The midges have disappeared. The aphids, demonstrating much less discretion, are still there.
That can happen after an Aphidoletes release even when the process has started. Adults are easy to miss, and they are not the stage doing the eating. The useful question is what is happening inside the aphid colonies.
Start the clock at the right event
A pupa arriving, an adult emerging and an egg hatching are separate events. Do not add “two days to hatch” to the delivery date: that clock starts when an egg is laid. Bioline reports egg hatch in about two days at 73°F and roughly six days of larval development at that temperature. Cooler conditions stretch the sequence. 4
| Checkpoint | Look for | What to do |
|---|---|---|
| Arrival day | Pupae in carrier; no movement can be normal. | Release promptly and photograph two or three colonies. |
| First several days | Adults at the open release point; later, larvae among aphids. | Check briefly each day. Keep the container sheltered and open; do not seal it to trap adults as proof. |
| One-week review | Emergence evidence, larvae, and whether live colonies are expanding. | If none of the first two is visible, contact the supplier with conditions and shipment details. If aphids are spreading, reassess coverage now. |
| Following week | Repeat photographs of the same sites, plus newly infested leaves. | Continue the confirmed release program if improving. If worsening, reduce severe hotspots and revisit host, conditions and treatment choice. |
These are monitoring appointments, not guaranteed biological deadlines. Their purpose is to catch a stalled treatment while the plant still has options.
Look where the larvae would eat
Use a hand lens to examine a few established colonies. Orange, legless larvae among the aphids are the clearest direct sign to look for. Tiny eggs are harder to find, and an absence of visible adults during the day says little by itself.
Some attacked aphids become collapsed remains. Those can support what you are seeing, but a dead aphid alone cannot tell you what killed it. Do not make yourself identify every speck on the leaf. Pair evidence of larvae with a simple comparison of live aphids.
Count the same little patch
Choose two or three spots you can recognize again: a growing tip, a leaf underside, perhaps the worst colony. Take a close photograph and repeat it from roughly the same angle every few days. If counting is practical, count the live aphids. If they are packed together, compare how much of that same tip or leaf they cover.
Smaller colonies, fewer newly colonized tips and healthier new growth together are encouraging. Old curled leaves may stay curled. Their appearance records earlier feeding, so they are poor witnesses to what happened this week.
A clean tip can hide a busy lower leaf
A greenhouse experiment found an important catch: when green peach and foxglove aphids shared plants, Aphidoletes control was more consistent for the green peach aphids. The two aphids occupied different parts of the plant, and female midges favored colonies on new growth. [2]
That makes checking both upper and lower growth worthwhile, even on a single houseplant. A release may be doing useful work while leaving another colony insufficiently controlled.
When the aphids keep gaining ground
Do not keep extending the deadline while new growth becomes more heavily infested. Check that adults emerged, the release point did not dry out or overheat, ants are not defending the colonies, and recent sprays are compatible. Confirm that the insects are aphids. Then review the release rate and repeat interval against the pressure you actually have.
If an overwhelmed tip can be removed without sacrificing the plant, removing that hotspot can reduce the workload. Keep any predators or mummies you can reasonably preserve elsewhere. A different compatible aphid predator or a correctly matched parasitoid may be useful if colonies remain difficult to reach.
The aphids need to be losing the argument. A weekly review makes sure you notice if they are winning.
Sources and further reading
- Boulanger et al. (2019). Optimizing aphid biocontrol with the predator Aphidoletes aphidimyza, based on biology and ecology. Pest Management Science 75, 1479–1493. Review of establishment, mating, climate and diapause.
- Jandricic et al. (2016). Biological Control Outcomes Using the Generalist Aphid Predator Aphidoletes aphidimyza under Multi-Prey Conditions. Insects 7, 75. Greenhouse study of aphid species and within-plant distribution.
- Cornell University. Aphidoletes aphidimyza. Extension guide to appearance, feeding and life stages; practical guidance supplementing the peer-reviewed research.
- Bioline AgroSciences. Aphidoline. Egg and larval timing at 73°F; producer guidance.
