When insecticides for combatting thrips no longer worked, plant cultivation and propagation company Damsigt considered discontinuing their most successful variety - Calathea zebrina. Fortunately, the combination of predatory mite Amblyseius swirskii with Nutrimite feed brought results. “Thrips is now well under control,” says Damsigt manager, Rob Matheusen; “saving both money and work.”
Based in Roosendaal in the Netherlands, Damsigt devotes 5 ha to the propagation and cultivation of Calathea zebrina. Thrips and spider mite provide the major pest challenges. “In the past, we dealt with them chemically, but the products didn’t work adequately,” says Matheusen. “Then we tried various types of predatory mites, but they proved ineffective. Phytoseiulus did work for a while, but because we still had to use chemicals it quickly disappeared.”
All advice was welcome
After consultation with Stefan Bohte, of Biobest, Matheusen adopted a different approach. “At a time where we were almost forced to discontinue our best variety, all advice was welcome,” he says. “So, in 2013 we introduced the Swirskii-System and fed with Nutrimite™ - a combination that worked brilliantly.”
One application is enough
To this day, the company continues to follow this strategy. “We introduce Swirskii-System directly after taking the cuttings and keep feeding the predatory mites until the plants leave our premises,” explains Matheusen. “Due to the presence of the swirskii, the thrips don’t get a chance to develop and we no longer have control issues.
“We only have to introduce swirskii once, unless there is extreme weather when we may need a follow-up. Three to four predatory mites per leaf is sufficient to keep thrips under control.”
“As we irrigate the pot plants from above, the dosage is different to usual,” says Matheusen. “We use 250 grams Nutrimite™ per hectare weekly, instead of 500 grams fortnightly. With the Makita blower system, spreading is straightforward. While we now have thrips under control, it is also reducing costs.”
Spider mite control also biological
As the thrips are so well controlled, the biological control of the spider mites has also improved. The team releases the predatory mite Phytoseiulus persimilis, using Phytoseiulus-System, to combat the spider mite. “We introduce this every other week, 10 per m2, as the plants are particularly prone to this pest. Doing it this way we don’t normally need to spray. In extreme spider mite weather we sometimes make an adjustment, however, that is an exception. As we are committed to using maximum biological control, we find that beneficial insects from the environment also help out, for example, the gallfly Feltiella acarisuga against spider mite.”
To tackle soil insects and the Duponchelia caterpillar, Damsigt employs the Atheta-System involving the predatory beetle Atheta coriaria. The team find the BT product Delfin a good alternative.
Aphids are kept under control with fortnightly releases of the lacewing fly Chrysoperla carnea, at a rate of 8 per m2, using the Chrysopa-System – a product that also works against thrips. “For all pests we now employ biological solutions to the maximum,” says Matheusen. “In this way, we can deliver residue-free plants to our customers.”