wildflowers and found species and numbers fluctuated between years but the majority of thrips recorded were not species damaging to strawberry. Further work is required in soft fruit crops to understand more about this relationship.

The Niab entomology team is also of the view that there will be a greater impact of natural enemies if the wildflowers are positioned within the crop rather than around the field margin. They also recorded an increased diversity of invertebrates in soils where wildflowers were sown, compared to single species mixes, potentially having a positive impact on soil health.

Niab organised a dedicated BEESPOKE event at East Malling in October 2022.

Developing wildflower mixes for UK fruit crops

When setting about developing Beespoke wildflower mixes for our different UK fruit crops, our scientists gave serious thought to the structure, size and composition of the areas to be established and how they should be managed.

It is important to include species that provide height to the mix, which provides improved habitat for insects and an increased biomass which is good for carbon capture. As a result, mowing should be kept to a minimum and if it must be carried out, it is better to mow every other crop row or in the case of large wildflower areas, only half the area. Ideally, the height should be maintained at a minimum of 20cm. If there has been little rainfall a single cut in the Autumn may be all that is needed.

Although semi-natural habitats are important habitat for pollinators and beneficials, alongside ditches, native hedgerows and woodlands (for nesting and shelter), purpose-sown flora can be tailored to specific needs, so growers can gain a lot of pollen and nectar resource from a small area. Some studies recommend a minimum of 6% natural habitat and ideally up to 10%. In addition, a total of 1km of flowering hedgerow per farm can be sufficient to support six common pollinator species. It is generally felt that several small habitat rich areas are more beneficial than one large area for supporting butterfly and parasitoid species. Should one large area fail or be damaged in any way, there are no alternatives, so several smaller areas provide a fall back in case of failure of one. Different areas can also host different seed mixes to further diversify on-farm biodiversity.

The seed mixes should ideally provide diversity of species which complement wildflower species that are already present in or around the farm. The mix should provide flowers outside of the crop flowering period, thereby extending the provision of pollen and nutrients, which can maintain insect population stability and fecundity. Late flowering species help insects to complete their lifecycle thereby helping them to survive from year to year.

When developing an optimum seed mix for each fruit crop, the scientists considered which bee and hoverfly species most commonly visit the crop, which non-crop flowers they visit most often, and which are likely to thrive in a sown area or regenerated strip. They undertook literature searches to identify the pollinators that visit each crop and ranked them according to the frequency of their visits.

Having chosen the top five or six pollinators, they considered the non-crop wildflowers most commonly visited by each pollinator and produced a final choice of seed for each fruit crop including annuals, perennials, biennials and weed species that will attract the five or six pollinators. Not all species will thrive on every site, and for each mix, there is a caveat that some flowering species may have potential to harbour crop pests or diseases, allowing growers to make informed decisions about their final choice of mix.
Some flower species were included repeatedly in a number of the crop mixes, including bird’s foot trefoil, dead nettle, clover, yarrow, hawksbeard and dandelion. Some are long flowering species and some are late flowering.

Niab has produced guides to selecting suitable seed mixes for all UK fruit crops and these can be found on the BEESPOKE website. In addition, other very helpful guides, evaluation tools and publications for growers have been produced as part of the project and are available on the website, including ‘Monitoring pollinators’, ‘Estimating pollination potential’, ‘Establishing perennial wildflower areas’ and ‘Supporting pollinators and farmland biodiversity’.