Why Aphidius colemani Underperforms in Late Summer — and How to Improve Aphid Control in Greenhouse Peppers

Controlling Green Peach Aphid (Myzus persicae) hotspots is a recurring challenge many greenhouse pepper Growers are experiencing in regions where late summer temperatures currently exceed 30°C (86 °F).

Many Growers rely on Aphidius colemani to prevent outbreaks of this aphid, but when heat rises, results often fall short. Here’s what’s causing the underperformance—and how to fix it.

What Makes Green Peach Aphids Harder to Control in Late Summer

• Faster reproduction: High temps shorten aphid life cycles, increasing population pressure.

• Winged forms increase spread: Under heat or crowding, aphids produce winged morphs that disperse across sections.

• Low visibility: Colonization starts on leaf undersides, delaying detection.

• Heat-stressed bios: Excessive heat reduces parasitoid lifespan and parasitism rate.

  
  

Takeaway: Summer conditions favor the pest—not the parasitoid.

Why Aphidius colemani Struggles in High Heat

While Aphidius colemani remains a reliable biocontrol option, its success depends on how—and when—it’s used. Common pitfalls include:

1. Releasing during peak heat

• Parasitoid adults live shorter under high temperatures.

• Reduced energy = lower parasitism success.
  

Tip: Release during cooler hours (early morning or evening).

2. Late-stage infestations

• Works best as a preventive or early curative agent.

• Struggles once aphids are well established.
  

Tip: Don’t wait for sticky card spikes—release at first signs.

3. Species mismatch

• Aphidius colemani targets Green Peach Aphids and Cotton-Melon Aphids.

• It’s ineffective against Potato Aphids or Foxglove Aphids.
  

Tip: Confirm aphid species before release.

4. Chemical interference

• Residues from previous sprays can harm adult parasitoids.

• Even compatible chemistries need time buffers before/after release.
  

Tip: Review your spray schedule and check product compatibility.

5. Expecting instant results

• It can take 6–9 days for mummies to appear.

• Many Growers might assume it's not working too early.
  

Tip: Consider timelines for evaluating impact.

Better Together: Use Aphidius colemani in Combination With Other Biological Control Agents

If Aphidius colemani is struggling to control aphid populations in the late summer heat, consider pairing it with other bios to boost control and prevent outbreaks from escalating. Here are some of the most effective pairings for greenhouse pepper crops:

Aphidius colemani + Aphidoletes aphidimyza

When to use: Curative

Why it works: Aphidoletes aphidimyza larvae feed directly on aphids

and clean up hotspots.

Aphidius colemani + Aphidius ervi

When to use: When Foxglove Aphids are also present in the crop

Why it works: Aphidius ervi controls larger aphid species like Foxglove Aphids, which Aphidius colemani cannot control.

Aphidius colemani + Hippodamia convergens (Lady Beetles)

When to use: Spot treatment

Why it works: Generalist predator. Useful for quick knockdown in hotspots, not necessarily full-area control.

Best Practice Summary

Common Pitfalls with Aphidius colemani	Solutions
Releasing during heat	Release during cooler hours
Waiting too long	Start at first signs of aphids
Wrong aphid species	Confirm species before choosing bios
Chemical residue	Review compatibility before/after release
Misjudged results	Expect visible impact after 6–9 days

Final Takeaway

Aphidius colemani remains a valuable part of every pepper Grower's aphid control strategy—but it can’t carry the load alone in high-heat conditions.

Pair it strategically with other bios, time releases right, and identify the aphid species present in your crop. That’s how Growers are protecting their margins and maintaining crop quality through peak aphid season.

Need help keeping your aphid control costs within budget?

We support pepper Growers across North America with:

• Species identification

• Strategic biocontrol planning

• Heat-adapted release planning

• Chemical compatibility reviews

Contact Us to connect with our pepper IPM Specialists, and we’ll help you build a strategy that works at keeping aphid pressure and costs down, when the heat is up.