Cultural and Physical Measures: Rapid Intervention Even when populations are escalating, foundational practices provide immediate and ongoing support:
- Intensive Monitoring: Continue to scout plants diligently, especially inspecting leaves and shoots. The presence of ants feeding on honeydew is a clear indicator of a heavy aphid infestation, signalling an urgent need for action.
- Targeted Removal: For isolated, visible aphid colonies, squash single aphids on sight to prevent further reproduction. In cases of significant aphid hotspots on a single plant, remove and destroy the affected plant, replace it with a clean one, and immediately treat the surrounding area with preventative amounts of predators and parasitoids.
- Ant Control: Ants actively protect aphids from their natural enemies to harvest honeydew. Implement ant control measures such as supplying them with additional sugar to capture or distract them. Reducing ant presence enhances the efficacy of biological controls.
- Enhanced Hygiene: Ensure rigorous weed control, as weeds can harbour aphid populations that may quickly migrate to your pepper crop.
Corrective Biological Controls: Deploying Reinforcements When aphid numbers are high, direct introduction or boosting of natural enemies is paramount:
-
Mixed Parasitoid Releases: When aphid species are unknown or multiple species are present, a mixture of parasitoids is often recommended.
- For smaller aphids like Myzus persicae and Aphis gossypii, introduce Aphidius colemani.
- For larger aphids such as Macrosiphum euphorbiae and Aulacorthum solani, release Aphidius ervi.
- Use higher introduction rates for Aulacorthum solani. A. ervi can induce panic in aphids, causing them to drop off plants and die.
- Consider Aphelinus abdominalis (identifiable by black mummies). This species controls both large and small aphids, causing high mortality through host-feeding and demonstrating greater resistance to hyperparasitism than Aphidius species.
-
Predator Releases:
- Introduce Aphidoletes aphidimyza (predatory gall midge) at up to to 5 individuals/m²/week (minimum 4 times), depending on hotspot density, as their larvae are voracious predators of most aphid species.
- Deploy Chrysoperla carnea (lacewings) larvae either full-field or concentrated in hotspots. Both adults and larvae of Micromus angulatus are effective, offering fast action.
- For localised outbreaks, Propylea quatuordecimpunctata and Adalia bipunctata (ladybirds) can be used curatively in aphid hotspots.
- Addressing Hyperparasitism: If you observe jagged exit holes on aphid mummies, this indicates hyperparasitism. In such cases, switch your control programme to rely more on predators like Aphidoletes, Sphaerophoria, or Chrysoperla, as a diverse parasitoid community is generally more resilient.
- Boosting Biocontrol After Chemicals: Following any chemical applications, it is crucial to boost natural enemy populations to prevent aphid re-establishment, always being mindful of residual effects.
Biorational Sprays: Targeted Support These products serve as a "second line of defence" and can provide rapid knockdown while being less disruptive than conventional pesticides:
- Soaps and Oils: Use insecticidal soaps and oils as a softer option. Apply them before releasing beneficials, especially if honeydew is present, as it can hinder predator search capabilities.
- Protac/Siltac: This product is effective against soft-bodied insect pests. Ensure quick drying to avoid plant damage. It is best used prior to beneficial releases, and re-release of beneficials should be considered once the spray has dried. Spot-sprays with short-persistence chemicals* like Spyro or Protac can manage small colonies and hotspots without severely impacting overall beneficial populations.
(*Note: check local legislation on plant protection products)
Sustaining Control and Key Considerations:
- Don't Stop Biocontrol Prematurely: Even if aphid populations appear to be under control, maintain steady introductions of beneficials to avoid "boom-and-bust" population cycles.
- Supplemental Feeding: Adult parasitoids and predators can benefit from supplemental sugar sources (e.g., Alyssum, honey stations, or sugar solution sprays) to extend their lifespan and prevent egg reabsorption, particularly when honeydew is scarce.
- Banker Plants: For long-term, sustained parasitoid production, consider using oat or barley grass banker plants infested with Bird Cherry-Oat Aphid (Rhopalosiphum padi). Introduce Aphidius colemani into these plants for continuous breeding. End banker plant production by July (or earlier in cooler climates) to prevent hyperparasitoid build-up.
By integrating these practical, corrective measures and adapting your strategy to the specific dynamics of the aphid outbreak and the beneficials present, you can regain control and maintain the health and productivity of your pepper crops.
Enhance Your IPM Skills! Enrol in our comprehensive course: 'Aphids and their natural enemies'.
