Eretmocerus eremicus is a small parasitic wasp used in biological pest control to target tobacco whitefly (Bemisia tabaci) and greenhouse whitefly (Trialeurodes vaporariorum) in protected crop systems. The species is available from Koppert under the product name Ercal, and it often complements other whitefly biocontrols such as Encarsia formosa in varied greenhouse conditions.

This beneficial wasp is particularly useful when whitefly pressure is high, or temperatures are warmer, as it remains active at higher greenhouse temperatures where some other parasitoids may slow down.

Here’s What They Look Like at Different Stages of Their Life:

Because the parasitoids are small and discreet, growers often recognize their activity by observing signs of parasitism on the pest rather than seeing the wasps themselves:

• Egg: Eggs are laid beneath immature whitefly nymphs and are not visible without magnification. The egg initially appears transparent, turning light brown after two to three days, and hatches when the whitefly reaches its fourth instar.
• Nymph: When the egg hatches, the larva enters the whitefly nymph. The wasp larva develops within the body of the whitefly nymph, consuming it from the inside.
• Pupa: Pupation occurs within the whitefly puparium, which remains attached to the underside of the leaf.
• Adult: Adult females are lemon-yellow with green compound eyes and red ocelli, measuring about 0.75 mm, while males are slightly smaller, dark yellow to brown, with distinguishing antennae differences. Females actively search leaves for suitable whitefly nymphs.

Why Growers Love It:

• Prevents pest reproduction by parasitizing whitefly nymphs.
• Complements other whitefly biocontrol agents such as Encarsia formosa.
• Helps reduce reliance on chemical insecticides
• Safe for workers, beneficials, and the environment
• Can cycle through the crop, providing ongoing suppression
• Active at higher average greenhouse temperatures, where some parasitoids may slow down.

Timing is critical to achieving success with parasitic wasps. They perform best when introduced before pests reach outbreak levels.

Preventive use:

• Introduce Eretmocerus eremicus at the first signs of whitefly or even preventively in crops with a history of whitefly pressure.

Curative use:

• Effective when Trialeurodes vaporariorum (Greenhouse) or Bemisia tabaci (Tobacco) whitefly species are already present, especially at low to moderate population levels.
• Multiple releases will be required if pest pressure is high or the crop is mature and dense.

Environmental Conditions:

• Most effective at temperatures between 20°C and 30°C (68 and 86°F).
• Very low humidity can slow its activity.
• At a 24 hour average temperature below 20°C/68°F, the control of whiteflies may be insufficient.
• Suitable for vegetables, ornamentals, herbs, and indoor plant production.

Note: Monitoring is essential. After 14-21 days from the first release, inspect the undersides of leaves to determine if additional releases are required. Specifically look for E. eremicus adults and parasitized whitefly or a chewed exit hole from the nymph.

Proper release techniques ensure Eretmocerus eremicus establish quickly and begins controlling pests effectively:

1. Timing: Release preventatively or when whiteflies first appear.
2. Distribution: Open package carefully inside the growing space. Bend and tear off the strips opposite to the hook. Make sure not to touch the pupae during handling. Suspend the cards in the crop, if possible approximately 75 cm under the plant head. Avoid hanging cards in places exposed to direct sunlight.
3. Recommended density: Release rates typically range from 1 to 10 adults per m², depending on crop type, infestation level and crop stage.
4. Release frequency: Weekly introductions are standard until whitefly numbers decrease and remain low. Adjust based on monitoring results.
5. Avoid interference: Do not release immediately before or after broad‑spectrum insecticide applications that could harm beneficial insects.

Tips for Selecting Rate:

• For dense crops, high pest pressure or curative use → choose a higher rate and repeat releases, weekly or bi-weekly (every 7-14 days).
• For preventive use in low‑pressure crops → choose a lower preventative rate, and watch for product establishment.
• Always match release strategy to crop size, foliage density, pest risk, and environment.

Visual checks: After 14-21 days from the first release, inspect the underside of leaves to determine if additional releases are required. Specifically look for adults, parasitized whitefly puparium, or the gnawed hole from the parasitoid chewing through the nymph casing.

Supplemental releases: If whitefly count remains high or increases, consider additional releases or review your IPM plan for gaps (e.g., residual pesticide effects, low humidity zones, new pest introduction).

Record‑keeping: Track release dates, environmental conditions, pest levels and predator observations to refine future programs.

What to Expect After Release:

• First week: Adult wasps begin parasitizing whitefly nymphs.
• 2-3 weeks: Whitefly nymphs will begin to turn yellow, indicating successful parasitism.
• Ongoing: New adult wasps emerge from parasitized nymphs, continuing whitefly parasitism control across the crop.

Because parasitic wasps work biologically, control is progressive, not instant. Monitoring whitefly levels and mummy formation is the best way to track success.

• Introduce Eretmocerus eremicus early or preventatively for best suppression
• Focus releases 75cm under the plant heads where whitefly nymphs is present
• Combine monitoring (sticky traps, leaf counts) with releases
• Avoid disruptive pesticides during and just after releases
• Maintain good greenhouse hygiene to reduce pest reservoirs