For many years, crop protection was achieved using the conventional chemical technologies. The greenhouse manager, Mr. Theo Baars explains: “Every time we sprayed against mildew or Botrytis, neither the crop nor the beneficial insects were exactly jumping for joy. So, we were actively looking for a non-chemical way to protect our crop without bothering the crop and our beneficial insects.”
There was an additional challenge when using chemical fungicides in this demonstration greenhouse. Sales Coordinator Ms. Carolijn Stokman explains: “The purpose of this greenhouse is to welcome rose growers from around the world. But pesticide legislation here in Holland is quite restrictive: When we spray we cannot permit visitors into our showroom, so to speak. This was an extra reason why we wanted to steer away from chemical crop protection as much as we reasonably speaking could.”
Stokman continues: In 2008, someone from a company that makes UV light installations for crop protection came by. They claimed their technology could control mildew and Botrytis with a special form of light, so that we could reduce our need for fungicides. Even though we had our doubts we agreed at that time to do a small trial, using an inexpensive hand operated cart.
Theo Baars explains the effects on the crop and on the disease: After a few weeks we noticed that newly developed foliage remained clean, more or less free of mildew. But only the section that was reached by the light. Initially, we kept on observing new mildew on the underside of the leaves, where our lamps could not reach. That was disappointing, because in effect it meant we had to keep on spraying with fungicides.
However, a few weeks later we observed that the underside of the leaves remained clean as well. The level of innoculum in the greenhouse had dropped. And the crop had become stronger, better able to defend itself against diseases. This was a True Revelation for us: We were able to keep top and bottom of the new leaves clean, so we could curtail our chemical crop protection program substantially:
- 1. The crop looked stronger and healthier.
- 2. The natural wax layer on the foliage remained intact. The leaves were shiny, once again.
- 3. We could discontinue the use of our sulfur burners.
- 4. The expenditures for beneficial insects as part of our IP program dropped, because we no longer “fought against the good guys” with chemicals and with sulfur
- 5. Our expenditures on fungicides for mildew control dropped from 85 cents to 10 cents per square meter
In 2009, when the effects of this technology became apparent to Lex+, they decided to abandon their handcarts, and they invested in an automated system that applied the lamps. In their case that was a SprayRobot from Berg Hortimotive, but a SprayRobot from Wanjet is also suitable for this technology. It rides fully automated through the greenhouse with a speed of 30 meters per minute.
Thanks to the automated control, the mildew has now virtually disappeared, from the crop, and also from the air in the greenhouse. Theo Baars concludes: “By now, the disease pressure is so low that several weeks go by without any need to interfere. If and when a little bit of mildew comes into our greenhouse and onto the crop, I run the machine for a few days, until the crop is vital and clean, once again.”
In 2011 en 2012 several of the other rose farms in Aalsmeer have followed the example set by Lex+. Carolijn Stokman, with a smile: “Yes, our neighbours follow our lead. And thus far they have saved 50%. Perhaps, one day, they will be as good as our own Theo Baars and reduce chemical crop protection altogether, just like we have managed.”