While whiteflies may appear delicate with their soft wings and tiny stature, these pests are anything but innocent in the greenhouse. For Silje Stenstad Nilsen, founder, biologist, and senior advisor at Biologisk AS, understanding the behaviour and lifecycle of pests like whiteflies is essential to helping growers protect their crops and profitability.
"Whiteflies might just be the most beautiful pest. They're only 1–2 millimetres long, with two pairs of white, milky wings that flutter elegantly—but don't let their appearance fool you. They pose serious risks to your crop."
© Biologisk AS
Wide host range and damaging effects
Thriving in warm greenhouse environments, whiteflies—commonly misidentified as mealybugs due to their white wings—attack a wide variety of crops.
"We see them on tomatoes, cucumbers, cabbages, and many ornamental plants," she explains. "They suck sap from the plant, leading to yellowing leaves, stunted growth, and in severe cases, significant yield losses."
Honeydew and fungus: A double blow
The damage doesn't stop at physical symptoms. According to Silje, whiteflies also secrete a sticky substance known as honeydew.
"This honeydew becomes a breeding ground for black mould fungus," she says. "It further weakens the plants and creates unsightly foliage, which is particularly problematic for ornamental growers."
Unseen danger: virus transmission
Perhaps the most alarming aspect of a whitefly infestation, however, is their ability to transmit viruses.
"Whiteflies are not just annoying; they are efficient virus vectors," she warns. "They can carry and spread plant viruses throughout the greenhouse, putting entire crops at risk."
In response to this threat, Biologisk AS offers growers tailored solutions based on biological control.
"Our job is to minimise waste, promote healthy plants, and help producers achieve profitable harvests. We do this by selecting the right beneficial insects in the right quantities, specific to each grower's needs."
© Biologisk AS
Prevention starts with good hygiene
She emphasises that prevention is the grower's strongest tool.
"A clean greenhouse is the first line of defence. Clear away old plant residues, sanitise regularly, and monitor pest populations closely."
Among the tools she recommends are glue traps—simple, effective, and essential.
"Yellow glue traps are a great way to catch adult whiteflies. They help growers understand the level of infestation early, so they can take action before it's too late."
Creating a healthy greenhouse ecosystem
Biologisk AS takes pride in being more than just a provider of beneficial insects.
"We see ourselves as advisors, not just suppliers. Choosing biological control means understanding pest dynamics, crop vulnerability, and environmental conditions. That's where our experience really makes a difference."
For growers grappling with whitefly outbreaks or those looking to prevent them altogether, Silje advises to think proactively. "Monitor your crops, maintain cleanliness, and trust biological solutions. It's not just about fighting pests—it's about creating an ecosystem where your crops can thrive."
For more information:
Biologisk AS
Silje Stenstad Nilsen
silje@biologisk.no
biologisk.no
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