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A step-by-step guide to whitefly control

Since the 1970s, whiteflies, particularly the greenhouse whitefly (Trialeurodes vaporariorum) and tobacco whitefly (Bemisia tabaci), have evolved into significant pests. Their escalating resistance to pesticides has driven a shift toward Integrated Pest Management (IPM), focusing on biological solutions. These pests favor a variety of crops such as tomatoes, roses, cucumbers, and even cannabis, necessitating a strategic, multi-pronged approach for effective control. Predatory mites, parasitic wasps, beneficial microorganisms and the use of sticky traps are all important tools in the IPM strategy for these crops. They integrate diverse control mechanisms to target various stages of the whitefly life cycle.

The foundation of effective whitefly control

Monitoring for early detection

  • Evenly distribute the sticky traps per hectare or per compartment and monitor weekly.
  • Scout plants regularly, leveraging historical data to predict infestation trends.
  • Introduce parasitic wasps at the first signs of whitefly presence on traps, with repeated applications until 80% parasitism is achieved.

Sticky traps will typically capture the first whiteflies weeks or even months before they are visible in the crop. Using sticky traps early provides essential time to respond to infestations proactively.

Accurate identification

The accurate identification of whitefly species is crucial because Tobacco whiteflies (Bemisia tabaci) require a different management strategy compared to Greenhouse whiteflies (Trialeurodes vaporariorum). Whiteflies have six developmental stages, starting as crawlers (first instar) and progressing to the pupal stage (fourth larval stage). Recognizing the differences between species is key:

Species Greenhouse whiteflies Tobacco whiteflies
Eggs Lay eggs at the tops of plants; eggs turn brown to black within days. Lay eggs across the plant; eggs transition from yellow-green to brown.
Fourth instar (pupa) Oval, white case with wax threads. Flat, transparent or yellow, with a visible red-eyed adult.
Adults Larger, whiter, triangular appearance from above. Smaller, yellower, elongated appearance with a gap in the wings.

Whitefly damage and economic impact

Greenhouse whitefly, Trialeurodes vaporariorum
Greenhouse whitefly, Trialeurodes vaporariorum

Whiteflies can cause substantial economic losses through direct plant damage and indirect virus transmission:

  • Plant sap feeding: Whiteflies, as phloem feeders, extract sap containing sugars like sucrose, reducing energy availability for plant growth and development, directly affecting yield.
  • Irregular ripening: Nymphal feeding disrupts normal ripening in fruits like tomatoes, leaving internal tissue unripe and hard despite normal external appearance.
  • Honeydew production: Whiteflies excrete excess sugars as honeydew, resulting in sticky, shiny deposits that reduce the visual appeal of crops, attract contaminants, and promote black sooty mold, which impairs photosynthesis and plant health.
  • Virus transmission: Particularly damaging, Bemisia tabaci spreads Tomato Yellow Leaf-Curl Virus (TYLCV), severely impacting tomato crops. Greenhouse whiteflies (Trialeurodes vaporariorum) transmit Beet Pseudo-Yellows Virus in cucumbers.

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Mass trapping - Horiver

Mass trapping with sticky traps (Horiver Wetstick) helps control whiteflies by attracting and capturing adults, reducing their population and ability to reproduce. This interrupts the whitefly life cycle and lowers infestation levels, while also serving as a monitoring tool for pest density.

Evenly distribute the sticky cards across the crop in a grid pattern. Alternatively, use yellow roller tape (Horiver Rollertrap) along each row to maximize the capture of whitefly adults. This practice effectively minimizes egg-laying and reduces whitefly movement within the growing area. For Tobacco whitefly management: Adjust the trapping density by using two Rollertraps per row, specifically for crops like tomatoes. Strategically position one tape between the crop and another above the plant canopy to enhance trapping efficiency.

Parasitic wasps

In the battle against whiteflies, parasitic wasps serve as essential allies, targeting whitefly larvae while engaging in host feeding. Their unique characteristics and strategic use are critical for effective biocontrol. Two standout parasitic wasps are Encarsia formosa and Eretmocerus eremicus, which bring distinctive strengths to the fight.

En-Strip – Encarsia formosa

  • Identification: Adult females have a black head and yellow abdomen, while males, rarely observed, are slightly larger and entirely black with clear wings.
  • Parasitism: Prefers L3-L4 whitefly larvae stages for parasitism and targets L2 larvae for host feeding.
  • Egg placement: Deposits a single egg in each host larva.
  • Pupal stage: After parasitization, the pupa darkens to black or brown within 14-21 days.
  • Temperature range: Performs optimally in lower temperature conditions compared to Eretmocerus eremicus.
  • Distribution: Actively searches the crop for infestations in a random pattern.

Ercal – Eretmocerus eremicus

Parasitic wasp Eretmocerus eremicus laying an egg underneath a whitefly nymph
Parasitic wasp Eretmocerus eremicus laying an egg underneath a whitefly nymph.
Parasitic wasp Eretmocerus eremicus laying an egg underneath a whitefly nymph
Parasitic wasp Eretmocerus eremicus laying an egg underneath a whitefly nymph.
  • Identification: Females are pale lemon yellow with green eyes and clubbed antennae, while males are yellowish-brown with longer, elbowed antennae.
  • Parasitism: Specializes in parasitizing L2-L3 whitefly larvae and engages in host feeding.
  • Egg placement: Lays eggs beneath whitefly larvae, penetrating the host at the fourth larval stage.
  • Life cycle: Shorter lifespan than E. formosa, but exhibits faster egg-laying rates.
  • Temperature range: Thrives in higher temperatures, making it more suitable for warmer climates.
  • Distribution: Actively disperses across crops, showing strong mobility in locating whitefly infestations.

Predatory bugs