Around two years ago, Dutch rose breeders Schreurs wanted to take their hygiene and quality control to a higher level. After setting up their own stock of mother plants they were looking for a new spraying method for newly stuck cuttings. This led to an innovative spraying technique that is both effective and efficient. It is perfect for cuttings and low, compact crops on mobile benches.
Peter Schreurs looks back on the upgrade of their hygiene and quality control programme with satisfaction. Their business processes and working methods around disease prevention and nursery hygiene have been reviewed and changed in various areas. “A lot of aspects are involved in this, such as temporarily isolating and testing plant material coming into the nursery, disinfecting Danish trolleys and tightening up some of our work routines,” he says.
One of the measures introduced to reduce the risk of infections is propagating rose crops in-house. “We used to buy plant material from rose growers,” Schreurs explains. “But that didn’t give us enough insight into the health status of the plant material, with all the risks that that entails. So we started expanding our mother plant stocks at our headquarters in the Dutch De Kwakel. Now propagation and production take place in separate departments on the same site.”
Optimise crop protection
The rose breeder was also looking to optimise crop protection during the production phase. “We do all we can to grow on cuttings perfectly and deliver clean plant material to the customer. Safety for people, animals and the crop are a top priority and we try to minimise our use of chemicals wherever possible.”
The first treatment takes place immediately after the cuttings are stuck. Up until the middle of last year, this was done in the greenhouse using standard spraying equipment. But despite the staff taking the utmost care, they did not always manage to cover all parts of the crop with the spray. So Schreurs turned to Theo Straathof of Micothon Spuittechniek to find out whether he could offer a better method.
New technique needed
“I didn’t have a better off-the-shelf spray technique to offer them,” Straathof says. “We mainly produce systems for production nurseries. They often have dense crops and there is usually a big gap between the spraying equipment and the crop. In those situations, air assistance is a standard tool for getting the spray liquid deep inside the crop and achieving maximum coverage. This kind of method is too heavy-handed for young cuttings material.”
A completely different technique was needed, so supplier decided to revisit the electrostatic spray technique he had experimented with in the past. This can produce a very fine spray mist with electrically-charged microdroplets which adhere perfectly to all parts of the crop. Because the mist does not penetrate well, Micothon had not pursued this technique for use in greenhouse horticulture at the time.
“But that’s not a problem for rose cuttings because they are less than 10 cm tall,” the spraying technician continues. “I thought this principle could be used to design a good system for the rose propagator.”
Straathof resumed development of his electrostatic spray technique. First he concentrated on developing a nozzle that could produce a mist with fine, electrically charged droplets. It was a real challenge to get the spray liquid, the electrical charge – supplied by a built-in spark plug – and air in contact with each other at the right time and in the right proportions. Air assistance is needed to create a swirling current that gets the spray into the crop. The electrical charge then ensures the spray is distributed homogeneously and adheres to all parts of the crop.
He reckons there will be more demand for the Micothon Topstart, as the spray cabin is now called. “This spraying technique is perfect for low crops on mobile benches combined with automated transport systems. Several plant propagators and pot plant growers have already expressed their interest. The pioneering work is done, but these kinds of systems still need a lot of customising.”
After a while they found the right recipe. Extensive trials with fluorescent powder showed perfect leaf coverage on both sides. Schreurs was impressed but as yet had nothing he could work with. “This technology lends itself best to automated application in enclosed spaces,” the supplier continues. “That meant building a closable spray cabin which the benches could roll through. Plus we had to integrate it into their existing internal transport system.”
The basic spray for rose cuttings consists of a tank mixture of various products. The spray liquid is cooled in the tank and kept moving to stop the mixture from separating. The pipes and the cabin are flushed clean every evening after use. Before treated benches leave the cabin, they are ventilated for thirty seconds via an active carbon filter to minimise emissions into the environment. The cabin has its own capture and drainage system for residual spray liquid and rinsing water.
80% saving on liquid
Schreurs first spoke to his supplier about this in November 2015. By January 2016 they had an action plan in place and the spray cabin was installed in early June last year. “It’s an expensive piece of kit, but we are delighted with it,” he says. “Firstly because it produces a better spray result, which means we have less trouble with pests and diseases in the greenhouse so we have to spray less. Secondly, the automated process means less work and we use less spray liquid.”
For a basic spray, they used to use 100 litres of spray liquid per 100 benches. Now that’s down to 17.5 litres and with a better end result. “I should mention that the pressure from pests and diseases is less anyway now since we have been propagating our roses in-house from our own mother plants. The fact remains that it’s a fantastic piece of kit.”
An innovative spray cabin has been developed which produces a fine, electrically charged spray mist. This provides highly homogeneous crop coverage and good pest control results with a very small quantity of spray solution. At present this technique is only suitable for cuttings, seedlings and low crops on mobile benches.
Text and images: Jan van Staalduinen.