Combating hairy roots disease via biological means

"Tomato cultivation has suffered from hairy roots disease for six years already, that is caused by a bacterium. The excessive root growth became worse every year," says Jan van der Voort. "In order to combat this, we started with ECA water (electro-chemical activation). We applied this for three years, but we did not get the hairy roots under control. Moreover with a high chlorine concentration you saw a less spontaneous crop growth and the membrane of the drippers broke."

Van der Voort then saw a test setup of the Triton bioreactor at Prominent, which made him enthusiastic. For the third cultivation season there are now two bioreactors, each with a maximum capacity of 5 hectares, to prevent plant diseases such as hairy roots and to keep the drip system clean.

A healthy microbiological population is built up in the reactor vessel by means of an advanced control system and smart interaction of air, water and a composite nutrient medium. This population, which consists mainly of bacteria, fungi and yeasts, ensures that the organic pollution is 'eaten up'. As a result, the pathogens in the irrigation system have less nutrition. For example, the agro bacterium that causes the hairy roots disease, does not have a chance to grow. A private immune system is created against pathogens.

At the tomato company, water (15 to 16 m³/hour) continuously circulates from the clean drain silo over the bioreactor. This is to get the good bacteria life in the water before the water enters the cultivation again. A liquid bacterial preparation from Agrona is also dripped into the cultivation water with a pulse pump.

Because the silos are outside, heating the water in winter is necessary to keep it at 19 to 20 degrees for the bioreactor. In addition, the water in the reactor, where a number of specific layers of filter material are located as a carrier of the biology, is saturated with oxygen. This is done by aerating the water both from below and above.

The tomato grower: "From the beginning we collect the first drip irrigation once a week and measure the oxygen content thereof. A lower content may indicate contamination of the drip system, which we want to keep clean. By measuring the oxygen content weekly, the development can be monitored well. We rinse the drip system every few weeks. In the first few seconds we'll see a little bit of pollution, but after that nothing at all. The drip system is and remains nicely clean."

"Because of the bioreactor, the bacterial preparation and more monitoring of the oxygen content, we see that we have a better resilient crop. Which is important in a time with all sorts of diseases and pathogens. Hairy roots disease will keep on troubling us, but we see less negative effects in the crop. We think that it is more manageable," according to Van der Voort. "With chemicals, which is becoming less and less, we have already tried a lot. Usually with little or no result. Which is why we are convinced that we will have to rely on biology in the future."