Aphytis melinus
A tiny yellow wasp, about 1/16 inch (1.5 mm) long, that parasitises armoured scales. These are the flat scales with a separate waxy cover, such as California red, oleander and San Jose scale. The female lays under the cover and the larva feeds on the scale beneath it, and she kills more scales by stabbing them and drinking from them. It is sold mainly for California red scale on citrus. It does nothing to soft scales such as brown soft scale.
At a glance
- Mode
- Parasitoid and host-feeder
- Rate
- 5–10 per plant; 5,000–10,000/acre
- Ships as
- Adults in a cup, 5,000–30,000
- Temp
- Release at 60–85 °F (16–29 °C)
- Humidity
- 40–50 % RH or more (suppliers differ)
- Setting
- Citrus, landscapes, greenhouses, interiors
How it works
The female prefers third-instar virgin female scales. She lays one or more eggs under the waxy cover, and the larva feeds on the scale beneath it, pupates there, and chews a round exit hole in the cover as an adult. She also punctures scales and drinks from them. UC notes that this host feeding and mutilation at times kills as many scales as parasitism does. Each female lays about 100 eggs over a life of about two weeks.
Egg to adult takes about two weeks in warm weather (Rincon-Vitova gives 13–17 days at 80 °F), so Aphytis fits two to three generations into each generation of scale and up to about a dozen into a year. Its weak point is that it needs the right stage of scale to lay in. An oil spray can leave no third-instar scales for a time. Ants, dust on the leaves and broad-spectrum sprays all reduce its effect, and UC's citrus guidelines say releases work only where broad-spectrum pesticide use is kept down.
Is it established?
The wasp works under the scale cover, so look under it. Lift a few covers with a pin on each check.
- WEEK 1Tiny yellow wasps walking over scale-infested leaves, twigs and fruit
- WEEKS 2–3Aphytis larvae or pupae under some of the scale covers you flip
- WEEKS 3–4Round exit holes in scale covers; dead, dried-out scales that rub off fruit
- MONTHS 2–3Indoors, Rincon-Vitova says regular releases control an infestation in this time
Release & handling
Aphytis ships as adults in a cup and does not keep. Release it the day it arrives. If you must hold it, keep it at about 60 °F (16 °C) in the dark. Do not refrigerate it or put it next to cold packs, and do not hold it long, because viability falls quickly in storage. Release on the shaded side of trees, below 90 °F (32 °C).
Release the same day
Arbico says not to hold them for later use. Koppert allows 1–2 days at 59–64 °F (15–18 °C) if necessary.
About 60 °F, dark, no fridge
Rincon-Vitova and Buglogical. Keep the cup away from cold packs.
Shade, dusk or morning
Outdoors, release on the shaded side below 90 °F. Indoors, release at dusk or with the windows shaded, waving the open cup around infested plants.
Test for residues
UC: put wasps in a jar with 10–12 treated twigs for 24 hours. If more than 35% die, residues are too high.
Pesticide sensitivity
Rincon-Vitova lists oil sprays, insecticidal soaps, Bt and sabadilla as compatible, and says to release again about four weeks after anything more toxic. UC found that carbaryl residues at the dilute red scale rate affected adults for five months. Check a product →
When to choose something else
Aphytis is a specialist for armoured scale in warm places. Choose something else when:
- The scale is a soft scale, such as brown soft or black scale, which makes honeydew. Aphytis lays only in armoured scales, so conserve Metaphycus wasps or release Rhyzobius lophanthae lady beetles
- It is purple scale on citrus: UC says its most effective parasite is a different species, Aphytis lepidosaphes, which is not sold
- The population is heavy: Rincon-Vitova suggests a summer oil spray 2–3 weeks before the first release, or insecticidal soap indoors
- Ants are tending the scale: control them first, because they disrupt the parasites
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics10,000 / 25,000 / 50,000US
- Buglogical5,000 / 25,000US
- Evergreen Growers Supply5,000–30,000US
- Koppert (Aphytis)10,000GLOBAL
- Nature's Good Guys5,000 / 10,000US
- Rincon-Vitova5,000–30,000US
Aphytis melinus by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.