Last year, by adopting biological control strategies, several raspberry propagators in Belgium and the Netherlands successfully controlled sciarid flies, Duponchelia and thrips without having to resort to chemicals.
Biobest advisor Arno Hellemons advises several large and small propagators in both countries. “These niche businesses supply small plants to raspberry growers in Europe and beyond,” he explains.
“In raspberry propagation sciarid flies (Sciaridae) are the most troublesome pest, however Duponchelia moth and thrips are also very common.
"The mother plants are initially grown outside in pots, attracting a wide range of insects,” he explains. “When the root balls are divided the propagator moves the plants indoors in containers, or on tables, and covers the roots with growing media. From this point, we recommend using a combination of three beneficial insects to ensure they are pest-free."
Arno advises propagators to first apply Steinernema-System to the growing media.
"These microscopically small Steinernema feltiae nematodes actively search for sciarid and thrips larvae. To be effective, we recommend repeating the treatment every two weeks."
The second component is Hypoaspis-System.
“This should be applied immediately after covering the roots,” says Arno. “This robust predatory mite - Stratiolaelaps scimitus (Hypoaspis miles) - lives in the top layer of the growing media feeding on Sciarid fly larvae and eggs as well as thrips pupae. This predator has the major advantage it can survive several weeks without prey. Again, it should be introduced fortnightly.”
The third element is Atheta-System. The predatory beetle Atheta coriaria feeds on sciarid eggs and larvae as well as moth larvae and thrips pupae.
"This beetle has a large flight range, complementing the other two biocontrols,” explains Arno. “It also actively searches for prey and should be introduced for three consecutive weeks.”
Supplemented with sticky traps
To complete the strategy, Arno recommends installing yellow sticky rolls. “The Bug-Scan® Roll Yellow can be hung between poles,” he explains. “We supply plastic clips - to secure the roll to the poles with tie wraps - so no glue residue is left behind."
Pest free without chemical products
“This three-prong biological control strategy is proving highly effective,” says Arno. “Without employing chemicals, pest infestation has been minimised.
Want to know more about the biological control in propagation of raspberry plants? Contact your local Biobest advisor.