Following East Riding Horticulture’s (ERH’s) successful trial to test the efficacy of the Nematode Spraying Kit, they trialled the kit on an estate where caterpillars were wreaking havoc on brassicas. Read the case study below to find out more!
Caterpillar infestations caused significant damage to outdoor brassicas grown on a hotel estate in
2024. As the vegetables are intended for use in the estate’s own kitchen, the gardening team was
seeking sustainable and chemical-free pest control.
The Situation
As part of its research into effective biological control methods for pest control, leading horticultural products supplier East Riding Horticulture (ERH) trialled the use of Heterorhabditis bacteriophora
nematodes at the estate. It compared the traditional watering can application method with using PSP’s
Nematode Spraying Kit Spraying Kit (with 7.6L Guarany Compression Sprayer) and the Guarany Dosimeter Valve.
The Trial
The trial was conducted one week after brassica seedlings were transplanted into the ground, laid out in 10 rows of 62 plants each, over weed-controlling ground cover. The challenge was delivering the nematodes efficiently and accurately to the base of each plant, despite ground cover and closely planted rows. Five rows were treated with the dosimeter and five rows were treated by watering can. The same dosage was applied for both methods with each brassica receiving two 25 ml doses.
The Nematode Spraying Kit
The Results
The Nematode Spraying Kit enabled precise and controlled application at the base of each brassica. The specially adapted compression sprayer allowed free passage of the nematode solution without clogging.
Unlike the watering can, which resulted in overspray onto ground cover andleaves, the Dosimeter allowed the grower to direct the solution exactly whereneeded – at the stem and soil interface. Small lab dishes confirmed thatnematodes remained active after passing through both the Dosimeter andwatering can.
The grower found the Dosimeter method far more accurate and less wasteful thanthe watering can approach. While the watering can required constant attention tospeed and mixture levels, the Dosimeter provided a measured, repeatable dose toeach plant. This reduced guesswork and minimised overspray.
On follow-up inspection (9th June 2025), all treated brassicas remained free fromcaterpillar damage. On inspection in mid-July 2025, some caterpillar damage wasnoted but this was minimal compared to the previous year.
ERH’s Melanie Breillat, who ran the trial, said: “Our estate client found the application of nematodes using the Nematode Kitand Dosimeter Valve very effective. This method is more accurate and avoidswasting the mixture on the ground cover. Our client is delighted and will be usingit again for outdoor vegetables.”
About the Guarany Dosimeter Valve
This innovative valve, featuring a trigger mechanism and application pipe, easily attaches to any standard sprayer to deliver precise, consistent volumes of fluid with every squeeze. Its pressure-retaining system ensures reliable performance regardless of pressure fluctuations in the sprayer. The delivery volume is fully adjustable between 2 ml and 25 ml per stroke, allowing for exceptional control and repeatability.
Discover the Dosimeter here.
Find out more about the Nematode Spraying Kit here.